Virtual Device Driver Reference for OS/2
By IBM
About This Book
The OS/2 Virtual Device Driver Referencedefines what a virtual device driver is, how it operates, and when to use one. In addition, a description of the types of virtual device drivers, their interfaces, and the available kernel services is provided. System and application programmers can use the information found in this book to write their own virtual device drivers and subsystems.
Knowledge of a programming language (such as C or assembler) that is used for writing OS/2 applications is necessary, and the programmer must be familiar with the workings of the OS/2 operating system.
How This Book is Organized
This book consists of three parts:
Part 1. Overview
IntroductionThis chapter contains a general description of the three types of OS/2 device drivers, and an overview of the virtual device driver mechanism and kernel services.
Virtual Device Driver Architecture and OperationsThis chapter contains a description of virtual device driver architecture, operations, and communication between device drivers.
Part 2. Virtual Device Drivers
Base Virtual Device DriversThis chapter contains a description of each base virtual device driver shipped with OS/2.
Installable Virtual Device DriversThis chapter contains a description of each installable virtual virtual device driver shipped with OS/2.
Virtual Mouse Device DriverThis chapter describes the virtual mouse device driver (VMOUSE), which is responsible for all mouse support in multiple DOS sessions.
Part 3. Reference Material
C Language Virtual DevHlp ServicesThis chapter contains full C language descriptions of the kernel functions available to virtual device drivers.
Appendixes
OS/2 Version Compatibility ConsiderationsThis table describes information added to or changed since the availability of OS/2 Warp, Version 3 in terms of version compatibility.
Assembler Language SyntaxThis appendix contains assembler language versions of the kernel functions covered in Chapter 6.
NoticesThis appendix contains legal notices and lists the trademarks of the IBM Corporation and trademarks of other companies.
A glossary and an index are included at the back of this book.
Assistance
Technical support for device driver development is provided by the IBM Driver Development Support Center (DDSC) through a bulletin board system ( BBS) known as the "DUDE." You are encouraged to use the DUDE to obtain support by sending in your questions and reviewing the question and answer database which can be downloaded for off-line review.
To access the DUDE, dial 512-838-9717 (using a modem) to register and access the support system. For voice support in the United States, call 512 -838-9493.
Additional assistance is available through the IBM Solution Developer Program. For membership information:
Internet: ibmsdp@vnet.ibm.com
US/Canada: 800-627-8363
International: 770-835-9902
International Fax: 770-835-9444
Ordering Information
For an illustration of OS/2 Technical Publications and other related product documents, see the figure labeled "OS/2 Technical Publications". The documents represented in this illustration are available only in English.
In addition to the actual tools and source code available on The IBM Developer Connection Device Driver Kit for OS/2, this CD-ROM also includes the following DDK reference books in online format.
- The Physical Device Driver Reference
- The Storage Device Driver Reference
- The Input/Output Device Driver Reference
- The Pen for OS/2 Device Driver Reference
- The Virtual Device Driver Reference
- The Presentation Device Driver Reference
- The Display Device Driver Reference
- The Printer Device Driver Reference
- The Graphics Adapter Device Driver Reference
- The MMPM/2 Device Driver Reference (Multimedia)
To order the DDK call:
/----------------------------------------------------------------\ |U.S.A.: |1-800-633-8266 | | |--------------------+---------------------+---------------------| |Canada: |1-800-561-5293 | | |--------------------+---------------------+---------------------| |When calling from |* English |(+45) 48101500 | |Europe, the Middle |* French |(+45) 48101200 | |East, or Africa, the|* Italian |(+45) 48101600 | |number depends on |* German |(+45) 48101000 | |the language you use|* Spanish |(+45) 48101100 | |to place the order: |* Dutch |(+45) 48101400 | | |* Danish |(+45) 48101300 | | |* Finish |(+45) 48101650 | | |* Swedish |(+45) 48101150 | | |* Norwegian |(+45) 48101250 | | |* FAX |(+45) 48142207 | |--------------------+---------------------+---------------------| |When ordering from |* Bolivia | 02-35 1840 | |Latin America or |* Columbia | 01-257-0111 | |South America, the |* Dominican Republic | 566-5161 | |number depends on |* El Salvador | 02-98 5011 | |the country from |* Honduras | 32-2319 | |which you are |* Paraguay | 021-444 094 | |calling: |* Urugruay | 02-923 617 | | |* Chile | 02-633-4400 | | |* Costa Rica | 223-6222 | | |* Ecuador | 02-56 5100 | | |* Guatemala | 02-31 5859 | | |* Panama | 02-639 977 | | |* Peru | 014-36 6345 | | |* Venezuela | 02-908-8901 | | |* Argentina | 01-313-0014 | |--------------------+---------------------+---------------------| |To order from Asia/ |* All except Japan |(61) 2-354-7684 | |Pacific: |* Japan |(81) 3-3495-2045(Fax)| | | |Fax request to: | | | |DAP-J, IBM Japan | |--------------------+---------------------+---------------------| |To order from SE |(021) 800-6120(Voice)| | |Brazil: |(021) 800-6936(Fax) | | |--------------------+---------------------+---------------------| |To order from |* Mexico City |627-2444 | |Mexico: |* Country |91-800-00639 | \----------------------------------------------------------------/
What's New
Following is a list of the changes made to the OS/2 Virtual Device Driver Reference(Fourth Edition) since it was published in April 1995.
Refer to OS/2 Version Compatibility Considerationsfor a table listing compatibility information about new information in this book.
Introduction
Virtual device drivers are used by the OS/2* operating system to act as virtual devices for DOS applications executing in a DOS session. These device drivers provide virtual hardwaresupport for DOS and DOS applications.
The virtual device drivers shipped with OS/2 will virtualize most of the standard devices, including:
- Asynchronous Communication (RS-232C)
*DMA (Direct Memory Access)
*Fixed Disk and Diskette
*Keyboard
*Mouse
*Parallel Port Printer
*PIC (Programmable Interrupt Controller)
*Timer
*Video
This book provides an overview of the virtual device driver mechanism and the available kernel services.
Types of OS/2 Device Drivers
Three types of device drivers are used in the OS/2 operating system:
- Virtual device drivers
*Physical device drivers
*Presentation drivers
Virtual Device Drivers
The virtual device driver is an installable module, responsible for virtualizing a particular piece of hardware and associated ROM BIOS in the manner expected by a DOS application. This device driver achieves virtualization by emulating I/O port and device memory operations. Virtual device drivers are 32-bit device drivers, operating at Ring 0, the most privileged level of the operating system. To achieve a certain level of hardware independence, a virtual device driver usually communicates with a physical device driver in order to interact with hardware.
Physical Device Drivers
Standard I/O devices are supported by base physical device drivers that are part of the OS/2 operating system. Additional or replacement physical device drivers can be loaded to extend the control provided by the base device drivers, or to support nonstandard I/O devices. Typical examples of these loadable device drivers are ANSI.SYS and ANSI.DLL, which are loaded by "DEVICE=" statements in the CONFIG.SYS file, and provide additional functions on the interfaces to the screen and keyboard. Physical device drivers are initialized at Ring 3 and operate at Ring 0.
Further information on physical device drivers, physical device driver interfaces (including detailed descriptions of the calling conventions), and the system services available to these drivers is found in the OS/2 Physical Device Driver Reference.
Presentation Drivers
The Presentation Manager* I/O interface for output devices is a high-level interface. This interface is similar to the API (Application Programming Interface) call interface, which uses the program stack to communicate with , or pass parameters to, the presentation drivers. These drivers are special-purpose I/O routines operating with I/O privilege at privilege level 2 (Ring 2) or privilege level 3 (Ring 3). Their main function is to process function calls made by the Presentation Manager interface on behalf of Presentation Manager applications. Hardcopy presentation drivers communicate with OS/2 device drivers through the file system emulation functions. Display presentation drivers interface directly with the hardware.
Presentation drivers are dynamic link library modules that are supplied as files and are identified by the extension ".DRV". When the Presentation Manager is initialized, the display presentation driver is automatically loaded and enabled. Other presentation drivers (for example, the hardcopy presentation drivers) are loaded and enabled when an application calls the DevOpenDCfunction to open the device.
Presentation drivers service requests only from applications running in Presentation Manager sessions in the OS/2 mode. Output data and requests for information are passed to the presentation driver as function calls to the presentation driver interface. The definition of the call interface is given in terms of the codes and data passed to the presentation driver interface through the program stack.
Include (.INC and .h) files are shipped with the Developer's Toolkit for OS /2to provide support for building presentation drivers that are written in either C or assembler language. These files contain function prototypes, defined values, and data structures used by the various functions.
Further information on presentation drivers, presentation driver interfaces (including detailed descriptions of the calling conventions), and the system services available to these drivers is found in the OS/2 Presentation Device Driver Reference.
When to Use a Virtual Device Driver
The device virtualization provided by OS/2 can be extended by creating a virtual device driver (VDD) and the corresponding physical device driver ( PDD). A user-supplied virtual device driver virtualizes the hardware interfaces of an option adapter or device, usually to migrate an existing DOS application into the OS/2 DOS environment.
Note that a virtual device driver is needed only in a limited number of cases. If there is no requirement for multiple sessions to share access to a device, a requirement for a virtual device driver is unlikely. OS/2 maps interrupts, I/O ports, and I/O memory directly to any DOS device driver or DOS application which attempts to access these resources. As long as a resource is not already claimed by another session or by the OS/2 kernel, it is directly accessible to the DOS program.
Where access-sharing is required, it is generally not necessary to create a virtual device driver if the I/O is handle-based. DOS INT 21h I/O requests are routed by the OS/2 file system to the protect-mode physical device driver. If all I/O is handle-based, it is necessary only to create the physical device driver.
For block devices, it is recommended that OS/2 support be provided only by a physical device driver. Both DOS and OS/2 sessions will then access the device through file system interfaces defined by DOS and the OS/2 operating system.
In the absence of a sharing requirement, a virtual device driver might be necessary if the device has strict interrupt service latency requirements. A virtual device driver/physical device driver pair improves the interrupt service latency for an option adapter or device.
Virtual Device Driver Architecture and Operations
The architecture and structure of virtual and physical device drivers differ considerably from one another. A physical device driver is considered a true device driver in the sense that it has a unique and rigid file structure, and interfaces directly with the hardware. A virtual device driver is essentially a dynamic link library, and generally does not interface directly with the hardware. Instead, it is responsible for presenting a virtual copy of a hardware resource to a DOS session, and for coordinating physical access to that resource.
Virtual Device Driver Architecture
Virtual device drivers manage I/O ports, device memory, and ROM BIOS services for the devices they virtualize. For hardware compatibility purposes, a virtual device driver should behave as much as possible like the physical hardware. Otherwise, incompatible emulation could result. In the case of system drivers, a virtual device driver should use a physical device driver to manipulate hardware, wherever possible.
Virtual Device Driver Structure
A virtual device driver is a 32-bit EXE file that may contain some or all of the following types of objects:
- Initialization code
*Initialization data
*Swappable global code
*Swappable global data
*Swappable instance data
*Resident global code
*Resident global data
*Resident instance data
The resident objects must be used for code and data that must be accessible at physical hardware interrupt time, that is, when a physical device driver calls the virtual device driver. A virtual device driver that does not interact with a physical device driver may not need any resident objects.
Virtual device drivers conform to the EXE32 Load Module format. A typical virtual device driver has a shared (global) code object, a shared (global) data object, and a private (instance) data object. It is possible for a virtual device driver to have multiple objects of each type. The global code and data objects are addressable in all process contexts. As with instance data for dynamic link libraries, the instance data object is per- DOS session data; that is, the same address in each DOS session context is initialized to the same initial state, but backed by different physical memory. Each object must be equal to or less than 64KB in size.
Run-time allocated memory can be allocated as either swappableor fixed. In addition, run-time allocated memory can also be:
- Private (per-DOS session), which is allocated out of the DOS session private memory area. This is the preferred method, and is suitable when memory is used only in the context of owning the DOS session.
*Shared (global), which is allocated from the system area. This should be used only when the allocation must be created, modified, or freed in an arbitrary process context.
Virtual Device Driver Operations
Virtual device drivers are loaded and initialized before the shell is started, but after all the physical device drivers have been loaded and initialized.
Virtual Device Driver Loading
After the physical device drivers have been loaded, the DOS Session Manager is initialized (at OS/2 system initialization time), which then initializes the 8086 emulation component, and loads and initializes the virtual device drivers. An initial V86-mode memory map is constructed at this time for later use at DOS session creation.
The DOS Session Manager calls the loader to load virtual device drivers. Base virtual device drivers are loaded first, followed by installable virtual device drivers. Basevirtual device drivers are those that must be present for multiple DOS sessions to function. Installablevirtual device drivers are those specified in the "DEVICE=" lines in the CONFIG.SYS file. The multiple DOS session environment is still operable if any or all of these installable drivers fail to load. The one exception to this rule is the virtual video device driver, which is a base virtual device driver that is loaded in the CONFIG.SYS file.
The global code and data objects are loaded into the system area. This is required so that a physical device driver can pass along a hardware interrupt by calling a virtual device driver at interrupt time, regardless of the current process context.
The instance data objects are loaded into the address space between 1MB and 4MB for that session. This is the private address space managed by the DOS session. The loader and DOS Session Manager cause this allocation to occur so that the full virtualstate of the DOS session is contained below the 4MB line, thus allowing a single Page Directory Entry (PDE) to map a DOS session context. This has two benefits:
- Context-switching DOS sessions are fast, because only a single PDE needs to be edited.
- It is simple to maintain an alias region in the system area for each DOS session. This alias region is a 4MB-aligned, 4MB region of linear address space, whose base is called a DOS session handle, which can be used in a base register to manipulate the instance data of that DOS session. This is an important feature, as it allows virtual device drivers to quickly access the instance data of any DOS session.
The virtual device driver entry point is called after the virtual device driver is loaded. The device driver returns a nonzero value to indicate a successful load, and returns 0 to indicate an unsuccessful load.
Virtual Device Driver Initialization
After a virtual device driver is loaded, it performs the following operations, as appropriate:
- Verifies the presence of corresponding hardware
*Establishes communication with the corresponding physical device driver
*Reserves regions of linear memory containing device ROM and RAM
*Saves the initial physical device state for initializing the virtual device state upon DOS session creation
*Set hooks for various DOS session events (creation, termination, foreground/background switch). See VDHInstallUserHookfor a complete list of user hooks.
Virtual device drivers are initialized at Ring 0. For this reason, they cannot make Ring-3 API calls, and they only interact with OS/2 through use of the virtual DevHlp services.
Installing User Hooks
Each virtual device driver must use VDHInstallUserHookto install a VDM_ CREATE hook. Virtual device drivers that use foreground and background (for example, video, keyboard, or mouse) must also install VDM_FOREGROUND and VDM_BACKGROUND hooks. For more information, see VDHInstallUserHook.
Allocating Global Resources
Global resources are allocated at this time.
Registering Virtual Device Driver for Communications
When virtual device drivers communicate with the kernel, physical device drivers, other virtual device drivers, or with the Presentation Manager interface, the Dynamic Link mechanism is used to:
- Export virtual DevHlp services to virtual device drivers
*Export kernel data to virtual device drivers
*Export services from one virtual device driver to another
To restrict the modifications required for physical device drivers (which remain 16:16), virtual DevHlp services are provided so that a virtual device driver can establish communication with a physical device driver. This is no more than an exchange of entry points. At this point, the physical device driver and the virtual device driver can use any protocol to communicate. Although a suggested protocol is provided in Inter-Device- Driver Communication, device drivers are not restricted to this.
DOS Session Creation and VDD Per-DOS Session Initialization
When the user starts a DOS application, the DOS Session Manager notifies the virtual device drivers that have registered creation hooks, and gives them an opportunity to do per-DOS session initialization. Memory is allocated and mapped into the V86-mode address space, and the DOS Emulation code is initialized. Control is passed to the DOS Emulation kernel to load the shell specified by DOS_SHELL (usually COMMAND.COM) and the application selected by the user.
Virtual device drivers perform the following operations (as appropriate) at DOS session creation time:
- Initialize the virtual device state
*Initialize the virtual ROM BIOS state
*Map linear regions (reserved at virtual device driver initialization time) to physical or linear memory
*Hook the I/O ports
*Enable or disable the I/O port trapping
*Hook the software interrupts
*Allocate per-DOS session memory
DOS Session Screen Switching
The OS/2 Session Manager notifies the DOS Session Manager of screen switches. The DOS Session Manager, in turn, notifies all virtual device drivers that are involved in these events (generally, the video, keyboard, and mouse virtual device drivers). The virtual video device driver (VVIDEO) takes appropriate steps to map in physical or logical video RAM and disable or enable I/O port trapping for the video hardware. The virtual keyboard device driver (VKBD) can set flags to control the reaction to keyboard polling behavior.
DOS Session Destruction
When a user exits a DOS session, the virtual device drivers are notified to clean up any resources owned by that DOS session (that is, the virtual device driver's DOS session termination entry points are called by the DOS Session Manager). Memory is released and the process is terminated, as is done with a normal OS/2 process. DOS sessions can also be terminated by a virtual device driver if unsupported behavior is detected, or by the DOS emulation component (if it is damaged or is otherwise unable to function).
Local and Global Information Regions
Most of the information available through information segments can be obtained by a virtual device driver using the virtual DevHlp service VDHQuerySysValue. For further information, see VDHQuerySysValue.
Virtual DevHlp (VDH) Services
A set of virtual DevHlp (VDH) services is used to provide an abstract but efficient means for virtual device drivers to interact with DOS sessions and the OS/2 kernel. These VDH services have the following characteristics:
- They are available through dynamic linking.
- They use the 32-bit calling conventions found in the function prototype definition VDHENTRY located in the MVDM.INC and .h include files.
- A return value of 0 (zero) usually means that the call failed. When 0 is returned, calling VDHGetErrorreturns a detailed error code. If this return is 0, the last call succeeded and 0 was a meaningful return value, not an error. A nonzero return value means that the call succeeded. See VDHGetError.
- All pointer parameters are 0:32 flat pointers.
The Memory Management Virtual DevHlp services are used for:
- Mapping
*Reservation
*Allocation/reallocation/free
See C Language Virtual DevHlp Servicesfor a list of the page-granular memory management services and a description of each virtual DevHlp.
Inter-Device-Driver Communication
A virtual device driver can communicate with a physical device driver by using the Inter-device-Driver Communication (IDC) mechanism provided by the OS/2 operating system. A virtual device driver communicates with a physical device driver directly though a callable 16:16 interface, or by using the virtual DevHlp services that map to file system APIs. Virtual device drivers communicate directly with other virtual device drivers by using a set of the virtual DevHlp services.
The type and form of communication is defined by the physical or virtual device driver that provides the IDC entry point to be called. These device drivers must be aware of addressability and be sensitive to interrupt-time performance. For example, a virtual device driver that is not reflecting hardware interrupts to applications, and is in communication with a physical device driver, should use the virtual DevHlp services that map to File System APIs to communicate. However, if the virtual device driver must reflect hardware interrupts, the physical device driver should use the 16: 32 callable interface because it provides a more sensitive interface in which to communicate.
Virtual Device Driver and Physical Device Driver Interaction
Many virtual device drivers virtualize hardware that generates interrupts. Generally, these drivers must interact with a physical device driver to fully virtualize a device. Virtual DevHlp services are provided for the Open, Close, Read, Write, and IOCtl functions of the File System, which is then routed to the corresponding physical device driver. This is the simplest IDC mechanism for VDD/PDD communication.
Where interrupt-time or other high-performance PDD/VDD IDC requirements exist, the VDHOpenPDDservice is used to establish communication between a virtual device driver and a physical device driver by exchanging entry points, which use a 32-bit calling convention (refer to the multiple DOS session-specific equates found in the MVDM.INC include files). At this point, the virtual device driver and physical device driver are free to communicate through whatever private protocol is chosen, including exchanging register-based entry points. However, both drivers must agree on a shutdown protocol, that is, what is used to stop the communication if the virtual device driver must shut down. See VDHOpenPDDfor more information.
Virtual Device Driver/Virtual Device Driver Communication
Because dynamic linking is supported between virtual device drivers, multiple virtual device drivers can support inter-virtual device driver communication through dynamic links. Where these device drivers are supplied by multiple parties and it is not required that all of the virtual device drivers in the set be present, dynamic linking does not work. The virtual DevHlp services, VDHRegisterVDD, VDHOpenVDD, VDHRequestVDD, and VDHCloseVDDare used to overcome this limitation of dynamic linking. For details, see VDHRegisterVDD, VDHOpenVDD, VDHRequestVDD, and VDHCloseVDD.
Hardware Emulation and Interrupt Support
The major functions of software interrupt emulation are:
- Hook interrupt service: see VDHInstallIntHook
*Return to DOS session interrupt handler service: see VDHPushInt
*Hook return service: see VDHArmReturnHook
Hook Interrupt Service (VDHInstallIntHook)
The handler supplied to this service is a post-reflection handler. Post- reflection handlers are called after the INT instruction is reflected into the DOS session interrupt code. A DOS session breakpoint address is put into the interrupt vector table entry at INIT time, so control returns to the kernel at the end of the DOS session's interrupt code chain. The virtual device driver interrupt handler chain is then called. The ROM routine address (or whatever was initially in the interrupt vector table), which was replaced by the DOS session breakpoint, is returned to, if the virtual device driver handlers do not call VDHPopInt. See VDHPopInt.
Return to DOS Session Interrupt Handler Service (VDHPushInt)
VDHPushIntcalls the interrupt reflection code to change the DOS session's execution flow to the DOS session's interrupt code. This is done by building a return IRET frame on the client's stack with the CS:IP and flags from the kernel stack frame. The DOS session's CS:IP on the kernel stack is edited with the address from the DOS session's interrupt vector table. See the figure in the next section.
Hook Return Service (VDHArmReturnHook)
The VDHArmReturnHookservice allows the IRET to be hooked after the VDHPushIntservice is called. A DOS session breakpoint is allocated, and the address replaces the client's CS:IP on the return IRET frame. The client's CS:IP is saved. For additional information, see VDHArmContextHookand VDHPushInt. These services are shown in the following figure.
When building the return IRET frame, the client's stack pointer can wrap around from 0 to 0FFFEH. This does not terminate the DOS session. If the client's stack pointer is equal to 1 when this function is begun (before the virtual device driver handlers are called), the DOS session is terminated (to emulate the 386 hardware when it is in real mode).
When the virtual device driver installs an interrupt handler, a DOS session breakpoint is installed in the interrupt vector table before any DOS session code hooks. The DOS session breakpoint is executed after the DOS session interrupt code chain is executed but before ROM. The virtual device driver interrupt handlers are executed until one returns the stop chainingindication, or the end-of-list is reached. ROM code is executed after the last virtual device driver handler is called unless one of these handlers calls VDHPopInt. See VDHPopInt. This service emulates the IRET when a V86 code interrupt handler has popped off the IRET frame and restored the DOS session's CS, IP, and flags to the IRET frame contents. VDHPushIntis used by the software interrupt instruction trap and by the virtual PIC device driver in the last stages of simulating hardware interrupts.
Kernel Stack Client Stack Kernel Stack Client Stack /------------\ /--------------\ /------------\ | 0 | SS | | | SS | | Flags | |------------| |--------------| |------------| | ESP | | ESP | | CS | |------------| |--------------| |------------| | EFlags | | EFlags | | IP | |------------| |--------------| \------------/ | 0 | CS | | |INT CS | |------------| |--------------| | IP | | INT IP | \------------/ \--------------/ Before VDHPushInt After VDHPushInt Kernel Stack Client Stack /--------------\ /------------\ | 0 | SS | | Flags | |--------------| |------------| | ESP | | VDMBP CS | |--------------| |------------| | EFlags | | VDMBP IP | |--------------| \------------/ | 0 |INT CS | |--------------| | INT IP | \--------------/ After VDHArmReturnHook
Access to Ports Not Trapped by a Virtual Device Driver
In order to support DOS applications that use hardware that does not have virtual device drivers, a mechanism is provided for DOS applications to access ports on those devices. This is done by having the default handler for each I/O port turn trapping OFF for the port in question. All accesses after the first one go straight through to the hardware. This is done only for ports that are not trapped by a virtual device driver.
Global and Local Context Hooks
Global context hooksare a mechanism to delay work until the CPU is at task time (as opposed to interrupt time). If a global context hook is set at task time, the handler is called immediately. Local context hooksare a mechanism to delay work until the CPU is at task time in the context of a specific process. When a virtual device driver sets a local context hook, that hook is guaranteed to execute before any user code (that is, code executing in V86 mode).
Interrupts Supported by Multiple DOS Sessions
The following interrupts are supported by multiple DOS sessions:
- BIOS hardware interrupt support
*BIOS software interrupt support
*DOS software interrupt support
*Other software interrupt support
BIOS Hardware Interrupt Support
In previous versions of the OS/2 operating system, DOS applications were prevented from hooking hardware interrupts when the IRQ level was owned by an OS/2 device driver. A DOS application that violated this rule was terminated. In the current version of OS/2 this restriction is significantly relaxed. Depending on the support provided by the device's virtual device driver, DOS applications can now hook the hardware interrupt vector. The following list summarizes the support provided by OS/2 virtual device drivers for each of the hardware interrupt request (IRQ) levels:
IRQ 0 Timer (INT 08h). The INT 08h handler is invoked on hardware interrupts from Channel 0 of the system timer. DOS applications can hook this interrupt. See the description of INT 08h in BIOS Software Interrupt Support.
IRQ 1 Keyboard (INT 09h). The INT 09h handler is invoked upon the make or break of every keystroke. DOS applications can hook this interrupt.
IRQ 2 The Cascade (Slave) Interrupt Controller. This controller supports interrupt request levels 8 through 15, as described below.
IRQ 3 Serial Ports (COM2, 3, 4). These ports are supported when the virtual and physical COM device drivers are installed.
IRQ 4 Serial Port (COM1). This port is supported when the virtual and physical COM device drivers are installed.
IRQ 5 Parallel Port 2. This hardware interrupt is simulated in DOS sessions .
IRQ 6 Diskette. This hardware interrupt is not simulated in DOS sessions. See the description of INT 0Eh in BIOS Software Interrupt Support.
IRQ 7 Parallel Port 1. This hardware interrupt is simulated in DOS sessions .
IRQ 8 Real-Time Clock. This hardware interrupt is not simulated in DOS sessions. See the description of INT 70h in BIOS Software Interrupt Support .
IRQ 9 Redirect Cascade. A virtual device driver to simulate this hardware interrupt is not provided.
IRQ 10 Reserved. A virtual device driver to simulate this hardware interrupt is not provided. See Reserved IRQ Support in OS/2for more information.
IRQ 11 Reserved. A virtual device driver to simulate this hardware interrupt is not provided. See Reserved IRQ Support in OS/2for further information.
IRQ 12 Auxiliary Device. A virtual device driver to simulate this hardware interrupt is not provided. See Reserved IRQ Support in OS/2for further information.
IRQ 13 Mathematics Coprocessor (NPX). NPX exception interrupts on IRQ 13 are reflected into the DOS session.
IRQ 14 Fixed Disk. This hardware interrupt is not simulated in DOS sessions .
IRQ 15 Reserved. A virtual device driver to simulate this hardware interrupt is not provided. See Reserved IRQ Support in OS/2below for more information.
Reserved IRQ Support in OS/2
The OS/2 operating system does not provide support for optional devices on the Reservedand Redirect Cascadeinterrupt levels in OS/2-mode sessions, or in DOS sessions. Hooking one of these hardware interrupt request levels in a DOS application has no effect. If there is no physical device driver/ virtual device driver pair to service an interrupt, the DOS application's interrupt handler is not invoked, even though the hardware interrupts are generated.
These hardware interrupt request levels can be supported in a DOS session by a user-installed virtual device driver. However, a user-installed physical device driver is also required to provide this support since there is no mechanism for a virtual device driver to directly service a hardware interrupt.
BIOS Software Interrupt Support
BIOS software interrupt compatibility considerations and restrictions for OS/2 DOS sessions are shown below. Notice that only specific compatibility considerations and functional restrictions for users of BIOS in the DOS session environment of the OS/2 operating system are listed.
02h Nonmaskable Interrupt (NMI). Not reflected to the DOS sessions; this BIOS interrupt handler is not invoked on NMI.
05h Print Screen. The BIOS INT 05h handler is supported. If the DOS application issues INT 05h, the contents of the video buffer is printed. The Shift+PrtScrkeystroke combination (or equivalent) also invokes this function.
08h System Timer. This interrupt is invoked every time the system timer Channel 0 counts down to zero (normally, 18.2 times per second). DOS applications can hook this interrupt. However, in a DOS session these timer interrupts can come in a burst and have variable latency. The INT 08h interrupt handler is emulated by the virtual timer device driver.
0Eh Diskette. The INT 0Eh handler is not used to service interrupts generated by the diskette device (IRQ 6). DOS applications should not hook this interrupt.
10h Video. The INT 10h functions are fully supported in DOS sessions. The following INT 10h functions are emulated by the virtual video device driver .
0Eh Write Teletype (TTY)
13h Write String
Note:These functions are emulated only if the INT 10h vector is unmodified. If any piece of DOS session code hooks INT 10h, emulation occurs only if these functions are passed to the virtual video device driver's interrupt hook.
13h Hard Disk/Diskette. INT 13h emulation in a DOS session supports both removable and nonremovable media. The following subset of INT 13h functions are supported in DOS sessions:
00h Reset Diskette
01h Read Status
02h Read Sectors
03h Write Sectors (Diskette only)
04h Verify Sectors
05h Format Track (Diskette only)
08h Get Drive Parameters
0Ah Read Long (Fixed Disk only)
15h Read DASD Type
16h Change Status (Diskette only)
17h Set Disk Type (Diskette only)
18h Set Media Type (Diskette only)
14h ASYNC. When the virtual COM device driver is installed, all BIOS INT 14h functions are supported. These functions are emulated by the virtual COM device driver to enhance performance:
00h Initialize Port
01h Send Character
02h Receive Character
03h Read Status
04h Extended Initialize
05h Extended Port Control
15h System Services. These services are listed in the following table:
/--------------------------------------------------------------\ |AH|Function |Description | |--+------------------------+----------------------------------| |00|Cassette Motor ON |Default. Routed to ROM BIOS. | |--+------------------------+----------------------------------| |01|Cassette Motor OFF |Default. Routed to ROM BIOS. | |--+------------------------+----------------------------------| |02|Cassette Read |Default. Routed to ROM BIOS. | |--+------------------------+----------------------------------| |03|Cassette Write |Default. Routed to ROM BIOS. | |--+------------------------+----------------------------------| |0F|Format Periodic INT |Error. On return, CF is set. | |--+------------------------+----------------------------------| |4F|Keyboard Intercept |Default. Routed to ROM BIOS. | |--+------------------------+----------------------------------| |80|Open Device |Default. Routed to ROM BIOS. | |--+------------------------+----------------------------------| |81|Close Device |Default. Routed to ROM BIOS. | |--+------------------------+----------------------------------| |82|Program Terminate |Default. Routed to ROM BIOS. | |--+------------------------+----------------------------------| |83|Event Wait |Support. Supported by VTIMER . | | -- + ---------- ---------- ---- + ---------- ---------- ---------- ---- | | 84 | Joystick Support | Default . Routed to ROM BIOS . | | -- + ---------- ---------- ---- + ---------- ---------- ---------- ---- | | 85 | SysReq Key Pressed | Support . Issued by VKBD . On | | | | return , AL = 0 ( key make ) , or AL = 1 | | | | ( key break ) . | | -- + ---------- ---------- ---- + ---------- ---------- ---------- ---- | | 86 | Wait | Support . Supported by VTIMER . | | -- + ---------- ---------- ---- + ---------- ---------- ---------- ---- | | 87 | Move Block | Error . Managed by VXMS . | | -- + ---------- ---------- ---- + ---------- ---------- ---------- ---- | | 88 | Get Extended Memory Size | Error . Managed by VXMS . On return , | | | | AX = 0 ( no Extended Memory ) . | | -- + ---------- ---------- ---- + ---------- ---------- ---------- ---- | | 89 | Switch to Protect Mode | Error . On return , AX ! = 0 ( fail | | | | switch ) . | | -- + ---------- ---------- ---- + ---------- ---------- ---------- ---- | | 90 | Device Wait | Default . Routed to ROM BIOS . | | -- + ---------- ---------- ---- + ---------- ---------- ---------- ---- | | 91 | Device Post | Default . Routed to ROM BIOS . | | -- + ---------- ---------- ---- + ---------- ---------- ---------- ---- | | C0 | Get System Config Parms | Default . Routed to ROM BIOS . | | -- + ---------- ---------- ---- + ---------- ---------- ---------- ---- | | C1 | Get EBIOS Data Area | Default . Routed to ROM BIOS . | | -- + ---------- ---------- ---- + ---------- ---------- ---------- ---- | | C2 | PS / 2 Mouse Functions | Error . On return , CF is set , and | | | | AH = 01 is an invalid function . | | | | Notice that all mouse support is | | | | through INT 33h . | | -- + ---------- ---------- ---- + ---------- ---------- ---------- ---- | | C3 | Watchdog Timeout | Ignore . On return , CF is clear . | | -- + ---------- ---------- ---- + ---------- ---------- ---------- ---- | | C4 | Prog Option Select | Default . Routed to ROM BIOS . | \ -- - ---------- ---------- ---- - ---------- ---------- ---------- ---- /
16h Keyboard. The keyboard is supported directly by the ROM BIOS INT 16h routines.
17h Printer. The printer is supported (emulated) by the virtual parallel port device driver.
19h Restart. Restart (reboot) is supported. However, this does not operate in the same manner as DOS (the system is not restarted). If the DOS setting DOS_STARTUP_DRIVE is set, the diskette or image restarts. Otherwise, the DOS session is terminated.
1Ah Time-of-Day. The virtual CMOS device driver component supports read- only access to the Real-Time Clock device. Because of this restriction, the following BIOS INT 1Ah functions are not supported in a DOS session:
01h Set RTC Count
03h Set RTC Time
05h Set RTC Date
06h Set RTC Alarm
07h Reset RTC Alarm
08h Set RTC Activated Power-on mode
0Bh Set System Timer Day Counter
80h Setup Sound Multiplexer
A DOS application can read the Real-Time Clock Count, Time, and Date. The INT 1Ah functions are not emulated by the virtual CMOS device driver. Instead, the BIOS ROM functions are executed directly. The CMOS/RTC hardware is virtualized by the virtual CMOS device driver.
1Eh Diskette Parameters. The segment address of the diskette parameters table is stored in the INT 1Eh entry.
70h Real-Time Clock Interrupt. Interrupts from the Real-Time Clock (IRQ 8) are not reflected into DOS sessions. This software interrupt handler is not used for either alarm or periodic interrupts.
DOS Software Interrupt Support
The DOS emulation component supports the documented aspects of the following DOS features:
20h Program Terminate.
21h DOS Function Request. All documented and undocumented INT 21h functions are supported by DOS emulation. However the following functions are supported, with restrictions:
4410h
4411h
4B05h
5Dh
5Eh
5Fh
64h
69h
6Dh
6Eh
Note:Function 53h is not supported by DOS emulation.
22h Terminate Address.
23h Ctrl+Break Exit Address.
24h Critical Error Handler.
25h Absolute Disk Read.
26h Absolute Disk Write. A hard error is reported on requests for nonremovable media.
27h Terminate-and-Stay-Resident.
28h Idle Loop.
2Fh Multiplex. Time slice yield (AX = 1680h) is supported. When a DOS application issues INT 2Fh with AX = 1680h, it offers to yield its time slice. This can be used by DOS applications in busy wait loops (preserves all registers).
Other Software Interrupt Support
The following are other software interrupts supported in an OS/2 DOS session:
INT 33h - Mouse
Supported. When the OS/2 virtual mouse driver is installed, the full range of INT 33h functions, as defined in the Microsoft Mouse Programmer's Reference Guideare available.
INT 4Bh - Virtual DMA Services (VDS) - Function 81h
Supported. When the OS/2 virtual DMA device driver is installed, the VDS INT 4Bh functions as defined in the Microsoft Virtual DMA Services Specification, Version 1.0are available.
INT 67h - LIM Expanded Memory Manager (EMM)
Supported. When the OS/2 virtual expanded memory manager device driver is installed, the LIM EMM V4.0 INT 67h functions as defined in the Lotus/Intel /Microsoft Expanded Memory Specification, Version 4.0are available.
Base Virtual Device Drivers
The following list contains all the base virtual device drivers included with OS/2:
- Virtual BIOS device driver (VBIOS)
*Virtual CMOS device driver (VCMOS)
*Virtual direct memory access device driver (VDMA)
*Virtual diskette device driver (VFLPY)
*Virtual hard disk device driver (VDSK)
*Virtual keyboard device driver (VKBD)
*Virtual numeric coprocessor device driver (VNPX)
*Virtual parallel port device driver (VLPT)
*Virtual programmable interrupt controller device driver (VPIC)
*Virtual timer device driver (VTIMER)
Virtual BIOS Device Driver
The virtual BIOS device driver (VBIOS) contains the mechanism to initialize the Interrupt Vector table, BIOS data area, extended BIOS data area (on a PS/2* personal computer adapter ROM area), and the system ROM. It also provides virtual access to Programmable Option Select (POS) registers (on a PS/2 personal computer) and supports some of the DOS settings.
DOS Session Creation
When a DOS session is created, the virtual BIOS device driver is responsible for allocating and initializing the following areas in the DOS session's address space with the respective values from physical memory:
- Interrupt Vector Table
*BIOS data area
*DOS communications area
*Extended BIOS data area (on a PS/2 personal computer).
The virtual BIOS device driver is also responsible for mapping the system ROM and adapter ROM into the address space of the DOS session. The per-DOS session copy of the POS registers is initialized at this time.
DOS Settings
The virtual BIOS device driver is responsible for Include/Exclude region support. The DOS setting MEM_INCLUDE_REGIONS gives the user an option to give more space to EMM/XMS. If the user knows that in a particular DOS session an adapter will not be used, then the linear region taken by that adapter can be given to EMM and XMS through MEM_INCLUDE_REGIONS. MEM_ EXCLUDE_REGIONS gives the user an option to restrict EMM and XMS from claiming a particular region. Both these options are provided through DOS settings. These DOS settings are only applicable at DOS session creation time.
Adapter ROM
At system initialization, the virtual BIOS device driver searches the region between the top of the DOS user space (RMSIZE) and 1MB to find all of the adapter ROM. Adapter ROMs that include the ROM signature will be found. In a normal DOS session creation (without any Include/Exclude properties specified), these linear addresses are mapped to corresponding physical ROM.
All the ranges specified in the DOS setting MEM_INCLUDE_REGIONS are taken out of the list used for mapping the linear addresses to corresponding physical ROM. As a result, MEM_INCLUDE_REGIONS is not mapped to physical ROM and it remains available to EMM or XMS.
For MEM_EXCLUDE_REGIONS, the virtual BIOS device driver reserves those regions and maps them to their corresponding physical addresses. This allows the user the ability to map adapter ROM that does not contain the ROM signature and adapter RAM.
Virtual CMOS Device Drivers
The virtual CMOS device driver consists of virtual support for the CMOS battery backed-up RAM, the Real-Time Clock (RTC) and the Nonmaskable Interrupt (NMI) disable logic. It provides virtual access to the address and data latches through virtual I/O ports. This component allows the majority of existing DOS applications that access its ports by direct access, or by normal BIOS calls, to operate without change.
Supported Functions
The following functions are supported by the virtual CMOS device driver:
- CMOS memory access
*I/O port support
*NMI-disable
*Read time-of-day and date
*Real-Time Clock and interrupt access
CMOS Memory Access
CMOS Memory Access provides support for passive reads and writes to virtual CMOS memory. The CMOS portion of the CMOS/RTC can be read or written. The virtual CMOS memory is initialized to the contents of the physical CMOS memory (at the time of DOS session initialization) through the physical clock device driver, which is the physical device driver of the virtual CMOS component. Values are written to the virtual CMOS memory in a buffer local to the DOS session. Unlike the physical CMOS memory, however, the contents of the virtual CMOS memory are lost when the DOS session is terminated.
Input/Output Port Support
The virtual CMOS device driver component monitors all accesses to its two DOS session I/O ports. The two ports are a write-only address latch and a read/write data latch. The address latch port has two functions, NMI Disable and CMOS/RTC Device Address Selection. The data latch is a register for holding a byte being transferred to or from the CMOS/RTC device.
Disabling Nonmaskable Interrupts
The Nonmaskable Interrupt (NMI)-Disable portion of the the address latch can be set or reset by a DOS application. However, changes to enable or disable NMI are otherwise ignored.
Read Time-of-Day and Date
This function presents the correct seconds, minutes, and hours to an application reading the appropriate locations. This function also provides atomic access to all values to avoid reading the values during time transition.
Real-Time Clock and Interrupt Access
The Real-Time Clock consists of a time-of-day clock, an alarm interrupt, and a periodic interrupt. Accesses to the Real-Time Clock to change the time of day or the timing mode, or to set an alarm or periodic interrupt, are disallowed. The CMOS/RTC registers related to the Real-Time Clock are supported for read-only access. Because interrupts can only be supported through write access to the ports, Real-Time Clock interrupts are not supported.
BIOS Support
The virtual CMOS device driver component does not emulate BIOS functions. Instead, it allows the existing BIOS functions to be used without change.
Unsupported Functions
From the perspective of the DOS session, the virtual CMOS device driver component supports access to I/O address space only. Therefore, the following functions are not supported:
- Set Time-of-Day and Date
*Set Time-of-Day Alarm
*Set/Enable Periodic Interrupt
*Enable Update Interrupt
Virtual Direct Memory Access Device Driver
The virtual direct memory access device driver (VDMA) provides per-DOS session per-direct memory access (DMA) channel virtualization. In addition, the virtual DMA device driver provides the following:
- Serializes the DOS session's DMA requests on a per-DMA channel basis (but allows simultaneous requests on different DMA channels)
- Converts the DOS session's linear addresses to physical addresses, and handles all the data movement required
- Handles all the restrictions of a DMA chip
- Supports the enhanced DMA operations and commands of a personal computer
- Optimizes DMA virtualization on personal computers by using the enhanced mode
- Supports INT 4Bh - Function 81h virtual DMA services
- Supports virtualized DMA in auto-initialization mode
In addition to the above features, the virtual DMA device driver also synchronizes the operations with other virtual device drivers registered on different DMA channels. A virtual device driver for a piece of hardware, which uses a DMA channel, registers with the virtual DMA device driver. The virtual device driver informs these virtual device drivers before starting and stopping the DMA operation on their channels.
Virtual Diskette Device Driver
The virtual diskette device driver (VFLPY) intercepts applications that try to access the diskette drive directly or issue INT 13h calls. This virtual device driver also serializes and coordinates I/O operations between multiple DOS sessions.
Obtaining Physical Diskette Hardware Ownership
When the system first starts up, the physical diskette device driver owns the physical diskette hardware. All diskette accesses from the OS/2 applications go through the file system or the physical diskette device driver, and are eventually serialized into requests. Initially, the virtual hard disk device driver does not own the diskette controller, and it hooks all the diskette ports. It requests ownership from the physical diskette device driver when the DOS session accesses any diskette port, or when the virtual DMA device driver informs the virtual hard disk device driver that the diskette DMA channel has been unmasked. If the immediate ownership request is not successful, the DOS session is blocked until the physical diskette device driver calls back and grants the ownership.
Releasing Physical Diskette Hardware Ownership
Once the virtual diskette device driver has obtained the diskette ownership , it does not release ownership until the physical diskette device driver requests it, or the diskette motor is turned OFF.
Physical Diskette Interrupt Routing
Physical diskette interrupts are always routed to the physical device driver by the interrupt manager. If the virtual diskette device driver has the exclusive hardware ownership when the interrupt happens, the physical diskette device driver routes the event to the virtual diskette device driver, which simulates the interrupt to the DOS session.
Virtual Hard Disk Device Driver
The virtual hard disk device driver (VDSK) provides virtual disk support for multiple DOS sessions and supports access to the disk through BIOS (INT 13h) calls. Since BIOS accesses the hardware ports directly, the virtual hard disk device driver component overrides the BIOS by directly emulating INT 13h for hard disks. The virtual hard disk device driver component does not provide I/O port level access to the disk controllers. Access to hardware ports that are supported for the diskette drive, and BIOS INT 13h calls, are not emulated; instead, they are run from the actual BIOS. INT 13h support includes:
AH=00h Reset diskette system
AH=01h Status of disk system
AH=02h Read sectors into memory (both diskette and hard disk)
AH=03h Write sectors from memory (diskette only)
AH=04h Verify sectors (both diskette and hard disk)
AH=05h Format track (diskette only)
AH=08h Get current drive parameters (both diskette and hard disk)
AH=0Ch Seek
AH=15h Get disk type (both diskette and hard disk)
AH=16h Change of disk status (diskette only)
AH=17h Set disk type (diskette only)
AH=18h Set media type for format (diskette only)
The INT 13h emulator is also responsible for maintaining the diskette and hard disk areas of the ROM BIOS data area.
Typical steps of an INT 13h access are listed below:
- A DOS application accesses the disk through the INT 13h interface. The INT 13h call is trapped by the virtual hard disk device driver.
- A request packet is built and sent to the physical hard disk device driver . The DOS session is then blocked, waiting for the request to finish.
- Upon receiving the request packet, if the disk is currently busy, the physical hard disk device driver queues the request.
- When the request is completed, the physical device driver notifies virtual device driver, which unblocks the DOS session.
Because the virtual hard disk device driver component does not support register level accesses of the disk controller, all accesses to its registers are trapped and ignored.
Note:Timing-related copy protection can fail because real-time access is not guaranteed. Sector WRITE and FORMAT requests are not supported for hard disk. Sector WRITE and FORMAT operations are supported for diskette.
Virtual Numeric Coprocessor Device Driver
The virtual numeric coprocessor device driver (VNPX) provides virtual coprocessor (80 x 87) support for multiple DOS sessions. The virtual numeric coprocessor device driver coordinates exception and interrupt reflection for the real coprocessor. Machines with the 80386 B1 processor, or without a coprocessor, do not have coprocessor support.
Virtual Keyboard Device Driver
The virtual keyboard device driver (VKBD) consists of virtual support for the keyboard. It allows keystrokes to be passed from the keyboard to the DOS session and text to be pasted from another application into the DOS session as keystrokes. This virtual device driver also allows existing DOS applications that access the keyboard to operate without change. Such applications can access the keyboard through BIOS calls, access to the BIOS data area, or monitoring of the keyboard interrupt, and reading keystroke data directly from the I/O ports.
The virtual keyboard device driver addresses the following issues:
- INT 21h Access. DOS applications can access the keyboard by opening the " CON:" (console) device, or by default standard input access.
- BIOS Access. DOS applications can access the keyboard through BIOS INT 09h and INT 16h.
- I/O Port Access. DOS applications can access the keyboard by reading and writing I/O ports 60h and 64h. This access is not restricted to reading scan codes, and can include other types of access (such as LED control).
- Pasting. Data can be pasted from other OS/2 applications.
- Internationalization. Keystrokes are translated according to the current keyboard translation table and code page.
- Idle Detection. DOS applications must not waste excessive CPU time when in input peek loops.
Levels of I/O Support
The various levels of support for the virtual keyboard device driver are as follows:
- BIOS support
*CON device driver support
*DOS support
*Idle detection support
*I/O port support
*Pasting support
BIOS Support
Since the BIOS INT 16h service only references the BIOS data area for keystrokes, the BIOS continues to provide this service.
The BIOS INT 09h interrupt service routine, however, is emulated within the virtual keyboard device driver. When the INT 09h vector is invoked, the virtual keyboard device driver passes the character to the physical device driver, which translates the character according to the current translation table.
It is possible for an application or a DOS memory-resident program to hook the INT 09h vector. Often, such applications simply monitor keystrokes, and pass them on to the previously-hooked interrupt service routine. In this case, the virtual keyboard device driver emulation code still runs and translates scan codes according to the current translation table. Otherwise , if an application that has hooked INT 09h fails to pass the scan code on, then the scan code is not translated, or placed into the BIOS data area by the virtual keyboard device driver.
CON Device Driver Support
This support consists of allowing the virtual console device driver to be replaced. Although the default virtual console device driver. restricts keyboard access to BIOS calls, user-supplied drivers can access the keyboard through I/O ports or through the BIOS data area.
DOS Support
This support consists of keyboard access through the various INT 21h functions. In particular, this is support for access from the DOS emulation component. For compatibility, DOS calls the virtual console device driver to read keystrokes. This allows the virtual console device driver to be replaced without ill effect.
Idle Detection Support
DOS applications waste CPU time in a multitasking system when they peek for input in a loop. Idle conditions are detected when:
- The application is polling the keyboard using INT 16h in a loop
*DOS is polling in an input loop
*Repeated INT 28h calls are received from a DOS application
*INT 2Fh, AX=1680h yield calls are received
*DOS INT 21h, service 0Bh calls are received
Two services are available to device drivers to assist and for handling, VDHReportPeekand VDHWakeIdle.
I/O Port Support
The virtual keyboard device driver is responsible for supporting programs that access the keyboard ports directly. These ports provide access to data ports on the hardware that controls I/O to the keyboard. This support is provided primarily for applications that simply read the scan code directly from the port. However, other functions are possible, such as setting the key repeat rate. Repeat rates affect the entire system; per-DOS session repeat rates are not supported. Extended scanner functions, such as providing keyboard pre-controller translation, are not supported; such commands are ignored.
Pasting Support
The virtual keyboard device driver supports two levels of pasting from the clipboard into a DOS session; fast pastingand slow pasting. In fast pasting support, characters from the clipboard are put directly into the BIOS buffer. For those DOS applications that get their key strokes from the BIOS key buffer (through INT 16h), fast pasting is adequate. For those DOS applications that hook INT 09h or INT 15h (AH=4Fh), key scan sequences are expected, which must be generated by the slow pasting mechanism.
In slow pasting, every character from the clipboard is reverse translated into scan sequence and can involve generating make-and-break scans of not only the character itself, but also the make and break of the shift keys in order to adjust the upper, lower, or control case of the character. It can even involve generating Alt+numeric keypadscan sequences for those characters, which cannot be directly typed on the keyboard (such as graphics characters or international characters).
Virtual Programmable Interrupt Controller Device Driver
The virtual PIC device driver (VPIC) is responsible for the virtualization of the 8259 Programmable Interrupt Controller (PIC) for multiple DOS sessions and for the simulation of interrupts to DOS sessions. Performance is a major requirement for hardware interrupt simulation. In this book, hardware interruptand interrupthave the same meaning. Simulated interrupt , interrupt simulation, and hardware interrupt simulationall refer to the virtual PIC device driver sending an interrupt to a DOS session.
The virtual PIC device driver supports the hardware interrupt-related services needed by virtual device drivers and DOS sessions. The services include setting handlers to trap EOI and IRET events, simulating interrupts to DOS sessions, and handling PIC I/O accesses by DOS sessions. See Virtual Interrupt Servicesfor a list of these virtual DevHlp services. The virtual PIC device driver maintains a per-DOS session virtual PIC state so that each DOS session appears to have its own independent 8259 Programmable Interrupt Controller. Provisions are included to demand page DOS sessions interrupt handling code. The virtual PIC device driver provides a DOS session with the following services:
- Virtualization of the 8259 PIC ports:
-Separate master and slave PICs
-Mask and unmask IRQ commands
-Specific and nonspecific EOI commands
-Read IR and IS register commands
- Hardware interrupts that can be be postponed until task time so that a DOS session can be paged
- Interrupts from an optional hardware adapter, which does not have a virtual device driver and a physical device driver, that can be simulated to a DOS application
The virtual PIC device driver provides virtual device drivers with:
- A high-performance mechanism to send hardware interrupts to DOS sessions:
-Support for more than one virtual device driver to share an interrupt level
-Support for a virtual device driver to regain control when a DOS session issues EOI commands, or when a DOS session executes the IRET at the end of the interrupt routine
- A mechanism for virtual device drivers to send a virtual EOI to the virtual PIC device driver
- A way to block until an interrupt is simulated
- A mechanism to query a DOS session's virtual IRQ state or status:
-Masked or unmasked state (IMR)
-Waiting to be sent to a DOS session state (IRR)
-Executing DOS session's interrupt handler code state (ISR)
-Pending interrupt routine IRET state
Hardware interrupt simulation is closely tied to the PIC virtualization. Virtual device drivers need a fast mechanism to call a DOS session's real- mode interrupt handler for a hardware interrupt. Because paging of DOS sessions (and therefore DOS session interrupt handlers) is required, simulated interrupts are delayed until the task-time context of the target DOS session.
Virtual Timer Device Driver
The virtual timer device driver (VTIMER) provides virtual timer support for multiple DOS sessions. This virtual timer device driver emulates the Intel* * 8254A Programmable Interval Timer.
DOS Support
The virtual timer device driver provides the following:
- Virtualization of timer ports to allow reprogramming of the interrupt rate and the speaker tone frequency
*Distribution of timer ticks to DOS sessions
*Maintenance of the timer tick count in the BIOS data area
*Serialization of Timer 0 and Timer 2 between the virtual timer device driver and the physical timer device driver
Virtual Parallel Port Device Driver
The virtual parallel port device driver (VLPT) consists of virtual support for direct hardware access to the three parallel ports (LPT1, LPT2, and LPT3), and for the printer-related BIOS entry points (Printer I/O INT 17h, Print Screen INT 05h). Existing DOS applications that access the parallel ports, either by direct access to the ports or by printer BIOS, operate without change. The VLPT provides the virtualization to allow multiple DOS applications to access virtual printer hardware simultaneously. This virtual device driver, in conjunction with the spooler, attempts to prevent multiple DOS applications that transmit data by using BIOS functions or direct hardware access, from intermixing output at the parallel port.
The virtual parallel port device driver consists of several sections:
- BIOS INT 17h Emulation
*BIOS INT 05h Emulation
*Printer Close Processing
*Direct I/O Access
BIOS INT 17h Emulation
One method DOS applications can use to send data to a printer is to use BIOS interrupt 17h. The VLPT emulates BIOS INT 17h and passes these requests through the file system to the physical parallel port device driver (PLPT) by using the system services VDHOpen, VDHWriteand VDHClose. See VDHOpen. VDHWrite, and VDHClose. These functions are not passed to the BIOS for processing.
The BIOS INT 17h emulation supports three functions:
- Print Character. The Print Character function buffers single character requests in the virtual device driver buffer associated with each device in a DOS session. When the buffer becomes full, its contents are sent to the VLPT by using VDHWrite. If the device is not open, the VLPT issues VDHOpento obtain a file handle and start a printer data stream. See VDHWriteand VDHOpen.
- Initialize. The virtual parallel port device driver buffer is sent to the physical parallel port device driver by using VDHWrite. The printer data stream is closed by using VDHClose. See VDHWriteand VDHClose.
When the spooler is enabled, closing the data stream closes the spool file. Any subsequent printing will open a new spool file. The beginning of the spool file contains escape sequences to reset the printer to its power-on defaults. When the spooler is disabled, no initialization of the device takes place.
- Read Status. The Read Status function returns the contents of the virtual device status register.
See Printer Close Processingfor the possible methods of closing a printer data stream opened with BIOS INT 17h.
BIOS INT 05h Emulation
The method used to send data from the display to the printer (LPT1) is to press the Print Screenkey. DOS applications can also initiate a Print Screen function by issuing a call to a BIOS INT 05h function. The virtual parallel port device driver passes this request to BIOS for processing. The virtual device driver performs some special processing to prevent the INT 05h request from intermixing with an INT 17h print request to the same device. Also, two BIOS INT 05h requests cannot be performed simultaneously from within the same DOS session. The second print screen request is ignored.
Printer Close Processing
BIOS printer interrupts operate on a single-character basis, which can have a negative impact on printer and system performance. For this reason, the VLPT buffers BIOS print requests. When the buffer becomes full, print requests are sent to the file system to be spooled and printed. The size of the application's print request is rarely an even multiple of the VLPT buffer size. This causes the virtual device driver to provide methods of flushing the remaining characters in its buffer.
A virtual parallel port device driver's BIOS INT 17h buffers are flushed in one of four ways:
- DOS settings PRINT_TIMEOUT automatic close feature
*Ctrl+Alt+Print Screen key sequence (VDHPrintClose)
*Application termination
*DOS session termination
DOS Settings PRINT_SEPARATE_OUTPUT
The user can set the DOS setting PRINT_SEPARATE_OUTPUT to specify whether or not the virtual parallel port device driver should separate INT 17h output sent to the same device by two different DOS programs that are running in the same DOS session.
If set OFF, the VLPT will not open a new data stream each time the Program Segment Prefix (PSP) changes.
PRINT_TIMEOUT
The user can set the DOS setting PRINT_TIMEOUT to specify the length of time in seconds that the VLPT will wait between occurrences of INT 17h before flushing its buffer. A setting of 0 (zero) specifies to wait indefinitely, that is, to never flush the buffer using the timeout mechanism. The PRINT_TIMEOUT mechanism flushes the buffer and closes the data stream automatically each time the DOS application stops printing by using INT 17h for the time specified.
Ctrl+Alt+Print Screen Key Sequence
After the DOS application has printed the entire file (issued INT 17h), the virtual parallel port device driver can be alerted to flush the remaining characters in its buffer by pressing Control+Alt+Print Screen. The virtual keyboard device driver calls VDHPrintClose(an exported virtual parallel port device driver entry point) to alert the virtual parallel port device driver that the key sequence has been pressed, and to flush the buffer. See VDHPrintClose.
Application and DOS Session Termination
The virtual parallel port device driver is notified when the application terminates or the DOS session is closed, and will flush the remaining characters in its buffer.
Direct I/O Access
The virtual parallel port device driver, at its initialization, registers an Inter-device Driver Communication (IDC) with the physical parallel port device driver. The VLPT requests exclusive access to the parallel port hardware through the VDD/PDD IDC when a DOS application interfaces directly with the hardware. Data transmitted using the direct I/O access method will bypass the spooler. Completion of exclusive access occurs when the key combination Ctrl+Alt+Print Screenis pressed, the application is terminated , or the DOS session is terminated.
Share Access is an option of the spooler that enables multiple DOS applications to simultaneously access the parallel port. The option is enabled by selecting the Share Accesscheckbox in the Parallel Port Settings dialog box found on the output page of the Print Object Setting Notebook.
Once enabled, multiple copies of DOS applications that access security devices attached to the parallel port can be started simultaneously. Use of this option turns OFF the serialization of accesses (the protection mechanism) to the parallel port.
One DOS application can overwrite another that is using the parallel port, causing the latter application to fail.
Interrupt-Driven Data Transfers
The virtual parallel port device driver reflects virtual hardware interrupts to applications executing in a DOS session.
Bidirectional Data Transfers
The extended mode of the PS/2 personal computer parallel port allows the port to be used as a bidirectional eight-bit parallel interface. This capability is supported by the virtual parallel port device driver when DOS applications directly access the parallel port hardware.
Enabling DOS Print TSRs
The DOS operating system implements its printing function by passing print requests from its INT 21h interface to the single character BIOS INT 17h interface. Many Terminate-and-Stay-Resident (TSR) DOS applications hook into the INT 17h vector chain to perform additional processing (such as font support, spooling, and character set downloading) before sending the print data to the device attached to the parallel port. They expect all print data to pass through to the INT 17h interface.
Since these additional functions are now provided by the OS/2 operating system and since BIOS INT 17h is not performance-sensitive, the operating system passes INT 21h print requests as buffers through the file system to the physical parallel port device driver for transmission instead of sending print requests as single character requests to BIOS INT 17h. The gain, by this approach, is the increased throughput and better utilization of the device attached to the parallel port. The trade-off has been the inability of some DOS TSR applications to perform their print functions.
LPTDD.SYS is a DOS device driver that can be installed to convert DOS session INT 21h print requests to INT 17h and thereby enable this class of DOS TSRs. By using the "DEVICE=" statement in the CONFIG.SYS file or the DOS_DEVICE option in DOS Settings, the device driver can perform the INT 17h conversion either in all DOS sessions, or in individual DOS sessions corresponding to the two methods, respectively.
Installable Virtual Device Drivers
The following list contains all the installable virtual device drivers included with OS/2:
- Virtual ASPI device driver (VASPI)
*Virtual CDROM device driver (VCDROM)
*Virtual COM device driver (VCOM)
*Virtual DOS protect-mode extender device driver (VDPX)
*Virtual DOS protect-mode interface device driver (VDPMI)
*Virtual WIN-OS/2 support device driver (VWIN)
*Virtual expanded memory specification device driver (VEMM)
*Virtual extended memory specification device driver (VXMS)
*Virtual keyboard device driver services
*Virtual Advanced OS/2 Joystick Device Driver
*Virtual mouse device driver (VMOUSE)
*Virtual touch device driver (VTOUCH), discussed in Chapter 5
*Virtual video device drivers (VCGA, VEGA, VMONO, VVGA, VXGA, V8514A), discussed in Chapter 5
Virtual ASPI Device Driver
The virtual ASPI device driver (VASPI) enables ASPI support for ASPI applications running in a DOS or WIN-OS/2 session of OS/2. Under DOS, users typically load an ASPI manager that routes all requests directly to the hardware. ASPI drivers, such as ASPIDISK and ASPICD, send requests to the ASPI manager, which then sends the command on to the appropriate device.
Under OS/2, applications that wish to send ASPI requests do so by routing the requests to a device manager (OS2ASPI.DMD), which converts them into requests that are recognizable to any SCSI-adapter device driver (ADD).
During initialization, VASPI establishes communication with OS2ASPI.DMD. This allows VASPI to route all DOS SCSI requests to OS2ASPI.DMD.
Virtual CDROM Device Driver
The virtual CDROM device driver (VCDROM) enables data and audio support for CDROM applications running in DOS sessions of OS/2. Under DOS, audio and other IOCtl support is provided through the pass-through function of the CDROM file system driver, MSCDEX* DOS applications build a device driver IOCtl request packet and then send it to MSCDEX to be forwarded to the CDROM device manager for service. The position of VCDROM in the CDROM subsystem is shown in the following figure.
/-------------\ /-------------\
| OS/2 CDROM | | DOS CDROM |
| Application | | Application |
\-------------/ \-------------/
� | | \-----�----\ INT 21h
/-------------\ | | /-------------\
| MMPM/2 | | | | DOS |
| Subsystem | | | | File System |
\-------------/ | INT 2fh | \-------------/
\--------�| / - - - - + - - - - - - - + - - - - \
| | � � |
| | /-------------\ /-------------\ |
| | | OS/2 Virtual| | DOS MSCD001 | |
| | |Device Driver| |Device Driver| |
| | \-------------/ \-------------/ |
| | � � |
| \ - - - - + - - - - - - - + - - - - /
| | |
File System API |�------------------------------/
� Virtual Device Helper API
/-------------\
| OS/2 CDROM |
| File System |
\-------------/
� File System Helper API
/-------------\
| OS/2 CDROM |
| Device Mgr |
\-------------/
| SCSI-2 Commands
|-------------\
| �
| /-------------\
| | SCSI-2 |
| | Emulation |
| | Filter |
| \-------------/
| | Vendor-Unique
/-----------------\ | SCSI-1 Commands
� � �
/-------------\ /-------------\
| Non-SCSI | | SCSI Bus |
| Host Adapter| | Adapter |
|Device Driver| |Device Driver|
\-------------/ \-------------/
� �
/-------------\ /-------------\
| Non-SCSI | | SCSI |
| Host Adapter| | Bus Adapter |
\-------------/ \-------------/
� �
/-------------\ /-------------\
| CDROM Drive | | CDROM Drive |
\-------------/ \-------------/
The virtual CDROM device driver provides two distinct features that are necessary to support DOS CDROM applications. First, this virtual device driver emulates MSCDEX by providing the services that CDROM applications require for installation (for example, the version of MSCDEX, the number of CDROM devices that are present in the system, and the drive letters that correspond to the CDROM devices). A listing of MSCDEX Command Codes is given in the following table:
/-------------------------------------------------------------\ |Command |Function Description | |--------------------+----------------------------------------| |00h |Get Number of CDROM Drive Letters | |--------------------+----------------------------------------| |01h |Get CDROM Drive Device List | |--------------------+----------------------------------------| |02h |Get Copyright File Name | |--------------------+----------------------------------------| |03h |Get Abstract File Name | |--------------------+----------------------------------------| |04h |Get Bibliographic File Name | |--------------------+----------------------------------------| |05h |Read VTOC | |--------------------+----------------------------------------| |06h |Reserved | |--------------------+----------------------------------------| |07h |Reserved | |--------------------+----------------------------------------| |08h |Absolute Disk Read | |--------------------+----------------------------------------| |09h |Absolute Disk Write | |--------------------+----------------------------------------| |0Ah |Reserved | |--------------------+----------------------------------------| |0Bh |CDROM Drive Check | |--------------------+----------------------------------------| |0Ch |MSCDEX Version | |--------------------+----------------------------------------| |0Dh |Get CDROM Drive Letters | |--------------------+----------------------------------------| |0Eh |Get/Set Volume Descriptor Preference | |--------------------+----------------------------------------| |0Fh |Get Directory Entry | |--------------------+----------------------------------------| |10h |Send Device Request | |--------------------+----------------------------------------| |11h - 0FFh |Reserved | \-------------------------------------------------------------/
The second, and major, function of the virtual CDROM device driver is to translate the DOS-style IOCtls into requests that the physical CDROM device driver can understand.
A comparison of DOS-style IOCtls and OS/2-style IOCtls is given in the following table:
/--------------------------------------------------------------------------\ |DOS | |OS/2 | | | |----------+----------+----------+----------+------------------------------| |Category |Function |Category |Function. |IOCtl/Command Description | |----------+----------+----------+----------+------------------------------| |02h |00h |*** (7) | |Return Address of Device | | | | | |Header | |----------+----------+----------+----------+------------------------------| |02h |01h |80h |70h |Return Location of Head | |----------+----------+----------+----------+------------------------------| |02h |04h |81h |60h |Return Audio-Channel | | | | | |Information | |----------+----------+----------+----------+------------------------------| |02h |06h |80h |60h |Return Device Status | |----------+----------+----------+----------+------------------------------| |02h |07h |80h |63h |Return Sector Size | |----------+----------+----------+----------+------------------------------| |02h |08h |80h |78h |Return Volume Size | |----------+----------+----------+----------+------------------------------| |02h |09h |*** (8) | |Return Changed Media Code | |----------+----------+----------+----------+------------------------------| |02h |0Ah |81h |61h |Return Audio-Disc Information | |----------+----------+----------+----------+------------------------------| |02h |0Bh |81h |62h |Return Audio-Track Information| |----------+----------+----------+----------+------------------------------| |02h |0Ch |81h |63h |Return Audio-Subchannel Q Info| |----------+----------+----------+----------+------------------------------| |02h |0Eh |80h |79h |Return UPC | |----------+----------+----------+----------+------------------------------| |02h |15h |81h |65h |Return Audio-Status | | | | | |Information | |----------+----------+----------+----------+------------------------------| |03h |00h |80h |44h |Eject Disc | |----------+----------+----------+----------+------------------------------| |03h |01h |80h |46h |Lock/Unlock Door | |----------+----------+----------+----------+------------------------------| |03h |02h |80h |40h |Reset Drive | |----------+----------+----------+----------+------------------------------| |03h |03h |81h |40h |Audio-Channel Control | |----------+----------+----------+----------+------------------------------| | |*** (1) |80h |61h |Identify CDROM Driver | |----------+----------+----------+----------+------------------------------| | |*** (2) |80h |72h | Read Long | | ---------- + ---------- + ---------- + ---------- + ---------- ---------- ---------- | | | * * * ( 3 ) | 80h | 50h | Seek | | ---------- + ---------- + ---------- + ---------- + ---------- ---------- ---------- | | | * * * ( 4 ) | 81h | 50h | Play Audio | | ---------- + ---------- + ---------- + ---------- + ---------- ---------- ---------- | | | * * * ( 5 ) | 81h | 51h | Stop Audio | | ---------- + ---------- + ---------- + ---------- + ---------- ---------- ---------- | | | * * * ( 6 ) | 81h | 52h | Resume Audio | \ ---------- - ---------- - ---------- - ---------- - ---------- ---------- ---------- /
Note:
1. Command is not available in DOS.
2. DOS Extended Device Driver Command 130h.
3. DOS Extended Device Driver Command 131h.
4. DOS Extended Device Driver Command 132h.
5. DOS Extended Device Driver Command 133h.
6.. DOS Extended Device Driver Command 136h.
7. Command is not available in OS/2.
8. Corresponds to OS/2 block device driver command 01h.
The virtual and physical CDROM device driver's provide roughly the same device services, but through different IOCtl interfaces. The DOS CDROM interface is available through the IOCtl input and output device driver request packets, while the physical CDROM device driver provides its services through the generic IOCtl interface. The virtual CDROM device driver maps the DOS IOCtls to their corresponding physical device driver IOCtls, and then passes them on to the physical CDROM device driver. On return from the physical CDROM device driver, the virtual CDROM device driver also maps the return information and the return codes back into the DOS-style environment.
The virtual CDROM device driver provides full emulation of MSCDEX. MSCDEX Version 2.21 is fully supported under IBM Operating System/2
Virtual COM Device Driver
The virtual COM device driver (VCOM) consists of virtual support for the serial communication I/O ports, and for the serial channel-related BIOS entry points. It provides support in each DOS session for up to four COM ports. In addition, this component allows existing DOS applications, which access communications channels by direct access to the I/O ports or by normal BIOS calls, to operate without change.
The VCOM only supports access to communication channels that are physically present on a given system. This does not include support for accessing communication devices that can be redirected by network software. From the perspective of the DOS session, the VCOM supports access through:
- BIOS
*I/O address space
Support Summary
The VCOM directly supports invocations of BIOS INT 14h, instead of allowing the BIOS to access the ports directly. However, direct access to the virtual I/O ports is also supported. Direct access to I/O ports results in emulation of a communication controller with the INS8250 UART. When referenced through the virtual I/O ports, the VCOM also provides all support for virtual interrupt indication. The hardware appears to the DOS session as a serial interface supported by standard expansion bus serial ports on a PS/2 personal computer.
Interrupt Service
The virtual COM device driver provides full support for the virtualization of communication channel interrupts, and follows the same logic as the actual hardware.
Virtual DOS Protect-Mode Extender Device Driver
The virtual DOS protect-mode extender device driver (VDPX) provides address translation from protect mode to V86 mode for DOS protect-mode interface ( DPMI) applications. This translation is necessary because DPMI applications run in protect mode but issue interrupt requests, which can be handled in V86 mode, to perform various system services. When running in protect mode, the application is using selectors instead of segments. Therefore, any data buffers in the protect-mode memory address space (above 1MB) must be copied into a region of memory within the V86 address space.
The vdpx registers the DOS setting DPMI_DOS_API, which controls whether the VDPX is active or not. If the user selects:
Enabled The VDPX always translates the interrupts it supports from protect mode to V86 mode.
Auto The application must first issue the following INT 2Fh in protect mode to begin the translation:
ENTRY AX = 168Ah
DS:(E)SI points to the ASCIIZ
string "MS-DOS"
EXIT If VDPX fails initialization:
AL = 0x8A
Note:MS-DOS is a trademark of Microsoft Corporation.
Disabled The VDPX does not perform any address translation.
DPMI applications can provide their own translation services. Therefore, it might be unnecessary for the VDPX to perform any address translation.
The VDPX translates various interrupts from protect mode to V86 mode, including INT 10h, 15h, 21h, 25h, 26h, 2Ah, 33h, and 5Ch. The VDPX translates most of the commonly-used functions for these interrupts. After the virtual device driver translates the interrupt, the V86-mode interrupt service routine (or the virtual device driver, if it has hooked the interrupt) handles the interrupt request. After issuing the interrupt in V86 mode, the VDPX ensures that any data returned from the V86 service is copied into the data area originally passed in by the DPMI application. The registers and flags returned by the V86-mode handler (other than mode- sensitive registers such as segment registers) are returned to the DPMI application.
Virtual DOS Protect-Mode Interface Device Driver
The virtual DOS protect-mode interface device driver (VDPMI) provides Version 0.9 DPMI support for applications in a DOS session. DPMI applications run in protect mode instead of V86 mode. The VDPMI provides the necessary support to allow DPMI applications to run under OS/2. The VDPMI supports the DPMI memory limit DOS setting, which allows the user to specify how much protect-mode memory should be available to the DOS session .
The VDPMI supports INT 31h in protect mode, which is issued by DPMI applications to request a DPMI service. The VDPMI device driver keeps track of the resources used by the application, such as memory, selector, interrupt, and debug watchpoint management. This virtual device driver also supports the mechanisms necessary to allow DPMI applications to switch the DOS session in and out of V86 mode (translation services). When a DPMI application terminates, the virtual DPMI device driver ensures that all of the DPMI application resources are freed.
If a DPMI application issues an interrupt in protect mode and there is no protect-mode interrupt handler, the request is reissued in V86 mode. Most virtual device drivers hook only interrupt requests in V86 mode, so they are not called until the interrupt is reflected to V86 mode unless the virtual device driver has issued VDHSetVPMIntVector. (see VDHSetVPMIntVector). However, it is up to the application or the virtual DOS protect-mode extender device driver (VDPX) to do any address translation that is necessary, such as converting the selector address to a segment address. See Virtual DOS Protect-Mode Extender Device Driverfor further information on address translation.
DPMI 1.0 Functions Supported
- 401 - Get DPMI Capabilities
- 504 - Allocate Linear Memory Block
- 509 - Map Conventional Memory in Memory Block
- E00 - Get Coprocessor Status
- E01 - Set Coprocessor Status
- Separate Local Descriptor Table (LDT) and Interrupt Descriptor Table (IDT) for each protect-mode client
Virtual WIN-OS/2 Support Device Driver
The virtual WIN-OS/2* support device driver (VWIN) provides interfaces and transport services which enable DOS and OS/2 applications to do communication between processes in a very fast, event-driven, specialized way. The clipboard, DDE and WIN-OS/2 window functions use these interfaces to exchange data between WIN-OS/2 sessions and the Presentation Manager desktop.
The data and messages which pass through VWIN are not actually inspected nor understood by the driver. Instead, the driver provides a store and forward mechanism. To accomplish this, an interface is exported for each environment. In an OS/2 session, a thread of the OS/2 process blocks in VWIN waiting for data from any of the other processes. In a DOS session and in a WIN-OS/2 session, the address of a notification routine is registered, and this routine is invoked when a message or data is available from one of the other processes using the interface. Interfaces are provided which allow for sending messages and data to other specific processes or for broadcasting to all processes. This system is outlined in the illustration below:
/------------\ /----------------\
| OS/2 | |DOS or WIN-OS/2 |
| Process | | Process |
\------------/ \----------------/
� �
| /------------\ |
| | VWIN | |
\---�| |�----/
\------------/
Virtual Expanded Memory Specification Device Driver
The Lotus/Intel/Microsoft Expanded Memory Specification, Version 4.0(LIM 4 ) provides a standard interface for the use of expanded memoryon 8086- family computers. This specification offers up to 32MB of expanded memory divided into as many as 255 expanded memory objects. Regions of these objects can be mapped at 8086 addresses (below 1MB), thus allowing DOS applications access to large memory allocations. However, the memory that is to be accessed must be explicitly mapped.
Alternate page tables are provided for quick switches among mappings and function calls with remapping. These tables are also used as the means to save and update mappings, or move and exchange memory contents.
The OS/2 virtual expanded memory specification (EMM) device driver:
- Implements all the INT 67h functions in the LIM 4.0 EMS, except those for the DMA registers.
- Provides each DOS session with a separate EMS emulation. A DOS session has its own set of expanded objects so that features such as interprocess communication work as if each DOS session was running on a different real 80386 DOS sessions cannot affect the availability of objects, or access memory in other DOS sessions.
- Provides support for remapping of conventional memory (below 640KB) for use by programs.
- Provides a configurable limit for the amount of EMS memory available per DOS session.
- Supports multiple physical to single logical mappings. Different 8086 addresses can map to the same expanded memory object address.
Configurable Defaults
Default values are set for properties in order to be appropriate in most instances. However, users can change these defaults, if desired. The following defaults can be set in the CONFIG.SYS file:
Default EMS Memory Size Default limit set by specifying the number of kilobytes of memory desired on a "DEVICE=" line in the CONFIG.SYS file. Alternately, the limit can be specified by using a switch, /S=xxx, on the line. For example:
DEVICE=path\VEMM.SYS 1024
or
DEVICE=path\VEMM.SYS/S=1024
Default EMS Low OS Map Region Size of remappable conventional memory set by using the /L switch. For example:
DEVICE=path\VEMM.SYS /L=256
EMS High OS Map Region Size of extra mappable memory (other than the 64KB minimum) set by using the /H switch. For example:
DEVICE=path\VEMM.SYS /H=32
EMS Frame Location Default frame position set by using the /F switch. Any value in the DOS setting list can be chosen as the default. For example:
DEVICE=path\VEMM.SYS /F=AUTO
or
DEVICE=path\VEMM.SYS/F=C800
When devices without virtual device drivers can directly map memory, the Include and Exclude regions are crucial for the virtual EMM device driver. These properties are supplied by another component, and determine which regions can be directly mapped to physical addresses by default when touched by applications.
The virtual DevHlp Mapping services allow the same master page to be aliased in by successive pages in the V86 address space. In particular, EMM allows an application to map in the same 16KB size range of memory repeatedly (for example, a 64KB page frame could consist of the same four pages mapped four times). Since DMA requires contiguous physical memory, I/ O that involves aliased pages, which map to the same physical page, must be handled by breaking up DMA requests.
Virtual Extended Memory Specification Device Driver
The Extended Memory Specification, Version 2provides a standard interface for the use of extended memoryon 80286- and 80386-based machines. The XMS specifications manage three distinct regions of memory:
- High Memory Area (HMA). Extended memory accessible from real mode by enabling the A20 address line. Code can be executed in the HMA, if the A20 line is enabled. The high memory area is exactly 65520 bytes (64KB-16 bytes ) long.
- Extended Memory Blocks (EMBs). Blocks of extended memory accessible by way of XMM function calls through a handle. Without leaving V86 mode, code cannot be executed from EMBs; they serve only for data storage. The specification offers up to 64MB of extended memory divided into as many as 255 blocks.
- Upper Memory Blocks (UMBs). Block of memory located between 640KB and 1MB. Once a UMB is allocated, its memory is always available. Since the memory lies in conventional memory, code can be executed in it at any time.
The virtual extended memory specification (XMS) device driver:
- Implements all the functions in XMS 2.0.
- Provides each DOS session with a separate XMS emulation. Each DOS session has its own high memory area, upper memory blocks, and extended memory blocks so that features such as interprocess communication perform as if each DOS session was running on a different real 80386. A DOS session cannot affect the availability of objects, or access memory in another DOS session.
- Provides configurable limits for the amount of XMM memory available across DOS sessions, and a limit per DOS session. An installed program in the start list should be able to override the per-DOS session limit, subject to the constraint given by the overall limit. In addition, it should be able to disable XMS completely for a particular DOS session, if its installation would conflict with the program running in the DOS session.
A CONFIG.SYS line of the form DEVICE=path\VXMS.SYS [options], will interpret optionsas "/keyword=value". These options are as follows:
/XMMLIMIT=g,i Set the global (system-wide) maximum memory usage of the virtual XMS device driver to gKB, and set a per-DOS session maximum of iKB. These values are large enough to accommodate an automatic 64KB allocation in each DOS session for the HMA. Values are restricted to the range 0 through 65535 (=64KB).
The values of gand iare rounded up to the nearest multiple of four. Specifying i=0 suppresses XMS installation in all DOS sessions unless overridden by a DOS session-specific configuration string. The default for /XMMLIMIT is 16384,2048.
/HMAMIN=d Set the minimum request size (in kilobytes) for an HMA request to succeed. Values are restricted to the range 0 through 63. The default for / HMAMIN is 0.
/NUMHANDLES=n Set the number of handles available in each DOS session. Each handle occupies eight bytes. Values are restricted to the range 0 through 128. The default for /NUMHANDLES is 32.
/UMB Instruct XMM to create Upper Memory Blocks (UMB). The default is / NOUMB.
/NOUMB Instruct XMM to not create Upper Memory Blocks (UMB). The default is /NOUMB.
Virtual Keyboard Device Driver Services
The virtual video device driver utilizes the Post Peek and Post Read requests from the virtual keyboard device driver to post events to the DOS session Window Manager when the windowed DOS session video state changes. In addition to generating the VVDEVENT_INPUT event to the DOS session Window Manager to adjust window orientation, these notifications also serve to suggest to the virtual video device driver when to check for palette and LVB changes, which generate VVDEVENT_PALETTE and VVDEVENT_LVB events.
The virtual keyboard device driver uses the Post Paste request to indicate whether paste operations can start or end. The virtual video device driver posts the VVDEVENT_PASTE or VVDEVENT_ENDPASTE event to the DOS session Window Manager, based on the type of paste operation requested.
Virtual Advanced OS/2 Joystick Device Driver
The virtual joystick device driver has two main purposes:
- To provide a reliable joystick device driver for DOS games running under OS/2.
- To provide a standard device driver for OS/2 game programmers that they can use as an interface between the PC game adapter port and their products .
See the OS/2 Input/Output Device Driver Referencefor detailed information on understanding how the IBM PC Game-Port Adapter works and using the Advanced OS/2 Joystick Device Driver.
Understanding How the Joystick Device Driver Works
The pre-emptive multi-tasking nature of OS/2 can cause DOS applications reading the game adapter port to deduce incorrect positions for the joysticks connected. The solution to this potential inaccuracy, implemented in the joystick device driver, is to regularly sample the game adapter port inside the Physical Device Driver (PDD) and then return fabricated values to the DOS application that reflect that state. With the logic for regular sampling already in the PDD, it is simply a matter of activating the procedure.
Before any of this can be initiated, however, access to the game port by the DOS application must first be trapped. Whenever I/O ports are to be trapped or emulated, an OS/2 Virtual Device Driver (VDD) is required. The VDD works in conjunction with the PDD to provide the device emulation. The VDD does this by capturing port reads and returning values that reflect the current state as determined by the PDD. The VDD is also responsible for determining whether a given virtual DOS machine (VDM) is to have direct access to the port and, if it is, for obtaining ownership of the VDM.
Virtual Mouse Device Driver
The virtual mouse device driver (VMOUSE) is responsible for all mouse support in the multiple DOS session environment.
Virtual Mouse Device Driver
This chapter describes the virtual mouse device driver (VMOUSE), which is responsible for all mouse support in multiple DOS sessions. The virtual mouse device driver also supports applications that use the BIOS INT 15h ( AH = C2h) pointing-device services.
Some of the most common mouse driver services, available through the INT 33h interface, are listed below:
- Driver-state save, restore, and disable
*Light-pen emulation
*Miscellaneous features
*Position and button-event notification
*Position and button-data tracking
*Selectable pel-to-coordinate and mickey-to-pel mappings
*Video-mode tracking
*Video pointer management (location and appearance)
There are no restrictions on any use of the INT 33h interface, even when a DOS session is in background mode. The only difference between background, focused, and foreground DOS session support is that no mouse events are posted for a background DOS session. Mouse events are posted to full-screen DOS session from the physical mouse device driver, and are posted through the Presentation Manager shield to focused, windowed DOS sessions. The pointer position should remain unchanged as long as a DOS session is in background mode, unless an application initiates pointer movement of its own. In that case, the virtual pointer position changes but nothing is drawn (not even in virtual video space).
The virtual mouse device driver also supports applications that use the BIOS INT 15h (AH=C2h) Pointing Device services.
INT 33h Support
INT 33h support is provided directly by the virtual mouse device driver. If a DOS session is running in a window (instead of full screen), and is in focus, the physical mouse device driver routes the mouse events to the Presentation Manager single queue device driver, then to the shield, and eventually to the virtual mouse device driver. The virtual mouse device driver then buffers the mouse event as if it were for the full-screen DOS session. When the DOS setting MOUSE_EXCLUSIVE_ACCESS is ON for a windowed DOS session, all mouse events go directly from the physical mouse device driver to the virtual mouse device driver, bypassing the Presentation Manager interface. This property is necessary for those applications that track and draw their own mouse pointer.
Driver-State Save, Restore, and Disable
Services are provided to copy all per-DOS session mouse-state information to an application-defined block and back again. When the driver is disabled , it ignores all INT 33h requests and physical mouse device driver events.
Light-Pen Emulation
Whenever this INT 33h feature is enabled, a virtual mouse device driver INT 10h hook is established, and INT 10h light-pen functions are emulated with mouse position and button data.
Miscellaneous Features
The INT 33h interface provides a function to read-and-reset mouse motion counters, which are simply software counters of total horizontal and vertical mickeys. These counters are simulated within the virtual mouse device driver by taking reported pel movements and converting them to mickeys (based on the current mickey-to-pel ratio). This interface must also provide counts of button presses and releases, and the positions at the time of the last press and release. These are maintained by the virtual mouse device driver without any assistance from the physical mouse device driver.
Position and Button-Event Notification
The INT 33h interface provides services to allow the DOS session to receive call-back notification for selectable motion and button events. These call- backs occur at DOS session task time, and do not involve the physical mouse device driver.
Each time the DOS session is notified of a mouse event, it might have to notify the DOS session's user-defined mouse-event subroutine, depending on whether the DOS session's application has registered the subroutine (by way of an INT 33h function) and what events the caller has asked to be notified of.
A registered subroutine is called by requesting a pseudointerrupt in the DOS session. A simulated interrupt service routine (loaded into each DOS session at creation) immediately EOIs (ends the interrupt) and then proceeds to notify the DOS session's registered subroutine. In order to pick an IRQ that is guaranteed not to conflict with any other virtual device driver, the DOS session queries the physical mouse device driver at initialization for its physical IRQ.
Note:It is not important to have the real mouse IRQ, but simply an IRQ that no other virtual device driver needs.
Movement-only events are coalesced. As an event is posted from the physical mouse device driver, the DOS session compares it with any previous event in the event buffer; if it is a movement-only event, the current event accumulates with the previous event in the buffer. This process continues until a non-movement-only event occurs or the current movement event is simulated, thus reducing interrupt-simulation overhead during rapid event- generation periods.
Position and Button-Data Tracking
Other services within the INT 33h interface allow the DOS session to poll the virtual mouse device driver on the current mouse status. There are also services to return the last button press and also the last button-release event.
Selectable Pel-to-Coordinate and Mickey-to-Pel Mapping
Through the INT 33h interface, the DOS session can control the acceleration of the DOS session mouse pointer by varying both the thresholds and the multipliers. This is managed by the entirely by the virtual mouse device driver, without assistance from the physical mouse device driver, which reports only raw mickey events to the DOS session for full-screen DOS sessions.
For windowed DOS sessions, the PM Shield reports absolute pel mouse events to the virtual mouse device driver The virtual mouse device driver maps the raw delta mickeys to the DOS session's current virtual-coordinate grid.
Video Mode Tracking
The virtual mouse device driver receives notification of video mode changes from the virtual video device driver, so that the pointer size and bounds can be appropriately set.
The virtual mouse device driver must be notified of changes in the physical dimensions of the screen. It uses that information to map the raw mickeys into pel coordinates. The virtual device driver uses a device-independent interface to notify the virtual mouse device driver of mode changes so that the virtual mouse driver is capable of supporting any video device without code changes.
Video Pointer Management
The virtual mouse device driver tracks the pointer location, and whether or not the pointer is visible. The actual drawing and hiding of the pointer, however, is handled by the virtual video device driver.
Interfaces are provided by the virtual video device driver to the virtual mouse device driver to perform the following operations:
Define pointer This describes the desired pointer shape and always is issued prior to making a pointer visible for the first time. An error might be returned if the virtual video device driver does not provide pointer support for the current video mode, thus permitting the virtual mouse device driver to skip further drawing and moving requests. The virtual video device driver refuses calls it cannot support.
Draw pointer A position, in pel coordinates, is provided. For text modes, the virtual video device driver maps chunksof pels to individual character locations. The size of a chunk is 8 pels x 8 pels, unless the mode is 40- column, in which case the chunk size is 16 pels x 8 pels. A video page parameter is provided to support the INT 33h SetCRTPage service. Draw requests without intervening Remove requests are treated as Move requests.
Remove pointer Deletes pointer from the screen.
INT 15h (AH=C2h) Support
All the published Pointing Device BIOS services (INT 15h, AH=C2H) are emulated in the virtual mouse device driver For a complete listing of these services, refer to the IBM Personal System/2 and Personal Computer BIOS Interface Technical Reference.
Virtual Mouse Device Driver Services
For the virtual mouse device driver, the virtual video device driver provides a VDHRequestVDDfunction, as well as several direct interfaces for pointer drawing operations. The following VDHRequestVDDservice is provided :
VDHRequestVDD
(
HVDD hvddVideo,
HVDM hvdm,
INT iFunc, /* Virtual video device driver EVREQ_POSTMOUSE (4) */
PVOID pReqIn, /* Undefined. */
PVOID pReqOut /* Undefined. */
); /* Returns TRUE. */
The virtual mouse device driver must return the address of a function that permits the virtual video device driver to obtain mouse position and button status during processing of the INT 10h, Query Light Pen function, when light pen emulation is enabled for the active DOS session. Also, whenever the DOS session changes video modes (including the initial mode change that takes place during DOS session creation), the virtual video device driver notifies the virtual mouse device driver of the new mode and screen dimensions.
Virtual Touch Device Driver
The virtual touch device driver (VTOUCH) provides support for the INT 7Fh in multiple DOS sessions. This virtual device driver is limited (by default ) to making actual touch XYZ data available only to full-screen DOS programs because the physical device driver, which handles the touch data interrupts, cannot determine which window to send the touch data to when running with the Presentation Manager session in the foreground.
In contrast, the physical mouse device driver can determine which window to send the mouse data to because it is able to feed the single queue of the Presentation Manager. The Presentation Manager can then determine, based upon the event XYZ data, which window is to receive the event. If the window is a DOS window, it calls the virtual device driver.
For those DOS applications that receive full screen XYZ touch data while running in a window, the DOS setting TOUCH_EXCLUSIVE_ACCESS is provided. This DOS setting effectively turns off mouse emulation and directs all touch data to that window. The (now device-independent) INT 7Fh continues to function in a window. However, touch data is not available to the application until it is switched to full screen. In all other respects, the application functions exactly as before.
DOS mouse applications are not subject to this restriction because they can run in a windowed or full screen DOS session with touch input in the form of emulated mouse data.
INT 7Fh Support
To access the touch-sensitive display device, DOS applications use the software interrupt 7Fh (INT 7Fh) interface. OS/2 applications use the Tou xxxAPI. The virtual touch-sensitive device driver provides this by using a standard DOS session software interrupt hook. This virtual device driver runs in protect mode (which allows it to share code in all DOS sessions) and virtualizes all the hardware-dependent features that the INT 7Fh interface provides (for example, changing thresholds).
In addition to the touch-sensitive device capability, it is also possible to use the touch-sensitive display to emulate the IBM* mouse. In this case, the standard mouse INT 33h API (for DOS) is used.
Note that only DOS sessions running full screen can obtain full touch XYZ data. Windowed DOS sessions running under Presentation Manager are restricted to emulated mouse data. A DOS touch application that started as full screen stops receiving touch data if it is switched to a window, and starts receiving data again if it switched back to full screen. Conversely, a DOS touch application that is started in a window does not receive data until it is switched to full screen, and does not stop receiving data until it is switched back to a window.
Discussion
A virtual video device driver is used by OS/2 as a virtual display device for DOS applications executing in a DOS session, by providing virtual hardware support. Virtual video device drivers are required when it is necessary for multiple DOS sessions to share one or more video devices.
The virtual video device driver manages access to video memory, video registers, and video adapter ROM BIOS Special functions have been defined to permit other OS/2 Ring 3 components (such as the DOS Session Manager and the Presentation Manager display device driver) to obtain the vital video state information necessary to window a DOS session on the Presentation Manager desktop.
For simplicity, a dedicated virtual video device driver should be targeted to a specific video device. This reference manual includes a set of virtual video device drivers that can be used as templates for enhancement modifications to any of the currently supported devices, or they can be used as samples to create a virtual device driver from scratchfor a similar but compatible device. For example, the OS/2 virtual Super VGA device driver (VSVGA.SYS) is a derivative of the virtual VGA device driver (VVGA.SYS).
The following virtual video device drivers, which cover an extensive range of the most commonly used video devices, are included in this reference manual:
/-----------------------------------------\ |Virtual CGA device driver|VCGA | |-------------------------+---------------| |Virtual EGA device driver|VEGA | |-------------------------+---------------| |Virtual MONO device |VMONO | |driver | | |-------------------------+---------------| |Virtual VGA device driver|VVGA | |-------------------------+---------------| |Virtual XGA* device |VXGA | |driver | | |-------------------------+---------------| |Virtual SVGA device |SVGA | |driver | | |-------------------------+---------------| |Virtual 8514/A device |V8514A | |driver | | \-----------------------------------------/
The video devices for which the OS/2 provides virtual video device drivers include:
- Western Digital**
*ATI**
*Cirrus Logic**
*Headland Technology**
*Trident** .
*Tseng**
*Video 7**
Note:Specific Super VGA chip revision and model support can be found in VVDP.H.
Installable Virtual Video Device Driver Architecture
The architecture of a virtual video device driver adheres to the architecture defined for all virtual device drivers. However, some parts of the multiple DOS sessions architecture have been designed primarily for virtual video device drivers, as follows:
- Foreground and background notification hooks
*Freezeand thawservices
*Title change and code-page change notification hooks
A significant amount of the primary virtual video device driver code involves communication with the DOS session Window Manager. A Remote Procedure Call (RPC) mechanism must be used to communicate between the DOS session Window Manager and a virtual video device driver under the following conditions:
- The DOS session Window Manager is a Ring 3 component (lowest privilege level)
*Virtual device drivers run at Ring 0 (highest privilege level)
*DOS sessions have no Local Descriptor Table (LDT), and therefore cannot attach to Dynamic Link Libraries (DLLs)
For this purpose the DOS session Window Manager creates a thread that calls the virtual video device driver to wait for a video event from any of the currently windowed DOS sessions.
Design of Installable Virtual Video Device Drivers
A virtual video device driver is a basedevice driver, although a "DEVICE=" statement in the CONFIG.SYS file is used to specify one or more virtual video device drivers to load. The DOS session Manager and DOS session Window Manager identify a virtual video device driver by its registered name. For example, a virtual video device driver for the primary display would register as VVIDEO1$, a virtual video device driver for the secondary display device would register as VVIDEO2$, and so forth.
Note:Support of multiple DOS sessions is disabled if no virtual video device driver claims ownership of the primary display device after virtual video device driver loading and initialization is completed.
Supporting DOS-Standard Adapters and Modes
IBM-compatible CGA, EGA, VGA, XGA, and 8514/A adapters are supported as primary display devices; monochrome adapters are supported as secondary display devices. For these devices, the standard configurations (including the amount of video memory, type of monitor and so forth), are supported. However, there are a few exceptions. For example, other dual-adapter combinations such as EGA/monochrome with CGA/color, or VGA/monochrome with CGA/color are not supported.
All EGA monitor combinations (RGB, ECD, and monochrome) and VGA, XGA, 8514/ A monitor combinations (i512/8513, 8514, and 8515), as well as all EGA memory combinations (64KB, 128KB, 192KB, and 256KB) of the 8514/A monitor are supported. The type of monitor used with a monochrome or CGA adapter is immaterial; that is, the behavior of the adapter is not affected.
There are some limitations, however. For example, an EGA, VGA, or Super VGA with a 2xxport configuration, instead of the standard 3xxconfiguration, is not supported. Also, an EGA display with only 64KB of display memory cannot support high-resolution graphic modes in a window, due in part to the video mode used concurrently by Presentation Manager (640 x 200, 16 colors), which consumes nearly all of the 64KB of on-board video memory. In addition, blinking attributes (whether in text or graphics modes) cannot be emulated in a DOS window.
A significant portion of the primary virtual video device drivers involves communication with the DOS session Window Manager. This includes providing a set of services to fully describe a DOS session's video state and a set of notifications to signal when the video state changes, so that a DOS session being windowed remains relatively synchronized with its associated DOS session that is executing in the background.
Because the DOS session Window Manager, OS/2 Session Manager, and Presentation Manager display device driver execute in Ring 3, and while the virtual video device driver runs in Ring 0, a system entry point is necessary for these Ring 3 components to communicate with the virtual video device driver. The virtual video device driver provides the following DosRequestVDDservice to:
- DOS session Window Manager
-Set Access
-Set Focus
-Set Lock
-Query Mode Info
-Query Cursor Info
-Query Palette Info
-Copy LVB Content
-Copy Bit Map Content
-Wait for Video Event
-Control Event
*PM Display Device Driver
-Set Display Requirements
-Request off-screen VRAM
-Free off-screen VRAM
-Request VGA Controller
-Free VGA Controller
-Query VRAM Status
Note:See the Display Device Driver Referencefor a detailed explanation of the DosRequestVDDfunctions provided by the virtual video device driver.
There are two kinds of DOS session window support:
- Displaying a running image in a window
*Displaying a frozen image in a window
The latter is a subset of the former. The virtual video device driver always attempts to provide support for displaying a running image and for standard text and CGA graphics modes this is always possible, but there are graphics modes cases where that is not possible. One example is the 64KB EGA mode; other examples are the XGA and 8514/A modes.
Support for the XGA or 8514/A graphics modes is not a matter of sufficient memory but of the sheer complexity of virtualizing the 8514/A hardware. In addition, if a DOS application uses VGA graphics modes on an 8514/A system, it will not be able to use the VGA memory if a monitor being used as a secondary display by other tasks in the system is connected to the VGA.
There is no known, reliable method of determining whether a monitor is connected to the VGA or Super VGA. The 8514/A can detect a limited set of IBM-compatible, fixed-frequency monitors whereas the XGA, using DMQS, has the potential of identifying all monitor types, including OEMs.
In an 8514/A system, there is no architected way for the virtual video device driver to determine whether the VGA is in use by another process or session. Conversely, there is no way for the virtual video device driver to claim the device and prevent other processes or sessions from later acquiring the device.
Notes:
1.256-color modes will not be accurately rendered in a window even when the PM display driver supports 256 colors, because the DOS session Window Manager does not provide Palette Manager support.
2.High-resolution graphics modes on a 64KB EGA currently will not be rendered properly in a DOS window because the memory organization is substantially different (planes 0 and 1 and planes 2 and 3 are chained together).
OS/2 provides a single, generic Super VGA virtual device driver that supports the majority of the Super VGA video adapters made with the above- mentioned Super VGA chip sets. However, there are a small number of adapters that cannot be reliably virtualized, due to the way they are designed. For example, adapters that require multiple OUTs to a specific port before permitting the extended clock bits to be programmed fall into that category.
Of the 8514/A graphics modes, only the 1024 x 768 256-color mode has been tested for accurate rendering in a window.
Virtual Video Device Drivers
The following list contains the installable virtual video device drivers that are included with the Developer's Tooklkit for OS/2:
- Virtual CGA device driver (VCGA)
*Virtual EGA device driver (VEGA)
*Virtual MONO device driver (VMONO)
*Virtual VGA device driver (VVGA)
*Virtual XGA device driver (VXGA)
*Virtual 8514/A device driver (V8514A)
The architecture of the virtual video device driver adheres to the architecture defined for all virtual device drivers. However, some portions of the multiple DOS session architecture have been designed primarily for ( or used by) virtual video device drivers:
- Foreground and background notification hooks
*Freeze and thaw services
*Title change and code-page change notification hooks
A significant portion of the primary display virtual device drivers involves communication with the DOS session Window Manager. This includes providing a set of services to fully describe a DOS session's video state and a set of notifications to signal selected changes in state, so that a window remains relatively synchronized with its associated DOS session.
Discussion
Because the DOS session Window Manager is a Ring 3 component, virtual device drivers run at Ring 0, and DOS sessions have no LDT (and therefore cannot attach to DLLs), a Remote Procedure Call (RPC) mechanism must be used to communicate between the DOS session Window Manager and a virtual device driver. The DOS session Window Manager creates a thread for this purpose, which calls the virtual video device driver to wait for a video event from any of the currently windowed DOS sessions.
Virtual video device drivers are base device drivers. "DEVICE=" statements in the CONFIG.SYS files are used to specify one or more virtual video device drivers to load. The DOS session Manager and DOS session Window Manager identify a virtual video device driver by its registered name (for example, a virtual video device driver for the primary display device would register as VVIDEO1$, one for the secondary display device would register as VVIDEO2$, and so forth). After virtual video device driver loading and initialization is complete, if no virtual device driver has registered for the primary display device, multiple DOS session support is disabled.
IBM-compatible CGA, EGA, VGA, XGA, and 8514/A adapters are supported as primary display devices, and MONO adapters are supported as secondary display devices. For these devices, all the standard configurations (that is, amount of video memory, type of monitor, and so forth) are supported. However, there are a a few exceptions. For example, support for other dual- adapter combinations, such as EGA/monochrome with CGA/color, or VGA/ monochrome with CGA/color, are not specifically supported. In addition, all EGA monitor combinations (RGB, ECD, and monochrome), EGA memory combinations (64KB, 128KB, 192KB, and 256KB), VGA and 8514/A monitor combinations (8512, 8513, and 8514), and VGA and XGA monitor combinations ( 8512, 8513, 8514, and 8515) are supported. The type of monitor used with a monochrome or CGA adapter does not affect the behavior of the adapter.
Virtual and Nonvirtual Operation
For optimal performance and compatibility, the virtual video device drivers support full-screen operation. In this mode, there is no visual difference between DOS and DOS session operation. For convenience, an option appears on the DOS session system menu to convert the DOS session from windowed mode to full-screen mode and back. Virtual video device drivers support full-screen operation by performing the following operations:
- Registering foreground and background VIDEO_SWITCH_NOTIFICATION hooks with the DOS session Manager
*Allocating a save and restore video buffer
*Installing I/O hooks to shadow key video port accesses
*Mapping physical video memory into the appropriate video address space
*Compelling text-mode fonts to match the currently selected code page
*Providing pointer drawing services to the virtual mouse device driver to define, draw, and erase pointer images
When a DOS session does not own the physical display (that is, when it is background), the virtual video device drivers:
- Install I/O hooks to track and emulate all video port accesses.
*Map appropriate system memory to the active portions of the video address space.
*Report video events to the DOS session Window Manager (assuming the Presentation Manager is active and the DOS session is an unminimized window ). This includes changes to:
-Mode
-Palette
-Cursor
-Video memory
-Input events
-Scroll or string events
-Paste continue or terminate (through the virtual keyboard device driver)
-Session title change
-Screen-switch or video memory allocation errors
At any time, the DOS session Window Manager (or other processes that have access to a DOS session's process ID) can update a DOS session's window state:
- Windowed or nonwindowed
*Focus or nonfocus
*Minimized or unminimized
*Lock or unlocked
as well as query any aspect of a DOS session's video state:
- Mode
*Palette
*Cursor
*Video memory
*Wait for video events
*Cancel wait for video event
Mouse-Independent Pointer Drawing Services
When the virtual video device driver creates a DOS session for the first time, it opens the virtual mouse device driver. If the open is successful, it provides the virtual mouse device driver with the following entry points :
- Show Pointer
*Hide Pointer
*Define Text Pointer
*Define Graphics Pointer
*Set Video Page
*Set Light-Pen Emulation
Also, whenever the DOS session changes video modes (including the initial mode change that takes place during DOS session creation), the virtual video device driver notifies the virtual mouse device driver of the new mode, the screen dimensions, and so forth.
Built-in Extended INT 10h and INT 2Fh Services
The EGA register interface is integrated into the virtual video device driver as part of its INT 10h interception logic. This interface is a set of INT 10h services that are used by applications to make drawing operations and simultaneous use of the mouse pointer possible on EGA and VGA hardware. The virtual video device driver's pointer drawing services are intended to replace this interface, but existing graphical applications still use it (generally when mouse support is also present), so the interface must be present or these applications will not function correctly .
The INT 2Fh services notify applications when they are about to be switched to full-screen or background mode. Applications can use this notification to stop accessing video memory, if they are using a video memory not supported for background operation. This will prevent them from freezing, and also redraw their screen in the event the virtual video device driver fails to fully restore it.
Summary of the 8514/A and XGA Virtual Device Drivers
DOS applications currently written to the 8514/A Adapter Interface (AI), the XGA AI, or directly to the 8514/A and XGA display adapters are able to run in a full-screen DOS session. This is due to the ability of each adapter's virtual device driver to:
- Grant I/O privilege
*Save or restore the video state
*Provide video bitmap images to the shield layer when the DOS session is being windowed
A DOS application is allowed to run only in a full-screen foreground DOS session, and is immediately frozen if it attempts to access the hardware when switched to the background.
The virtual 8514/A device driver statements, which are required in the CONFIG.SYS file, are added during installation when the presence of an 8514 /A display adapter is noted:
DEVICE=C:\OS2\MDOS\VVGA.SYS
DEVICE=C:\OS2\MDOS\V8514A.SYS
The virtual XGA device driver statements, which are required in the CONFIG. SYS file, are added during installation when the presence of an XGA display adapter is noted:
DEVICE=C:\OS2\MDOS\VVGA.SYS
DEVICE=C:\OS2\MDOS\VXGA.SYS
The following items should be set in DOS to enable a DOS session:
- Enable I/O trapping to permit the virtual video device driver to save and restore the hardware instance used by a DOS application when the application switches away from the foreground DOS session. The virtual video device driver allocates a buffer to save the video image. The maximum size of this buffer is 1MB and is obtained each time a full-screen DOS session is created.
Enabling I/O trapping is the default. Although multiple instances of XGA can be present on a system, the virtual XGA device driver saves or restores only the state of the first instance used by a DOS application. It is the application's responsibility to save or restore the other XGA instances.
- Register for screen switch notification. This implies that a DOS application has hooked INT 2Fh so as to be notified when it is to be switched to full-screen foreground or background. This notification informs the application that it must restore the screen when switched to full- screen foreground, and must stop accessing video memory (to avoid freezing) when switched to background.
An application that uses more than one instance of XGA must specify this option to save and restore the states of the other XGA adapters. The default is no VIDEO_SWITCH_NOTIFICATION.
Any DOS session that is not saved or restored by the virtual video device driver cannot be displayed in a window. DOS 8514/A and XGA applications are not interactive in a window; they can only be viewed.
C Language Virtual DevHlp Services
Virtual DevHlp functions are used by virtual device drivers to access various services provided by the OS/2 operating system and by other virtual device drivers. These functions are provided because normal OS/2 API calls from a virtual device driver and routines in a C-language run-time library cannot be used for access purposes.
The virtual DevHlp services are categorized in the following list and subsequent sections. Individual functions follow and are listed alphabetically with an explanation of their purpose, parameters, and calling conventions.
Function Type
VDHAllocBlockbyte-granular memory management service
VDHAllocDMABufferDMA service
VDHAllocDOSMembyte-granular memory management service
VDHAllocHookhook management service
VDHAllocMembyte-granular memory management service
VDHAllocPagespage-granular memory management service
VDHArmBPHookhook management service
VDHArmContextHookhook management service
VDHArmReturnHookhook management service
VDHArmSTIHookhook management service
VDHArmTimerHooktimer service
VDHArmVPMBPHookDPMI service
VDHBeginUseVPMStackDPMI service
VDHCallOutDMADMA service
VDHChangeVPMIFDPMI service
VDHCheckPagePermDPMI service
VDHCheckVPMIntVectorDPMI service
VDHClearVIRRVirtual interrupt service
VDHClosefile or device I/O service
VDHCloseVDDinter-device communication service
VDHCloseVIRQVirtual interrupt service
VDHCopyMembyte-granular memory management service
VDHCreateBlockPoolbyte-granular memory management service
VDHCreateSelGDT selector service
VDHCreateSemsemaphore service
VDHDecodePropertyDOS settings service
VDHDestroyBlockPoolbyte-granular memory management service
VDHDestroySelGDT selector service
VDHDestroySemsemaphore service
VDHDevBeepmiscellaneous virtual DevHlp service
VDHDevIOCtlfile or device I/O service
VDHDisarmTimerHooktimer service
VDHEndUseVPMStackDPMI service
VDHEnumerateVDMsmiscellaneous virtual DevHlp service
VDHExchangeMembyte-granular memory management service
VDHFindFreePagespage-granular memory management service
VDHFreeBlockbyte-granular memory management service
VDHFreeDMABufferDMA service
VDHFreeHookhook management service
VDHFreeMembyte-granular memory management service
VDHFreePagespage-granular memory management service
VDHFreezeVDMDOS session control service
VDHGetCodePageFontmiscellaneous virtual DevHlp service
VDHGetDirtyPageInfopage-granular memory management service
VDHGetErrormiscellaneous virtual DevHlp service
VDHGetFlagsmiscellaneous virtual DevHlp service
VDHGetSelBaseDPMI service
VDHGetVPMExceptDPMI service
VDHGetVPMIntVectorDPMI service
VDHHaltSystemDOS session control service
VDHHandleFromPIDmiscellaneous virtual DevHlp service
VDHHandleFromSGIDmiscellaneous virtual DevHlp service
VDHInstallFaultHookpage-granular memory management service
VDHInstallIntHookhook management service
VDHInstallIOHookhook management service
VDHInstallUserHookhook management service
VDHIsVDMFrozenDOS session control service
VDHKillVDMDOS session control service
VDHLockMemmemory-locking memory management service
VDHMapPagespage-granular memory management service
VDHOpenfile or device I/O service
VDHOpenPDDinter-device communication service
VDHOpenVDDinter-device communication service
VDHOpenVIRQVirtual interrupt service
VDHPhysicalDiskfile or device I/O service
VDHPopIntV8086 stack manipulation service
VDHPopRegsV8086 stack manipulation service
VDHPopStackV8086 stack manipulation service
VDHPopupmiscellaneous virtual DevHlp service
VDHPostEventSemsemaphore service
VDHPrintCloseparallel port and printer service
VDHPushFarCallV8086 stack manipulation service
VDHPushIntV8086 stack manipulation service
VDHPushRegsV8086 stack manipulation service
VDHPushStackV8086 stack manipulation service
VDHPutSysValuemiscellaneous virtual DevHlp service
VDHQueryFreePagespage-granular memory management service
VDHQueryHookDatahook management service
VDHQueryLinmiscellaneous virtual DevHlp service
VDHQueryKeyShiftkeyboard service
VDHQueryPropertyDOS settings service
VDHQuerySelGDT selector service
VDHQuerySemsemaphore service
VDHQuerySysValuemiscellaneous virtual DevHlp service
VDHQueryVIRQVirtual interrupt service
VDHRaiseExceptionDPMI service
VDHReadfile or device I/O service
VDHReadUBufDPMI service
VDHReallocPagespage-granular memory management service
VDHRegisterAPIRegister API handler
VDHRegisterDMAChannelDMA service
VDHRegisterPropertyDOS settings service
VDHRegisterVDDinter-device communication service
VDHReleaseCodePageFontmiscellaneous virtual DevHlp service
VDHReleaseMutexSemsemaphore service
VDHRemoveFaultHookpage-granular memory management service
VDHRemoveIOHookhook management service
VDHReportPeekidle DOS application management service
VDHRequestMutexSemsemaphore service
VDHRequestVDDinter-device communication service
VDHReservePagespage-granular memory management service
VDHResetEventSemsemaphore service
VDHSeekfile or device I/O service
VDHSendVEOIVirtual interrupt service
VDHSetDosDevicemiscellaneous virtual DevHlp service
VDHSetErrormiscellaneous virtual DevHlp service
VDHSetFlagsmiscellaneous virtual DevHlp service
VDHSetIOHookStatehook management service
VDHSetPriorityDOS session control service
VDHSetVIRRVirtual interrupt service
VDHSetVPMExceptDPMI service
VDHSetVPMIntVectorDPMI service
VDHSwitchToVPMDPMI service
VDHSwitchToV86DPMI service
VDHThawVDMDOS session control service
VDHUnlockMemmemory-locking memory management service
VDHUnreservePagespage-granular memory management service
VDHWaitEventSemsemaphore service
VDHWaitVIRRsVirtual interrupt service
VDHWakeIdleidle DOS application management service
VDHWakeVIRRsVirtual interrupt service
VDHWritefile or device I/O service
VDHWriteUBufDPMI service
VDHYieldDOS session control service
Some Notes on Virtual DevHlp Services
Passing Addresses of Buffers
The SSToDS macro must be used when passing the address of a frame ( automatic) variable in a function call because the 32-bit code assumes SS= DS. Pointers allocated from the stack must be DS-relative.
Function Definitions and Calling Conventions
All virtual DevHlp services are 32-bit NEAR functions. For a description of the calling conventions, refer to the function prototype definition VDHENTRY located in the MVDM.INC include file included with the Developer's Toolkit for OS/2.
When using the virtual DevHlp services, the function being called is responsible for cleaning up the stack. This means that when you call a virtual DevHlp service, the function you call cleans up the stack; you do not have to pop the parameters off the stack after the call. This also means that when you register a hook (or callback) routine with a virtual DevHlp service, your hook routine is responsible for cleaning up the stack before it returns to the function that called it.
The virtual DevHlp services are called directly, as in CALL VDHFunction. This is in contrast to the physical device driver Device Helper services, which are called indirectly as in CALL [DevHlpFunction].
Syntax Examples
The syntax examples are shown in C language. For assembler language syntax examples, see Assembler Language Syntax.
Defined Constants and Type Definitions
Defined constants, that is, equatestatements in an includefile, and type definitions are widely used in OS/2. These constant values are defined in the master header files, MVDM.INC or .h, or in one of the files that MVDM. INC or .h includes. The defined constants and type definitions that are seen in the syntax examples should be used to provide a degree of machine and version independence.
Invalid Parameters and System Halts
In many of the virtual DevHlp functions, invalid parameters or other error conditions often cause a system halt because virtual device drivers run at Ring 0 and have free access to everything in the system.
Remarks Section
Each function description has a Remarkssection at the end, which consists of three parts:
- Context Issues: Indicates the specific contexts in which virtual DevHlps should be called.
- DOS Session Termination: Indicates what the virtual device driver must do upon termination of a DOS session, for example, release resources.
- Notes: These are miscellaneous function-specific notes about the function.
Virtual DevHlp Services by Category
Virtual DevHlp services can be divided into categories based on the type of service the virtual DevHlp provides. These categories are:
DMA Services
VDHAllocDMABufferAllocate DMA buffer
VDHCallOutDMACall virtual DMA device driver
VDHFreeDMABufferFree DMA buffer
VDHRegisterDMAChannelRegister DMA channel
DOS Session Control Services
VDHFreezeVDMFreeze DOS session
VDHHaltSystemCause system halt
VDHIsVDMFrozenDetermine if DOS session is frozen
VDHKillVDMTerminate DOS session
VDHSetPriorityAdjust DOS session scheduler priority
VDHThawVDMAllow frozen DOS session to resume executing
VDHYieldYield the processor
DOS Settings Services
VDHDecodePropertyDecode property string
VDHQueryPropertyQuery virtual device driver property value
VDHRegisterPropertyRegister virtual device driver property
DPMI Services
VDHArmVPMBPHookObtain address of DOS session protect-mode breakpoint
VDHBeginUseVPMStackBegin using DOS session protect-mode stack
VDHChangeVPMIFChange virtual Interrupt Flag (IF)
VDHCheckPagePermCheck Ring 3 page permissions
VDHCheckVPMIntVectorDetermine if DOS session protect-mode handler exists
VDHEndUseVPMStackEnd use of DOS session protect-mode stack
VDHGetSelBaseGet flat base address
VDHGetVPMExceptGet DOS session protect-mode exception vector
VDHGetVPMIntVectorReturn DOS session protect-mode interrupt vector
VDHRaiseExceptionRaise an exception to a DOS session
VDHReadUBufRead from protect-mode address space
VDHSetVPMExceptSet DOS session protect-mode exception vector
VDHSetVPMIntVectorSet DOS session protect-mode interrupt vector
VDHSwitchToVPMSwitch DOS session to protect mode
VDHSwitchToV86Switch DOS session to V86 mode
VDHWriteUBufWrite to protect-mode address space
Note:"VPM", as found in the function names above, stands for Virtual Protect Mode.
File or Device I/O Services
VDHCloseClose a file handle
VDHDevIOCtlIssue device-specific commands
VDHOpenOpen a file or device
VDHPhysicalDiskGet information about partitionable disks
VDHReadRead bytes from file or device
VDHSeekMove read or write file pointer for a handle
VDHWriteWrite bytes to file or device
GDT Selector Services
VDHCreateSelCreate GDT selector to map a linear range
VDHDestroySelDestroy GDT selector
VDHQuerySelGet selector for data or stack address
Hook Management Services
VDHAllocHookAllocate hooks needed for interrupt simulation
VDHArmBPHookObtain address of V86 breakpoint
VDHArmContextHookSet local or global context hook
VDHArmReturnHookSet handler to receive control
VDHArmSTIHookSet handler to receive control
VDHFreeHookDisarm and free hook
VDHInstallIntHookSet handler for V86 interrupt
VDHInstallIOHookInstall I/O port hooks
VDHInstallUserHookInstall handler for DOS session event
VDHQueryHookDataReturns pointer to hook reference data
VDHRemoveIOHookRemove hooks for PIC I/O ports
VDHSetIOHookStateEnable/disable I/O port trapping
Idle DOS Application Management Services
VDHReportPeekReport DOS session polling activity
VDHWakeIdleWake up DOS session
Note:The services above indicate when a DOS application appears to be idle, and when activity exists that could make the DOS application BUSY.
Inter-Device-Communication Services
VDHCloseVDDClose virtual device driver
VDHOpenPDDOpen physical device driver
VDHOpenVDDOpen virtual device driver
VDHRegisterVDDRegister virtual device driver entry points
VDHRequestVDDIssue request for virtual device driver operation
Keyboard Services
VDHQueryKeyShiftQuery keyboard shift state
Memory Management Services
There are three sub-categories of the memory management virtual DevHlp services. The first two are used for the granularity of the memory allocation unit; the third category is used for memory-locking services.
Byte-Granular Memory Management Services
VDHAllocBlockAllocate block from memory block pool
VDHAllocDOSMemAllocate block of memory from DOS area
VDHAllocMemAllocate small amount of memory
VDHCopyMemCopy from one linear memory address to another
VDHCreateBlockPoolCreate memory block pool
VDHDestroyBlockPoolDestroy memory block pool
VDHExchangeMemExchange contents of two linear memory regions
VDHFreeBlockFree block of memory
VDHFreeMemFree memory
Page-Granular Memory Management Services
VDHAllocPagesAllocate page-aligned memory object
VDHFindFreePagesFind largest available linear memory
VDHFreePagesFree memory object
VDHGetDirtyPageInfoReturn status of dirty bits
VDHInstallFaultHookInstall page fault handler
VDHMapPagesMap specified linear address
VDHQueryFreePagesReturn amount of free virtual memory
VDHReallocPagesReallocate memory object
VDHRemoveFaultHookRemove page fault handler
VDHReservePagesReserve range of linear addresses
VDHUnreservePagesUnreserve range of linear addresses
Memory-Locking Memory Management Services
VDHLockMemVerify access or lock memory
VDHUnlockMemRelease memory lock
Note:The services above allow virtual device drivers to allocate, free, reallocate, and lock memory for global, per-DOS session, page-granular, or byte-granular objects.
Four types of mappings are supported:
- Mapping to a physical address
*Mapping to another linear address
*Mapping to black holes (don't care) pages
*Mapping to invalid (unmapped) pages
Virtual device drivers can also request smaller memory allocations from the kernel heap, which is global and fixed. Small, fixed size block services are available to speed up frequent allocations and freeing of memory. For a particular block size, a pool of blocks is maintained and the requirements are met by taking off a block from the block pool.
Miscellaneous Virtual DevHlp Services
VDHDevBeepDevice beep virtual DevHlp service
VDHEnumerateVDMsRun worker function for each DOS session
VDHGetCodePageFontReturn information of DOS session code page font
VDHGetErrorGet error code from last virtual DevHlp service
VDHGetFlagsGet DOS Session's EFLAGS Register
VDHHandleFromPIDGet handle for given Process ID
VDHHandleFromSGIDGet DOS session handle from Screen Group ID
VDHPopupDisplay message
VDHPutSysValueSet system value
VDHQueryLinGet linear address for Far16 address
VDHQuerySysValueQuery system value
VDHRegisterAPIRegister API handler
VDHReleaseCodePageFontRelease code page font
VDHSetDosDeviceRegister/install DOS device driver
VDHSetErrorSet error code
VDHSetFlagsSet DOS session flags register
Parallel Port and Printer Services
VDHPrintCloseFlush and close open printers for DOS session
Semaphore Services
VDHCreateSemCreate event or mutex semaphore
VDHDestroySemDestroy semaphore
VDHPostEventSemPost event semaphore
VDHQuerySemQuery semaphore state
VDHReleaseMutexSemRelease mutex semaphore
VDHRequestMutexSemRequest mutex semaphore
VDHResetEventSemReset event semaphore
VDHWaitEventSemWait on event semaphore
Note:The services above are used for synchronizing with an OS/2 process. Virtual device drivers must be careful not to block (VDHRequestMutexSem/ VDHWaitEventSem) in the context of a DOS session task. Otherwise, that task will receive no more simulated hardware interrupts until it becomes unblocked.
Timer Services
VDHArmTimerHookSet timer service/handler
VDHDisarmTimerHookCancel timer service
Virtual Interrupt Services
VDHClearVIRRClear virtual IRR
VDHCloseVIRQDeregister IRQ handler
VDHOpenVIRQRegister IRQ handler
VDHQueryVIRQQuery IRQ status on a DOS session
VDHSendVEOISend virtual EOI to VPIC
VDHSetVIRRSet virtual interrupt request register (IRR)
VDHWaitVIRRsWait until interrupt is simulated
VDHWakeVIRRsWake up DOS session
V8086 Stack Manipulation Services
VDHPopIntRemove IRET frame from client DOS session stack
VDHPopRegsPop client DOS session registers from client stack
VDHPopStackPop data off client stack
VDHPushFarCallSimulate Far Call to V86 code
VDHPushIntTransfer control to V86 interrupt handler
VDHPushRegsPush client DOS session registers onto client stack
VDHPushStackPush data onto client stack
VDHAllocBlock
Select an item:
Format Parameters Return Codes Purpose Glossary
This function allocates a block from the specified memory block pool. This block is allocated from fixed or swappable memory, depending on the value of the OptionFlagflag when the block is created with VDHCreateBlockPool.
#include mvdm.h HBLOCK SourceBlockPool; /* Handle to a memory block pool */ PVOID rc; rc = VDHAllocBlock(SourceBlockPool);
VDHAllocBlock - Format
This function allocates a block from the specified memory block pool. This block is allocated from fixed or swappable memory, depending on the value of the OptionFlagflag when the block is created with VDHCreateBlockPool.
#include mvdm.h HBLOCK SourceBlockPool; /* Handle to a memory block pool */ PVOID rc; rc = VDHAllocBlock(SourceBlockPool);
VDHAllocBlock Parameter - SourceBlockPool
SourceBlockPool(HBLOCK) Handle to the pool of memory blocks from which to allocate a memory block.
VDHAllocBlock Return Value - rc
rc(PVOID) - returns
Success If the function is successful, it returns the address of the allocated memory block.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. Note that passing an invalid memory block handle causes a system halt to occur.
VDHAllocBlock - Parameters
SourceBlockPool(HBLOCK) Handle to the pool of memory blocks from which to allocate a memory block.
rc(PVOID) - returns
Success If the function is successful, it returns the address of the allocated memory block.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. Note that passing an invalid memory block handle causes a system halt to occur.
VDHAllocBlock - Purpose
Context Issues: This function can be called in the initialization or task context.
DOS Session Terminations: Any blocks allocated by a virtual device driver for use by the terminating DOS session are freed by using VDHFreeBlock. Any block pools created for the DOS session should also be freed.
VDHAllocBlock - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHAllocDMABuffer
Select an item:
Format Parameters Return Codes Purpose Glossary
This function allocates a DMA buffer.
#include mvdm.h
ULONG RequestSize; /* Request size */
BOOL Align64kFlag; /* Alignment flag */
PULONG PhysAddrPtr; /* Location to store the physical address returned */
PVOID rc;
rc = VDHAllocDMABuffer(RequestSize, Align64kFlag,
PhysAddrPtr);
VDHAllocDMABuffer - Format
This function allocates a DMA buffer.
#include mvdm.h
ULONG RequestSize; /* Request size */
BOOL Align64kFlag; /* Alignment flag */
PULONG PhysAddrPtr; /* Location to store the physical address returned */
PVOID rc;
rc = VDHAllocDMABuffer(RequestSize, Align64kFlag,
PhysAddrPtr);
VDHAllocDMABuffer Parameter - RequestSize
RequestSize(ULONG) Request Size.
If the Align64kFlag=1, RequestSizeis always less than or equal to 64KB. If the Align64kFlag=0, RequestSizeis always less than or equal to 128KB.
VDHAllocDMABuffer Parameter - Align64kFlag
Align64kFlag(BOOL) Alignment flag.
If Align64kFlag=1, the buffer is at a 64KB alignment in physical memory. If Align64kFlag=0, the buffer is at a 128KB alignment in physical memory.
VDHAllocDMABuffer Parameter - PhysAddrPtr
PhysAddrPtr(PULONG) Location where VDHAllocDMABufferreturns the physical address of the allocation.
VDHAllocDMABuffer Return Value - rc
rc(PVOID) - returns
Success If the function is successful, it returns the linear address of allocation (system memory).
Failure If the function fails, it returns -1. VDHGetErrorshould be called to determine the nature of the problem.
VDHAllocDMABuffer - Parameters
RequestSize(ULONG) Request Size.
If the Align64kFlag=1, RequestSizeis always less than or equal to 64KB. If the Align64kFlag=0, RequestSizeis always less than or equal to 128KB.
Align64kFlag(BOOL) Alignment flag.
If Align64kFlag=1, the buffer is at a 64KB alignment in physical memory. If Align64kFlag=0, the buffer is at a 128KB alignment in physical memory.
PhysAddrPtr(PULONG) Location where VDHAllocDMABufferreturns the physical address of the allocation.
rc(PVOID) - returns
Success If the function is successful, it returns the linear address of allocation (system memory).
Failure If the function fails, it returns -1. VDHGetErrorshould be called to determine the nature of the problem.
VDHAllocDMABuffer - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: The virtual device driver frees the buffer by using VDHFreeDMABufferat DOS session termination.
Notes: Physical memory is allocated resident and contiguous, and is always in the first 16MB. The Linear Memory range comes from the system arena. The contents of the returned buffer are not important; that is, the buffer is not zero-filled.
VDHAllocDMABuffer - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHAllocDOSMem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function allocates a block of memory from the DOS memory area. Allocations start at 0 bytes and go to 256KB.
#include mvdm.h ULONG BlockSize; /* Size of the desired memory block (in bytes) */ PVOID rc; rc = VDHAllocDOSMem(BlockSize);
VDHAllocDOSMem - Format
This function allocates a block of memory from the DOS memory area. Allocations start at 0 bytes and go to 256KB.
#include mvdm.h ULONG BlockSize; /* Size of the desired memory block (in bytes) */ PVOID rc; rc = VDHAllocDOSMem(BlockSize);
VDHAllocDOSMem Parameter - BlockSize
BlockSize(ULONG) Size of the desired memory block; the number of bytes to allocate.
VDHAllocDOSMem Return Value - rc
rc(PVOID) - returns
Success If the function is successful, it returns the address of the allocated memory block.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. If BlockSize= 0, or if the function is called in an invalid context (see "Context Issues" below), a system halt occurs.
VDHAllocDOSMem - Parameters
BlockSize(ULONG) Size of the desired memory block; the number of bytes to allocate.
rc(PVOID) - returns
Success If the function is successful, it returns the address of the allocated memory block.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. If BlockSize= 0, or if the function is called in an invalid context (see "Context Issues" below), a system halt occurs.
VDHAllocDOSMem - Purpose
Context Issues: This function can be called only in the DOS session-task context (DOS session creation).
DOS Session Terminations: There are no DOS session termination implications for this function. The DOS Session Manager frees this memory.
Notes: There is no way to free memory taken from the DOS heap. If there is no free memory in the DOS memory area, the allocation fails. Allocations always start on paragraph (16-byte) boundaries.
VDHAllocDOSMem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHAllocHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used to allocate a hook handle for the arm hook services: Context, STI, Return, Timer, and BP (breakpoint).
#include mvdm.h ULONG HookType; /* Hook type */ PFNARM ArmHookFcn; /* Arm hook function */ ULONG RefDataSize; /* Size of the reference data */ HHOOK rc; rc = VDHAllocHook(HookType, ArmHookFcn, RefDataSize);
VDHAllocHook - Format
This function is used to allocate a hook handle for the arm hook services: Context, STI, Return, Timer, and BP (breakpoint).
#include mvdm.h ULONG HookType; /* Hook type */ PFNARM ArmHookFcn; /* Arm hook function */ ULONG RefDataSize; /* Size of the reference data */ HHOOK rc; rc = VDHAllocHook(HookType, ArmHookFcn, RefDataSize);
VDHAllocHook Parameter - HookType
HookType(ULONG) Hook type.
Possible values are:
VDH_CONTEXT_HOOK VDHArmContextHook
VDH_STI_HOOK VDHArmSTIHook
VDH_RETURN_HOOK VDHArmReturnHook
VDH_TIMER_HOOK VDHArmTimerHook
VDH_BP_HOOK VDHArmBPHook
VDHAllocHook Parameter - ArmHookFcn
ArmHookFcn(PFNARM) Arm hook function.
VDHAllocHook Parameter - RefDataSize
RefDataSize(ULONG) Size of the reference data.
VDHAllocHook Return Value - rc
rc(HHOOK) - returns
Success If the function is successful, it returns a hook handle, which is used in the Arm services.
Failure If there is an error, the function returns NULL. VDHGetErrorshould be called to determine the nature of the problem. If HookTypeor ArmHookFcnis invalid, a system halt occurs.
VDHAllocHook - Parameters
HookType(ULONG) Hook type.
Possible values are:
VDH_CONTEXT_HOOK VDHArmContextHook
VDH_STI_HOOK VDHArmSTIHook
VDH_RETURN_HOOK VDHArmReturnHook
VDH_TIMER_HOOK VDHArmTimerHook
VDH_BP_HOOK VDHArmBPHook
ArmHookFcn(PFNARM) Arm hook function.
RefDataSize(ULONG) Size of the reference data.
rc(HHOOK) - returns
Success If the function is successful, it returns a hook handle, which is used in the Arm services.
Failure If there is an error, the function returns NULL. VDHGetErrorshould be called to determine the nature of the problem. If HookTypeor ArmHookFcnis invalid, a system halt occurs.
VDHAllocHook - Purpose
Context Issues: This function can be called in the initialization or DOS session-task context. However, VDH_RETURN_HOOK and VDH_BP_HOOK require the DOS session-task context.
DOS Session Terminations: During initialization time, hooks are allocated globally; that is, they are not associated with a DOS session process. These hooks are not automatically freed when a DOS session terminates. During DOS session creation time or thereafter, allocated hooks are associated with the current DOS session, and are freed when that DOS session terminates.
Notes: Use VDHQueryHookDatato get a pointer to any reference data allocated.
VDHAllocHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHAllocMem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function allocates a small amount of memory on a LONG/DWORD boundary. The memory is allocated from the system area, so the address is valid in all process contexts.
#include mvdm.h ULONG NumBytes; ULONG OptionFlag; /* Number of bytes to allocate */ PVOID rc; rc = VDHAllocMem(NumBytes, OptionFlag);
VDHAllocMem - Format
This function allocates a small amount of memory on a LONG/DWORD boundary. The memory is allocated from the system area, so the address is valid in all process contexts.
#include mvdm.h ULONG NumBytes; ULONG OptionFlag; /* Number of bytes to allocate */ PVOID rc; rc = VDHAllocMem(NumBytes, OptionFlag);
VDHAllocMem Parameter - NumBytes
NumBytes(ULONG) Number of bytes to allocate.
VDHAllocMem Parameter - OptionFlag
OptionFlag(ULONG) Bit flag describing the allocation options.
Possible value:
VDHAM_SWAPPABLE Allocate memory from the swappable heap. Otherwise, memory is allocated from the fixed heap and can be accessed at hardware interrupt time.
VDHAllocMem Return Value - rc
rc(PVOID) - returns
Success If the function is successful, it returns the address of the allocated space.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. If either NumBytesor OptionFlagis invalid, a system halt occurs.
VDHAllocMem - Parameters
NumBytes(ULONG) Number of bytes to allocate.
OptionFlag(ULONG) Bit flag describing the allocation options.
Possible value:
VDHAM_SWAPPABLE Allocate memory from the swappable heap. Otherwise, memory is allocated from the fixed heap and can be accessed at hardware interrupt time.
rc(PVOID) - returns
Success If the function is successful, it returns the address of the allocated space.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. If either NumBytesor OptionFlagis invalid, a system halt occurs.
VDHAllocMem - Purpose
Context Issues: This function can be called in the initialization or task context.
DOS Session Terminations: All memory allocated by a virtual device driver for use by the terminating DOS session is freed by using VDHFreeMem.
Notes: Allocations larger than one page are performed by using VDHAllocPages. To access the allocated memory at hardware interrupt time, be sure to allocate memory from the fixed heap.
VDHAllocMem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHAllocPages
Select an item:
Format Parameters Return Codes Purpose Glossary
This function allocates a page-aligned, page-granular memory object.
#include mvdm.h
PVOID StartingAddress; /* A specific linear address */
ULONG NumPages; /* The number of pages to allocate */
ULONG OptionFlag; /* Allocation options bit-flag */
PVOID rc;
rc = VDHAllocPages(StartingAddress, NumPages,
OptionFlag);
VDHAllocPages - Format
This function allocates a page-aligned, page-granular memory object.
#include mvdm.h
PVOID StartingAddress; /* A specific linear address */
ULONG NumPages; /* The number of pages to allocate */
ULONG OptionFlag; /* Allocation options bit-flag */
PVOID rc;
rc = VDHAllocPages(StartingAddress, NumPages,
OptionFlag);
VDHAllocPages Parameter - StartingAddress
StartingAddress(PVOID) A specific address used with the available options (see Option Flag).
VDHAllocPages Parameter - NumPages
NumPages(ULONG) Number of pages of linear memory to allocate.
VDHAllocPages Parameter - OptionFlag
OptionFlag(ULONG) Bit flag indicating choices in allocation options.
This flag can take one or more of the following values:
VDHAP_SPECIFIC VDHAllocPagesattempts to allocate pages starting at the linear address, StartingAddress. Otherwise, an arbitrary linear address is selected.
VDHAP_SYSTEM The linear address is allocated from the system (global) area, essentially allocating global memory. Otherwise, it is allocated from the private area of this process.
VDHAP_FIXED The allocated memory is fixed. Otherwise, the memory is swappable. This flag cannot be used if VDHAP_PHYSICAL is specified.
VDHAP_PHYSICAL The allocated linear address range maps the physical address range, starting at StartingAddress. Otherwise, an arbitrary physical page is assigned. Note that this flag cannot be used if VDHAP_FIXED is specified .
VDHAllocPages Return Value - rc
rc(PVOID) - returns
Success If the function is successful, it returns the address of the allocated memory.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. If the OptionFlagflag is invalid, a system halt occurs.
VDHAllocPages - Parameters
StartingAddress(PVOID) A specific address used with the available options (see Option Flag).
NumPages(ULONG) Number of pages of linear memory to allocate.
OptionFlag(ULONG) Bit flag indicating choices in allocation options.
This flag can take one or more of the following values:
VDHAP_SPECIFIC VDHAllocPagesattempts to allocate pages starting at the linear address, StartingAddress. Otherwise, an arbitrary linear address is selected.
VDHAP_SYSTEM The linear address is allocated from the system (global) area, essentially allocating global memory. Otherwise, it is allocated from the private area of this process.
VDHAP_FIXED The allocated memory is fixed. Otherwise, the memory is swappable. This flag cannot be used if VDHAP_PHYSICAL is specified.
VDHAP_PHYSICAL The allocated linear address range maps the physical address range, starting at StartingAddress. Otherwise, an arbitrary physical page is assigned. Note that this flag cannot be used if VDHAP_FIXED is specified .
rc(PVOID) - returns
Success If the function is successful, it returns the address of the allocated memory.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. If the OptionFlagflag is invalid, a system halt occurs.
VDHAllocPages - Purpose
Context Issues: This function can be called in the initialization or task context. If called in the initialization context, VDHAP_SYSTEM must be specified. If called in the OS/2 task context, VDHAP_SYSTEM must also be specified.
DOS Session Terminations: Any allocations that are not in the terminating DOS sessions private area must be released by using VDHFreePages.
Notes: When an allocation made with VDHAllocPagesis shrunk by VDHReallocPages, the linear range between the end of the allocation and the original end of the allocation remains available for object growth without movement. Regardless of VDHReallocPagesactivity, all pages in the allocation retain the same properties (that is fixed, system, and physical) .
VDHAllocPages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHArmBPHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function obtains the address of the V86 breakpoint allocated by a previous call to VDHAllocHookwith the VDH_BP_HOOK flag.
#include mvdm.h HHOOK HookHandle; /* Hook handle */ VPVOID rc; rc = VDHArmBPHook(HookHandle);
VDHArmBPHook - Format
This function obtains the address of the V86 breakpoint allocated by a previous call to VDHAllocHookwith the VDH_BP_HOOK flag.
#include mvdm.h HHOOK HookHandle; /* Hook handle */ VPVOID rc; rc = VDHArmBPHook(HookHandle);
VDHArmBPHook Parameter - HookHandle
HookHandle(HHOOK) Hook handle allocated with VDHAllocHook.
Hook routine interface:
VOID HOOKENTRY fnarm(pRefData, pcrf)
ENTRY pRefData - Pointer to hook-specific reference data
pcrf - Pointer to client register frame
EXIT None
CONTEXT DOS session-task
VDHArmBPHook Return Value - rc
rc(VPVOID) - returns
Success If the function is successful, it returns a V86 breakpoint address.
Failure If HookHandleis invalid, a system halt occurs.
VDHArmBPHook - Parameters
HookHandle(HHOOK) Hook handle allocated with VDHAllocHook.
Hook routine interface:
VOID HOOKENTRY fnarm(pRefData, pcrf)
ENTRY pRefData - Pointer to hook-specific reference data
pcrf - Pointer to client register frame
EXIT None
CONTEXT DOS session-task
rc(VPVOID) - returns
Success If the function is successful, it returns a V86 breakpoint address.
Failure If HookHandleis invalid, a system halt occurs.
VDHArmBPHook - Purpose
Context Issues: This function can be called only in the task context, and needs to be called only at DOS session creation time.
DOS Session Terminations: There are no DOS session termination implications for this function. BP (breakpoint) hooks are automatically removed during DOS session termination.
Notes: This VDH service provides a raw breakpoint service. Upon entry to the arm hook function, the client's CS:IP is randomly set. Therefore, it is crucial that this function set the CS:IP to a valid address. Typically, the CS:IP is retrieved from the client's stack through use of VDHPopStack. This is a low-level service. Appropriate care should be exercised to ensure that the client's CS:IP and stack remain valid.
Unlike other hooks, breakpoint hooks are armed until explicitly disarmed by a call to VDHFreeHook. When the V86 breakpoint address is called from V86 mode, the hook function is called. Any changes made to the client register frame cause the corresponding registers to take on these values upon return to V86 mode. The pparameter in the hook routine points to the cbRefDatabytes of data allocated by VDHAllocHook.
VDHArmBPHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHArmContextHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used to get to a task-time context from interrupt time when an interrupt is simulated. This service adds a handler to the list of routines called the next time the task context is entered (global context), or the next time a specific DOS session-task context is reached (local context). This is done only once; the handler is removed from the list after it is executed.
#include mvdm.h HHOOK HookHandle; /* Hook handle allocated with VDHAllocHook */ HVDM VDMHandle; /* DOS session handle */ VDHArmContextHook(HookHandle, VDMHandle);
VDHArmContextHook - Format
This function is used to get to a task-time context from interrupt time when an interrupt is simulated. This service adds a handler to the list of routines called the next time the task context is entered (global context), or the next time a specific DOS session-task context is reached (local context). This is done only once; the handler is removed from the list after it is executed.
#include mvdm.h HHOOK HookHandle; /* Hook handle allocated with VDHAllocHook */ HVDM VDMHandle; /* DOS session handle */ VDHArmContextHook(HookHandle, VDMHandle);
VDHArmContextHook Parameter - HookHandle
HookHandle(HHOOK) Hook handle allocated with VDHAllocHook.
VDHArmContextHook Parameter - VDMHandle
VDMHandle(HVDM) DOS session handle. A value of -1 indicates a global context.
Hook routine interface:
VOID HOOKENTRY fnarm(pRefData, pcrf)
ENTRY pRefData - Pointer to reference data
pcrf - Pointer to client register frame
EXIT None
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT Task (global) or DOS session-task (local)
NOTE pcrf is valid only for local context hook handlers
VDHArmContextHook - Return Value
Success If the function was successful, it returns nothing.
Failure If HookHandleor VDMHandleis invalid, or if the hook is already armed, a system halt occurs.
VDHArmContextHook - Parameters
HookHandle(HHOOK) Hook handle allocated with VDHAllocHook.
VDMHandle(HVDM) DOS session handle. A value of -1 indicates a global context.
Hook routine interface:
VOID HOOKENTRY fnarm(pRefData, pcrf)
ENTRY pRefData - Pointer to reference data
pcrf - Pointer to client register frame
EXIT None
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT Task (global) or DOS session-task (local)
NOTE pcrf is valid only for local context hook handlers
Success If the function was successful, it returns nothing.
Failure If HookHandleor VDMHandleis invalid, or if the hook is already armed, a system halt occurs.
VDHArmContextHook - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: Any context hooks allocated in the context of the terminating DOS session are deallocated by the DOS Session Manager.
Notes: After calling this routine, the caller is guaranteed that the context hook will be executed before any user-space code (global context) or any V86 code in the specified DOS session (local context).
VDHArmContextHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHArmReturnHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function sets a service to receive control when an Interrupt Return ( IRET) or Far Return (RETF) instruction is executed in V86 mode or when VDHPopIntis executed.
#include mvdm.h HHOOK HookHandle; /* Hook handle */ ULONG RetHookType; /* Return hook type */ BOOL rc; rc = VDHArmReturnHook(HookHandle, RetHookType);
VDHArmReturnHook - Format
This function sets a service to receive control when an Interrupt Return ( IRET) or Far Return (RETF) instruction is executed in V86 mode or when VDHPopIntis executed.
#include mvdm.h HHOOK HookHandle; /* Hook handle */ ULONG RetHookType; /* Return hook type */ BOOL rc; rc = VDHArmReturnHook(HookHandle, RetHookType);
VDHArmReturnHook Parameter - HookHandle
HookHandle(HHOOK) Hook handles the routine to get control on an IRET/RETF. Allocated with VDHAllocHook.
VDHArmReturnHook Parameter - RetHookType
RetHookType(ULONG) Return hook type.
Possible values are:
VDHARH_NORMAL_IRET
VDHARH_NORMAL_RET
VDHARH_RECURSIVE_IRET
VDHARH_RECURSIVE_RET
VDHARH_CSEIP_HOOK
VDHARH_RECURSIVE_CSEIP_HOOK
Hook routine interface:
VOID HOOKENTRY fnarm(pRefData, pcrf)
ENTRY pRefData - Pointer to reference data
pcrf - Pointer to client register frame
EXIT None
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT DOS session-task
VDHArmReturnHook Return Value - rc
rc(BOOL) - returns
Success If the function was successful it returns a nonzero value.
Failure If VDHARH_NORMAL_x is already armed, the function returns 0. If HookHandleis invalid, a system halt occurs.
VDHArmReturnHook - Parameters
HookHandle(HHOOK) Hook handles the routine to get control on an IRET/RETF. Allocated with VDHAllocHook.
RetHookType(ULONG) Return hook type.
Possible values are:
VDHARH_NORMAL_IRET
VDHARH_NORMAL_RET
VDHARH_RECURSIVE_IRET
VDHARH_RECURSIVE_RET
VDHARH_CSEIP_HOOK
VDHARH_RECURSIVE_CSEIP_HOOK
Hook routine interface:
VOID HOOKENTRY fnarm(pRefData, pcrf)
ENTRY pRefData - Pointer to reference data
pcrf - Pointer to client register frame
EXIT None
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT DOS session-task
rc(BOOL) - returns
Success If the function was successful it returns a nonzero value.
Failure If VDHARH_NORMAL_x is already armed, the function returns 0. If HookHandleis invalid, a system halt occurs.
VDHArmReturnHook - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: Any return hooks allocated in the context of the terminating DOS session are deallocated automatically by the DOS Session Manager.
Notes: The VDHARH_NORMAL_RET and VDHARH_RECURSIVE_RET return hook types can be made only after VDHPushFarCallhas been called, but before returning to V86 mode. The return hook types, VDHARH_NORMAL_IRET and VDHARH_RECURSIVE_ IRET, can be made only in the following contexts:
- Within a software interrupt handler set by VDHInstallIntHook
*After VDHPushInthas been called, but before returning to V86 mode
The VDHARH_RECURSIVE_x return types push two extra WORDs on the client's stack before the IRET or RET frame. VDHARH_CSEIP_HOOK and VDHARH_RECURSIVE_ CSEIP_HOOK are meant to be used before a VDHPushIntor VDHPushFarCall, as it is more efficient to do this type of return hook first. Only the normal and recursive CS:EIP hooks will work in DOS session protected mode.
VDHArmReturnHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHArmSTIHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function sets a handler to receive control when the current DOS session enables simulated interrupts. This handler is called only once. If interrupts are already enabled in the DOS session, the handler is called immediately.
#include mvdm.h HHOOK HookHandle; /* Hook handle allocated with VDHAllocHook */ HVDM VDMHandle; /* DOS session handle */ VDHArmSTIHook(HookHandle, VDMHandle);
VDHArmSTIHook - Format
This function sets a handler to receive control when the current DOS session enables simulated interrupts. This handler is called only once. If interrupts are already enabled in the DOS session, the handler is called immediately.
#include mvdm.h HHOOK HookHandle; /* Hook handle allocated with VDHAllocHook */ HVDM VDMHandle; /* DOS session handle */ VDHArmSTIHook(HookHandle, VDMHandle);
VDHArmSTIHook Parameter - HookHandle
HookHandle(HHOOK) Hook handle allocated with VDHAllocHook.
VDHArmSTIHook Parameter - VDMHandle
VDMHandle(HVDM) DOS session handle.
Hook routine interface:
VOID HOOKENTRY fnarm(pRefData, pcrf)
ENTRY pRefData - Pointer to reference data
pcrf - Pointer to client register frame
EXIT None
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT DOS session-task
VDHArmSTIHook - Return Value
Success If the function was successful, it returns nothing.
Failure If either HookHandleor VDMHandleis invalid, or if the hook is already armed, a system halt occurs.
VDHArmSTIHook - Parameters
HookHandle(HHOOK) Hook handle allocated with VDHAllocHook.
VDMHandle(HVDM) DOS session handle.
Hook routine interface:
VOID HOOKENTRY fnarm(pRefData, pcrf)
ENTRY pRefData - Pointer to reference data
pcrf - Pointer to client register frame
EXIT None
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT DOS session-task
Success If the function was successful, it returns nothing.
Failure If either HookHandleor VDMHandleis invalid, or if the hook is already armed, a system halt occurs.
VDHArmSTIHook - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: Any STI hooks allocated in the context of the terminating DOS session are deallocated automatically by the DOS Session Manager.
Notes: Interrupt re-enabling detection is performed when the DOS session runs with IOPL = 0. This causes any instructions that might modify the interrupt flag to fault.
VDHArmSTIHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHArmTimerHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function sets a timer handler to be called after a specified period of time has elapsed. The handler is called only once.
#include mvdm.h HHOOK HookHandle; /* Timer hook handle */ ULONG Duration; /* Duration of the timeout in milliseconds */ HVDM VDMHandle; /* DOS session handle */ VDHArmTimerHook(HookHandle, Duration, VDMHandle);
VDHArmTimerHook - Format
This function sets a timer handler to be called after a specified period of time has elapsed. The handler is called only once.
#include mvdm.h HHOOK HookHandle; /* Timer hook handle */ ULONG Duration; /* Duration of the timeout in milliseconds */ HVDM VDMHandle; /* DOS session handle */ VDHArmTimerHook(HookHandle, Duration, VDMHandle);
VDHArmTimerHook Parameter - HookHandle
HookHandle(HHOOK) Timer hook handle.
VDHArmTimerHook Parameter - Duration
Duration(ULONG) Timer duration in milliseconds.
VDHArmTimerHook Parameter - VDMHandle
VDMHandle(HVDM) DOS session handle.
Possible values are:
DOS Session Handle or 0 When the specified time duration expires, a local context hook is automatically armed by using the specified HookHandle.
VDH_TIMER_GLOBAL_CONTEXT When the specified time duration expires, a global context hook is automatically armed by using the specified HookHandle.
VDH_TIMER_INTERRUPT_HOOK When the specified time duration expires, the timer hook specified by HookHandleis called at interrupt time.
Hook routine interface:
VOID HOOKENTRY pfn(pRefData)
ENTRY pRefData - Pointer to reference data
EXIT None
CONTEXT Interrupt
Note: This hook routine interface is for interrupt-type hooks only.
For context-type hooks, see hook routine interface listed under
VDHArmContextHook.
VDHArmTimerHook - Return Value
Success If the function is successful, it returns nothing.
Failure If either Durationor HookHandleis invalid or the hook is already armed, a system halt occurs.
VDHArmTimerHook - Parameters
HookHandle(HHOOK) Timer hook handle.
Duration(ULONG) Timer duration in milliseconds.
VDMHandle(HVDM) DOS session handle.
Possible values are:
DOS Session Handle or 0 When the specified time duration expires, a local context hook is automatically armed by using the specified HookHandle.
VDH_TIMER_GLOBAL_CONTEXT When the specified time duration expires, a global context hook is automatically armed by using the specified HookHandle.
VDH_TIMER_INTERRUPT_HOOK When the specified time duration expires, the timer hook specified by HookHandleis called at interrupt time.
Hook routine interface:
VOID HOOKENTRY pfn(pRefData)
ENTRY pRefData - Pointer to reference data
EXIT None
CONTEXT Interrupt
Note: This hook routine interface is for interrupt-type hooks only.
For context-type hooks, see hook routine interface listed under
VDHArmContextHook.
Success If the function is successful, it returns nothing.
Failure If either Durationor HookHandleis invalid or the hook is already armed, a system halt occurs.
VDHArmTimerHook - Purpose
Context Issues: This function can be called in the initialization, task, or interrupt context.
DOS Session Terminations: Any timer hooks allocated in the context of the terminating DOS session are deallocated automatically by the DOS Session Manager at DOS session termination.
Notes: If type VDH_TIMER_INTERRUPT_HOOK, the timer handler cannot block since it executes at physical interrupt time.
VDHArmTimerHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHArmVPMBPHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function obtains the address of the DOS session's protected-mode breakpoint allocated by a previous call to VDHAllocHookwith the VDH_BP_ HOOK flag.
#include mvdm.h HHOOK HookHandle; /* Hook handle allocated with VDHAllocHook */ FPFN rc; rc = VDHArmVPMBPHook(HookHandle);
VDHArmVPMBPHook - Format
This function obtains the address of the DOS session's protected-mode breakpoint allocated by a previous call to VDHAllocHookwith the VDH_BP_ HOOK flag.
#include mvdm.h HHOOK HookHandle; /* Hook handle allocated with VDHAllocHook */ FPFN rc; rc = VDHArmVPMBPHook(HookHandle);
VDHArmVPMBPHook Parameter - HookHandle
HookHandle(HHOOK) Hook handle allocated with VDHAllocHook.
The hook routine interface:
VOID HOOKENTRY fnarm(pRefData, pcrf)
ENTRY pRefData - Pointer to hook-specific reference data
pcrf - Pointer to client register frame
EXIT None
CONTEXT DOS session-task
VDHArmVPMBPHook Return Value - rc
rc(FPFN) - returns
Success If the function is successful, it returns a DOS session protected- mode breakpoint address.
Failure If HookHandleis invalid, a system halt occurs.
VDHArmVPMBPHook - Parameters
HookHandle(HHOOK) Hook handle allocated with VDHAllocHook.
The hook routine interface:
VOID HOOKENTRY fnarm(pRefData, pcrf)
ENTRY pRefData - Pointer to hook-specific reference data
pcrf - Pointer to client register frame
EXIT None
CONTEXT DOS session-task
rc(FPFN) - returns
Success If the function is successful, it returns a DOS session protected- mode breakpoint address.
Failure If HookHandleis invalid, a system halt occurs.
VDHArmVPMBPHook - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Unlike other hooks, breakpoint hooks are armed until explicitly disarmed by a call to VDHFreeHook. When the breakpoint address is executed from DOS session protected mode, the hook function is called. Any changes made to the client register frame cause the corresponding registers to take on these values after returning to the DOS session. The pparameter in the hook routine points to the RefDataSizebytes of data allocated by VDHAllocHook.
VDHArmVPMBPHookprovides a raw breakpoint service. On entry to the arm hook function, the client's CS:EIP is randomly set. It is therefore crucial that the virtual device driver's hook handler sets the CS:EIP to a valid address . Typically, the CS:EIP is retrieved from the client's stack through the use of VDHPopStack, which is a low-level service. Appropriate care should be exercised to ensure that the client's CS:EIP and stack remain valid.
The breakpoint address returned will be valid for all DPMI clients within the DOS session. The breakpoint address may be placed in the DPMI application's IDT (see VDHSetVPMIntVector), but will have to be rehooked each time a DPMI task starts (see VDHInstallUserHook).
There must be a protected-mode DPMI client running in the DOS session before calling this function.
VDHArmVPMBPHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHBeginUseVPMStack
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used to switch to the DOS session's protected-mode stack for hardware interrupts, exceptions, and so forth. This service can be called repeatedly, but only the first call will switch stacks. Subsequent calls increment use, count but remain on the VPM stack.
#include mvdm.h VOID ; VDHBeginUseVPMStack();
VDHBeginUseVPMStack - Format
This function is used to switch to the DOS session's protected-mode stack for hardware interrupts, exceptions, and so forth. This service can be called repeatedly, but only the first call will switch stacks. Subsequent calls increment use, count but remain on the VPM stack.
#include mvdm.h VOID ; VDHBeginUseVPMStack();
VDHBeginUseVPMStack Parameter -
None.
VDHBeginUseVPMStack - Return Value
None.
VDHBeginUseVPMStack - Parameters
None.
None.
VDHBeginUseVPMStack - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: There must be a DPMI client running in the DOS session before calling this function.
VDHBeginUseVPMStack - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCallOutDMA
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used by the virtual DMA device driver (VDMA) to check how much DMA transfer has been completed, and to copy the contents from the temporary buffer to the DOS area.
If a virtual device driver owns a DMA channel, it must call the virtual DMA device driver for those interrupts that occur when a DMA request is pending on that channel. This service also indicates when the DOS session is done with the channel so that the channel can be given to another waiting DOS session.
#include mvdm.h VOID ; VDHCallOutDMA();
VDHCallOutDMA - Format
This function is used by the virtual DMA device driver (VDMA) to check how much DMA transfer has been completed, and to copy the contents from the temporary buffer to the DOS area.
If a virtual device driver owns a DMA channel, it must call the virtual DMA device driver for those interrupts that occur when a DMA request is pending on that channel. This service also indicates when the DOS session is done with the channel so that the channel can be given to another waiting DOS session.
#include mvdm.h VOID ; VDHCallOutDMA();
VDHCallOutDMA Parameter -
None.
VDHCallOutDMA - Return Value
None.
VDHCallOutDMA - Parameters
None.
None.
VDHCallOutDMA - Purpose
Context Issues: This function can be called in any context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHCallOutDMA - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHChangeVPMIF
Select an item:
Format Parameters Return Codes Purpose Glossary
This function changes the virtual Interrupt Flag (IF) that enables or disables protected-mode interrupts. This change is reflected in a bit in the flVDMStatuskernel variable (see "Notes" under Purpose). If the STI hooks are waiting and interrupts are enabled, the hooks are called.
#include mvdm.h BOOL SetIFFlag; /* Indicates whether to turn the IF flag on or off */ BOOL rc; rc = VDHChangeVPMIF(SetIFFlag);
VDHChangeVPMIF - Format
This function changes the virtual Interrupt Flag (IF) that enables or disables protected-mode interrupts. This change is reflected in a bit in the flVDMStatuskernel variable (see "Notes" under Purpose). If the STI hooks are waiting and interrupts are enabled, the hooks are called.
#include mvdm.h BOOL SetIFFlag; /* Indicates whether to turn the IF flag on or off */ BOOL rc; rc = VDHChangeVPMIF(SetIFFlag);
VDHChangeVPMIF Parameter - SetIFFlag
SetIFFlag(BOOL) Indicates whether to turn the IF flag ON or OFF. If nonzero, set IF flag to 1 (one). If zero, set IF flag to 0 (zero).
VDHChangeVPMIF Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure Not applicable to this function.
VDHChangeVPMIF - Parameters
SetIFFlag(BOOL) Indicates whether to turn the IF flag ON or OFF. If nonzero, set IF flag to 1 (one). If zero, set IF flag to 0 (zero).
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure Not applicable to this function.
VDHChangeVPMIF - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: The flVDMStatuskernel variable is exported from the kernel. Any virtual device driver can refer to it directly. flVDMStatusis a DD-sized variable that contains various DOS session status flags relating to protected mode and the DOS Protected Mode Interface (DPMI).
The flVDMStatusflags indicate:
- DPMI was initialized (protected mode was enabled)
*16-bit or 32-bit
*The current execution mode (V86 or protected)
These flags and their values are:
VDM_STATUS_VPM_32 0x00000001 /* 32-bit DPMI application */ VDM_STATUS_VPM_APP 0x00000002 /* DPMI application started */ VDM_STATUS_VPM_EXEC 0x00000004 /* In DOS session protected mode*/ VDM_STATUS_VPM_IF_FLAG 0x00000010 /* Virtual IF flag */ VDM_STATUS_VPM_PERM 0x00000080 /* Protected mode allowed? */ VDM_STATUS_VPM_XDOS 0x00000100 /* DOS API extension active? */
VDHChangeVPMIF - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCheckPagePerm
Select an item:
Format Parameters Return Codes Purpose Glossary
This function checks Ring 3 page permissions for a range of pages. This service fails if a Ring 3 client faults on any of the pages that have been checked.
#include mvdm.h
ULONG BasePage; /* Base virtual page number */
PVOID Reserved; /* Reserved; must be set to zero */
ULONG NumPages; /* Number of pages to verify */
ULONG Flag; /* Flag */
BOOL rc;
rc = VDHCheckPagePerm(BasePage, Reserved,
NumPages, Flag);
VDHCheckPagePerm - Format
This function checks Ring 3 page permissions for a range of pages. This service fails if a Ring 3 client faults on any of the pages that have been checked.
#include mvdm.h
ULONG BasePage; /* Base virtual page number */
PVOID Reserved; /* Reserved; must be set to zero */
ULONG NumPages; /* Number of pages to verify */
ULONG Flag; /* Flag */
BOOL rc;
rc = VDHCheckPagePerm(BasePage, Reserved,
NumPages, Flag);
VDHCheckPagePerm Parameter - BasePage
BasePage(ULONG) Base virtual page number.
VDHCheckPagePerm Parameter - Reserved
Reserved(PVOID) Reserved. Must be set to 0.
VDHCheckPagePerm Parameter - NumPages
NumPages(ULONG) Number of pages to verify.
VDHCheckPagePerm Parameter - Flag
Flag(ULONG) Values are:
VPMPG_U Are the pages user-accessible?
VPMPG_W Are the pages writable?
VPMPG_R Are the pages readable (valid)?
VPMPG_X Are the pages executable?
VDHCheckPagePerm Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0.
VDHCheckPagePerm - Parameters
BasePage(ULONG) Base virtual page number.
Reserved(PVOID) Reserved. Must be set to 0.
NumPages(ULONG) Number of pages to verify.
Flag(ULONG) Values are:
VPMPG_U Are the pages user-accessible?
VPMPG_W Are the pages writable?
VPMPG_R Are the pages readable (valid)?
VPMPG_X Are the pages executable?
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0.
VDHCheckPagePerm - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHCheckPagePerm - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCheckVPMIntVector
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns a nonzero value if the application protected-mode interrupt vector is set.
#include mvdm.h ULONG Vector; /* Interrupt vector number */ BOOL rc; rc = VDHCheckVPMIntVector(Vector);
VDHCheckVPMIntVector - Format
This function returns a nonzero value if the application protected-mode interrupt vector is set.
#include mvdm.h ULONG Vector; /* Interrupt vector number */ BOOL rc; rc = VDHCheckVPMIntVector(Vector);
VDHCheckVPMIntVector Parameter - Vector
Vector(ULONG) Interrupt vector number.
VDHCheckVPMIntVector Return Value - rc
rc(BOOL) - returns
Success If the function is successful it returns a nonzero value.
Failure If there is no user-registered interrupt handler for the interrupt in Vector, the function returns 0 (zero).
VDHCheckVPMIntVector - Parameters
Vector(ULONG) Interrupt vector number.
rc(BOOL) - returns
Success If the function is successful it returns a nonzero value.
Failure If there is no user-registered interrupt handler for the interrupt in Vector, the function returns 0 (zero).
VDHCheckVPMIntVector - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: There must be a DPMI client running in the DOS session before calling this function.
VDHCheckVPMIntVector - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHClearVIRR
Select an item:
Format Parameters Return Codes Purpose Glossary
This function clears the virtual Interrupt Request Register (IRR) in the Virtual Programmable Interrupt Controller (VPIC) of the specified DOS session for the IRQ specified. The simulation of interrupts to the specified DOS session is stopped on this IRQ level.
#include mvdm.h HVDM VDMHandle; /* DOS session handle */ HIRQ IRQHandle; /* IRQ handle from VDHOpenVIRQ */ VDHClearVIRR(VDMHandle, IRQHandle);
VDHClearVIRR - Format
This function clears the virtual Interrupt Request Register (IRR) in the Virtual Programmable Interrupt Controller (VPIC) of the specified DOS session for the IRQ specified. The simulation of interrupts to the specified DOS session is stopped on this IRQ level.
#include mvdm.h HVDM VDMHandle; /* DOS session handle */ HIRQ IRQHandle; /* IRQ handle from VDHOpenVIRQ */ VDHClearVIRR(VDMHandle, IRQHandle);
VDHClearVIRR Parameter - VDMHandle
VDMHandle(HVDM) DOS session handle. A value of 0 (zero) indicates the current DOS session.
VDHClearVIRR Parameter - IRQHandle
IRQHandle(HIRQ) IRQ handle from VDHOpenVIRQ.
VDHClearVIRR - Return Value
Success If the function was successful, it returns nothing.
Failure If either of the parameters is invalid, a system halt occurs.
VDHClearVIRR - Parameters
VDMHandle(HVDM) DOS session handle. A value of 0 (zero) indicates the current DOS session.
IRQHandle(HIRQ) IRQ handle from VDHOpenVIRQ.
Success If the function was successful, it returns nothing.
Failure If either of the parameters is invalid, a system halt occurs.
VDHClearVIRR - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHClearVIRR - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHClose
Select an item:
Format Parameters Return Codes Purpose Glossary
This function closes a file or device that was opened with VDHOpen.
#include mvdm.h HFILE FileHandle; /* Handle to the file or device to close */ VDHClose(FileHandle);
VDHClose - Format
This function closes a file or device that was opened with VDHOpen.
#include mvdm.h HFILE FileHandle; /* Handle to the file or device to close */ VDHClose(FileHandle);
VDHClose Parameter - FileHandle
FileHandle(HFILE) Handle (from VDHOpen) to the file or device to close.
VDHClose - Return Value
Success If the function is successful, it returns nothing.
Failure If FileHandleis invalid or if the DOS session is not in the DOS session-task context, a system halt occurs.
VDHClose - Parameters
FileHandle(HFILE) Handle (from VDHOpen) to the file or device to close.
Success If the function is successful, it returns nothing.
Failure If FileHandleis invalid or if the DOS session is not in the DOS session-task context, a system halt occurs.
VDHClose - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: Any handles opened by the virtual device driver for the terminating DOS session must be closed.
VDHClose - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCloseVDD
Select an item:
Format Parameters Return Codes Purpose Glossary
This function closes a virtual device driver/virtual device driver (VDD/VDD ) Inter-Device-Driver Communication (IDC) session that was opened with VDHOpenVDD.
#include mvdm.h HVDD VDDHandle; /* Handle to the file or device to close */ VDHCloseVDD(VDDHandle);
VDHCloseVDD - Format
This function closes a virtual device driver/virtual device driver (VDD/VDD ) Inter-Device-Driver Communication (IDC) session that was opened with VDHOpenVDD.
#include mvdm.h HVDD VDDHandle; /* Handle to the file or device to close */ VDHCloseVDD(VDDHandle);
VDHCloseVDD Parameter - VDDHandle
VDDHandle(HVDD) Handle (from VDHOpenVDD) to the virtual device driver to close.
VDHCloseVDD - Return Value
Success If the function is successful, it returns nothing.
Failure If VDMHandleis invalid, a system halt occurs.
VDHCloseVDD - Parameters
VDDHandle(HVDD) Handle (from VDHOpenVDD) to the virtual device driver to close.
Success If the function is successful, it returns nothing.
Failure If VDMHandleis invalid, a system halt occurs.
VDHCloseVDD - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: If a virtual device driver has a VDD/VDD session for a particular DOS session, that session is closed when the DOS session terminates.
Notes: This service is used to close the type of VDD/VDD connections, which are temporary or are on a per-DOS session basis.
VDHCloseVDD - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCloseVIRQ
Select an item:
Format Parameters Return Codes Purpose Glossary
This function closes the virtual IRQ handle passed to it.
#include mvdm.h HIRQ IRQHandl; /* Handle of the virtual device driver to close */ VDHCloseVIRQ(IRQHandl);
VDHCloseVIRQ - Format
This function closes the virtual IRQ handle passed to it.
#include mvdm.h HIRQ IRQHandl; /* Handle of the virtual device driver to close */ VDHCloseVIRQ(IRQHandl);
VDHCloseVIRQ Parameter - IRQHandl
IRQHandl(HIRQ) Handle to the IRQ (from VDHOpenVIRQ) to close.
VDHCloseVIRQ - Return Value
Success If the function was successful, it returns nothing.
Failure If IRQHandleis invalid, a system halt occurs.
VDHCloseVIRQ - Parameters
IRQHandl(HIRQ) Handle to the IRQ (from VDHOpenVIRQ) to close.
Success If the function was successful, it returns nothing.
Failure If IRQHandleis invalid, a system halt occurs.
VDHCloseVIRQ - Purpose
Context Issues: This function can be called only in the initialization context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHCloseVIRQ - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCopyMem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function copies memory from one user linear address to another.
#include mvdm.h PVOID Source; /* Address of the data to copy */ PVOID Destination; /* Address to copy the data to */ ULONG NumBytes; /* Number of bytes to copy */ VDHCopyMem(Source, Destination, NumBytes);
VDHCopyMem - Format
This function copies memory from one user linear address to another.
#include mvdm.h PVOID Source; /* Address of the data to copy */ PVOID Destination; /* Address to copy the data to */ ULONG NumBytes; /* Number of bytes to copy */ VDHCopyMem(Source, Destination, NumBytes);
VDHCopyMem Parameter - Source
Source(PVOID) Address of the source data to be copied.
VDHCopyMem Parameter - Destination
Destination(PVOID) Address to which the data is to be copied.
VDHCopyMem Parameter - NumBytes
NumBytes(ULONG) Number of bytes to copy.
VDHCopyMem - Return Value
Success If the function is successful, it returns nothing.
Failure If NumBytesis 0 (zero), a system halt occurs.
VDHCopyMem - Parameters
Source(PVOID) Address of the source data to be copied.
Destination(PVOID) Address to which the data is to be copied.
NumBytes(ULONG) Number of bytes to copy.
Success If the function is successful, it returns nothing.
Failure If NumBytesis 0 (zero), a system halt occurs.
VDHCopyMem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Protection faults are handled as if a user application had performed the access. Therefore, writing to an invalid page causes a virtual device driver page fault handler to gain control. If there is no virtual device driver fault handler, a "don't care" page is mapped in at the faulting linear address.
Note that touching invalid pages is allowed only in the context of the DOS session. A virtual device driver cannot touch invalid pages through the HVDM (DOS session Handle) alias region if it is not in the context of that DOS session. A virtual device driver that violates this rule causes a system halt.
This function yields the CPU if it is necessary to ensure that the thread dispatch latency limit is not exceeded. This function also supports overlapping linear regions. However, the results are undefined when copying between regions with aliases (through VDHMapPages) to the same physical page.
If necessary, VDHLockMemis used to ensure that the status of the source and destination linear ranges does not change. This is required only if the source and destination ranges are in private DOS session memory (accessed through the HVDM), and the call to VDHCopyMemis made in the context of some other process.
VDHCopyMem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCreateBlockPool
Select an item:
Format Parameters Return Codes Purpose Glossary
This function creates a pool of memory blocks of a specified size. The blocks are allocated from the system area so that the block addresses are valid in all process contexts.
#include mvdm.h ULONG BlockSize; /* Size of block to initialize (in bytes) */ ULONG OptionFlag; /* Allocation options bit flag */ HBLOCK rc; rc = VDHCreateBlockPool(BlockSize, OptionFlag);
VDHCreateBlockPool - Format
This function creates a pool of memory blocks of a specified size. The blocks are allocated from the system area so that the block addresses are valid in all process contexts.
#include mvdm.h ULONG BlockSize; /* Size of block to initialize (in bytes) */ ULONG OptionFlag; /* Allocation options bit flag */ HBLOCK rc; rc = VDHCreateBlockPool(BlockSize, OptionFlag);
VDHCreateBlockPool Parameter - BlockSize
BlockSize(ULONG) Size of block to initialize (in bytes).
VDHCreateBlockPool Parameter - OptionFlag
OptionFlag(ULONG) Allocation options bit flag. Possible value:
VDHCBP_SWAPPABLE Blocks are allocated from the swappable heap. Otherwise, blocks are allocated from the fixed heap and can be accessed at hardware interrupt time.
VDHCreateBlockPool Return Value - rc
rc(HBLOCK) - returns
Success If the function is successful, it returns a handle to the pool of memory blocks.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If OptionFlagis invalid, or if BlockSizeis equal to 0 (zero), a system halt occurs.
VDHCreateBlockPool - Parameters
BlockSize(ULONG) Size of block to initialize (in bytes).
OptionFlag(ULONG) Allocation options bit flag. Possible value:
VDHCBP_SWAPPABLE Blocks are allocated from the swappable heap. Otherwise, blocks are allocated from the fixed heap and can be accessed at hardware interrupt time.
rc(HBLOCK) - returns
Success If the function is successful, it returns a handle to the pool of memory blocks.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If OptionFlagis invalid, or if BlockSizeis equal to 0 (zero), a system halt occurs.
VDHCreateBlockPool - Purpose
Context Issues: This function can be called in the initialization or task context.
DOS Session Terminations: Any block pools allocated by a virtual device driver for use by the terminating DOS session is freed by using VDHDestroyBlockPool.
VDHCreateBlockPool - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCreateSel
Select an item:
Format Parameters Return Codes Purpose Glossary
This function creates a GDT selector that maps a linear range. This service is used to create a 16:16 pointer, which is passed to a 16-bit physical device driver.
#include mvdm.h PVOID LinearAddress; /* Linear address of the start of the buffer */ ULONG BufferSize; /* Size of the buffer in bytes */ SEL rc; rc = VDHCreateSel(LinearAddress, BufferSize);
VDHCreateSel - Format
This function creates a GDT selector that maps a linear range. This service is used to create a 16:16 pointer, which is passed to a 16-bit physical device driver.
#include mvdm.h PVOID LinearAddress; /* Linear address of the start of the buffer */ ULONG BufferSize; /* Size of the buffer in bytes */ SEL rc; rc = VDHCreateSel(LinearAddress, BufferSize);
VDHCreateSel Parameter - LinearAddress
LinearAddress(PVOID) Linear address of the beginning of the buffer.
VDHCreateSel Parameter - BufferSize
BufferSize(ULONG) Size of the buffer in bytes. The expected range is 0- 65535 with 0 interpreted as 65536.
VDHCreateSel Return Value - rc
rc(SEL) - returns
Success If the function is successful, it returns a nonzero selector value such that SELECTOR:0 points to the first byte of the linear range.
Failure If BufferSizeis greater than 65535 or if there are no more selectors available, a system halt occurs.
VDHCreateSel - Parameters
LinearAddress(PVOID) Linear address of the beginning of the buffer.
BufferSize(ULONG) Size of the buffer in bytes. The expected range is 0- 65535 with 0 interpreted as 65536.
rc(SEL) - returns
Success If the function is successful, it returns a nonzero selector value such that SELECTOR:0 points to the first byte of the linear range.
Failure If BufferSizeis greater than 65535 or if there are no more selectors available, a system halt occurs.
VDHCreateSel - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: Any selectors created to map memory in the terminating DOS session must be destroyed with VDHDestroySel. The virtual device driver must ensure that any physical device driver that was given these selectors is finished with them.
Notes: The linear address must be in system memory. To create a 16:16 pointer to a DOS session address (in the 0 to 1MB+64KB range), use the HVDM (DOS session handle) alias linear address. VDHDestroySelmust be called when finished with this pointer.
VDHCreateSel - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCreateSem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used to create an event or mutex semaphore.
#include mvdm.h PHVDHSEM SemHandlePointer; /* Semaphore handle address */ ULONG SemType; /* Type of semaphore of create */ BOOL rc; rc = VDHCreateSem(SemHandlePointer, SemType);
VDHCreateSem - Format
This function is used to create an event or mutex semaphore.
#include mvdm.h PHVDHSEM SemHandlePointer; /* Semaphore handle address */ ULONG SemType; /* Type of semaphore of create */ BOOL rc; rc = VDHCreateSem(SemHandlePointer, SemType);
VDHCreateSem Parameter - SemHandlePointer
SemHandlePointer(PHVDHSEM) Semaphore handle address.
VDHCreateSem Parameter - SemType
SemType(ULONG) Type of semaphore to create.
Values are:
VDH_EVENTSEM Event semaphore
VDH_MUTEXSEM Mutex semaphore
VDHCreateSem Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value and places a handle to the semaphore in SemHandlePointer.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. An invalid semaphore type causes a system halt to occur.
VDHCreateSem - Parameters
SemHandlePointer(PHVDHSEM) Semaphore handle address.
SemType(ULONG) Type of semaphore to create.
Values are:
VDH_EVENTSEM Event semaphore
VDH_MUTEXSEM Mutex semaphore
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value and places a handle to the semaphore in SemHandlePointer.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. An invalid semaphore type causes a system halt to occur.
VDHCreateSem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: These semaphores are global and are not attached to a specific DOS session. If a virtual device driver maintains semaphores on a per-DOS session basis, it destroys the semaphores by using VDHDestroySemwhen the DOS session they are associated with is terminated.
VDHCreateSem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHDecodeProperty
Select an item:
Format Parameters Return Codes Purpose Glossary
This function decodes the specified format of a property string. (See Notes )
#include mvdm.h
PPSZ ppProperty; /* Pointer to a pointer to property string */
PULONG StartNumberPtr; /* Location to return the starting number */
PULONG EndNumberPtr; /* Location to return the ending number */
ULONG BaseFlag; /* Flag indicating the numeric base to use */
BOOL rc;
rc = VDHDecodeProperty(ppProperty, StartNumberPtr,
EndNumberPtr, BaseFlag);
VDHDecodeProperty - Format
This function decodes the specified format of a property string. (See Notes )
#include mvdm.h
PPSZ ppProperty; /* Pointer to a pointer to property string */
PULONG StartNumberPtr; /* Location to return the starting number */
PULONG EndNumberPtr; /* Location to return the ending number */
ULONG BaseFlag; /* Flag indicating the numeric base to use */
BOOL rc;
rc = VDHDecodeProperty(ppProperty, StartNumberPtr,
EndNumberPtr, BaseFlag);
VDHDecodeProperty Parameter - ppProperty
ppProperty(PPSZ) A pointer to a pointer to the property string to be decoded.
VDHDecodeProperty Parameter - StartNumberPtr
StartNumberPtr(PULONG) Location for storing the returned starting number.
VDHDecodeProperty Parameter - EndNumberPtr
EndNumberPtr(PULONG) Location for storing the returned ending number.
VDHDecodeProperty Parameter - BaseFlag
BaseFlag(ULONG) Flag indicating which numeric base to use:
VDH_DP_DECIMAL Decimal
VDH_DP_HEX Hex
VDHDecodeProperty Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value and the ppPropertypointer is modified to point to the next range in the property string. StartNumberPtrand EndNumberPtrwill have the range values. ppPropertyis returned NULL after processing the last range.
Failure If the function fails, it returns 0, indicating an invalid parameter. If BaseFlagcontains an invalid value or if ppPropertyis NULL, a system halt occurs.
VDHDecodeProperty - Parameters
ppProperty(PPSZ) A pointer to a pointer to the property string to be decoded.
StartNumberPtr(PULONG) Location for storing the returned starting number.
EndNumberPtr(PULONG) Location for storing the returned ending number.
BaseFlag(ULONG) Flag indicating which numeric base to use:
VDH_DP_DECIMAL Decimal
VDH_DP_HEX Hex
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value and the ppPropertypointer is modified to point to the next range in the property string. StartNumberPtrand EndNumberPtrwill have the range values. ppPropertyis returned NULL after processing the last range.
Failure If the function fails, it returns 0, indicating an invalid parameter. If BaseFlagcontains an invalid value or if ppPropertyis NULL, a system halt occurs.
VDHDecodeProperty - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: If a single value is found, EndNumberPtris a -1. All the numbers are decoded in the specified base. A negative sign is used only as range delimiter. Numbers cannot have more than eight digits or a failure is returned. If this service returns Failure, it is still possible that the contents of StartNumberPtror EndNumberPtrmight have changed.
Because pointers passed are from a virtual device driver (not a user), there is no verification of addresses. Bad pointers result in page faults.
This function decodes the specified format of a property string as shown below:
String Syntax = "N1-N2,N3-N4,N5,N6-N7,..."
Notice that Nxare valid numbers in a specified base.
VDHDecodeProperty - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHDestroyBlockPool
Select an item:
Format Parameters Return Codes Purpose Glossary
This function releases a memory block pool.
#include mvdm.h HBLOCK PoolHandle; /* Handle to the memory block pool to release */ HBLOCK rc; rc = VDHDestroyBlockPool(PoolHandle);
VDHDestroyBlockPool - Format
This function releases a memory block pool.
#include mvdm.h HBLOCK PoolHandle; /* Handle to the memory block pool to release */ HBLOCK rc; rc = VDHDestroyBlockPool(PoolHandle);
VDHDestroyBlockPool Parameter - PoolHandle
PoolHandle(HBLOCK) Handle to the memory block pool to release.
VDHDestroyBlockPool Return Value - rc
rc(HBLOCK) - returns
Success If the function was successful, it returns nothing.
Failure An invalid memory block pool handle causes a system halt to occur.
VDHDestroyBlockPool - Parameters
PoolHandle(HBLOCK) Handle to the memory block pool to release.
rc(HBLOCK) - returns
Success If the function was successful, it returns nothing.
Failure An invalid memory block pool handle causes a system halt to occur.
VDHDestroyBlockPool - Purpose
Context Issues: This function can be called in the initialization or task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHDestroyBlockPool - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHDestroySel
Select an item:
Format Parameters Return Codes Purpose Glossary
This function destroys a GDT selector created by VDHCreateSel.
#include mvdm.h SEL GDTSelector; /* GDT selector to destroy */ VDHDestroySel(GDTSelector);
VDHDestroySel - Format
This function destroys a GDT selector created by VDHCreateSel.
#include mvdm.h SEL GDTSelector; /* GDT selector to destroy */ VDHDestroySel(GDTSelector);
VDHDestroySel Parameter - GDTSelector
GDTSelector(SEL) GDT selector to be destroyed.
VDHDestroySel - Return Value
Success If the function is successful, it returns nothing.
Failure If GDTSelectorwas not created by VDHCreateSel, a system halt occurs.
VDHDestroySel - Parameters
GDTSelector(SEL) GDT selector to be destroyed.
Success If the function is successful, it returns nothing.
Failure If GDTSelectorwas not created by VDHCreateSel, a system halt occurs.
VDHDestroySel - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: All selectors created with VDHCreateSelthat map the terminating DOS session must be destroyed.
VDHDestroySel - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHDestroySem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function destroys a semaphore previously created with VDHCreateSem. The semaphore must be posted or unowned before calling this service.
#include mvdm.h HVDHSEM SemHandle; /* Semaphore handle to destroy */ VDHDestroySem(SemHandle);
VDHDestroySem - Format
This function destroys a semaphore previously created with VDHCreateSem. The semaphore must be posted or unowned before calling this service.
#include mvdm.h HVDHSEM SemHandle; /* Semaphore handle to destroy */ VDHDestroySem(SemHandle);
VDHDestroySem Parameter - SemHandle
SemHandle(HVDHSEM) Handle of the semaphore to destroy.
VDHDestroySem - Return Value
Success If the function is successful, it returns nothing.
Failure If SemHandleis invalid or if the semaphore is reset or owned, a system halt occurs.
VDHDestroySem - Parameters
SemHandle(HVDHSEM) Handle of the semaphore to destroy.
Success If the function is successful, it returns nothing.
Failure If SemHandleis invalid or if the semaphore is reset or owned, a system halt occurs.
VDHDestroySem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHDestroySem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHDevBeep
Select an item:
Format Parameters Return Codes Purpose Glossary
This function performs the preempt beep request on behalf of the requesting virtual device driver.
#include mvdm.h ULONG Frequency; /* Frequency of the beep in hertz */ ULONG Duration; /* Duration of the beep in milliseconds */ BOOL rc; rc = VDHDevBeep(Frequency, Duration);
VDHDevBeep - Format
This function performs the preempt beep request on behalf of the requesting virtual device driver.
#include mvdm.h ULONG Frequency; /* Frequency of the beep in hertz */ ULONG Duration; /* Duration of the beep in milliseconds */ BOOL rc; rc = VDHDevBeep(Frequency, Duration);
VDHDevBeep Parameter - Frequency
Frequency(ULONG) Frequency of the beep in hertz.
VDHDevBeep Parameter - Duration
Duration(ULONG) Duration of the beep in milliseconds.
VDHDevBeep Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0.
VDHDevBeep - Parameters
Frequency(ULONG) Frequency of the beep in hertz.
Duration(ULONG) Duration of the beep in milliseconds.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0.
VDHDevBeep - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHDevBeep - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHDevIOCtl
Select an item:
Format Parameters Return Codes Purpose Glossary
This function allows a virtual device driver to send device-specific commands to a physical device driver through the generic IOCtl interface. The parameters and error return codes are identical to the ones found in the DosDevIOCtlAPI. Refer to the OS/2 Control Program Programming Referencefor a complete description of each DosDevIOCtlAPI parameter.
#include mvdm.h
HFILE DevHandle; /* Device handle returned by VDHOpen or VDHPhysicalDisk */
ULONG Category; /* Category of function performed */
ULONG Function; /* Function within category performed */
PVOID ParmList; /* Pointer to command-specific input parameter area */
ULONG ParmLengthMax; /* Maximum size of input parameter area, in bytes */
PULONG ParmLengthInOut; /* Pointer to length of the parameters passed, in bytes */
PVOID DataArea; /* Pointer to the data area */
ULONG DataLengthMax; /* Maximum size of the parameters passed, in bytes */
PULONG DataLengthInOut; /* Pointer to length of the parameters passed, in bytes */
HFILE rc;
rc = VDHDevIOCtl(DevHandle, Category, Function,
ParmList, ParmLengthMax, ParmLengthInOut,
DataArea, DataLengthMax, DataLengthInOut);
VDHDevIOCtl - Format
This function allows a virtual device driver to send device-specific commands to a physical device driver through the generic IOCtl interface. The parameters and error return codes are identical to the ones found in the DosDevIOCtlAPI. Refer to the OS/2 Control Program Programming Referencefor a complete description of each DosDevIOCtlAPI parameter.
#include mvdm.h
HFILE DevHandle; /* Device handle returned by VDHOpen or VDHPhysicalDisk */
ULONG Category; /* Category of function performed */
ULONG Function; /* Function within category performed */
PVOID ParmList; /* Pointer to command-specific input parameter area */
ULONG ParmLengthMax; /* Maximum size of input parameter area, in bytes */
PULONG ParmLengthInOut; /* Pointer to length of the parameters passed, in bytes */
PVOID DataArea; /* Pointer to the data area */
ULONG DataLengthMax; /* Maximum size of the parameters passed, in bytes */
PULONG DataLengthInOut; /* Pointer to length of the parameters passed, in bytes */
HFILE rc;
rc = VDHDevIOCtl(DevHandle, Category, Function,
ParmList, ParmLengthMax, ParmLengthInOut,
DataArea, DataLengthMax, DataLengthInOut);
VDHDevIOCtl Parameter - DevHandle
DevHandle(HFILE) Device handle returned by VDHOpenor VDHPhysicalDisk.
VDHDevIOCtl Parameter - Category
Category(ULONG) Category of function performed.
VDHDevIOCtl Parameter - Function
Function(ULONG) Function within category performed.
VDHDevIOCtl Parameter - ParmList
ParmList(PVOID) Pointer to the command-specific input parameter area.
VDHDevIOCtl Parameter - ParmLengthMax
ParmLengthMax(ULONG) Maximum size of the application input parameter area, in bytes. ParmLengthInOutcan be longer than this on input, but not on output.
VDHDevIOCtl Parameter - ParmLengthInOut
ParmLengthInOut(PULONG) Pointer to the length (in bytes) of the parameters passed by the caller in ParmList.
VDHDevIOCtl Parameter - DataArea
DataArea(PVOID) Pointer to the data area.
VDHDevIOCtl Parameter - DataLengthMax
DataLengthMax(ULONG) Maximum size of the application data area, in bytes.
VDHDevIOCtl Parameter - DataLengthInOut
DataLengthInOut(PULONG) Pointer to the length (in bytes) of the parameters passed by the caller in ParmList. ParmLengthInOutcan be longer than this on input, but not on output.
VDHDevIOCtl Return Value - rc
rc(HFILE) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. VDHGetErrorcan return the following errors:
ERROR_INVALID_HANDLE
ERROR_INVALID_FUNCTION
ERROR_INVALID_CATEGORY
ERROR_INVALID_DRIVE
ERROR_INVALID_PARAMETER.
If the function is called when not at DOS session-task time, a system halt occurs.
VDHDevIOCtl - Parameters
DevHandle(HFILE) Device handle returned by VDHOpenor VDHPhysicalDisk.
Category(ULONG) Category of function performed.
Function(ULONG) Function within category performed.
ParmList(PVOID) Pointer to the command-specific input parameter area.
ParmLengthMax(ULONG) Maximum size of the application input parameter area, in bytes. ParmLengthInOutcan be longer than this on input, but not on output.
ParmLengthInOut(PULONG) Pointer to the length (in bytes) of the parameters passed by the caller in ParmList.
DataArea(PVOID) Pointer to the data area.
DataLengthMax(ULONG) Maximum size of the application data area, in bytes.
DataLengthInOut(PULONG) Pointer to the length (in bytes) of the parameters passed by the caller in ParmList. ParmLengthInOutcan be longer than this on input, but not on output.
rc(HFILE) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. VDHGetErrorcan return the following errors:
ERROR_INVALID_HANDLE
ERROR_INVALID_FUNCTION
ERROR_INVALID_CATEGORY
ERROR_INVALID_DRIVE
ERROR_INVALID_PARAMETER.
If the function is called when not at DOS session-task time, a system halt occurs.
VDHDevIOCtl - Purpose
Context Issues: This function can be called only in the DOS session task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Addresses (pointers) inside device-specific Data or Parameter Packets are not translated.
VDHDevIOCtl - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHDisarmTimerHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function cancels a timer that was installed by VDHArmTimerHookbefore the handler was called.
#include mvdm.h HHOOK TimerHook; /* Handle to the timer hook to disarm */ BOOL rc; rc = VDHDisarmTimerHook(TimerHook);
VDHDisarmTimerHook - Format
This function cancels a timer that was installed by VDHArmTimerHookbefore the handler was called.
#include mvdm.h HHOOK TimerHook; /* Handle to the timer hook to disarm */ BOOL rc; rc = VDHDisarmTimerHook(TimerHook);
VDHDisarmTimerHook Parameter - TimerHook
TimerHook(HHOOK) Handle to the timer hook to disarm.
VDHDisarmTimerHook Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If TimerHookis invalid, a system halt occurs.
VDHDisarmTimerHook - Parameters
TimerHook(HHOOK) Handle to the timer hook to disarm.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If TimerHookis invalid, a system halt occurs.
VDHDisarmTimerHook - Purpose
Context Issues: This function can be called in the initialization, task, or interrupt context.
DOS Session Terminations: Any timer hooks allocated in the context of the terminating DOS session are deallocated automatically by the DOS Session Manager at DOS session termination.
VDHDisarmTimerHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHEndUseVPMStack
Select an item:
Format Parameters Return Codes Purpose Glossary
This function must be called once with every call made to VDHBeginUseVPMStack. It switches back to the original DOS session protected -mode stack when the use count goes to zero.
#include mvdm.h VOID ; VDHEndUseVPMStack();
VDHEndUseVPMStack - Format
This function must be called once with every call made to VDHBeginUseVPMStack. It switches back to the original DOS session protected -mode stack when the use count goes to zero.
#include mvdm.h VOID ; VDHEndUseVPMStack();
VDHEndUseVPMStack Parameter -
None.
VDHEndUseVPMStack - Return Value
None.
VDHEndUseVPMStack - Parameters
None.
None.
VDHEndUseVPMStack - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: There must be a DPMI client running in the DOS session before calling this function.
VDHEndUseVPMStack - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHEnumerateVDMs
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used to run a worker function for each DOS session in the system. The worker function can stop the enumeration by returning 0.
#include mvdm.h PENUMHOOK WorkerFcn; /* Worker function */ ULONG FcnData; /* Function-specific data to be passed each call */ BOOL rc; rc = VDHEnumerateVDMs(WorkerFcn, FcnData);
VDHEnumerateVDMs - Format
This function is used to run a worker function for each DOS session in the system. The worker function can stop the enumeration by returning 0.
#include mvdm.h PENUMHOOK WorkerFcn; /* Worker function */ ULONG FcnData; /* Function-specific data to be passed each call */ BOOL rc; rc = VDHEnumerateVDMs(WorkerFcn, FcnData);
VDHEnumerateVDMs Parameter - WorkerFcn
WorkerFcn(PENUMHOOK) Worker function, the routine that does the work.
The worker function uses the following interface:
BOOL HOOKENTRY fnworker (hVDM, ulData)
ENTRY hVDM - Handle to DOS session
ulData - Function-specific data
EXIT-SUCCESS Return a non-zero value, enumeration continues
EXIT-FAILURE Return 0, stop enumeration
VDHEnumerateVDMs Parameter - FcnData
FcnData(ULONG) Function-specific data to be passed each call.
VDHEnumerateVDMs Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 indicating that a worker function stopped the enumeration.
VDHEnumerateVDMs - Parameters
WorkerFcn(PENUMHOOK) Worker function, the routine that does the work.
The worker function uses the following interface:
BOOL HOOKENTRY fnworker (hVDM, ulData)
ENTRY hVDM - Handle to DOS session
ulData - Function-specific data
EXIT-SUCCESS Return a non-zero value, enumeration continues
EXIT-FAILURE Return 0, stop enumeration
FcnData(ULONG) Function-specific data to be passed each call.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 indicating that a worker function stopped the enumeration.
VDHEnumerateVDMs - Purpose
Context Issues: This function can be called in the task and interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHEnumerateVDMs - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHExchangeMem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function exchanges the contents of two regions of linear address space . Overlapping regions are not supported.
#include mvdm.h PVOID Source; /* Source data address */ PVOID Destination; /* Destination address */ ULONG NumBytes; /* Number of bytes to be exchanged */ BOOL rc; rc = VDHExchangeMem(Source, Destination, NumBytes);
VDHExchangeMem - Format
This function exchanges the contents of two regions of linear address space . Overlapping regions are not supported.
#include mvdm.h PVOID Source; /* Source data address */ PVOID Destination; /* Destination address */ ULONG NumBytes; /* Number of bytes to be exchanged */ BOOL rc; rc = VDHExchangeMem(Source, Destination, NumBytes);
VDHExchangeMem Parameter - Source
Source(PVOID) Address of the source data.
VDHExchangeMem Parameter - Destination
Destination(PVOID) Address of the target region.
VDHExchangeMem Parameter - NumBytes
NumBytes(ULONG) Number of bytes to exchange.
VDHExchangeMem Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHExchangeMem - Parameters
Source(PVOID) Address of the source data.
Destination(PVOID) Address of the target region.
NumBytes(ULONG) Number of bytes to exchange.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHExchangeMem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This function fails if the two memory regions to be exchanged overlap. Protection faults are handled as if a user application had performed the access. Therefore, writing to read-only pages or invalid page -table entries causes a virtual device driver page fault handler to gain control or causes the default behavior (that is, DOS session termination). This function also yields the CPU, if it is necessary to ensure that the thread dispatch latency limit is not exceeded.
VDHExchangeMem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHFindFreePages
Select an item:
Format Parameters Return Codes Purpose Glossary
This function starts at a specified linear address and searches linear memory (up to a specified limit) for the largest free linear memory block. The address and size of the largest region found are returned.
#include mvdm.h PVOID StartAddress; /* Starting address */ PULONG Pages; /* Size of the range (in pages) */ PVOID rc; rc = VDHFindFreePages(StartAddress, Pages);
VDHFindFreePages - Format
This function starts at a specified linear address and searches linear memory (up to a specified limit) for the largest free linear memory block. The address and size of the largest region found are returned.
#include mvdm.h PVOID StartAddress; /* Starting address */ PULONG Pages; /* Size of the range (in pages) */ PVOID rc; rc = VDHFindFreePages(StartAddress, Pages);
VDHFindFreePages Parameter - StartAddress
StartAddress(PVOID) Starting address of the linear memory range to be searched. Must be page-aligned and between 0 and 110000H (1MB+64KB).
VDHFindFreePages Parameter - Pages
Pages(PULONG) On input: The size of the linear memory range to search, in pages.
On output: The size of the region found, in pages.
VDHFindFreePages Return Value - rc
rc(PVOID) - returns
Success If the function is successful, it returns the address of the region found and sets Pagesto the size of the region found (in pages).
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHFindFreePages - Parameters
StartAddress(PVOID) Starting address of the linear memory range to be searched. Must be page-aligned and between 0 and 110000H (1MB+64KB).
Pages(PULONG) On input: The size of the linear memory range to search, in pages.
On output: The size of the region found, in pages.
rc(PVOID) - returns
Success If the function is successful, it returns the address of the region found and sets Pagesto the size of the region found (in pages).
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHFindFreePages - Purpose
Context Issues: This function can be called in the initialization context where it searches only the global linear map. This function can also be called in DOS session-task context (DOS session creation only), where it searches only the DOS session's private linear map.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHFindFreePages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHFreeBlock
Select an item:
Format Parameters Return Codes Purpose Glossary
This function releases a memory block previously allocated by VDHAllocBlock . The memory block is returned to the user's memory block pool for reuse.
#include mvdm.h HBLOCK PoolHandle; /* Handle to a memory block pool */ PVOID BlockToFree; /* Address of the memory block to free */ VDHFreeBlock(PoolHandle, BlockToFree);
VDHFreeBlock - Format
This function releases a memory block previously allocated by VDHAllocBlock . The memory block is returned to the user's memory block pool for reuse.
#include mvdm.h HBLOCK PoolHandle; /* Handle to a memory block pool */ PVOID BlockToFree; /* Address of the memory block to free */ VDHFreeBlock(PoolHandle, BlockToFree);
VDHFreeBlock Parameter - PoolHandle
PoolHandle(HBLOCK) Handle (from VDHCreateBlockPool) to the pool of memory blocks that contains the memory block to free.
VDHFreeBlock Parameter - BlockToFree
BlockToFree(PVOID) Address of the memory block to free.
VDHFreeBlock - Return Value
Success If the function is successful, it returns nothing.
Failure If BlockPoolis not a valid handle to a memory block pool, or if BlockToFreeis not a block allocated from the BlockPoolmemory block pool, a system halt occurs.
VDHFreeBlock - Parameters
PoolHandle(HBLOCK) Handle (from VDHCreateBlockPool) to the pool of memory blocks that contains the memory block to free.
BlockToFree(PVOID) Address of the memory block to free.
Success If the function is successful, it returns nothing.
Failure If BlockPoolis not a valid handle to a memory block pool, or if BlockToFreeis not a block allocated from the BlockPoolmemory block pool, a system halt occurs.
VDHFreeBlock - Purpose
Context Issues: This function can be called in the initialization or task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: The only way to reclaim memory for freed blocks is to call VDHDestroyBlockPool.
VDHFreeBlock - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHFreeDMABuffer
Select an item:
Format Parameters Return Codes Purpose Glossary
This function frees a DMA buffer previously allocated by VDHAllocDMABuffer.
#include mvdm.h PVOID LinearAddress; /* Starting linear address of the DMA buffer */ VDHFreeDMABuffer(LinearAddress);
VDHFreeDMABuffer - Format
This function frees a DMA buffer previously allocated by VDHAllocDMABuffer.
#include mvdm.h PVOID LinearAddress; /* Starting linear address of the DMA buffer */ VDHFreeDMABuffer(LinearAddress);
VDHFreeDMABuffer Parameter - LinearAddress
LinearAddress(PVOID) Starting linear address of the DMA buffer.
VDHFreeDMABuffer - Return Value
Success If the function is successful, it returns nothing.
Failure If LinearAddressis invalid, a system halt occurs.
VDHFreeDMABuffer - Parameters
LinearAddress(PVOID) Starting linear address of the DMA buffer.
Success If the function is successful, it returns nothing.
Failure If LinearAddressis invalid, a system halt occurs.
VDHFreeDMABuffer - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHFreeDMABuffer - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHFreeHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function disarms and frees a hook.
#include mvdm.h HHOOK HookHandle; /* Hook handle from VDHAllocHook */ VDHFreeHook(HookHandle);
VDHFreeHook - Format
This function disarms and frees a hook.
#include mvdm.h HHOOK HookHandle; /* Hook handle from VDHAllocHook */ VDHFreeHook(HookHandle);
VDHFreeHook Parameter - HookHandle
HookHandle(HHOOK) Hook handle (from VDHAllocHook) for the hook to free.
VDHFreeHook - Return Value
Success If the function is successful, it returns nothing.
Failure If HookHandleis invalid, a system halt occurs.
VDHFreeHook - Parameters
HookHandle(HHOOK) Hook handle (from VDHAllocHook) for the hook to free.
Success If the function is successful, it returns nothing.
Failure If HookHandleis invalid, a system halt occurs.
VDHFreeHook - Purpose
Context Issues: This function can be called in the initialization or DOS session-task context.
DOS Session Terminations: Any context hooks allocated in the context of the terminating DOS session are deallocated automatically by the DOS Session Manager.
VDHFreeHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHFreeMem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function frees memory that was previously allocated by VDHAllocMem.
#include mvdm.h PVOID MemAddress; /* Address of the memory block to free */ VDHFreeMem(MemAddress);
VDHFreeMem - Format
This function frees memory that was previously allocated by VDHAllocMem.
#include mvdm.h PVOID MemAddress; /* Address of the memory block to free */ VDHFreeMem(MemAddress);
VDHFreeMem Parameter - MemAddress
MemAddress(PVOID) Address of the memory block to be freed. Pointer is originally obtained from VDHAllocMem.
VDHFreeMem - Return Value
Success If the function is successful, it returns nothing.
Failure If MemAddressis not an address pointer allocated by VDHAllocMem, a system halt occurs.
VDHFreeMem - Parameters
MemAddress(PVOID) Address of the memory block to be freed. Pointer is originally obtained from VDHAllocMem.
Success If the function is successful, it returns nothing.
Failure If MemAddressis not an address pointer allocated by VDHAllocMem, a system halt occurs.
VDHFreeMem - Purpose
Context Issues: This function can be called in the initialization or task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHFreeMem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHFreePages
Select an item:
Format Parameters Return Codes Purpose Glossary
This function frees a memory object. All the memory associated with the memory object is released.
#include mvdm.h PVOID ObjectAddress; /* Address of the memory object to free */ VDHFreePages(ObjectAddress);
VDHFreePages - Format
This function frees a memory object. All the memory associated with the memory object is released.
#include mvdm.h PVOID ObjectAddress; /* Address of the memory object to free */ VDHFreePages(ObjectAddress);
VDHFreePages Parameter - ObjectAddress
ObjectAddress(PVOID) Address of the memory object to free.
VDHFreePages - Return Value
Success If the function is successful, it returns nothing.
Failure If ObjectAddresswas not allocated by VDHAllocPagesor VDHReallocPages, a system halt occurs.
VDHFreePages - Parameters
ObjectAddress(PVOID) Address of the memory object to free.
Success If the function is successful, it returns nothing.
Failure If ObjectAddresswas not allocated by VDHAllocPagesor VDHReallocPages, a system halt occurs.
VDHFreePages - Purpose
Context Issues: This function can be called in the initialization or task context. At initialization time, only global memory can be freed.
DOS Session Terminations: Any allocations made in the terminating DOS session's private area, or on behalf of the terminating DOS session, must be released by using VDHFreePages.
Notes: This function succeeds only if the linear range specified was allocated by a previous call to VDHAllocPagesor VDHReallocPages. Freeing a memory region that was not allocated causes an internal error (a probable system halt).
If the region, starting at ObjectAddress, has been broken into two or more regions by calls to VDHMapPages, then VDHFreePagesis not used.
VDHFreePages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHFreezeVDM
Select an item:
Format Parameters Return Codes Purpose Glossary
This function freezes a DOS session, which prevents it from executing. The specified DOS session is not allowed to execute any V86-mode code until VDHThawVDMis called. This freeze occurs when the specified DOS session leaves kernel mode. The DOS session does not execute any V86-mode code from the time VDHFreezeVDMis called until the matching VDHThawVDMis called.
#include mvdm.h HVDM VDMHandle; /* Handle to the DOS session to freeze */ BOOL rc; rc = VDHFreezeVDM(VDMHandle);
VDHFreezeVDM - Format
This function freezes a DOS session, which prevents it from executing. The specified DOS session is not allowed to execute any V86-mode code until VDHThawVDMis called. This freeze occurs when the specified DOS session leaves kernel mode. The DOS session does not execute any V86-mode code from the time VDHFreezeVDMis called until the matching VDHThawVDMis called.
#include mvdm.h HVDM VDMHandle; /* Handle to the DOS session to freeze */ BOOL rc; rc = VDHFreezeVDM(VDMHandle);
VDHFreezeVDM Parameter - VDMHandle
VDMHandle(HVDM) Handle to the DOS session to freeze.
VDHFreezeVDM Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If VDMHandleis not a valid DOS session handle, a system halt occurs.
VDHFreezeVDM - Parameters
VDMHandle(HVDM) Handle to the DOS session to freeze.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If VDMHandleis not a valid DOS session handle, a system halt occurs.
VDHFreezeVDM - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: The DOS Session Manager thaws a frozen DOS session prior to calling any VDM_TERMINATE user hooks.
Notes: Each DOS session has a freeze count. This count starts at zero when the DOS session is created. Each VDHFreezeVDMcall adds one to this count. Each VDHThawVDMcall subtracts one from this count. The DOS session is frozen when the freeze count is 1 (one) or greater. The DOS session is thawed when the freeze count is 0 (zero). This allows multiple virtual device drivers to perform freeze and thaw operations without inadvertently causing the DOS session to run. If this count exceeds MAX_FREEZE_COUNT, VDHFreezeVDMreturns VDHERR_FROZEN_LIMIT.
VDHFreezeVDM - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHGetCodePageFont
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns the address of the code page font information, if code page support is active and a font is available for the given character cell dimensions.
#include mvdm.h
ULONG CellWidth; /* Width of character cells, in pels */
ULONG CellHeight; /* Height of character cells, in pels */
PPVOID FontAddress; /* Address where font table addresses will be copied */
ULONG rc;
rc = VDHGetCodePageFont(CellWidth, CellHeight,
FontAddress);
VDHGetCodePageFont - Format
This function returns the address of the code page font information, if code page support is active and a font is available for the given character cell dimensions.
#include mvdm.h
ULONG CellWidth; /* Width of character cells, in pels */
ULONG CellHeight; /* Height of character cells, in pels */
PPVOID FontAddress; /* Address where font table addresses will be copied */
ULONG rc;
rc = VDHGetCodePageFont(CellWidth, CellHeight,
FontAddress);
VDHGetCodePageFont Parameter - CellWidth
CellWidth(ULONG) Width of character cells, measured in pels.
VDHGetCodePageFont Parameter - CellHeight
CellHeight(ULONG) Height of character cells, measured in pels.
VDHGetCodePageFont Parameter - FontAddress
FontAddress(PPVOID) Address to which font table addresses will be copied.
VDHGetCodePageFont Return Value - rc
rc(ULONG) - returns
Success If the function is successful, it returns the size of the font table in bytes.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHGetCodePageFont - Parameters
CellWidth(ULONG) Width of character cells, measured in pels.
CellHeight(ULONG) Height of character cells, measured in pels.
FontAddress(PPVOID) Address to which font table addresses will be copied.
rc(ULONG) - returns
Success If the function is successful, it returns the size of the font table in bytes.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHGetCodePageFont - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: If this function was called on behalf of the terminating DOS session, VDHReleaseCodePageFontmust be called to release the fonts.
Notes: System memory can be allocated to hold the font, especially if it is a merged font (that is, merged from two separate font tables). When the virtual device driver is finished with the font, it must call VDHReleaseCodePageFont.
VDHGetCodePageFont - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHGetDirtyPageInfo
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns a bit vector for the dirty pages of a specified DOS session for a specified range of pages. The dirty bits for the range are reset.
#include mvdm.h
HVDM VDMHandle; /* Handle to the DOS session that owns the object */
PVOID StartingAddress; /* Address to start the scan */
ULONG PageRange; /* Range of pages to scan */
ULONG rc;
rc = VDHGetDirtyPageInfo(VDMHandle, StartingAddress,
PageRange);
VDHGetDirtyPageInfo - Format
This function returns a bit vector for the dirty pages of a specified DOS session for a specified range of pages. The dirty bits for the range are reset.
#include mvdm.h
HVDM VDMHandle; /* Handle to the DOS session that owns the object */
PVOID StartingAddress; /* Address to start the scan */
ULONG PageRange; /* Range of pages to scan */
ULONG rc;
rc = VDHGetDirtyPageInfo(VDMHandle, StartingAddress,
PageRange);
VDHGetDirtyPageInfo Parameter - VDMHandle
VDMHandle(HVDM) Handle to the DOS session that owns the object. A 0 (zero) value indicates the current DOS session.
VDHGetDirtyPageInfo Parameter - StartingAddress
StartingAddress(PVOID) Starting address of the range of pages to scan.
VDHGetDirtyPageInfo Parameter - PageRange
PageRange(ULONG) Range (number of pages) to scan. Maximum allowed is 32.
VDHGetDirtyPageInfo Return Value - rc
rc(ULONG) - returns
Success If the function is successful, it returns the bit vector. The low- order bit (that is, bit 0, the rightmost bit) is the dirty bit for the first page scanned. Bit 1 (from the right) is the dirty bit for the next page, and so forth for all the pages scanned.
Failure If any of the input parameters are invalid, a system halt occurs.
VDHGetDirtyPageInfo - Parameters
VDMHandle(HVDM) Handle to the DOS session that owns the object. A 0 (zero) value indicates the current DOS session.
StartingAddress(PVOID) Starting address of the range of pages to scan.
PageRange(ULONG) Range (number of pages) to scan. Maximum allowed is 32.
rc(ULONG) - returns
Success If the function is successful, it returns the bit vector. The low- order bit (that is, bit 0, the rightmost bit) is the dirty bit for the first page scanned. Bit 1 (from the right) is the dirty bit for the next page, and so forth for all the pages scanned.
Failure If any of the input parameters are invalid, a system halt occurs.
VDHGetDirtyPageInfo - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: The virtual dirty bits remain set until cleared by this function, regardless of the swapping activity that has occurred. The actual dirty bits in the page tables are reset whenever a page is swapped to the swap device and brought back into memory. This function is valid only for linear addresses up to 110000H (1MB+64KB) in a DOS session.
VDHGetDirtyPageInfo - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHGetError
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns the error code from the last virtual DevHlp service called.
#include mvdm.h VOID ; ULONG rc; rc = VDHGetError();
VDHGetError - Format
This function returns the error code from the last virtual DevHlp service called.
#include mvdm.h VOID ; ULONG rc; rc = VDHGetError();
VDHGetError Parameter -
None.
VDHGetError Return Value - rc
rc(ULONG) - returns
Success If the function is successful, it returns the error code.
Failure If the function fails, it returns 0, indicating that the last virtual DevHlp call did not have an error.
VDHGetError - Parameters
None.
rc(ULONG) - returns
Success If the function is successful, it returns the error code.
Failure If the function fails, it returns 0, indicating that the last virtual DevHlp call did not have an error.
VDHGetError - Purpose
Context Issues: This function can be called in any context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: The return value is guaranteed to be valid as long as the virtual device driver does not block or yield between the virtual DevHlp service that failed and the call to VDHGetError. VDHGetErrorand VDHSetErrorwork at hardware interrupt time. Each level of interrupt nesting (where task time is Level 0) has a separate error code variable.
VDHGetError - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHGetFlags
Select an item:
Format Parameters Return Codes Purpose Glossary
This function gets the DOS session's EFlags Register.
#include mvdm.h ULONG ulFlagsAddr; /* DOS session flag address. */ VDHGetFlags(ulFlagsAddr);
VDHGetFlags - Format
This function gets the DOS session's EFlags Register.
#include mvdm.h ULONG ulFlagsAddr; /* DOS session flag address. */ VDHGetFlags(ulFlagsAddr);
VDHGetFlags Parameter - ulFlagsAddr
ulFlagsAddr(ULONG) Address of the ULONG in which the EFLAGs value is to be returned.
VDHGetFlags - Return Value
None.
VDHGetFlags - Parameters
ulFlagsAddr(ULONG) Address of the ULONG in which the EFLAGs value is to be returned.
None.
VDHGetFlags - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Virtual device drivers must use this interface instead of the client register frame pointer to change the DOS session's flags. Changes to the interrupt flag and the I/O Privilege Level (IOPL) field must be under the control of 8086 emulation so that VDHArmSTIHookworks correctly.
Getting the Interrupt Flag (IF) must be under 8086 emulation control due to virtual mode extensions and DPMI.
VDHGetFlags - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHGetSelBase
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns the base address for a Local Descriptor Table (LDT) selector.
#include mvdm.h SEL Selector; /* LDT selector */ PULONG pBasePointer; /* Pointer for returned address */ BOOL rc; rc = VDHGetSelBase(Selector, pBasePointer);
VDHGetSelBase - Format
This function returns the base address for a Local Descriptor Table (LDT) selector.
#include mvdm.h SEL Selector; /* LDT selector */ PULONG pBasePointer; /* Pointer for returned address */ BOOL rc; rc = VDHGetSelBase(Selector, pBasePointer);
VDHGetSelBase Parameter - Selector
Selector(SEL) LDT Selector.
VDHGetSelBase Parameter - pBasePointer
pBasePointer(PULONG) Pointer for returned address.
VDHGetSelBase Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value. The base address is returned in the variable pointed to by pBasePointer.
Failure If the function fails, it returns 0 (zero).
VDHGetSelBase - Parameters
Selector(SEL) LDT Selector.
pBasePointer(PULONG) Pointer for returned address.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value. The base address is returned in the variable pointed to by pBasePointer.
Failure If the function fails, it returns 0 (zero).
VDHGetSelBase - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Error checking is performed only to ensure that the selector is allocated.
VDHGetSelBase - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHGetVPMExcept
Select an item:
Format Parameters Return Codes Purpose Glossary
This function gets the current value from the protected-mode exception table.
#include mvdm.h
ULONG Vector; /* Exception vector number */
PFPFN pHandlerAddressPointer; /* Pointer to put handler address */
PBYTE pFlag; /* Pointer to a flag variable */
BOOL rc;
rc = VDHGetVPMExcept(Vector, pHandlerAddressPointer,
pFlag);
VDHGetVPMExcept - Format
This function gets the current value from the protected-mode exception table.
#include mvdm.h
ULONG Vector; /* Exception vector number */
PFPFN pHandlerAddressPointer; /* Pointer to put handler address */
PBYTE pFlag; /* Pointer to a flag variable */
BOOL rc;
rc = VDHGetVPMExcept(Vector, pHandlerAddressPointer,
pFlag);
VDHGetVPMExcept Parameter - Vector
Vector(ULONG) Exception vector number (0-1FH).
VDHGetVPMExcept Parameter - pHandlerAddressPointer
pHandlerAddressPointer(PFPFN) Pointer to put handler address.
VDHGetVPMExcept Parameter - pFlag
pFlag(PBYTE) Pointer to a flag variable for returning the flag value. Possible values are:
VPMXCPT32 A 32-bit handler was registered.
VPMXCPT_REFLECT The exception is reflected back to a V86-mode handler.
VDHGetVPMExcept Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0.
VDHGetVPMExcept - Parameters
Vector(ULONG) Exception vector number (0-1FH).
pHandlerAddressPointer(PFPFN) Pointer to put handler address.
pFlag(PBYTE) Pointer to a flag variable for returning the flag value. Possible values are:
VPMXCPT32 A 32-bit handler was registered.
VPMXCPT_REFLECT The exception is reflected back to a V86-mode handler.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0.
VDHGetVPMExcept - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: There must be a DPMI client running in the DOS session before calling this function.
VDHGetVPMExcept - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHGetVPMIntVector
Select an item:
Format Parameters Return Codes Purpose Glossary
This function gets the application Ring 3 protected-mode interrupt handler. This service is used only for DOS Protected-Mode Interface (DPMI) support.
#include mvdm.h ULONG Vector; /* Interrupt vector number */ PFPFN HandlerAddressPointer; /* Pointer for return of handler address */ BOOL rc; rc = VDHGetVPMIntVector(Vector, HandlerAddressPointer);
VDHGetVPMIntVector - Format
This function gets the application Ring 3 protected-mode interrupt handler. This service is used only for DOS Protected-Mode Interface (DPMI) support.
#include mvdm.h ULONG Vector; /* Interrupt vector number */ PFPFN HandlerAddressPointer; /* Pointer for return of handler address */ BOOL rc; rc = VDHGetVPMIntVector(Vector, HandlerAddressPointer);
VDHGetVPMIntVector Parameter - Vector
Vector(ULONG) Interrupt vector number.
VDHGetVPMIntVector Parameter - HandlerAddressPointer
HandlerAddressPointer(PFPFN) Pointer for return of the handler address.
VDHGetVPMIntVector Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0.
VDHGetVPMIntVector - Parameters
Vector(ULONG) Interrupt vector number.
HandlerAddressPointer(PFPFN) Pointer for return of the handler address.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0.
VDHGetVPMIntVector - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Note:There must be a DPMI client in the DOS session before calling this function.
VDHGetVPMIntVector - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHHaltSystem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function causes a system halt.
#include mvdm.h VOID ; VDHHaltSystem();
VDHHaltSystem - Format
This function causes a system halt.
#include mvdm.h VOID ; VDHHaltSystem();
VDHHaltSystem Parameter -
None.
VDHHaltSystem - Return Value
None.
VDHHaltSystem - Parameters
None.
None.
VDHHaltSystem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Calling VDHHaltSystemis an extremely drastic action. Calling VDHPopupand VDHKillVDMis the preferred method for handling a problem. VDHHaltSystemis used only if the virtual device driver is certain that the entire multiple DOS session environment is inoperable. In general, this function is used only by a base virtual device driver (for example, the virtual video device driver or virtual keyboard device driver), whose absence would render the multiple DOS session environment unusable. VDHPopupis called prior to VDHHaltSystemto tell the user what has happened.
VDHHaltSystem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHHandleFromPID
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns the DOS session handle for a given Process ID.
#include mvdm.h PID ProcessID; /* A DOS session process ID */ HVDM rc; rc = VDHHandleFromPID(ProcessID);
VDHHandleFromPID - Format
This function returns the DOS session handle for a given Process ID.
#include mvdm.h PID ProcessID; /* A DOS session process ID */ HVDM rc; rc = VDHHandleFromPID(ProcessID);
VDHHandleFromPID Parameter - ProcessID
ProcessID(PID) A DOS session Process ID.
VDHHandleFromPID Return Value - rc
rc(HVDM) - returns
Success If the function is successful, it returns the DOS session handle for the Process ID.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHHandleFromPID - Parameters
ProcessID(PID) A DOS session Process ID.
rc(HVDM) - returns
Success If the function is successful, it returns the DOS session handle for the Process ID.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHHandleFromPID - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHHandleFromPID - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHHandleFromSGID
Select an item:
Format Parameters Return Codes Purpose Glossary
This function determines the DOS session handle given the Screen Group ID.
#include mvdm.h SGID ScreenGroupID; /* Screen Group ID */ HVDM rc; rc = VDHHandleFromSGID(ScreenGroupID);
VDHHandleFromSGID - Format
This function determines the DOS session handle given the Screen Group ID.
#include mvdm.h SGID ScreenGroupID; /* Screen Group ID */ HVDM rc; rc = VDHHandleFromSGID(ScreenGroupID);
VDHHandleFromSGID Parameter - ScreenGroupID
ScreenGroupID(SGID) Screen Group ID.
VDHHandleFromSGID Return Value - rc
rc(HVDM) - returns
Success If the function is successful, it returns a handle to the DOS session that was given the Screen Group ID.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHHandleFromSGID - Parameters
ScreenGroupID(SGID) Screen Group ID.
rc(HVDM) - returns
Success If the function is successful, it returns a handle to the DOS session that was given the Screen Group ID.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHHandleFromSGID - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHHandleFromSGID - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHInstallFaultHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function sets a page fault handler for a region of linear address space. The page fault handler receives control when a DOS session touches a page in a reserved region that was invalidated by VDHMapPages. The handler does not get control if the page was indicated "not present" by the Page Manager.
#include mvdm.h
HVDM VDMHandle; /* DOS session handle; 0 = current DOS session */
PVOID StartingAddress; /* Starting linear address */
ULONG Pages; /* Number of pages */
PFAULTHOOK PageFaultHandlerFcnPtr; /* Page fault handler function */
BOOL OptionFlag; /* Options bit flag */
BOOL rc;
rc = VDHInstallFaultHook(VDMHandle, StartingAddress,
Pages, PageFaultHandlerFcnPtr, OptionFlag);
VDHInstallFaultHook - Format
This function sets a page fault handler for a region of linear address space. The page fault handler receives control when a DOS session touches a page in a reserved region that was invalidated by VDHMapPages. The handler does not get control if the page was indicated "not present" by the Page Manager.
#include mvdm.h
HVDM VDMHandle; /* DOS session handle; 0 = current DOS session */
PVOID StartingAddress; /* Starting linear address */
ULONG Pages; /* Number of pages */
PFAULTHOOK PageFaultHandlerFcnPtr; /* Page fault handler function */
BOOL OptionFlag; /* Options bit flag */
BOOL rc;
rc = VDHInstallFaultHook(VDMHandle, StartingAddress,
Pages, PageFaultHandlerFcnPtr, OptionFlag);
VDHInstallFaultHook Parameter - VDMHandle
VDMHandle(HVDM) DOS session handle. If the parameter contains a 0 (zero), use the currently active DOS session.
VDHInstallFaultHook Parameter - StartingAddress
StartingAddress(PVOID) Starting linear address.
VDHInstallFaultHook Parameter - Pages
Pages(ULONG) Number of pages.
VDHInstallFaultHook Parameter - PageFaultHandlerFcnPtr
PageFaultHandlerFcnPtr(PFAULTHOOK) Page fault handler function.
The PageFaultHandlerFcnPtr function pointer contains the address of a function with the following interface:
VOID HOOKENTRY PageFaultHandler(pVDM)
ENTRY PARAMETERS pVDM - Address of the page in which fault occurred
EXIT-SUCCESS None
EXIT-FAILURE None
CONTEXT DOS session-task
VDHInstallFaultHook Parameter - OptionFlag
OptionFlag(BOOL) Options bit flag.
Possible value:
VDHIFH_ADDR If set, pVDM is a byte-granular address. Otherwise, pVDM is a page-granular address.
VDHInstallFaultHook Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetError should be called to determine the nature of the problem. If any of the input parameters are invalid, a system halt occurs.
VDHInstallFaultHook - Parameters
VDMHandle(HVDM) DOS session handle. If the parameter contains a 0 (zero), use the currently active DOS session.
StartingAddress(PVOID) Starting linear address.
Pages(ULONG) Number of pages.
PageFaultHandlerFcnPtr(PFAULTHOOK) Page fault handler function.
The PageFaultHandlerFcnPtr function pointer contains the address of a function with the following interface:
VOID HOOKENTRY PageFaultHandler(pVDM)
ENTRY PARAMETERS pVDM - Address of the page in which fault occurred
EXIT-SUCCESS None
EXIT-FAILURE None
CONTEXT DOS session-task
OptionFlag(BOOL) Options bit flag.
Possible value:
VDHIFH_ADDR If set, pVDM is a byte-granular address. Otherwise, pVDM is a page-granular address.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetError should be called to determine the nature of the problem. If any of the input parameters are invalid, a system halt occurs.
VDHInstallFaultHook - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: Any fault hooks for the terminating DOS session must be released by using VDHRemoveFaultHook.
Notes: In order for the fault handler to terminate the DOS session, it must call VDHKillVDM and return. Page fault hooks are stored on a per-DOS session basis.
VDHInstallFaultHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHInstallIntHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function sets a handler for a V86 interrupt. The virtual device driver 's interrupt handler gets control after any subsequently hooked DOS interrupt handlers.
#include mvdm.h
ULONG Reserved; /* Reserved; must be set to 0 */
ULONG Vector; /* Number of the interrupt vector to hook */
PFNHOOK HookFcn; /* Address of the hook routine */
FLAGS OptionFlag; /* Interface options flag */
BOOL rc;
rc = VDHInstallIntHook(Reserved, Vector, HookFcn,
OptionFlag);
VDHInstallIntHook - Format
This function sets a handler for a V86 interrupt. The virtual device driver 's interrupt handler gets control after any subsequently hooked DOS interrupt handlers.
#include mvdm.h
ULONG Reserved; /* Reserved; must be set to 0 */
ULONG Vector; /* Number of the interrupt vector to hook */
PFNHOOK HookFcn; /* Address of the hook routine */
FLAGS OptionFlag; /* Interface options flag */
BOOL rc;
rc = VDHInstallIntHook(Reserved, Vector, HookFcn,
OptionFlag);
VDHInstallIntHook Parameter - Reserved
Reserved(ULONG) Reserved. Must be set to 0.
VDHInstallIntHook Parameter - Vector
Vector(ULONG) Number of the interrupt vector to hook (0-255).
VDHInstallIntHook Parameter - HookFcn
HookFcn(PFNHOOK) Address of the hook routine.
VDHInstallIntHook Parameter - OptionFlag
OptionFlag(FLAGS) Interface options flag.
Possible values:
VDH_ASM_HOOK Use assembler language hook interface (for the assembler language interface refer to the function VDHInstallIOHook). Otherwise, use the calling convention in the function prototype VDHENTRY found in the MVDM .INC include file, which is included with the Toolkit.
VDH_PRE_HOOK If set, install handler as a pre-reflection hook; that is, call the hook routine before reflecting the interrupt to V86 mode.
C Language Interface for the interrupt hook routine:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY EBX - pcrf - Client register frame pointer ; EXIT If carry flag set, chain to next virtual device driver ; If carry flag clear, don't chain to the next virtual ; device driver ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS Session-task
VDHInstallIntHook Return Value - rc
rc(BOOL) - returns
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If HookFcnis invalid or if Vectoris out of range, a system halt occurs.
VDHInstallIntHook - Parameters
Reserved(ULONG) Reserved. Must be set to 0.
Vector(ULONG) Number of the interrupt vector to hook (0-255).
HookFcn(PFNHOOK) Address of the hook routine.
OptionFlag(FLAGS) Interface options flag.
Possible values:
VDH_ASM_HOOK Use assembler language hook interface (for the assembler language interface refer to the function VDHInstallIOHook). Otherwise, use the calling convention in the function prototype VDHENTRY found in the MVDM .INC include file, which is included with the Toolkit.
VDH_PRE_HOOK If set, install handler as a pre-reflection hook; that is, call the hook routine before reflecting the interrupt to V86 mode.
C Language Interface for the interrupt hook routine:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY EBX - pcrf - Client register frame pointer ; EXIT If carry flag set, chain to next virtual device driver ; If carry flag clear, don't chain to the next virtual ; device driver ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS Session-task
rc(BOOL) - returns
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If HookFcnis invalid or if Vectoris out of range, a system halt occurs.
VDHInstallIntHook - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function. Interrupt hooks are automatically removed during DOS session termination.
Notes: The effect of this service is per-DOS session; the software interrupt handler must be installed as each DOS session is created. The return value from the interrupt hook controls whether the next virtual device driver is chained to or not. An explicit VDHPopIntis needed to remove the software interrupt (so that the ROM code is not executed).
VDHInstallIntHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHInstallIOHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used to install I/O port hooks.
#include mvdm.h
ULONG Reserved; /* Reserved; must be set to 0 */
PORT StartingPort; /* Starting port number */
ULONG NumPorts; /* The number of ports from the starting point */
PIOH IOPortHookEntry; /* Pointer to I/O port hook entry */
FLAGS Flags; /* Indicates interface and trapping options */
BOOL rc;
rc = VDHInstallIOHook(Reserved, StartingPort,
NumPorts, IOPortHookEntry, Flags);
VDHInstallIOHook - Format
This function is used to install I/O port hooks.
#include mvdm.h
ULONG Reserved; /* Reserved; must be set to 0 */
PORT StartingPort; /* Starting port number */
ULONG NumPorts; /* The number of ports from the starting point */
PIOH IOPortHookEntry; /* Pointer to I/O port hook entry */
FLAGS Flags; /* Indicates interface and trapping options */
BOOL rc;
rc = VDHInstallIOHook(Reserved, StartingPort,
NumPorts, IOPortHookEntry, Flags);
VDHInstallIOHook Parameter - Reserved
Reserved(ULONG) Reserved. Must be set to 0 (zero).
VDHInstallIOHook Parameter - StartingPort
StartingPort(PORT) Number of the starting port.
VDHInstallIOHook Parameter - NumPorts
NumPorts(ULONG) The number of ports from the starting port.
VDHInstallIOHook Parameter - IOPortHookEntry
IOPortHookEntry(PIOH) Pointer to I/O port hook entry.
VDHInstallIOHook Parameter - Flags
Flags(FLAGS) Indicates interface and trapping options.
Possible values:
VDHIIH_ASM_HOOK Use assembler language hook interface (register-based). Otherwise, use a C hook interface (stack-based).
VDHIIH_ALWAYS_TRAP Always trap this range of addresses. The virtual device driver cannot call VDHSetIOHookState on any ports in the range.
VDHIIH_NO_SIMULATE Does not change WORD or other I/O handlers to simulation routines; allows WORD handlers for 1-port ranges.
VDHIIH_IGNORE Sets a system handler that does the following:
On WRITES: The OUT succeeds, but no actual I/O is performed.
On READS: The IN succeeds, and always returns -1 (all bits set to 1).
This is also the default behavior of unhooked ports. This behavior is compatible with the behavior of a machine when there is no hardware on a particular I/O address.
VDHInstallIOHook Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If IOPortHookEntryis invalid, or if StartingPortor NumPortsare out of range, a system halt occurs.
VDHInstallIOHook - Parameters
Reserved(ULONG) Reserved. Must be set to 0 (zero).
StartingPort(PORT) Number of the starting port.
NumPorts(ULONG) The number of ports from the starting port.
IOPortHookEntry(PIOH) Pointer to I/O port hook entry.
Flags(FLAGS) Indicates interface and trapping options.
Possible values:
VDHIIH_ASM_HOOK Use assembler language hook interface (register-based). Otherwise, use a C hook interface (stack-based).
VDHIIH_ALWAYS_TRAP Always trap this range of addresses. The virtual device driver cannot call VDHSetIOHookState on any ports in the range.
VDHIIH_NO_SIMULATE Does not change WORD or other I/O handlers to simulation routines; allows WORD handlers for 1-port ranges.
VDHIIH_IGNORE Sets a system handler that does the following:
On WRITES: The OUT succeeds, but no actual I/O is performed.
On READS: The IN succeeds, and always returns -1 (all bits set to 1).
This is also the default behavior of unhooked ports. This behavior is compatible with the behavior of a machine when there is no hardware on a particular I/O address.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If IOPortHookEntryis invalid, or if StartingPortor NumPortsare out of range, a system halt occurs.
VDHInstallIOHook - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function. I/O hooks are automatically removed during DOS session termination.
Notes: This function installs I/O port trap handlers for a contiguous range of I/O addresses. Trapping is initially enabled for the specified ports. The I/O hook entry contains the handlers for each kind of I/O operation. If an entry in the table is NULL, that I/O type is simulated by using a lower I/O type (for example, WORD-I/O is simulated by performing two-byte I/O operations). I/O port hooks are kept on a per-DOS session basis; a virtual device driver generally installs I/O hooks at DOS session creation time.
VDHSetIOHookState can be used to enable or disable I/O trapping on a per- port, per-DOS session basis except when the VDHIIH_ALWAYS_TRAP option is specified. In this case, VDHSetIOHookState cannot be called on any port in the range for the current DOS session.
I/O hooks can take their parameters either from registers or the stack. High-performance hooks take register parameters (the I/O hook router is optimized for this case). Hooks with lower performance requirements take stack parameters, and therefore can be written in the C language.
WordInput, WordOutput and Other hooks can be NULL. In this case, the DOS Session Manager simulates these routines by using the ByteInput and ByteOutput routines. If the ByteInput or ByteOutput handlers are NULL, the DOS Session Manager uses default internal routines that do input and output to the hardware ports. This is most useful when a virtual device driver shadows the hardware state (by trapping OUT instructions) but does not care what is returned by IN instructions.
The client register frame (CRF) is updated as the instructions are simulated. For example, when the string I/O instructions are simulated, the client's EDI/ESI and ECX is incremented or decremented.
In a particular DOS session, a particular I/O port address can be hooked only by a single virtual device driver. If this function fails, no I/O hooks are installed.
The routing of I/O instructions to the supplied port hooks covers the specified range exactly. If an I/O instruction overlaps port address ranges hooked on separate VDHInstallIOHook calls, the instruction is simulated with smaller I/O operations to ensure that the hooks in each range are called correctly. For example, a virtual device driver that hooks 100H-103H , and installs a byte, WORD, and DWORD (other) handler would work as follows:
VDHInstallIOHook (reserved,0x100,4,&iohA,NULL);
The I/O instructions to each address with the length indicated cause the following hooks to be called:
/--------------------------------------------------------------\ |Address |Length |Hooks Called | |---------------+---------------+------------------------------| | 100 | 4 |iohA.Other(100,DWORD) | |---------------+---------------+------------------------------| | 101 | 4 |iohA.Word(101) iohA.Byte(103) | |---------------+---------------+------------------------------| | 102 | 4 |iohA.Word(102) | |---------------+---------------+------------------------------| | 103 | 4 |iohA.Byte(103) | \--------------------------------------------------------------/
VDHRemoveIOHook must be called with identical StartingPort and NumPorts in order to remove these I/O hooks. Port hooks cannot be removed for a subset of the range of ports hooked on the call to VDHInstallIOHook. If the IOPortHookEntry is in instance data, the address passed to VDHInstallIOHook must be the same address passed to VDHRemoveIOHook or VDHSetIOHookState.
Virtual device drivers hook ports in all cases, even if the desired behavior is to act as though direct port access were allowed. This keeps the I/O Permissions Map small. Only a port that requires high performance ( for example, a graphics card) is allowed to go straight through. The existence of such ports increases the size of the I/O Permissions Map in the Task State segment even if SetIOHookState is never called for them.
Interfaces for IOPortHookEntry are as follows:
typedef struct ioh {
PBIH ioh_pbihByteInput;
PBOH ioh_pbohByteOutput;
PWIH ioh_pwihWordInput;
PWOH ioh_pwohWordOutput;
POTH ioh_pothOther;
} IOH;
BYTE HOOKENTRY ByteInput(port, pcrf)
ENTRY port - Port number
pcrf - Client register frame pointer
EXIT Returns data read
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT DOS session-task
BYTE HOOKENTRY ByteOutput(bOutputData, port, pcrf)
ENTRY bOutputData - Data to write
port - Port number
pcrf - Client register frame pointer
EXIT None
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT DOS session-task
USHORT HOOKENTRY WordInput(port, pcrf)
ENTRY port - Port number
pcrf - Client register frame pointer
EXIT Returns data read
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT DOS session-task
USHORT HOOKENTRY WordOutput(usOutputData, port, pcrf)
ENTRY usOutputData - Data to write
port - Port number
pcrf - Client register frame pointer
EXIT None
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT DOS session-task
ULONG HOOKENTRY Other(ulOutputData, pulInputData, port, flType, pcrf)
ENTRY ulOutputData - Data for DWORD writes
pulInputData - Pointer to put input data
port - Port number
flType - I/O type
IO_TYPE_SHIFT - Shift for type
IO_TYPE_MASK - Mask for type
IO_TYPE_INPUT - If set input else output
IO_TYPE_BYTE - If set byte else WORD/DWORD
IO_TYPE_DWORD
IO_TYPE_STRING
IO_TYPE_REVERSE
IO_TYPE_ADDR32
IO_TYPE_REP
IO_SEG_SHIFT - Shift for SEG field
IO_SEG_MASK - Mask for SEG field
IO_SEG_CS
IO_SEG_SS
IO_SEG_ES
IO_SEG_FS
IO_SEG_GS
pcrf - Client register frame pointer
EXIT *pulInputData - Data from DWORD reads
if returns 0, simulate the I/O operation
if returns a nonzero value, I/O is done
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT DOS session-task
NOTES (1) The ASM Other hook does not need the pulInputData
parameter because it returns DWORD input values in EAX,
with the carry flag used to indicate done/simulate. See
"VDHInstallIOHook" in Assembler Language Syntax.
The C hook has to use EAX to return status, and so needs
the additional parameter.
VDHInstallIOHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHInstallUserHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used to set a handler for a specific DOS session event.
#include mvdm.h ULONG Event; /* A DOS session event for which a handler is installed */ PUSERHOOK UserHook; /* User's handler for this event */ BOOL rc; rc = VDHInstallUserHook(Event, UserHook);
VDHInstallUserHook - Format
This function is used to set a handler for a specific DOS session event.
#include mvdm.h ULONG Event; /* A DOS session event for which a handler is installed */ PUSERHOOK UserHook; /* User's handler for this event */ BOOL rc; rc = VDHInstallUserHook(Event, UserHook);
VDHInstallUserHook Parameter - Event
Event(ULONG) A DOS session event (such as DOS session termination).
Possible values are:
VDD_EXIT DOS session support is shutting down
VDM_CREATE DOS session creation
VDM_TERMINATE DOS session termination
VDM_FOREGROUND DOS session to the foreground
VDM_BACKGROUND DOS session to the background
VDM_CREATE_DONE DOS session creation completed successfully
VDM_VDD_CREATE_DONE DOS session virtual device driver creation completed
VDM_PDB_DESTROY DOS Program Data Block (PDB) destroyed in DOS session
VDM_PDB_CHANGE PDB changed in DOS session
VDM_CODEPAGE_CHANGE Code page change event
VDM_TITLE_CHANGE DOS session title change event
VDM_MEMORY_MAPPED_IN Pages mapped into a DOS session (0 to 1MB+64KB)
VDM_MEMORY_UN_MAPPED Pages unmapped from a DOS session (0 to 1MB+64KB).
VDM_BEGIN_VPM_TASK Protected-mode task has started
VDM_END_VPM_TASK Protected-mode task has ended
The interfaces for the UserHookhandlers (depending on the event that is handled) are:
RETCODE HOOKENTRY pfnExit()
ENTRY None
EXIT None
CONTEXT INIT
Task
RETCODE HOOKENTRY pfnCreate(hvdm)
ENTRY hvdm
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
DOS session creation fails; the DOS Session Manager
calls all the VD_TERMINATE hooks for all
virtual device drivers that returned Successful on this
DOS session creation.
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnTerminate(hvdm)
ENTRY hvdm - DOS session being terminated
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnForeground(hvdm)
ENTRY hvdm - DOS session coming foreground
EXIT None
CONTEXT Task
RETCODE HOOKENTRY pfnBackground(hvdm)
ENTRY hvdm - DOS session going background
EXIT None
CONTEXT Task
RETCODE HOOKENTRY pfnCreateDone(hvdm)
ENTRY hvdm
EXIT None
CONTEXT DOS session creation
RETCODE HOOKENTRY pfnVDDCreateDone(hvdm)
ENTRY hvdm
EXIT None
CONTEXT DOS session Creation
RETCODE HOOKENTRY pfnPDBDestroy(hvdm,segPDB)
ENTRY hvdm
segPDB V86 segment of terminating PDB
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnPDBChange(hvdm,segPDB)
ENTRY hvdm
segPDB V86 segment of new PDB
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
VOID HOOKENTRY pfnCodePageChange(ulCodePage)
ENTRY ulCodePage - New code page
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
An error is returned on the set code-page operation, but
the rest of the device-code-page handlers are called.
CONTEXT DOS session-task
VOID HOOKENTRY pfnVDMTitleChange (pszTitle)
ENTRY pszTitle new DOS session Title
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
NOTES 1. This event is called for both full screen and windowed
DOS session.
2. If pszTitle is NULL, the virtual device driver should
treat it as DOS session's default and original title.
3. Ideally there should be only one virtual device driver for this
hook, but this is not a restriction. One of the
virtual device drivers registered is responsible for
putting the title. Only this virtual device driver returns
a nonzero value; all others return 0.
RETCODE HOOKENTRY pfnMemoryMappedIn (hvdm,page,cpages,fl)
ENTRY hvdm
page page address
cpages # of pages mapped in from
the starting page address
fl type of mapping, (see VDHMapPages)
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnMemoryUnMapped (hvdm,page,cpages,fl)
ENTRY hvdm
page page address
cpages # of pages unmapped from the starting page address
fl type of mapping, (see VDHMapPages)
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnBeginVDMTask (hvdm,page,cpages,fl)
ENTRY hvdm
page page address
cpages # of pages unmapped from the starting page address
fl type of mapping, (see VDHMapPages)
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnEndVDMTask (hvdm,page,cpages,fl)
ENTRY hvdm
page page address
cpages # of pages unmapped from the starting page address
fl type of mapping, (see VDHMapPages)
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnBeginVPMTask (hvdm,page,cpages,fl)
ENTRY hvdm
page page address
cpages # of pages unmapped from the starting page address
fl type of mapping, (see VDHMapPages)
EXIT None
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnEndVPMTask (hvdm,page,cpages,fl)
ENTRY hvdm
page page address
cpages # of pages unmapped from the starting page address
fl type of mapping, (see VDHMapPages)
EXIT None
CONTEXT DOS session-task
VDHInstallUserHook Parameter - UserHook
UserHook(PUSERHOOK) A user-defined handler for the event.
VDHInstallUserHook Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, an invalid input parameter or a kernel heap overflow (that is, if the system runs out of memory) causes a system halt.
VDHInstallUserHook - Parameters
Event(ULONG) A DOS session event (such as DOS session termination).
Possible values are:
VDD_EXIT DOS session support is shutting down
VDM_CREATE DOS session creation
VDM_TERMINATE DOS session termination
VDM_FOREGROUND DOS session to the foreground
VDM_BACKGROUND DOS session to the background
VDM_CREATE_DONE DOS session creation completed successfully
VDM_VDD_CREATE_DONE DOS session virtual device driver creation completed
VDM_PDB_DESTROY DOS Program Data Block (PDB) destroyed in DOS session
VDM_PDB_CHANGE PDB changed in DOS session
VDM_CODEPAGE_CHANGE Code page change event
VDM_TITLE_CHANGE DOS session title change event
VDM_MEMORY_MAPPED_IN Pages mapped into a DOS session (0 to 1MB+64KB)
VDM_MEMORY_UN_MAPPED Pages unmapped from a DOS session (0 to 1MB+64KB).
VDM_BEGIN_VPM_TASK Protected-mode task has started
VDM_END_VPM_TASK Protected-mode task has ended
The interfaces for the UserHookhandlers (depending on the event that is handled) are:
RETCODE HOOKENTRY pfnExit()
ENTRY None
EXIT None
CONTEXT INIT
Task
RETCODE HOOKENTRY pfnCreate(hvdm)
ENTRY hvdm
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
DOS session creation fails; the DOS Session Manager
calls all the VD_TERMINATE hooks for all
virtual device drivers that returned Successful on this
DOS session creation.
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnTerminate(hvdm)
ENTRY hvdm - DOS session being terminated
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnForeground(hvdm)
ENTRY hvdm - DOS session coming foreground
EXIT None
CONTEXT Task
RETCODE HOOKENTRY pfnBackground(hvdm)
ENTRY hvdm - DOS session going background
EXIT None
CONTEXT Task
RETCODE HOOKENTRY pfnCreateDone(hvdm)
ENTRY hvdm
EXIT None
CONTEXT DOS session creation
RETCODE HOOKENTRY pfnVDDCreateDone(hvdm)
ENTRY hvdm
EXIT None
CONTEXT DOS session Creation
RETCODE HOOKENTRY pfnPDBDestroy(hvdm,segPDB)
ENTRY hvdm
segPDB V86 segment of terminating PDB
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnPDBChange(hvdm,segPDB)
ENTRY hvdm
segPDB V86 segment of new PDB
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
VOID HOOKENTRY pfnCodePageChange(ulCodePage)
ENTRY ulCodePage - New code page
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
An error is returned on the set code-page operation, but
the rest of the device-code-page handlers are called.
CONTEXT DOS session-task
VOID HOOKENTRY pfnVDMTitleChange (pszTitle)
ENTRY pszTitle new DOS session Title
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
NOTES 1. This event is called for both full screen and windowed
DOS session.
2. If pszTitle is NULL, the virtual device driver should
treat it as DOS session's default and original title.
3. Ideally there should be only one virtual device driver for this
hook, but this is not a restriction. One of the
virtual device drivers registered is responsible for
putting the title. Only this virtual device driver returns
a nonzero value; all others return 0.
RETCODE HOOKENTRY pfnMemoryMappedIn (hvdm,page,cpages,fl)
ENTRY hvdm
page page address
cpages # of pages mapped in from
the starting page address
fl type of mapping, (see VDHMapPages)
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnMemoryUnMapped (hvdm,page,cpages,fl)
ENTRY hvdm
page page address
cpages # of pages unmapped from the starting page address
fl type of mapping, (see VDHMapPages)
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnBeginVDMTask (hvdm,page,cpages,fl)
ENTRY hvdm
page page address
cpages # of pages unmapped from the starting page address
fl type of mapping, (see VDHMapPages)
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnEndVDMTask (hvdm,page,cpages,fl)
ENTRY hvdm
page page address
cpages # of pages unmapped from the starting page address
fl type of mapping, (see VDHMapPages)
EXIT-SUCCESS Return a nonzero value
EXIT-FAILURE Return 0
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnBeginVPMTask (hvdm,page,cpages,fl)
ENTRY hvdm
page page address
cpages # of pages unmapped from the starting page address
fl type of mapping, (see VDHMapPages)
EXIT None
CONTEXT DOS session-task
RETCODE HOOKENTRY pfnEndVPMTask (hvdm,page,cpages,fl)
ENTRY hvdm
page page address
cpages # of pages unmapped from the starting page address
fl type of mapping, (see VDHMapPages)
EXIT None
CONTEXT DOS session-task
UserHook(PUSERHOOK) A user-defined handler for the event.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, an invalid input parameter or a kernel heap overflow (that is, if the system runs out of memory) causes a system halt.
VDHInstallUserHook - Purpose
Context Issues: This function can be called only in the initialization context.
DOS Sessions Terminations: The VDM_TERMINATE hook is called at DOS session termination. In the case of a partially created DOS session, the VDM_ TERMINATE handler is called only if all the registered VDM_CREATE handlers are called successfully. Partially created DOS sessions might occur when, for example, the Create_Handlerfor Virtual Device Driver A returned successfully, but the Create_Handlerfor Virtual Device Driver B failed. In this case, the Terminate_Handlerfor Virtual Device Driver A will not be called. This should be taken into consideration when deciding what to do in a Create_Handlerand a Create_Done_Handler.
VDHInstallUserHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHIsVDMFrozen
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns the freeze state of a DOS session.
#include mvdm.h HVDM VDMHandle; /* Handle to the DOS session */ BOOL rc; rc = VDHIsVDMFrozen(VDMHandle);
VDHIsVDMFrozen - Format
This function returns the freeze state of a DOS session.
#include mvdm.h HVDM VDMHandle; /* Handle to the DOS session */ BOOL rc; rc = VDHIsVDMFrozen(VDMHandle);
VDHIsVDMFrozen Parameter - VDMHandle
VDMHandle(HVDM) Handle to the DOS session in question.
VDHIsVDMFrozen Return Value - rc
rc(BOOL) - returns
Success If the DOS session is not frozen, the function returns 0 (zero). Otherwise, the function returns a nonzero value indicating the DOS session' s freeze count.
Failure If VDMHandleis an invalid DOS session handle, a system halt occurs .
VDHIsVDMFrozen - Parameters
VDMHandle(HVDM) Handle to the DOS session in question.
rc(BOOL) - returns
Success If the DOS session is not frozen, the function returns 0 (zero). Otherwise, the function returns a nonzero value indicating the DOS session' s freeze count.
Failure If VDMHandleis an invalid DOS session handle, a system halt occurs .
VDHIsVDMFrozen - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: See VDHFreezeVDMfor a full discussion of freeze counting.
VDHIsVDMFrozen - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHKillVDM
Select an item:
Format Parameters Return Codes Purpose Glossary
This function terminates the DOS session at the earliest opportunity. V86 code is no longer executed in the context of the terminated DOS session.
#include mvdm.h HVDM VDMHandle; /* Handle to the DOS session to terminate */ VDHKillVDM(VDMHandle);
VDHKillVDM - Format
This function terminates the DOS session at the earliest opportunity. V86 code is no longer executed in the context of the terminated DOS session.
#include mvdm.h HVDM VDMHandle; /* Handle to the DOS session to terminate */ VDHKillVDM(VDMHandle);
VDHKillVDM Parameter - VDMHandle
VDMHandle(HVDM) Handle to the DOS session to terminate. A value of 0 (zero ) indicates the current DOS session.
VDHKillVDM - Return Value
Success If the function is successful, it returns nothing.
Failure If VDMHandleis not a valid DOS session handle, a system halt occurs.
VDHKillVDM - Parameters
VDMHandle(HVDM) Handle to the DOS session to terminate. A value of 0 (zero ) indicates the current DOS session.
Success If the function is successful, it returns nothing.
Failure If VDMHandleis not a valid DOS session handle, a system halt occurs.
VDHKillVDM - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: When a DOS session is terminating, all virtual device drivers that registered a VDM_TERMINATE hook by using VDHInstallUserHookare called.
Notes: This function sets a flag and returns. If the calling virtual device driver is in the context of the DOS session to be terminated, it must return to its caller in order for the termination to occur.
VDHKillVDM - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHLockMem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function verifies that a specified region is accessible in the requested manner, and locks the memory in the requested manner.
#include mvdm.h
PVOID StartingLinAddr; /* Starting address of region in user process */
ULONG NumBytes; /* The size of the region to lock, in bytes. */
ULONG OptionFlag; /* Access option flags */
ULONG PagelistArrayPtr; /* Pointer to array of VDHPageList_s structures */
ULONG ArrayCountPtr; /* Points to count of VDHPageList_selements */
HLOCK rc;
rc = VDHLockMem(StartingLinAddr, NumBytes,
OptionFlag, PagelistArrayPtr, ArrayCountPtr);
VDHLockMem - Format
This function verifies that a specified region is accessible in the requested manner, and locks the memory in the requested manner.
#include mvdm.h
PVOID StartingLinAddr; /* Starting address of region in user process */
ULONG NumBytes; /* The size of the region to lock, in bytes. */
ULONG OptionFlag; /* Access option flags */
ULONG PagelistArrayPtr; /* Pointer to array of VDHPageList_s structures */
ULONG ArrayCountPtr; /* Points to count of VDHPageList_selements */
HLOCK rc;
rc = VDHLockMem(StartingLinAddr, NumBytes,
OptionFlag, PagelistArrayPtr, ArrayCountPtr);
VDHLockMem Parameter - StartingLinAddr
StartingLinAddr(PVOID) Starting linear address of the region in the user process that is to be locked.
VDHLockMem Parameter - NumBytes
NumBytes(ULONG) Size in bytes of the region to lock.
VDHLockMem Parameter - OptionFlag
OptionFlag(ULONG) Used to set access options for the locked region. The VDHLM_READ and VDHLM_WRITE flags are for verification purposes and are not mixed with the VDHLM_RESIDENT flag. Either the VDHLM_READ, VDHLM_WRITE, or VDHLM_RESIDENT flag must be used. Note that VDHLM_RESIDENT cannot be combined with other flags.
Possible values are:
VDHLM_RESIDENT Lock physical pages.
VDHLM_READ Verify read access. VDHLM_READ is a verify lock, and is not mixed with other flags. Nonverify locks always make the region resident.
VDHLM_WRITE Verify write access. VDHLM_WRITE is a verify lock, and is not mixed with other flags. Nonverify locks always make the region resident.
VDHLM_CONTIGUOUS Force physical pages contiguous; can be used only for 64KB or less.
VDHLM_NOBLOCK Lock must not give up the CPU.
VDHLM_16M Must reside below the 16MB physical memory address.
VDHLockMem Parameter - PagelistArrayPtr
PagelistArrayPtr(ULONG) Pointer to array of VDHPageList_s structures.
VDHLockMemfills this array. Each VDHPageList_sstructure describes a single physically contiguous sub-area of the physical memory that was locked. If PagelistArrayPtris set to VDHLM_NO_ADDR, no array is returned. The area that PagelistArrayPtrpoints to must contain enough VDHPageList_sstructures to handle a worst case of one structure per page plus one more structure, that is, the region does not begin on a page boundary.
VDHLockMem Parameter - ArrayCountPtr
ArrayCountPtr(ULONG) Pointer to a variable where a count of the number of elements returned in the PagelistArrayPtrarray is placed by VDHLockMem. If PagelistArrayPtris set to VDHLM_NO_ADDR, ArrayCountPtris ignored.
VDHLockMem Return Value - rc
rc(HLOCK) - returns
Success If the function is successful, it returns a lock handle. This is a global handle that can be used in any task context.
Failure If the function fails, it returns 0. If the function fails, call VDHGetErrorto determine the nature of the problem. If NumBytesequals 0, a system halt occurs.
VDHLockMem - Parameters
StartingLinAddr(PVOID) Starting linear address of the region in the user process that is to be locked.
NumBytes(ULONG) Size in bytes of the region to lock.
OptionFlag(ULONG) Used to set access options for the locked region. The VDHLM_READ and VDHLM_WRITE flags are for verification purposes and are not mixed with the VDHLM_RESIDENT flag. Either the VDHLM_READ, VDHLM_WRITE, or VDHLM_RESIDENT flag must be used. Note that VDHLM_RESIDENT cannot be combined with other flags.
Possible values are:
VDHLM_RESIDENT Lock physical pages.
VDHLM_READ Verify read access. VDHLM_READ is a verify lock, and is not mixed with other flags. Nonverify locks always make the region resident.
VDHLM_WRITE Verify write access. VDHLM_WRITE is a verify lock, and is not mixed with other flags. Nonverify locks always make the region resident.
VDHLM_CONTIGUOUS Force physical pages contiguous; can be used only for 64KB or less.
VDHLM_NOBLOCK Lock must not give up the CPU.
VDHLM_16M Must reside below the 16MB physical memory address.
PagelistArrayPtr(ULONG) Pointer to array of VDHPageList_s structures.
VDHLockMemfills this array. Each VDHPageList_sstructure describes a single physically contiguous sub-area of the physical memory that was locked. If PagelistArrayPtris set to VDHLM_NO_ADDR, no array is returned. The area that PagelistArrayPtrpoints to must contain enough VDHPageList_sstructures to handle a worst case of one structure per page plus one more structure, that is, the region does not begin on a page boundary.
ArrayCountPtr(ULONG) Pointer to a variable where a count of the number of elements returned in the PagelistArrayPtrarray is placed by VDHLockMem. If PagelistArrayPtris set to VDHLM_NO_ADDR, ArrayCountPtris ignored.
rc(HLOCK) - returns
Success If the function is successful, it returns a lock handle. This is a global handle that can be used in any task context.
Failure If the function fails, it returns 0. If the function fails, call VDHGetErrorto determine the nature of the problem. If NumBytesequals 0, a system halt occurs.
VDHLockMem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function. There cannot be any memory locked on behalf of a particular DOS session.
Notes: The caller must call VDHUnlockMemto remove this lock. All locks are long-term. This function must be used prior to using any pointers passed to a virtual device driver from an OS/2 process (through DOSRequestVDD). This might also be useful to the callers of VDHCopyMemand VDHExchangeMem.
VDHMapPages, VDHReallocPages, and VDHFreePageswill block if applied to pages that are locked. They unblock when the lock is released.
VDHLockMem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHMapPages
Select an item:
Format Parameters Return Codes Purpose Glossary
This function maps a linear address region in the V86 address space.
#include mvdm.h
PVDHMAPSOURCE pvdhmsSourceRegion; /* Pointer to source region definition */
PVDHMAPTARGET pvdhmtTargetRegion; /* Target region definition */
ULONG flMappingFlag; /* Mapping options flag */
BOOL rc;
rc = VDHMapPages(pvdhmsSourceRegion, pvdhmtTargetRegion,
flMappingFlag);
VDHMapPages - Format
This function maps a linear address region in the V86 address space.
#include mvdm.h
PVDHMAPSOURCE pvdhmsSourceRegion; /* Pointer to source region definition */
PVDHMAPTARGET pvdhmtTargetRegion; /* Target region definition */
ULONG flMappingFlag; /* Mapping options flag */
BOOL rc;
rc = VDHMapPages(pvdhmsSourceRegion, pvdhmtTargetRegion,
flMappingFlag);
VDHMapPages Parameter - pvdhmsSourceRegion
pvdhmsSourceRegion(PVDHMAPSOURCE) Pointer to VDHMAPSOURCE structure.
VDHMAPSOURCE is the source region definition for VDHMapPageswith a data structure as follows:
typedef struct VDHMapSource_s {
ULONG vdhms_laddr; /* Source linear address of source */
/* memory object. Source address */
/* to be mapped. Defines the start*/
/* of the source region for the */
/* mapping. The region is the same*/
/* length as the target region. */
ULONG vdhms_hobj; /* Memory object handle set by the */
/* service to hold a source handle */
/* for VDHMT_LINEAR mappings. */
/* See the VDHMT_LINEAR */
/* description under MappingFlag. */
} VDHMAPSOURCE;
typedef VDHMAPSOURCE *PVDHMAPSOURCE;
VDHMapPages Parameter - pvdhmtTargetRegion
pvdhmtTargetRegion(PVDHMAPTARGET) Target region definition. Pointer to VDHMAPTARGET structure.
VDHMAPTARGET is the target region definition for VDHMapPageswith a data structure as follows:
typedef struct VDHMapTarget_s {
ULONG vdhmt_laddr; /* Address in V86-space to be */
/* mapped. */
/* (0 <= vdhmt_laddr < 1MB+64KB) */
ULONG vdhmt_cpg; /* Count of pages to map. */
ULONG vdhmt_hmap; /* Mapping handle. Must be zero on */
/* the first call to VDHMapPages */
/* for region. Set by the service */
/* to hold a handle used for */
/* remapping the region. The handle*/
/* is reset each time it is used. */
/* vdhmt_hmap must be the value */
/* returned from the previous */
/* VDHMapPages call for the region */
/* unless the pages are either */
/* already invalid or else are */
/* being made invalid. If either */
/* the old or new mapping is */
/* invalid pages, vdhmt_hmap can */
/* be 0. */
/* Making a region invalid restores*/
/* pages in the region to their */
/* reserved state, and sets */
/* vdhmt_hmap to 0. */
} VDHMAPTARGET;
typedef VDHMAPTARGET *PVDHMAPTARGET;
VDHMapPages Parameter - flMappingFlag
flMappingFlag(ULONG) Mapping options flag.
Possible values are:
VDHMT_INVALID Make target region pages invalid. vdhmt_hmapcan be 0 (zero). This service is faster when the handle is provided, but virtual device drivers that do not store handles can map to invalid before remapping a region. Note that pvdhmsSourceRegionis ignored.
VDHMT_LINEAR Map linear source region into target region. vdhms_laddrcontains the linear address to map at the start of the target region. This can only be a page-granular address in a memory allocation that was obtained by using VDHAllocPagesor VDHReallocPages. After a successful mapping, the target region aliases the corresponding region of the source.
vdhms_hobjmust be 0 (zero) the first time a newly allocated or reallocated source object is mapped. On a successful mapping, vdhms_hobjis filled in. Using this handle on the next mapping that uses the same source object speeds up that mapping call. Any linear address (laddr) at the start of the target region can be mapped using the handle. The returned result must be stored after each mapping call. Virtual device drivers can avoid storing this handle and always use 0 (zero), however, the call will be slower.
VDHMT_PHYSICAL Map physical source region into target region. vdhms_laddrcontains the physical address to map at the start of the target region. vdhms_hobjis ignored.
VDHMT_BLACK_HOLE Map target region to black hole pages. pvdhmsSourceRegionis ignored.
VDHMapPages Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHMapPages - Parameters
pvdhmsSourceRegion(PVDHMAPSOURCE) Pointer to VDHMAPSOURCE structure.
VDHMAPSOURCE is the source region definition for VDHMapPageswith a data structure as follows:
typedef struct VDHMapSource_s {
ULONG vdhms_laddr; /* Source linear address of source */
/* memory object. Source address */
/* to be mapped. Defines the start*/
/* of the source region for the */
/* mapping. The region is the same*/
/* length as the target region. */
ULONG vdhms_hobj; /* Memory object handle set by the */
/* service to hold a source handle */
/* for VDHMT_LINEAR mappings. */
/* See the VDHMT_LINEAR */
/* description under MappingFlag. */
} VDHMAPSOURCE;
typedef VDHMAPSOURCE *PVDHMAPSOURCE;
pvdhmtTargetRegion(PVDHMAPTARGET) Target region definition. Pointer to VDHMAPTARGET structure.
VDHMAPTARGET is the target region definition for VDHMapPageswith a data structure as follows:
typedef struct VDHMapTarget_s {
ULONG vdhmt_laddr; /* Address in V86-space to be */
/* mapped. */
/* (0 <= vdhmt_laddr < 1MB+64KB) */
ULONG vdhmt_cpg; /* Count of pages to map. */
ULONG vdhmt_hmap; /* Mapping handle. Must be zero on */
/* the first call to VDHMapPages */
/* for region. Set by the service */
/* to hold a handle used for */
/* remapping the region. The handle*/
/* is reset each time it is used. */
/* vdhmt_hmap must be the value */
/* returned from the previous */
/* VDHMapPages call for the region */
/* unless the pages are either */
/* already invalid or else are */
/* being made invalid. If either */
/* the old or new mapping is */
/* invalid pages, vdhmt_hmap can */
/* be 0. */
/* Making a region invalid restores*/
/* pages in the region to their */
/* reserved state, and sets */
/* vdhmt_hmap to 0. */
} VDHMAPTARGET;
typedef VDHMAPTARGET *PVDHMAPTARGET;
flMappingFlag(ULONG) Mapping options flag.
Possible values are:
VDHMT_INVALID Make target region pages invalid. vdhmt_hmapcan be 0 (zero). This service is faster when the handle is provided, but virtual device drivers that do not store handles can map to invalid before remapping a region. Note that pvdhmsSourceRegionis ignored.
VDHMT_LINEAR Map linear source region into target region. vdhms_laddrcontains the linear address to map at the start of the target region. This can only be a page-granular address in a memory allocation that was obtained by using VDHAllocPagesor VDHReallocPages. After a successful mapping, the target region aliases the corresponding region of the source.
vdhms_hobjmust be 0 (zero) the first time a newly allocated or reallocated source object is mapped. On a successful mapping, vdhms_hobjis filled in. Using this handle on the next mapping that uses the same source object speeds up that mapping call. Any linear address (laddr) at the start of the target region can be mapped using the handle. The returned result must be stored after each mapping call. Virtual device drivers can avoid storing this handle and always use 0 (zero), however, the call will be slower.
VDHMT_PHYSICAL Map physical source region into target region. vdhms_laddrcontains the physical address to map at the start of the target region. vdhms_hobjis ignored.
VDHMT_BLACK_HOLE Map target region to black hole pages. pvdhmsSourceRegionis ignored.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHMapPages - Purpose
This function maps a linear address region in the V86 address space to:
- Part of a virtual memory object
*Specific physical addresses (for physical devices)
*Undefined memory (black holes)
*Invalid pages (the unmapped state, which is the default state for reserved pages)
VDHMapPagesalso changes the virtual address contents of regions in the V86 address space (below 11000H (1MB+64KB)). Pages in this range can be made to address:
- Part of a memory object previously allocated using VDHAllocPagesor VDHReallocPages
*Physical addresses for a device
*Black hole (undefined memory) addresses that are read or written but do not retain their values
*Invalid pages, which cause faults when accessed (see VDHInstallFaultHook)
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Mapping succeeds only if it completely replaces a previous mapping, or if the region contains only invalid pages. To change the size of a region, it must first be made invalid. The entire target region must lie below 11000H (1MB+64KB) and must be contained in pages previously reserved by VDHReservePages. VDHMapPagesand VDHAllocPagescan be used on the same target region but care must be taken. Before switching from one service to the other, the pages affected must first be made invalid. If pages are left invalid, a pagefault handler must be registered (through VDHInstallFaultHook) to handle page faults, in case the pages are accessed.
Both target and source addresses must be on page boundaries. If they are not, the page offset part of the address is ignored.
VDHMapPages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHOpen
Select an item:
Format Parameters Return Codes Purpose Glossary
This function opens a file or device and returns a handle. The handle can be used with VDHRead, VDHWrite, VDHSeek, VDHClose,and VDHDevIOCtl. The parameters and error return codes are the same as those found in the DosOpenAPI. Refer to the OS/2 Control Program Programming Referencefor a complete descriptions of each DosOpenAPI parameter.
#include mvdm.h
PSZ FileName; /* Pointer to the name of the file or device to open */
PHFILE FileHandle; /* Where the system returns the file handle */
PULONG ActionTaken; /* Where a description of the action taken is returned */
ULONG FileSize; /* The new file's logical size (EOD) in bytes */
ULONG FileAttribute; /* File attribute bits used on file creation */
ULONG OpenFLag; /* Specifies action taken, based on whether file exists */
ULONG OpenMode; /* Describes the mode of the Open function */
PVDH_EOAP EABuf; /* Address of a VDH_EAOP structure or NULL */
BOOL rc;
rc = VDHOpen(FileName, FileHandle, ActionTaken,
FileSize, FileAttribute, OpenFLag,
OpenMode, EABuf);
VDHOpen - Format
This function opens a file or device and returns a handle. The handle can be used with VDHRead, VDHWrite, VDHSeek, VDHClose,and VDHDevIOCtl. The parameters and error return codes are the same as those found in the DosOpenAPI. Refer to the OS/2 Control Program Programming Referencefor a complete descriptions of each DosOpenAPI parameter.
#include mvdm.h
PSZ FileName; /* Pointer to the name of the file or device to open */
PHFILE FileHandle; /* Where the system returns the file handle */
PULONG ActionTaken; /* Where a description of the action taken is returned */
ULONG FileSize; /* The new file's logical size (EOD) in bytes */
ULONG FileAttribute; /* File attribute bits used on file creation */
ULONG OpenFLag; /* Specifies action taken, based on whether file exists */
ULONG OpenMode; /* Describes the mode of the Open function */
PVDH_EOAP EABuf; /* Address of a VDH_EAOP structure or NULL */
BOOL rc;
rc = VDHOpen(FileName, FileHandle, ActionTaken,
FileSize, FileAttribute, OpenFLag,
OpenMode, EABuf);
VDHOpen Parameter - FileName
FileName(PSZ) Pointer to the ASCIIZ string containing the name of the device or file to open.
VDHOpen Parameter - FileHandle
FileHandle(PHFILE) Where the system returns the file handle.
VDHOpen Parameter - ActionTaken
ActionTaken(PULONG) Where the system returns a description of the action taken as a result of this function call.
VDHOpen Parameter - FileSize
FileSize(ULONG) The new file's logical size (EOD) in bytes.
VDHOpen Parameter - FileAttribute
FileAttribute(ULONG) File attribute bits used on file creation.
VDHOpen Parameter - OpenFLag
OpenFLag(ULONG) Specifies the action taken depending on whether the file exists.
Possible actions are:
VDHOPEN_FILE_EXISTED File existed
VDHOPEN_FILE_CREATED File created
VDHOPEN_FILE_TRUNCATED File replaced
VDHOpen Parameter - OpenMode
OpenMode(ULONG) Describes the mode of the Openfunction.
VDHOpen Parameter - EABuf
EABuf(PVDH_EOAP) Address of a VDH_EAOP structure, or NULL.
VDHOpen Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). If the function fails, VDHGetErrorshould be called to determine the nature of the problem. VDHGetErrorcan return the following errors:
ERROR_DISK_FULL
ERROR_OPEN_FAILED
ERROR_FILE_NOT_FOUND
ERROR_INVALID_PARAMETER
ERROR_PATH_NOT_FOUND
ERROR_ACCESS_DENIED
ERROR_DRIVE_LOCKED
ERROR_NOT_DOS_DISK
ERROR_SHARING_BUFFER_EXCEEDED
ERROR_SHARING_VIOLATION
ERROR_INVALID_ACCESS
ERROR_CANNOT_MAKE
ERROR_TOO_MANY_OPEN_FILES
ERROR_NOT_ENOUGH_MEMORY
If the function is called at other than DOS session-task time, or if the pszFileNamepointer is invalid, a system halt occurs.
VDHOpen - Parameters
FileName(PSZ) Pointer to the ASCIIZ string containing the name of the device or file to open.
FileHandle(PHFILE) Where the system returns the file handle.
ActionTaken(PULONG) Where the system returns a description of the action taken as a result of this function call.
FileSize(ULONG) The new file's logical size (EOD) in bytes.
FileAttribute(ULONG) File attribute bits used on file creation.
OpenFLag(ULONG) Specifies the action taken depending on whether the file exists.
Possible actions are:
VDHOPEN_FILE_EXISTED File existed
VDHOPEN_FILE_CREATED File created
VDHOPEN_FILE_TRUNCATED File replaced
OpenMode(ULONG) Describes the mode of the Openfunction.
EABuf(PVDH_EOAP) Address of a VDH_EAOP structure, or NULL.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). If the function fails, VDHGetErrorshould be called to determine the nature of the problem. VDHGetErrorcan return the following errors:
ERROR_DISK_FULL
ERROR_OPEN_FAILED
ERROR_FILE_NOT_FOUND
ERROR_INVALID_PARAMETER
ERROR_PATH_NOT_FOUND
ERROR_ACCESS_DENIED
ERROR_DRIVE_LOCKED
ERROR_NOT_DOS_DISK
ERROR_SHARING_BUFFER_EXCEEDED
ERROR_SHARING_VIOLATION
ERROR_INVALID_ACCESS
ERROR_CANNOT_MAKE
ERROR_TOO_MANY_OPEN_FILES
ERROR_NOT_ENOUGH_MEMORY
If the function is called at other than DOS session-task time, or if the pszFileNamepointer is invalid, a system halt occurs.
VDHOpen - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: Any handles the virtual device driver opened for the terminating DOS session must be closed with VDHClose.
Notes: Using VDHOpendoes not interfere with the handle space available to the DOS session with INT 21H, except that it does count against the system- wide limit on the number of open file handles. These VDHOpenhandles and the handles returned from INT 21H $Open cannot be used interchangeably.
VDHOpen - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHOpenPDD
Select an item:
Format Parameters Return Codes Purpose Glossary
This function gets the address of the routine in a physical device driver that the virtual device driver uses to communicate with the physical device driver. The physical device driver's device must have previously registered its name and entry point using the DevHlp service RegisterPDD.
#include mvdm.h PSZ DeviceName; /* Pointer to device name of physical device driver to open */ FPFNVDD VDDEntryPoint; /* VDD entry point for VDD/PDD communication */ FPFNPDD rc; rc = VDHOpenPDD(DeviceName, VDDEntryPoint);
VDHOpenPDD - Format
This function gets the address of the routine in a physical device driver that the virtual device driver uses to communicate with the physical device driver. The physical device driver's device must have previously registered its name and entry point using the DevHlp service RegisterPDD.
#include mvdm.h PSZ DeviceName; /* Pointer to device name of physical device driver to open */ FPFNVDD VDDEntryPoint; /* VDD entry point for VDD/PDD communication */ FPFNPDD rc; rc = VDHOpenPDD(DeviceName, VDDEntryPoint);
VDHOpenPDD Parameter - DeviceName
DeviceName(PSZ) Pointer to the device name of the physical device driver to open.
VDHOpenPDD Parameter - VDDEntryPoint
VDDEntryPoint(FPFNVDD) Virtual device driver entry point for use by the physical device driver. Since physical device drivers are 16:16 modules, this is a 16:32 entry point.
The interface for the VDDEntryPoint:
USHORT VDDENTRY VDDEntryPoint (ulFunc, ul1, ul2)
ENTRY
ULONG ulFunc - function code
All function codes are private to a physical device driver/
virtual device driver pair.
ULONG ul1 - function/specific;
If a pointer, it is 16:16, and will generally be an input packet
ULONG ul2 - function/specific;
If a pointer, it is 16:16, and will generally be an output packet
EXIT-SUCCESS Returns !0
EXIT-FAILURE Returns 0
VDHOpenPDD Return Value - rc
rc(FPFNPDD) - returns
Success If the function is successful, it returns a pointer to the physical device driver Inter-Device-Driver Communication (IDC) function. See " RegisterPDD" in the OS/2 Physical Device Driver Referencefor a description of the physical device driver's IDC function.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHOpenPDD - Parameters
DeviceName(PSZ) Pointer to the device name of the physical device driver to open.
VDDEntryPoint(FPFNVDD) Virtual device driver entry point for use by the physical device driver. Since physical device drivers are 16:16 modules, this is a 16:32 entry point.
The interface for the VDDEntryPoint:
USHORT VDDENTRY VDDEntryPoint (ulFunc, ul1, ul2)
ENTRY
ULONG ulFunc - function code
All function codes are private to a physical device driver/
virtual device driver pair.
ULONG ul1 - function/specific;
If a pointer, it is 16:16, and will generally be an input packet
ULONG ul2 - function/specific;
If a pointer, it is 16:16, and will generally be an output packet
EXIT-SUCCESS Returns !0
EXIT-FAILURE Returns 0
rc(FPFNPDD) - returns
Success If the function is successful, it returns a pointer to the physical device driver Inter-Device-Driver Communication (IDC) function. See " RegisterPDD" in the OS/2 Physical Device Driver Referencefor a description of the physical device driver's IDC function.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHOpenPDD - Purpose
Context Issues: This function can be called only in the initialization context.
DOS Session Terminations: The virtual device driver must communicate with the physical device driver to ensure that any resources the physical device driver has for the terminating DOS session are freed.
VDHOpenPDD - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHOpenVDD
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns a handle to a virtual device driver that can be used with VDHRequestVDDto enable a virtual device driver to communicate with another virtual device driver. The name must be one that was previously registered by using VDHRegisterVDD.
#include mvdm.h PSZ VDDName; /* Pointer to the name of the virtual device driver to open */ HVDD rc; rc = VDHOpenVDD(VDDName);
VDHOpenVDD - Format
This function returns a handle to a virtual device driver that can be used with VDHRequestVDDto enable a virtual device driver to communicate with another virtual device driver. The name must be one that was previously registered by using VDHRegisterVDD.
#include mvdm.h PSZ VDDName; /* Pointer to the name of the virtual device driver to open */ HVDD rc; rc = VDHOpenVDD(VDDName);
VDHOpenVDD Parameter - VDDName
VDDName(PSZ) Pointer to a string containing the name of the virtual device driver to open.
VDHOpenVDD Return Value - rc
rc(HVDD) - returns
Success If the function is successful, it returns a handle to the virtual device driver.
Failure If the function fails, it returns 0 (zero). This can occur if:
- The virtual device driver referenced by VDDNameis not found.
*The virtual device driver was found, but has not registered a worker function (the routine that gets control when this interface is called) for virtual device driver/virtual device driver communication.
If this function is called with invalid parameters or in the incorrect context, a system halt occurs.
VDHOpenVDD - Parameters
VDDName(PSZ) Pointer to a string containing the name of the virtual device driver to open.
rc(HVDD) - returns
Success If the function is successful, it returns a handle to the virtual device driver.
Failure If the function fails, it returns 0 (zero). This can occur if:
- The virtual device driver referenced by VDDNameis not found.
*The virtual device driver was found, but has not registered a worker function (the routine that gets control when this interface is called) for virtual device driver/virtual device driver communication.
If this function is called with invalid parameters or in the incorrect context, a system halt occurs.
VDHOpenVDD - Purpose
Context Issues: This function can be called only in the DOS session-task context, typically during DOS session creation.
DOS Session Terminations: The virtual device driver must communicate with the opened virtual device driver to ensure that any resources for the terminating DOS session are freed. In addition, the virtual device driver must communicate with any virtual device driver or OS/2 clients to ensure that any resources created due to the connection are freed. Notes: The recommended way for two virtual device drivers to rendezvous with this function is for each to attempt to open the other at the first creation of a DOS session. This allows the two virtual device drivers to work together regardless of the order in which they are initialized.
VDHOpenVDD - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHOpenVIRQ
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns an IRQ handle for use with the other Virtual Programmable Interrupt Controller (VPIC) services and, optionally, sets handlers called when an End Of Interrupt (EOI) or Interrupt Return (IRET) is executed during a simulated interrupt.
#include mvdm.h
IRQN IRQNumber; /* Number of the IRQ to open */
PFN EOIHandler; /* Address of End-Of-Interrupt (EOI) handler */
PFN IRETHandler; /* Address of Interrupt Return (IRET) handler */
ULONG Timeout; /* IRET timeout value in milliseconds */
ULONG OptionFlag; /* Indicates whether the IRQ can be shared */
HIRQ rc;
rc = VDHOpenVIRQ(IRQNumber, EOIHandler, IRETHandler,
Timeout, OptionFlag);
VDHOpenVIRQ - Format
This function returns an IRQ handle for use with the other Virtual Programmable Interrupt Controller (VPIC) services and, optionally, sets handlers called when an End Of Interrupt (EOI) or Interrupt Return (IRET) is executed during a simulated interrupt.
#include mvdm.h
IRQN IRQNumber; /* Number of the IRQ to open */
PFN EOIHandler; /* Address of End-Of-Interrupt (EOI) handler */
PFN IRETHandler; /* Address of Interrupt Return (IRET) handler */
ULONG Timeout; /* IRET timeout value in milliseconds */
ULONG OptionFlag; /* Indicates whether the IRQ can be shared */
HIRQ rc;
rc = VDHOpenVIRQ(IRQNumber, EOIHandler, IRETHandler,
Timeout, OptionFlag);
VDHOpenVIRQ Parameter - IRQNumber
IRQNumber(IRQN) Number of the IRQ to open.
VDHOpenVIRQ Parameter - EOIHandler
EOIHandler(PFN) Address of End-Of-Interrupt (EOI) handler.
Linear address of the handler to be called when EOI is received by VPIC from a DOS session for the IRQ. If this is not desired, put a 0 (zero) in this parameter. Note that the IRQ is no longer "in service" (the ISR bit has been cleared) when the virtual device driver's EOI handler is called. The interface to the EOI handler is:
VOID HOOKENTRY EOIHdlr(pcrf)
ENTRY pcrf - Pointer to client register frame
EXIT None
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT DOS session-task
VDHOpenVIRQ Parameter - IRETHandler
IRETHandler(PFN) Address of Interrupt Return (IRET) handler.
Linear address of the handler to be called when the IRET in the DOS session 's interrupt code is executed for this IRQ. If this is not desired, set the parameter to 0 (zero). The interface for the IRET routine is:
VOID HOOKENTRY IRETHdlr(pcrf)
ENTRY pcrf - Pointer to client register frame
EXIT None
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT DOS session-task
VDHOpenVIRQ Parameter - Timeout
Timeout(ULONG) IRET timeout value in milliseconds. When the timeout expires, the virtual device driver's IRET handler is called as if the IRET had occurred. A value of -1 indicates that no timeout occurs.
VDHOpenVIRQ Parameter - OptionFlag
OptionFlag(ULONG) Option flag. Indicates whether the IRQ can be shared.
Possible value:
VPIC_SHARE_IRQ Indicates that the virtual device driver is willing to share the IRQ with another virtual device driver. All virtual device drivers that virtualize the same IRQ must pass this flag. Whether a particular IRQ is shared or unshared is determined by the setting of OptionFlagby the first virtual device driver to open the IRQ.
VDHOpenVIRQ Return Value - rc
rc(HIRQ) - returns
Success If the function is successful, it returns an IRQ handle.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If IRQNumber, EOIHandler, IRETHandler, or OptionFlagare invalid, a system halt occurs.
VDHOpenVIRQ - Parameters
IRQNumber(IRQN) Number of the IRQ to open.
EOIHandler(PFN) Address of End-Of-Interrupt (EOI) handler.
Linear address of the handler to be called when EOI is received by VPIC from a DOS session for the IRQ. If this is not desired, put a 0 (zero) in this parameter. Note that the IRQ is no longer "in service" (the ISR bit has been cleared) when the virtual device driver's EOI handler is called. The interface to the EOI handler is:
VOID HOOKENTRY EOIHdlr(pcrf)
ENTRY pcrf - Pointer to client register frame
EXIT None
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT DOS session-task
IRETHandler(PFN) Address of Interrupt Return (IRET) handler.
Linear address of the handler to be called when the IRET in the DOS session 's interrupt code is executed for this IRQ. If this is not desired, set the parameter to 0 (zero). The interface for the IRET routine is:
VOID HOOKENTRY IRETHdlr(pcrf)
ENTRY pcrf - Pointer to client register frame
EXIT None
USES EAX, ECX, EDX, FS, GS, Flags
CONTEXT DOS session-task
Timeout(ULONG) IRET timeout value in milliseconds. When the timeout expires, the virtual device driver's IRET handler is called as if the IRET had occurred. A value of -1 indicates that no timeout occurs.
OptionFlag(ULONG) Option flag. Indicates whether the IRQ can be shared.
Possible value:
VPIC_SHARE_IRQ Indicates that the virtual device driver is willing to share the IRQ with another virtual device driver. All virtual device drivers that virtualize the same IRQ must pass this flag. Whether a particular IRQ is shared or unshared is determined by the setting of OptionFlagby the first virtual device driver to open the IRQ.
rc(HIRQ) - returns
Success If the function is successful, it returns an IRQ handle.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If IRQNumber, EOIHandler, IRETHandler, or OptionFlagare invalid, a system halt occurs.
VDHOpenVIRQ - Purpose
Context Issues: This function can be called only in the initialization context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: A maximum of 32 virtual device drivers can share an IRQ.
VDHOpenVIRQ - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPhysicalDisk
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns information about partitionable disks.
#include mvdm.h
ULONG Function; /* Type of partitionable disks' information */
PULONG DataPtr; /* Pointer to the return buffer */
ULONG DataLen; /* Length of the return buffer */
PULONG ParmPtr; /* Pointer to the user-supplied information */
ULONG ParmLen; /* Length of the user-supplied information */
BOOL rc;
rc = VDHPhysicalDisk(Function, DataPtr, DataLen,
ParmPtr, ParmLen);
VDHPhysicalDisk - Format
This function returns information about partitionable disks.
#include mvdm.h
ULONG Function; /* Type of partitionable disks' information */
PULONG DataPtr; /* Pointer to the return buffer */
ULONG DataLen; /* Length of the return buffer */
PULONG ParmPtr; /* Pointer to the user-supplied information */
ULONG ParmLen; /* Length of the user-supplied information */
BOOL rc;
rc = VDHPhysicalDisk(Function, DataPtr, DataLen,
ParmPtr, ParmLen);
VDHPhysicalDisk Parameter - Function
Function(ULONG) Type of partitionable disks' information to obtain.
Possible values are:
VDHPHYD_GET_DISKS Obtain the total number of partitionable disks
VDHPHYD_GET_HANDLE Obtain a handle to use with the Category 9 IOCtls
VDHPHYD_RELEASE_HANDLE Release a handle for a partitionable disk
VDHPhysicalDisk Parameter - DataPtr
DataPtr(PULONG) Pointer to the return buffer.
VDHPhysicalDisk Parameter - DataLen
DataLen(ULONG) Length of the return buffer.
The returned data for each function is described as follows (all lengths are in bytes):
VDHPHYD_GET_DISKS Data Length=2. Total number of partitionable disks in the system. 1-based.
VDHPHYD_GET_HANDLE Data Length=2. Handle for the specified partitionable disk for Category 9 IOCtls.
VDHPHYD_RELEASE_HANDLE Data Length=0. None; pointer must be 0 (zero).
VDHPhysicalDisk Parameter - ParmPtr
ParmPtr(PULONG) Pointer to the user-supplied information.
VDHPhysicalDisk Parameter - ParmLen
ParmLen(ULONG) Length of the user-supplied information (all lengths are in bytes):
VDHPHYD_GET_DISKS Parm Length=0. None; must be set to 0 (zero). 1-based.
VDHPHYD_GET_HANDLE Parm Length=string length. ASCIIZ string that specifies the partitionable disk.
VDHPHYD_RELEASE_HANDLE Parm Length=2. Handle obtained from VDHPHYD_GET_ HANDLE.
VDHPhysicalDisk Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. VDHGetErrorcan return the following error codes:
ERROR_ACCESS_DENIED
ERROR_INVALID_FUNCTION
ERROR_INVALID_HANDLE
ERROR_INVALID_PARAMETER
ERROR_LOCK_VIOLATION
If VDHPhysicalDiskis called in any context except DOS session task time, a system halt occurs.
VDHPhysicalDisk - Parameters
Function(ULONG) Type of partitionable disks' information to obtain.
Possible values are:
VDHPHYD_GET_DISKS Obtain the total number of partitionable disks
VDHPHYD_GET_HANDLE Obtain a handle to use with the Category 9 IOCtls
VDHPHYD_RELEASE_HANDLE Release a handle for a partitionable disk
DataPtr(PULONG) Pointer to the return buffer.
DataLen(ULONG) Length of the return buffer.
The returned data for each function is described as follows (all lengths are in bytes):
VDHPHYD_GET_DISKS Data Length=2. Total number of partitionable disks in the system. 1-based.
VDHPHYD_GET_HANDLE Data Length=2. Handle for the specified partitionable disk for Category 9 IOCtls.
VDHPHYD_RELEASE_HANDLE Data Length=0. None; pointer must be 0 (zero).
ParmPtr(PULONG) Pointer to the user-supplied information.
ParmLen(ULONG) Length of the user-supplied information (all lengths are in bytes):
VDHPHYD_GET_DISKS Parm Length=0. None; must be set to 0 (zero). 1-based.
VDHPHYD_GET_HANDLE Parm Length=string length. ASCIIZ string that specifies the partitionable disk.
VDHPHYD_RELEASE_HANDLE Parm Length=2. Handle obtained from VDHPHYD_GET_ HANDLE.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. VDHGetErrorcan return the following error codes:
ERROR_ACCESS_DENIED
ERROR_INVALID_FUNCTION
ERROR_INVALID_HANDLE
ERROR_INVALID_PARAMETER
ERROR_LOCK_VIOLATION
If VDHPhysicalDiskis called in any context except DOS session task time, a system halt occurs.
VDHPhysicalDisk - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: The handle obtained with Function Value=2 is released with Function Value=3. The ASCIIZ string used to specify the partitionable disk must be of the following format:
number:<null byte>
Where:
number Specifies the partitionable disk (1-based) number in ASCII
: Must be present
<null byte> Specifies the byte of 0 for the ASCIIZ string
Notes: If the pointers passed by this function are allocated from the stack , then the SSToDSmacro must be used to make the DS pointer relative. Addresses (pointers) inside device-specific data and parameter packets are not translated.
VDHPhysicalDisk - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPopInt
Select an item:
Format Parameters Return Codes Purpose Glossary
This function reverses the effects of VDHPushInt. It removes the Interrupt Return (IRET) frame from the client's stack and restores the client's CS:IP to what was in the IRET frame.
#include mvdm.h VOID ; BOOL rc; rc = VDHPopInt();
VDHPopInt - Format
This function reverses the effects of VDHPushInt. It removes the Interrupt Return (IRET) frame from the client's stack and restores the client's CS:IP to what was in the IRET frame.
#include mvdm.h VOID ; BOOL rc; rc = VDHPopInt();
VDHPopInt Parameter -
None.
VDHPopInt Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack overflow would occur. A stack exception will be simulated to the client.
VDHPopInt - Parameters
None.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack overflow would occur. A stack exception will be simulated to the client.
VDHPopInt - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This function always returns Successful when the DOS session is in client mode because no data accesses below 1MB can cause a fault.
VDHPopInt - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPopRegs
Select an item:
Format Parameters Return Codes Purpose Glossary
This function reverses the VDHPushRegsby popping the specified client registers into the Client Register Frame (CRF) from the client's stack.
#include mvdm.h FLAGS RegFlag; /* Indicates which client registers to pop */ BOOL rc; rc = VDHPopRegs(RegFlag);
VDHPopRegs - Format
This function reverses the VDHPushRegsby popping the specified client registers into the Client Register Frame (CRF) from the client's stack.
#include mvdm.h FLAGS RegFlag; /* Indicates which client registers to pop */ BOOL rc; rc = VDHPopRegs(RegFlag);
VDHPopRegs Parameter - RegFlag
RegFlag(FLAGS) Flag indicating which client registers to pop.
These flags can be "ORed" together to indicate more than one register. Possible values are:
VDHREG_AX Pop the AX register
VDHREG_BX Pop the BX register
VDHREG_CX Pop the CX register
VDHREG_DX Pop the DX register
VDHREG_SI Pop the SI register
VDHREG_DI Pop the DI register
VDHREG_BP Pop the BP register
VDHREG_SP Pop the SP register
VDHREG_DS Pop the DS register
VDHREG_ES Pop the ES register
VDHREG_SS Pop the SS register
VDHREG_FLAG Pop the Flags register
VDHREG_ALL Pop all the registers
VDHREG_GENERAL Pop all the registers except SS and SP
VDHPopRegs Return Value - rc
rc(BOOL) - returns
Success If the function was successful, it returns a nonzero value.
Failure If this function fails, it returns 0 (zero) if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception is simulated to the client. If RegFlagis invalid, a system halt occurs.
VDHPopRegs - Parameters
RegFlag(FLAGS) Flag indicating which client registers to pop.
These flags can be "ORed" together to indicate more than one register. Possible values are:
VDHREG_AX Pop the AX register
VDHREG_BX Pop the BX register
VDHREG_CX Pop the CX register
VDHREG_DX Pop the DX register
VDHREG_SI Pop the SI register
VDHREG_DI Pop the DI register
VDHREG_BP Pop the BP register
VDHREG_SP Pop the SP register
VDHREG_DS Pop the DS register
VDHREG_ES Pop the ES register
VDHREG_SS Pop the SS register
VDHREG_FLAG Pop the Flags register
VDHREG_ALL Pop all the registers
VDHREG_GENERAL Pop all the registers except SS and SP
rc(BOOL) - returns
Success If the function was successful, it returns a nonzero value.
Failure If this function fails, it returns 0 (zero) if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception is simulated to the client. If RegFlagis invalid, a system halt occurs.
VDHPopRegs - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: The caller should be careful to pass the same RegFlagvalue to VDHPopRegsthat was used for the corresponding VDHPushRegscall. If the caller does not do this, the client stack can become damaged. This function always returns Successful when RegFlagis valid and the DOS session is in V86 mode because no data accesses below 1MB can cause a fault.
VDHPopRegs - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPopStack
Select an item:
Format Parameters Return Codes Purpose Glossary
This function pops the data off the client's stack.
#include mvdm.h ULONG NumBytes; /* Number of bytes to pop off the client's stack */ PVOID DataPtr; /* Pointer to data to pop off client's stack */ BOOL rc; rc = VDHPopStack(NumBytes, DataPtr);
VDHPopStack - Format
This function pops the data off the client's stack.
#include mvdm.h ULONG NumBytes; /* Number of bytes to pop off the client's stack */ PVOID DataPtr; /* Pointer to data to pop off client's stack */ BOOL rc; rc = VDHPopStack(NumBytes, DataPtr);
VDHPopStack Parameter - NumBytes
NumBytes(ULONG) Number of bytes to pop off the client's stack. Must be an even number.
VDHPopStack Parameter - DataPtr
DataPtr(PVOID) Pointer to the data to pop off the client's stack.
VDHPopStack Return Value - rc
rc(BOOL) - returns
Success If the function was successful, it returns a nonzero value.
Failure If this function fails, it returns 0 (zero) if a fault would occur when accessing the user stack. If NumBytesis odd, a system halt occurs.
VDHPopStack - Parameters
NumBytes(ULONG) Number of bytes to pop off the client's stack. Must be an even number.
DataPtr(PVOID) Pointer to the data to pop off the client's stack.
rc(BOOL) - returns
Success If the function was successful, it returns a nonzero value.
Failure If this function fails, it returns 0 (zero) if a fault would occur when accessing the user stack. If NumBytesis odd, a system halt occurs.
VDHPopStack - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This is a very low-level service. Appropriate care should be exercised in its use to ensure that the client's stack is not damaged. This service handles stack wraparound, and always returns successful when the DOS session is in V86-mode because no data accesses below 1MB can cause a fault.
VDHPopStack - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPopup
Select an item:
Format Parameters Return Codes Purpose Glossary
This function displays a message according to the Message ID, and gets a response from the user.
#include mvdm.h
PSZ ParmTable; /* Pointer to a table of substitution strings */
ULONG StrCount; /* Number of substitution strings */
ULONG MsgNumber; /* Message number */
PULONG RespPtr; /* Pointer to a DD to receive the response */
ULONG RespAllowed; /* Bit field describing the allowed responses */
PVOID Reserved; /* Reserved; must be set to NULL */
BOOL rc;
rc = VDHPopup(ParmTable, StrCount, MsgNumber,
RespPtr, RespAllowed, Reserved);
VDHPopup - Format
This function displays a message according to the Message ID, and gets a response from the user.
#include mvdm.h
PSZ ParmTable; /* Pointer to a table of substitution strings */
ULONG StrCount; /* Number of substitution strings */
ULONG MsgNumber; /* Message number */
PULONG RespPtr; /* Pointer to a DD to receive the response */
ULONG RespAllowed; /* Bit field describing the allowed responses */
PVOID Reserved; /* Reserved; must be set to NULL */
BOOL rc;
rc = VDHPopup(ParmTable, StrCount, MsgNumber,
RespPtr, RespAllowed, Reserved);
VDHPopup Parameter - ParmTable
ParmTable(PSZ) Pointer to a table of substitution strings.
VDHPopup Parameter - StrCount
StrCount(ULONG) Number of substitution strings.
VDHPopup Parameter - MsgNumber
MsgNumber(ULONG) Message number.
VDHPopup Parameter - RespPtr
RespPtr(PULONG) Pointer to a DD to receive the returned response, filled on exit.
VDHPopup Parameter - RespAllowed
RespAllowed(ULONG) Bit field describing the allowed responses.
The allowed values are (any combination of these flags can be specified):
VDHP_FAIL (0001H)
VDHP_RETRY (0004H)
VDHP_IGNORE (0008H)
VDHP_TERMINATE_SESSION (0002H)
VDHPopup Parameter - Reserved
Reserved(PVOID) Reserved. Must be set to NULL.
VDHPopup Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value and the variable pointed to by RespPtris filled in with actual response selected by the user.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHPopup - Parameters
ParmTable(PSZ) Pointer to a table of substitution strings.
StrCount(ULONG) Number of substitution strings.
MsgNumber(ULONG) Message number.
RespPtr(PULONG) Pointer to a DD to receive the returned response, filled on exit.
RespAllowed(ULONG) Bit field describing the allowed responses.
The allowed values are (any combination of these flags can be specified):
VDHP_FAIL (0001H)
VDHP_RETRY (0004H)
VDHP_IGNORE (0008H)
VDHP_TERMINATE_SESSION (0002H)
Reserved(PVOID) Reserved. Must be set to NULL.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value and the variable pointed to by RespPtris filled in with actual response selected by the user.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHPopup - Purpose
Context Issues: This function can be called in the initialization context or the DOS session-task context. If it is called at initialization time, the message is displayed as a string on the console as if a DosWriteto standard output (stdout) had been made. No prompt is displayed, and no user response is returned. ResponsePtris filled in with 0 (zero).
DOS Session Terminations: A DOS session cannot be terminated if it is waiting in this call for a user response.
Notes: This service is intended for virtual device drivers, which must inform the user of some extraordinary circumstance. For example, the virtual COM device driver (VCOM) issues this call to inform the user that a COM port is busy and gives the user a choice of how to handle the situation .
The input value of ResponsePtris not used. "Retry" is the default action chosen for hard errors. If Retry is not allowed, "End the Program" is chosen as the default.
VDHPopup - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPostEventSem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function posts an event semaphore. All the threads blocked on this semaphore will wake up.
#include mvdm.h HVDHSEM EventSemHandle; /* Handle of an event semaphore */ VDHPostEventSem(EventSemHandle);
VDHPostEventSem - Format
This function posts an event semaphore. All the threads blocked on this semaphore will wake up.
#include mvdm.h HVDHSEM EventSemHandle; /* Handle of an event semaphore */ VDHPostEventSem(EventSemHandle);
VDHPostEventSem Parameter - EventSemHandle
EventSemHandle(HVDHSEM) Handle of the event semaphore to post.
VDHPostEventSem - Return Value
Success If the function is successful, it will return nothing.
Failure Posting a semaphore that is invalid or is already posted causes a system halt to occur.
VDHPostEventSem - Parameters
EventSemHandle(HVDHSEM) Handle of the event semaphore to post.
Success If the function is successful, it will return nothing.
Failure Posting a semaphore that is invalid or is already posted causes a system halt to occur.
VDHPostEventSem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHPostEventSem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPrintClose
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is called by other virtual device drivers to flush and close a DOS session's open printers that have been opened for INT 17H printing. A DOS session can have more than one printer open. This service flushes and closes all of them.
#include mvdm.h HVDM VDMHandle; /* DOS session handle */ VDHPrintClose(VDMHandle);
VDHPrintClose - Format
This function is called by other virtual device drivers to flush and close a DOS session's open printers that have been opened for INT 17H printing. A DOS session can have more than one printer open. This service flushes and closes all of them.
#include mvdm.h HVDM VDMHandle; /* DOS session handle */ VDHPrintClose(VDMHandle);
VDHPrintClose Parameter - VDMHandle
VDMHandle(HVDM) DOS session handle.
VDHPrintClose - Return Value
None.
VDHPrintClose - Parameters
VDMHandle(HVDM) DOS session handle.
None.
VDHPrintClose - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: The system will flush and close any open printers when the DOS session is terminated.
Notes: If a printer has been left open because of direct access to the parallel ports, it will also be closed.
VDHPrintClose - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPushFarCall
Select an item:
Format Parameters Return Codes Purpose Glossary
This function simulates a Far Call to V86 code as if a DOS program had executed a Far Call instruction.
#include mvdm.h FPFN SegOffAddr; /* Address of V86 mode or protected mode code to call */ BOOL rc; rc = VDHPushFarCall(SegOffAddr);
VDHPushFarCall - Format
This function simulates a Far Call to V86 code as if a DOS program had executed a Far Call instruction.
#include mvdm.h FPFN SegOffAddr; /* Address of V86 mode or protected mode code to call */ BOOL rc; rc = VDHPushFarCall(SegOffAddr);
VDHPushFarCall Parameter - SegOffAddr
SegOffAddr(FPFN) The V86-mode segment:offset address of the V86-mode code to call, or selector:offset of protected-mode code to call.
VDHPushFarCall Return Value - rc
rc(BOOL) - returns
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception is simulated to the client.
VDHPushFarCall - Parameters
SegOffAddr(FPFN) The V86-mode segment:offset address of the V86-mode code to call, or selector:offset of protected-mode code to call.
rc(BOOL) - returns
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception is simulated to the client.
VDHPushFarCall - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This function does not take effect until the operating system returns to the DOS session. In most cases, VDHArmReturnHookis called after this service. This allows the virtual device driver to regain control when the called V86 code executes its Far Return (RETF).
This function always returns successful when the DOS session is in V86 mode because no data accesses below 1MB can cause a fault.
VDHPushFarCall - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPushInt
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used to change the DOS session's control flow to the interrupt handler when an interrupt is simulated. This function also simulates an interrupt to a specified V86-interrupt vector as if a DOS program has executed an INT ninstruction. Any virtual device driver hooked on this interrupt with VDHInstallIntHookwill get control as expected. The VDHArmReturnHookservice can be used after this function is called to regain control when the V86 code executes the Interrupt Return (IRET).
If the DOS session is in V86-mode, the V86-mode handler from the IVT is called. If the DOS session is in protected mode, the protected-mode interrupt handler is called.
#include mvdm.h ULONG Vector; /* Number of the interrupt vector to push */ BOOL rc; rc = VDHPushInt(Vector);
VDHPushInt - Format
This function is used to change the DOS session's control flow to the interrupt handler when an interrupt is simulated. This function also simulates an interrupt to a specified V86-interrupt vector as if a DOS program has executed an INT ninstruction. Any virtual device driver hooked on this interrupt with VDHInstallIntHookwill get control as expected. The VDHArmReturnHookservice can be used after this function is called to regain control when the V86 code executes the Interrupt Return (IRET).
If the DOS session is in V86-mode, the V86-mode handler from the IVT is called. If the DOS session is in protected mode, the protected-mode interrupt handler is called.
#include mvdm.h ULONG Vector; /* Number of the interrupt vector to push */ BOOL rc; rc = VDHPushInt(Vector);
VDHPushInt Parameter - Vector
Vector(ULONG) Number of the interrupt vector to push (0-255).
VDHPushInt Return Value - rc
rc(BOOL) - returns
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception will be simulated to the client. If Vectoris invalid, a system halt occurs.
VDHPushInt - Parameters
Vector(ULONG) Number of the interrupt vector to push (0-255).
rc(BOOL) - returns
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception will be simulated to the client. If Vectoris invalid, a system halt occurs.
VDHPushInt - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This function does not take effect until the operating system returns to V86 mode. This function always returns successful when the DOS session is in V86 mode because no data accesses below 1MB can cause a fault .
VDHPushInt - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPushRegs
Select an item:
Format Parameters Return Codes Purpose Glossary
This function pushes the specified client register from the Client Register Frame (CRF) to the client's stack. This service is usually used in conjunction with VDHPushFarCall to preserve user registers.
#include mvdm.h FLAGS RegFlag; /* Flag indicating which client registers to push */ BOOL rc; rc = VDHPushRegs(RegFlag);
VDHPushRegs - Format
This function pushes the specified client register from the Client Register Frame (CRF) to the client's stack. This service is usually used in conjunction with VDHPushFarCall to preserve user registers.
#include mvdm.h FLAGS RegFlag; /* Flag indicating which client registers to push */ BOOL rc; rc = VDHPushRegs(RegFlag);
VDHPushRegs Parameter - RegFlag
RegFlag(FLAGS) Flag indicating which client registers to push. These flags can be ORed together to indicate more than one register.
Possible values are:
VDHREG_AX Push the AX register
VDHREG_BX Push the BX register
VDHREG_CX Push the CX register
VDHREG_DX Push the DX register
VDHREG_SI Push the SI register
VDHREG_DI Push the DI register
VDHREG_BP Push the BP register
VDHREG_SP Push the SP register
VDHREG_DS Push the DS register
VDHREG_ES Push the ES register
VDHREG_SS Push the SS register
VDHREG_FLAG Push the Flags register
VDHREG_ALL Push all the registers
VDHREG_GENERAL Push all the registers except SS and SP
VDHPushRegs Return Value - rc
rc(BOOL) - returns
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception will be simulated to the client. If RegFlagis invalid, a system halt occurs.
VDHPushRegs - Parameters
RegFlag(FLAGS) Flag indicating which client registers to push. These flags can be ORed together to indicate more than one register.
Possible values are:
VDHREG_AX Push the AX register
VDHREG_BX Push the BX register
VDHREG_CX Push the CX register
VDHREG_DX Push the DX register
VDHREG_SI Push the SI register
VDHREG_DI Push the DI register
VDHREG_BP Push the BP register
VDHREG_SP Push the SP register
VDHREG_DS Push the DS register
VDHREG_ES Push the ES register
VDHREG_SS Push the SS register
VDHREG_FLAG Push the Flags register
VDHREG_ALL Push all the registers
VDHREG_GENERAL Push all the registers except SS and SP
rc(BOOL) - returns
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception will be simulated to the client. If RegFlagis invalid, a system halt occurs.
VDHPushRegs - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Because the registers are saved on the DOS session stack (as opposed to a virtual device driver data structure), the virtual device driver is in no danger of losing track of data if the DOS session does not return to the virtual device driver. This service is used sparingly as it consumes DOS session stack space, and most DOS applications cannot tolerate excessive stack usage beyond their own needs.
This function always returns successful when RegFlagis valid and the DOS session is in V86 mode because no data accessed below 1MB can cause a fault .
VDHPushRegs - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPushStack
Select an item:
Format Parameters Return Codes Purpose Glossary
This function pushes data onto the client's stack.
#include mvdm.h ULONG NumBytes; /* Number of bytes to push on the client's stack */ PVOID DataPtr; /* Pointer to the data to push on the stack */ BOOL rc; rc = VDHPushStack(NumBytes, DataPtr);
VDHPushStack - Format
This function pushes data onto the client's stack.
#include mvdm.h ULONG NumBytes; /* Number of bytes to push on the client's stack */ PVOID DataPtr; /* Pointer to the data to push on the stack */ BOOL rc; rc = VDHPushStack(NumBytes, DataPtr);
VDHPushStack Parameter - NumBytes
NumBytes(ULONG) Number of bytes to push onto the client's stack. Must be an even number.
VDHPushStack Parameter - DataPtr
DataPtr(PVOID) A pointer to the data to be pushed.
VDHPushStack Return Value - rc
rc(BOOL) - returns
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception will be simulated to the client. If NumBytes is odd, a system halt occurs.
VDHPushStack - Parameters
NumBytes(ULONG) Number of bytes to push onto the client's stack. Must be an even number.
DataPtr(PVOID) A pointer to the data to be pushed.
rc(BOOL) - returns
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception will be simulated to the client. If NumBytes is odd, a system halt occurs.
VDHPushStack - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This is a very low-level service. Appropriate care should be exercised in its use to ensure that the client's stack is not corrupted. This service handles stack wraparound, and always returns successful when the DOS session is in V86-mode because no data accesses below 1MB can cause a fault.
VDHPushStack - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPutSysValue
Select an item:
Format Parameters Return Codes Purpose Glossary
This function sets a system value.
#include mvdm.h ULONG Index; /* Index of the system variable to set */ ULONG Value; /* New value for the system variable */ VDHPutSysValue(Index, Value);
VDHPutSysValue - Format
This function sets a system value.
#include mvdm.h ULONG Index; /* Index of the system variable to set */ ULONG Value; /* New value for the system variable */ VDHPutSysValue(Index, Value);
VDHPutSysValue Parameter - Index
Index(ULONG) Index of the system value to set. System value indexes are defined in VDMM.INC and listed in VDHQuerySysValue.
VDHPutSysValue Parameter - Value
Value(ULONG) New value for the system variable.
VDHPutSysValue - Return Value
Success If the function was successful, it returns nothing.
Failure If Index is invalid, a system halt occurs.
VDHPutSysValue - Parameters
Index(ULONG) Index of the system value to set. System value indexes are defined in VDMM.INC and listed in VDHQuerySysValue.
Value(ULONG) New value for the system variable.
Success If the function was successful, it returns nothing.
Failure If Index is invalid, a system halt occurs.
VDHPutSysValue - Purpose
Context Issues: This function can be called in the initialization or DOS session-task (DOS session creation) context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This service is intended for system virtual device drivers to export system constants, such as ROM memory size. The behavior of the system is undefined if this service is used for any other purpose.
VDHPutSysValue - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQueryFreePages
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns the total amount of free virtual memory in bytes. This is the amount of memory that could be allocated successfully.
#include mvdm.h VOID ; ULONG rc; rc = VDHQueryFreePages();
VDHQueryFreePages - Format
This function returns the total amount of free virtual memory in bytes. This is the amount of memory that could be allocated successfully.
#include mvdm.h VOID ; ULONG rc; rc = VDHQueryFreePages();
VDHQueryFreePages Parameter -
None.
VDHQueryFreePages Return Value - rc
rc(ULONG) - returns
Success If the function is successful, it returns the number of bytes of free virtual memory.
Failure If the function fails, it returns nothing.
VDHQueryFreePages - Parameters
None.
rc(ULONG) - returns
Success If the function is successful, it returns the number of bytes of free virtual memory.
Failure If the function fails, it returns nothing.
VDHQueryFreePages - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This is a system-wide value that is not specific to the virtual address space of the DOS session.
VDHQueryFreePages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQueryHookData
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns a pointer to the reference data created during the call to VDHAllocHook.
#include mvdm.h HHOOK HookHandle; /* Hook handle from VDHAllocHook */ PVOID rc; rc = VDHQueryHookData(HookHandle);
VDHQueryHookData - Format
This function returns a pointer to the reference data created during the call to VDHAllocHook.
#include mvdm.h HHOOK HookHandle; /* Hook handle from VDHAllocHook */ PVOID rc; rc = VDHQueryHookData(HookHandle);
VDHQueryHookData Parameter - HookHandle
HookHandle(HHOOK) Hook handle (from VDHAllocHook) for the hook to query.
VDHQueryHookData Return Value - rc
rc(PVOID) - returns
Success If the function is successful, it returns a pointer to the reference data block.
Failure If HookHandle is invalid or if there is no reference data (that is, the RefDataSize parameter for VDHAllocHook is 0), a system halt occurs.
VDHQueryHookData - Parameters
HookHandle(HHOOK) Hook handle (from VDHAllocHook) for the hook to query.
rc(PVOID) - returns
Success If the function is successful, it returns a pointer to the reference data block.
Failure If HookHandle is invalid or if there is no reference data (that is, the RefDataSize parameter for VDHAllocHook is 0), a system halt occurs.
VDHQueryHookData - Purpose
Context Issues: This function can be called in the initialization, task, or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHQueryHookData - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQueryLin
Select an item:
Format Parameters Return Codes Purpose Glossary
This function converts a 16:16 (Far16) address to a 0:32 address. The 16:16 address can be a LDT-based or GDT-based address. The function is also callable on stack-based addresses.
#include mvdm.h F16PVOID Far16Addr; /* 16:16 addressto be converted */ PVOID rc; rc = VDHQueryLin(Far16Addr);
VDHQueryLin - Format
This function converts a 16:16 (Far16) address to a 0:32 address. The 16:16 address can be a LDT-based or GDT-based address. The function is also callable on stack-based addresses.
#include mvdm.h F16PVOID Far16Addr; /* 16:16 addressto be converted */ PVOID rc; rc = VDHQueryLin(Far16Addr);
VDHQueryLin Parameter - Far16Addr
Far16Addr(F16PVOID) The 16:16 address to be converted to a 0:32 address.
VDHQueryLin Return Value - rc
rc(PVOID) - returns
Success If the function is successful, it returns the 0:32 address that corresponds to Far16Addr.
Failure If Far16Addr is an invalid selector, a system halt occurs.
VDHQueryLin - Parameters
Far16Addr(F16PVOID) The 16:16 address to be converted to a 0:32 address.
rc(PVOID) - returns
Success If the function is successful, it returns the 0:32 address that corresponds to Far16Addr.
Failure If Far16Addr is an invalid selector, a system halt occurs.
VDHQueryLin - Purpose
Context Issues: This function can be called in the initialization, task, or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This service does minimal checking on Far16Addr. The caller should make sure that Far16Addr is not invalid. If an invalid address is passed, this service can return an invalid address.
VDHQueryLin - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQueryKeyShift
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is called by the virtual mouse device driver to query the keyboard shift state of a DOS session.
#include mvdm.h HVDM VDMHandle; /* DOS session handle */ USHORT rc; rc = VDHQueryKeyShift(VDMHandle);
VDHQueryKeyShift - Format
This function is called by the virtual mouse device driver to query the keyboard shift state of a DOS session.
#include mvdm.h HVDM VDMHandle; /* DOS session handle */ USHORT rc; rc = VDHQueryKeyShift(VDMHandle);
VDHQueryKeyShift Parameter - VDMHandle
VDMHandle(HVDM) DOS session handle.
VDHQueryKeyShift Return Value - rc
rc(USHORT) - returns Returns a USHORT which is a bitmask that indicates the current key state:
Right Shift 1
Left Shift 2
Ctrl 4
ALT 8
Left Ctrl 100
Left ALT 200
Right Ctrl 400
Right ALT 800
VDHQueryKeyShift - Parameters
VDMHandle(HVDM) DOS session handle.
rc(USHORT) - returns Returns a USHORT which is a bitmask that indicates the current key state:
Right Shift 1
Left Shift 2
Ctrl 4
ALT 8
Left Ctrl 100
Left ALT 200
Right Ctrl 400
Right ALT 800
VDHQueryKeyShift - Purpose
Context Issues: This function can be called only in the interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHQueryKeyShift - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQueryProperty
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns the current value of the specified DOS Setting.
#include mvdm.h PSZ PropertyName; /* Pointer to a property name */ ULONG rc; rc = VDHQueryProperty(PropertyName);
VDHQueryProperty - Format
This function returns the current value of the specified DOS Setting.
#include mvdm.h PSZ PropertyName; /* Pointer to a property name */ ULONG rc; rc = VDHQueryProperty(PropertyName);
VDHQueryProperty Parameter - PropertyName
PropertyName(PSZ) Pointer to an ASCIIZ string containing the property name for which information is being sought. Maximum length is 40 characters, including the terminating NULL.
VDHQueryProperty Return Value - rc
rc(ULONG) - returns
Success The format of the return value for successful depends on the type of the property being queried:
VDMP_BOOL The return value is a BOOL (Boolean). A 0value represents FALSE and a nonzero value represents TRUE.
VDMP_INT The return value is a DD. It is guaranteed to be valid with respect to the bounding information specified in VDHRegisterVDD. Only the low half (DW) of the DD is significant. The high half is always 0.
VDMP_ENUM The return value is a pointer to a NULL-terminated string. The string is guaranteed to be one of those specified in VDHRegisterVDD.
VDMP_STRING The return value is a pointer to a NULL-terminated string. The string is guaranteed to be, at most, as long as the limit specified in VDHRegisterVDD.
VDMP_MLSTR The return value is a pointer to a NULL-terminated string. The string is guaranteed to be, at most, as long as the limit specified in VDHRegisterVDD.
Note:For property types VDMP_ENUM, VDMP_STRING, and VDMP_MLSTR, a pointer to the current value is returned to the virtual device driver, thereby avoiding a condition where an OS/2 process might be trying to change the same value. The virtual device driver calls VDHFreeMem to free the string after the virtual device driver is finished with it.
Failure If the function fails, it returns NULL for property types VDMP_ENUM , VDMP_STRING, and VDMP_MLSTR, if there is insufficient memory to create a copy of the string value. In this case, the virtual device driver uses the default property value. NULL is also returned if pszName is invalid or is not a registered virtual device driver name.
VDHQueryProperty - Parameters
PropertyName(PSZ) Pointer to an ASCIIZ string containing the property name for which information is being sought. Maximum length is 40 characters, including the terminating NULL.
rc(ULONG) - returns
Success The format of the return value for successful depends on the type of the property being queried:
VDMP_BOOL The return value is a BOOL (Boolean). A 0value represents FALSE and a nonzero value represents TRUE.
VDMP_INT The return value is a DD. It is guaranteed to be valid with respect to the bounding information specified in VDHRegisterVDD. Only the low half (DW) of the DD is significant. The high half is always 0.
VDMP_ENUM The return value is a pointer to a NULL-terminated string. The string is guaranteed to be one of those specified in VDHRegisterVDD.
VDMP_STRING The return value is a pointer to a NULL-terminated string. The string is guaranteed to be, at most, as long as the limit specified in VDHRegisterVDD.
VDMP_MLSTR The return value is a pointer to a NULL-terminated string. The string is guaranteed to be, at most, as long as the limit specified in VDHRegisterVDD.
Note:For property types VDMP_ENUM, VDMP_STRING, and VDMP_MLSTR, a pointer to the current value is returned to the virtual device driver, thereby avoiding a condition where an OS/2 process might be trying to change the same value. The virtual device driver calls VDHFreeMem to free the string after the virtual device driver is finished with it.
Failure If the function fails, it returns NULL for property types VDMP_ENUM , VDMP_STRING, and VDMP_MLSTR, if there is insufficient memory to create a copy of the string value. In this case, the virtual device driver uses the default property value. NULL is also returned if pszName is invalid or is not a registered virtual device driver name.
VDHQueryProperty - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: All memory allocated by a virtual device driver for use by the terminating DOS session is freed by using VDHFreeMem.
Notes: A virtual device driver can assume that the property value is valid. The system validates all types, except VDMP_STRING and VDMP_MLSTR, by using the validation values passed on the call to VDHRegisterProperty. The string types are validated by calling the virtual device driver function registered through VDHRegisterProperty.
VDHQueryProperty - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQuerySel
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns the selector part of a 16:16 far pointer from a flat 0:32 address. The selector is in the Global Descriptor Table (GDT).
#include mvdm.h PVOID VirtAddress; /* 0:32 virtual address */ SEL rc; rc = VDHQuerySel(VirtAddress);
VDHQuerySel - Format
This function returns the selector part of a 16:16 far pointer from a flat 0:32 address. The selector is in the Global Descriptor Table (GDT).
#include mvdm.h PVOID VirtAddress; /* 0:32 virtual address */ SEL rc; rc = VDHQuerySel(VirtAddress);
VDHQuerySel Parameter - VirtAddress
VirtAddress(PVOID) A 0:32 virtual address.
VDHQuerySel Return Value - rc
rc(SEL) - returns
Success If the function is successful, it returns a nonzero selector.
Failure If the specified linear address is not in a virtual device driver data object, a system halt occurs.
VDHQuerySel - Parameters
VirtAddress(PVOID) A 0:32 virtual address.
rc(SEL) - returns
Success If the function is successful, it returns a nonzero selector.
Failure If the specified linear address is not in a virtual device driver data object, a system halt occurs.
VDHQuerySel - Purpose
Context Issues: This function can be called in the initialization and task context:
- During initialization time; query is allowed only on initialization and global data.
*Global, instance, and stack data are allowed during task time (typically DOS session creation time), but initialization data is not.
DOS Session Terminations: Selectors for virtual device driver instance data are destroyed when the DOS session terminates. The virtual device driver must ensure that any physical device driver that was given this kind of selector is finished with it.
Notes: This function works only on 0:32 addresses in virtual device driver data objects and stacks. Each virtual device driver data object is limited to a maximum of 64KB in size so that the following formula can be used. A virtual device driver that needs more than 64KB of a particular class (INIT , global, or instance) must use multiple objects.
Notice that the selectors for virtual device driver data are created to map starting at a 64KB linear address boundary. As a result, VDHQuerySelneeds to be called only once. The returned selector is valid for any memory in the particular object that contains the passed address, because the DOS Session Manager does not allow a virtual device driver data object to span a 64KB linear address boundary.
For virtual device driver instance data, this function returns a different GDT selector for each DOS session, and it can be called only in the context of a DOS session.
VDHQuerySel - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQuerySem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function queries the state of an event or mutex semaphore.
#include mvdm.h HVDHSEM SemHandle; /* Handle to an event or mutex semaphore */ PVDHSEMSTATE SemStatePtr; /* Pointer to a VDHSEMSTATE data area */ VDHQuerySem(SemHandle, SemStatePtr);
VDHQuerySem - Format
This function queries the state of an event or mutex semaphore.
#include mvdm.h HVDHSEM SemHandle; /* Handle to an event or mutex semaphore */ PVDHSEMSTATE SemStatePtr; /* Pointer to a VDHSEMSTATE data area */ VDHQuerySem(SemHandle, SemStatePtr);
VDHQuerySem Parameter - SemHandle
SemHandle(HVDHSEM) Semaphore handle.
VDHQuerySem Parameter - SemStatePtr
SemStatePtr(PVDHSEMSTATE) A pointer to the data area to be filled with the state of the semaphore.
SemStatePtr points to a variable defined in VDMM.INC and structured as follows:
typedef struct VDHSemState_s {
UCHAR vss_SemType; /* VDH_EVENTSEM/VDH_MUTEXSEM */
UCHAR vss_fOwned; /* 0 = Not Owned; 1 = Owned */
USHORT vss_fWaiter; /* 0 = No one waiting; 1 = Waiting */
USHORT vss_cRequest; /* Request count in mutex case */
TID vss_tid; /* TID of the owner, if owned */
}VDHSEMSTATE;
VDHQuerySem - Return Value
None.
VDHQuerySem - Parameters
SemHandle(HVDHSEM) Semaphore handle.
SemStatePtr(PVDHSEMSTATE) A pointer to the data area to be filled with the state of the semaphore.
SemStatePtr points to a variable defined in VDMM.INC and structured as follows:
typedef struct VDHSemState_s {
UCHAR vss_SemType; /* VDH_EVENTSEM/VDH_MUTEXSEM */
UCHAR vss_fOwned; /* 0 = Not Owned; 1 = Owned */
USHORT vss_fWaiter; /* 0 = No one waiting; 1 = Waiting */
USHORT vss_cRequest; /* Request count in mutex case */
TID vss_tid; /* TID of the owner, if owned */
}VDHSEMSTATE;
None.
VDHQuerySem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for state checking services.
Notes: The validity of SemStatePtr is not checked. The calling program must pass the address of a valid data area.
VDHQuerySem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQuerySysValue
Select an item:
Format Parameters Return Codes Purpose Glossary
This function queries a system value.
#include mvdm.h HVDM VDMHandle; /* Index of the system variable handle of the DOS session */ ULONG Index; /* Index values */ ULONG rc; rc = VDHQuerySysValue(VDMHandle, Index);
VDHQuerySysValue - Format
This function queries a system value.
#include mvdm.h HVDM VDMHandle; /* Index of the system variable handle of the DOS session */ ULONG Index; /* Index values */ ULONG rc; rc = VDHQuerySysValue(VDMHandle, Index);
VDHQuerySysValue Parameter - VDMHandle
VDMHandle(HVDM) Index of the system variable handle of the DOS session to query. A value of 0 (zero) indicates the current DOS session.
VDHQuerySysValue Parameter - Index
Index(ULONG) VDHQuerySysValueindex values (as defined in VDMM.INC) and descriptions:
Global Values Ordinal Type Units Range _____________ _______ ____ _____ _____ VDHGSV_DAY 0 ULONG days 1 < = x < = 31 VDHGSV_MONTH 1 ULONG months 1 < = x < = 12 VDHGSV_YEAR 2 ULONG years 1980 < = x < = MAXULONG VDHGSV_DAYOFWEEK 3 ULONG days 0 < = x < = 6 VDHGSV_HOUR 4 ULONG hours 0 < = x < = 24 VDHGSV_MINUTE 5 ULONG minutes 0 < = x < = 60 VDHGSV_SECOND 6 ULONG seconds 0 < = x < = 60 VDHGSV_HUNDREDTH 7 ULONG 1/100S 0 < = x < = 100 VDHGSV_SECONDS1970 8 ULONG seconds 0 < = x < = MAXULONG VDHGSV_TIMEZONE 9 ULONG minutes 0 < = x < = MAXULONG VDHGSV_MSECSBOOT 10 ULONG milliseconds 0 < = x < = MAXULONG VDHGSV_TIMERINTERVAL 11 ULONG milliseconds 0 < = x < = 1000 VDHGSV_DYNVARIATION 12 BOOL TRUE(nonzero)/FALSE(0) VDHGSV_MAXWAIT 13 ULONG seconds 0 < = x < = MAXULONG VDHGSV_MINTIMESLICE 14 ULONG milliseconds 0 < = x < = MAXULONG VDHGSV_MAXTIMESLICE 15 ULONG milliseconds 0 < = x < = MAXULONG VDHGSV_YIELD 16 BOOL TRUE(nonzero)/FALSE(0) VDHGSV_TCYIELD 17 BOOL TRUE(nonzero)/FALSE(0) VDHGSV_VERMAJOR 18 ULONG 0 < = x < = MAXULONG VDHGSV_VERMINOR 19 ULONG 0 < = x < = MAXULONG VDHGSV_VERREVISION 20 CHAR 0 < = x < = 255
Global Values Ordinal Type Units Range
_____________ _______ ____ _____ _____
VDHGSV_MACHINETYPE 21 ULONG MACHINE_TYPE_
VDHGSV_BLACKHOLEADDR 22 PVOID bytes 0 < = x < = MAXULONG
VDHGSV_BLACKHOLESIZE 23 ULONG bytes 0 < = x < = MAXULONG
VDHGSV_FGNDSESSIONID 24 ULONG 0 < = x < = MAXSESSIONS
VDHGSV_ARPLADDR 29 ULONG
VDHGSV_MACHINEINFO 30 ULONG Pointer to System
Configuration table
VDHGSV_PPOSREGS 31 ULONG Pointer to POS Regs
structure
VDHGSV_PICMASK 32 ULONG Original PIC mask values
Local Values Ordinal Type Units Range
____________ _______ ____ _____ _____
VDHLSV_HVDM 4096 HVDM
VDHLSV_PID 4097 PID
VDHLSV_PCRF 4098 PCFR
VDHLSV_SESSIONID 4099 ULONG N < = x < MAXSESSIONS
VDHLSV_FOREGROUND 4100 BOOL TRUE(nonzero)/FALSE(0)
VDHLSV_RMSIZE 4101 ULONG KB 0 < x < = 640
VDHLSV_CODEPAGEID 4102 ULONG See DosGetCP
VDHLSV_PRIORITYCLASS 4103 ULONG See VDHSetPriority
VDHLSV_PRIORITYLEVEL 4104 ULONG See VDHSetPriority
VDHLSV_VPICBASE 4105 UCHAR[4]
VDHQuerySysValue Return Value - rc
rc(ULONG) - returns
Success If the function is successful, it returns the value of the system variable. If the value is 0 and VDHGetErrorreturns 0, then 0 is the correct value.
Failure If VDMHandleor Indexis invalid, a system halt occurs.
VDHQuerySysValue - Parameters
VDMHandle(HVDM) Index of the system variable handle of the DOS session to query. A value of 0 (zero) indicates the current DOS session.
Index(ULONG) VDHQuerySysValueindex values (as defined in VDMM.INC) and descriptions:
Global Values Ordinal Type Units Range _____________ _______ ____ _____ _____ VDHGSV_DAY 0 ULONG days 1 < = x < = 31 VDHGSV_MONTH 1 ULONG months 1 < = x < = 12 VDHGSV_YEAR 2 ULONG years 1980 < = x < = MAXULONG VDHGSV_DAYOFWEEK 3 ULONG days 0 < = x < = 6 VDHGSV_HOUR 4 ULONG hours 0 < = x < = 24 VDHGSV_MINUTE 5 ULONG minutes 0 < = x < = 60 VDHGSV_SECOND 6 ULONG seconds 0 < = x < = 60 VDHGSV_HUNDREDTH 7 ULONG 1/100S 0 < = x < = 100 VDHGSV_SECONDS1970 8 ULONG seconds 0 < = x < = MAXULONG VDHGSV_TIMEZONE 9 ULONG minutes 0 < = x < = MAXULONG VDHGSV_MSECSBOOT 10 ULONG milliseconds 0 < = x < = MAXULONG VDHGSV_TIMERINTERVAL 11 ULONG milliseconds 0 < = x < = 1000 VDHGSV_DYNVARIATION 12 BOOL TRUE(nonzero)/FALSE(0) VDHGSV_MAXWAIT 13 ULONG seconds 0 < = x < = MAXULONG VDHGSV_MINTIMESLICE 14 ULONG milliseconds 0 < = x < = MAXULONG VDHGSV_MAXTIMESLICE 15 ULONG milliseconds 0 < = x < = MAXULONG VDHGSV_YIELD 16 BOOL TRUE(nonzero)/FALSE(0) VDHGSV_TCYIELD 17 BOOL TRUE(nonzero)/FALSE(0) VDHGSV_VERMAJOR 18 ULONG 0 < = x < = MAXULONG VDHGSV_VERMINOR 19 ULONG 0 < = x < = MAXULONG VDHGSV_VERREVISION 20 CHAR 0 < = x < = 255
Global Values Ordinal Type Units Range
_____________ _______ ____ _____ _____
VDHGSV_MACHINETYPE 21 ULONG MACHINE_TYPE_
VDHGSV_BLACKHOLEADDR 22 PVOID bytes 0 < = x < = MAXULONG
VDHGSV_BLACKHOLESIZE 23 ULONG bytes 0 < = x < = MAXULONG
VDHGSV_FGNDSESSIONID 24 ULONG 0 < = x < = MAXSESSIONS
VDHGSV_ARPLADDR 29 ULONG
VDHGSV_MACHINEINFO 30 ULONG Pointer to System
Configuration table
VDHGSV_PPOSREGS 31 ULONG Pointer to POS Regs
structure
VDHGSV_PICMASK 32 ULONG Original PIC mask values
Local Values Ordinal Type Units Range
____________ _______ ____ _____ _____
VDHLSV_HVDM 4096 HVDM
VDHLSV_PID 4097 PID
VDHLSV_PCRF 4098 PCFR
VDHLSV_SESSIONID 4099 ULONG N < = x < MAXSESSIONS
VDHLSV_FOREGROUND 4100 BOOL TRUE(nonzero)/FALSE(0)
VDHLSV_RMSIZE 4101 ULONG KB 0 < x < = 640
VDHLSV_CODEPAGEID 4102 ULONG See DosGetCP
VDHLSV_PRIORITYCLASS 4103 ULONG See VDHSetPriority
VDHLSV_PRIORITYLEVEL 4104 ULONG See VDHSetPriority
VDHLSV_VPICBASE 4105 UCHAR[4]
rc(ULONG) - returns
Success If the function is successful, it returns the value of the system variable. If the value is 0 and VDHGetErrorreturns 0, then 0 is the correct value.
Failure If VDMHandleor Indexis invalid, a system halt occurs.
VDHQuerySysValue - Purpose
Context Issues: This function can be called in any context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Systems values are of two classes, global and per-DOS session. These classes are distinguished by the prefix of the index name. Variables with prefixes of VDHGSV_are global. Variables with a VDHLSV_prefix are per-DOS session.
VDHQuerySysValue - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQueryVIRQ
Select an item:
Format Parameters Return Codes Purpose Glossary
This function returns information about the virtual mask, interrupt request flag, interrupt in-service flag, and pending virtual device driver Interrupt Return (IRET) handlers for the specified IRQ, device, or DOS session.
#include mvdm.h HVDM VDMHandle; /* IRQ handle from DOS session handle */ HIRQ IRQHandle; /* IRQ handle from VDHOpenVIRQ */ ULONG rc; rc = VDHQueryVIRQ(VDMHandle, IRQHandle);
VDHQueryVIRQ - Format
This function returns information about the virtual mask, interrupt request flag, interrupt in-service flag, and pending virtual device driver Interrupt Return (IRET) handlers for the specified IRQ, device, or DOS session.
#include mvdm.h HVDM VDMHandle; /* IRQ handle from DOS session handle */ HIRQ IRQHandle; /* IRQ handle from VDHOpenVIRQ */ ULONG rc; rc = VDHQueryVIRQ(VDMHandle, IRQHandle);
VDHQueryVIRQ Parameter - VDMHandle
VDMHandle(HVDM) IRQ handle from VDHOpenVIRQDOS session handle. A value of 0 (zero) indicates the current DOS session.
VDHQueryVIRQ Parameter - IRQHandle
IRQHandle(HIRQ) IRQ handle from VDHOpenVIRQ.
VDHQueryVIRQ Return Value - rc
rc(ULONG) - returns
Success If the function is successful, it returns the IRQ status as a DD of flag bits:
VPICQ_REQUEST_PENDING Request is pending for the queried IRQ
VPICQ_IN_SERVICE Queried IRQ is in service
VPICQ_VIRT_MASK Mask is turned ON for the queried IRQ
VPICQ_STAT_IRET_PENDING IRET is pending for the queried IRQ.
Failure If VDMHandleor IRQHandleis invalid, a system halt occurs.
VDHQueryVIRQ - Parameters
VDMHandle(HVDM) IRQ handle from VDHOpenVIRQDOS session handle. A value of 0 (zero) indicates the current DOS session.
IRQHandle(HIRQ) IRQ handle from VDHOpenVIRQ.
rc(ULONG) - returns
Success If the function is successful, it returns the IRQ status as a DD of flag bits:
VPICQ_REQUEST_PENDING Request is pending for the queried IRQ
VPICQ_IN_SERVICE Queried IRQ is in service
VPICQ_VIRT_MASK Mask is turned ON for the queried IRQ
VPICQ_STAT_IRET_PENDING IRET is pending for the queried IRQ.
Failure If VDMHandleor IRQHandleis invalid, a system halt occurs.
VDHQueryVIRQ - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHQueryVIRQ - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRaiseException
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used to raise an exception, which is reflected to a DOS session as if the exception were caused by the hardware.
#include mvdm.h
ULONG Exception; /* An exception number */
ULONG ErrorCode; /* Error code for the exception */
ULONG ExtraCode; /* Extra error code */
BOOL rc;
rc = VDHRaiseException(Exception, ErrorCode,
ExtraCode);
VDHRaiseException - Format
This function is used to raise an exception, which is reflected to a DOS session as if the exception were caused by the hardware.
#include mvdm.h
ULONG Exception; /* An exception number */
ULONG ErrorCode; /* Error code for the exception */
ULONG ExtraCode; /* Extra error code */
BOOL rc;
rc = VDHRaiseException(Exception, ErrorCode,
ExtraCode);
VDHRaiseException Parameter - Exception
Exception(ULONG) An exception number that might be caused by the 80386 microprocessor.
VDHRaiseException Parameter - ErrorCode
ErrorCode(ULONG) Error code for the exception defined for the 80386 microprocessor.
VDHRaiseException Parameter - ExtraCode
ExtraCode(ULONG) Extra error code for DPMI 1.0 page faults.
VDHRaiseException Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero).
VDHRaiseException - Parameters
Exception(ULONG) An exception number that might be caused by the 80386 microprocessor.
ErrorCode(ULONG) Error code for the exception defined for the 80386 microprocessor.
ExtraCode(ULONG) Extra error code for DPMI 1.0 page faults.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero).
VDHRaiseException - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHRaiseException - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRead
Select an item:
Format Parameters Return Codes Purpose Glossary
This function reads bytes from a file or device previously opened by VDHOpen.
#include mvdm.h HFILE FileHandle; /* Handle to the file or device to read */ PVOID ReadBufferPtr; /* Address of the buffer to store the bytes read */ ULONG NumBytes; /* Number of bytes to read */ ULONG rc; rc = VDHRead(FileHandle, ReadBufferPtr, NumBytes);
VDHRead - Format
This function reads bytes from a file or device previously opened by VDHOpen.
#include mvdm.h HFILE FileHandle; /* Handle to the file or device to read */ PVOID ReadBufferPtr; /* Address of the buffer to store the bytes read */ ULONG NumBytes; /* Number of bytes to read */ ULONG rc; rc = VDHRead(FileHandle, ReadBufferPtr, NumBytes);
VDHRead Parameter - FileHandle
FileHandle(HFILE) Handle to the file or device to read.
VDHRead Parameter - ReadBufferPtr
ReadBufferPtr(PVOID) Address of the buffer to store the bytes read.
VDHRead Parameter - NumBytes
NumBytes(ULONG) Number of bytes to read.
VDHRead Return Value - rc
rc(ULONG) - returns
Success If the function is successful, it returns a count of the number of bytes read; this can be equal to 0 (zero).
Failure If the function fails, it returns 0FFFFFFFFH. VDHGetErrorshould be called to determine the nature of the problem. If FileHandleis invalid or this function is called in any context except DOS session-task, a system halt occurs.
VDHRead - Parameters
FileHandle(HFILE) Handle to the file or device to read.
ReadBufferPtr(PVOID) Address of the buffer to store the bytes read.
NumBytes(ULONG) Number of bytes to read.
rc(ULONG) - returns
Success If the function is successful, it returns a count of the number of bytes read; this can be equal to 0 (zero).
Failure If the function fails, it returns 0FFFFFFFFH. VDHGetErrorshould be called to determine the nature of the problem. If FileHandleis invalid or this function is called in any context except DOS session-task, a system halt occurs.
VDHRead - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHRead - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHReadUBuf
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used to read from protected-mode address space as if the read were done at Ring 3. This means any other faults are trapped. All faults are passed on to the DOS session application handler through VDHRaiseException.
#include mvdm.h
PVOID DestBuffer; /* Destination buffer for copy. */
ULONG ByteCount; /* Count of bytes */
SEL Selector; /* Application selector */
PULONG OffsetPointer; /* Address of the variable containing the offset */
ULONG Flag; /* Checking controls flag */
BOOL rc;
rc = VDHReadUBuf(DestBuffer, ByteCount, Selector,
OffsetPointer, Flag);
VDHReadUBuf - Format
This function is used to read from protected-mode address space as if the read were done at Ring 3. This means any other faults are trapped. All faults are passed on to the DOS session application handler through VDHRaiseException.
#include mvdm.h
PVOID DestBuffer; /* Destination buffer for copy. */
ULONG ByteCount; /* Count of bytes */
SEL Selector; /* Application selector */
PULONG OffsetPointer; /* Address of the variable containing the offset */
ULONG Flag; /* Checking controls flag */
BOOL rc;
rc = VDHReadUBuf(DestBuffer, ByteCount, Selector,
OffsetPointer, Flag);
VDHReadUBuf Parameter - DestBuffer
DestBuffer(PVOID) Destination buffer for copy.
VDHReadUBuf Parameter - ByteCount
ByteCount(ULONG) Count of bytes.
VDHReadUBuf Parameter - Selector
Selector(SEL) Application selector.
VDHReadUBuf Parameter - OffsetPointer
OffsetPointer(PULONG) Address of the variable containing the offset for the start of the read.
VDHReadUBuf Parameter - Flag
Flag(ULONG) Flag containing checking controls.
Possible values are:
VPM_PROT_READ Check for read.
VPM_PROT_WRITE Check for write.
VPM_FAULT_IF_SU_SET Fault, if supervisor pages.
VPM_FAULT_IF_RO Fault, if writing to read-only descriptor.
VPM_SEL_PRESENT Caller knows descriptor is present.
VPM_SEL_WRITEABLE Caller knows descriptor is writable.
VPM_SEL_IS_SS Selector is client's stack.
VPM_XCPTRET_ALT After exception, return to alternate mode. For example, if the client was in protected mode when the service was called, return in V86 mode after the exception is handled.
VDHReadUBuf Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if a bad address reference is causing the fault. In this case, OffsetPointeris updated with the address of the fault. For selector faults, OffsetPointeris unchanged.
VDHReadUBuf - Parameters
DestBuffer(PVOID) Destination buffer for copy.
ByteCount(ULONG) Count of bytes.
Selector(SEL) Application selector.
OffsetPointer(PULONG) Address of the variable containing the offset for the start of the read.
Flag(ULONG) Flag containing checking controls.
Possible values are:
VPM_PROT_READ Check for read.
VPM_PROT_WRITE Check for write.
VPM_FAULT_IF_SU_SET Fault, if supervisor pages.
VPM_FAULT_IF_RO Fault, if writing to read-only descriptor.
VPM_SEL_PRESENT Caller knows descriptor is present.
VPM_SEL_WRITEABLE Caller knows descriptor is writable.
VPM_SEL_IS_SS Selector is client's stack.
VPM_XCPTRET_ALT After exception, return to alternate mode. For example, if the client was in protected mode when the service was called, return in V86 mode after the exception is handled.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if a bad address reference is causing the fault. In this case, OffsetPointeris updated with the address of the fault. For selector faults, OffsetPointeris unchanged.
VDHReadUBuf - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: If the routine fails, the caller must clean up and exit so that the exception can be simulated to the user. Supervisor pages can be read without faults to avoid the overhead of checking.
VDHReadUBuf - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHReallocPages
Select an item:
Format Parameters Return Codes Purpose Glossary
This function expands or shrinks a memory object.
#include mvdm.h
PVOID ObjectAddress; /* Address of the memory object to resize */
ULONG NumPages; /* New size of the memory object (in 4KB pages) */
ULONG Reserved; /* Must be zero */
PVOID rc;
rc = VDHReallocPages(ObjectAddress, NumPages,
Reserved);
VDHReallocPages - Format
This function expands or shrinks a memory object.
#include mvdm.h
PVOID ObjectAddress; /* Address of the memory object to resize */
ULONG NumPages; /* New size of the memory object (in 4KB pages) */
ULONG Reserved; /* Must be zero */
PVOID rc;
rc = VDHReallocPages(ObjectAddress, NumPages,
Reserved);
VDHReallocPages Parameter - ObjectAddress
ObjectAddress(PVOID) Address of the memory object to reallocate or resize.
VDHReallocPages Parameter - NumPages
NumPages(ULONG) The new size of the memory object (in 4KB pages).
VDHReallocPages Parameter - Reserved
Reserved(ULONG) Must be set to zero.
VDHReallocPages Return Value - rc
rc(PVOID) - returns
Success If the function is successful, it returns that address of the reallocated memory block.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If the memory object at ObjectAddresswas not allocated by VDHAllocPagesor VDHReallocPages, or if the NumPagesor Reservedparameters are invalid, a system halt occurs.
VDHReallocPages - Parameters
ObjectAddress(PVOID) Address of the memory object to reallocate or resize.
NumPages(ULONG) The new size of the memory object (in 4KB pages).
Reserved(ULONG) Must be set to zero.
rc(PVOID) - returns
Success If the function is successful, it returns that address of the reallocated memory block.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If the memory object at ObjectAddresswas not allocated by VDHAllocPagesor VDHReallocPages, or if the NumPagesor Reservedparameters are invalid, a system halt occurs.
VDHReallocPages - Purpose
Context Issues: This function can be called in the initialization or task context.
DOS Session Terminations: Any allocations that are not in the terminating DOS session's private area must be released by using VDHFreePages.
Notes: When an allocation made with VDHAllocPagesis shrunk by VDHReallocPages, the linear range between the end of the allocation and the original end of the allocation remains available for object growth without movement. If the linear range encompassed by the new size was reserved ( with VDHReservePages), reallocation occurs without movement. Reallocation also succeeds without movement if the object was larger than the desired size since it last moved. Regardless of VDHReallocPagesactivity, all pages in the allocation retain the same properties, that is, fixed, system, and physical.
VDHReallocPages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRegisterAPI
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used to register a virtual device driver's API handler that can be called by a DOS or DPMI application in the DOS session. A V86- mode or protected-mode (or both) API handler is set for a particular virtual device driver. Each virtual device driver must register with a unique virtual device driver name. This service provides a mechanism for DOS applications to communicate directly with the virtual device driver.
#include mvdm.h PSZ VDDName; /* Pointer to the name of the virtual device driver */ PFNHook pfnV86Hook; /* V86-mode hook routine address */ PFNHook pfnVPMHook; /* VPM-mode hook routine address */ BOOL rc; rc = VDHRegisterAPI(VDDName, pfnV86Hook, pfnVPMHook);
VDHRegisterAPI - Format
This function is used to register a virtual device driver's API handler that can be called by a DOS or DPMI application in the DOS session. A V86- mode or protected-mode (or both) API handler is set for a particular virtual device driver. Each virtual device driver must register with a unique virtual device driver name. This service provides a mechanism for DOS applications to communicate directly with the virtual device driver.
#include mvdm.h PSZ VDDName; /* Pointer to the name of the virtual device driver */ PFNHook pfnV86Hook; /* V86-mode hook routine address */ PFNHook pfnVPMHook; /* VPM-mode hook routine address */ BOOL rc; rc = VDHRegisterAPI(VDDName, pfnV86Hook, pfnVPMHook);
VDHRegisterAPI Parameter - VDDName
VDDName(PSZ) Pointer to the name of the virtual device driver. Maximum length is MAXLENXDD.
VDHRegisterAPI Parameter - pfnV86Hook
pfnV86Hook(PFNHook) V86-mode hook routine address (NULL if no V86-mode handler is needed).
VDHRegisterAPI Parameter - pfnVPMHook
pfnVPMHook(PFNHook) VPM-mode hook routine address (NULL if no VPM-mode handler is needed).
VDHRegisterAPI Return Value - rc
rc(BOOL) - returns
Success Returns TRUE
Failure Returns FALSE
VDHRegisterAPI - Parameters
VDDName(PSZ) Pointer to the name of the virtual device driver. Maximum length is MAXLENXDD.
pfnV86Hook(PFNHook) V86-mode hook routine address (NULL if no V86-mode handler is needed).
pfnVPMHook(PFNHook) VPM-mode hook routine address (NULL if no VPM-mode handler is needed).
rc(BOOL) - returns
Success Returns TRUE
Failure Returns FALSE
VDHRegisterAPI - Purpose
Context Issues: This function can only be called in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function. The hook(s) are freed when the DOS session is terminated .
Notes:
Hook routine:
VOID HOOKENTRY pfnHook(p,prcf)
ENTRY PVOID p-reserved
PCRF pcrf-pointer to client register frame
EXIT None
CONTEXT DOS session-task
DOS or DPMI applications issue the following INT 2F calls to determine if they are running under OS/2, and then get the virtual device driver API entry point.
Get OS/2 version (DOS or DPMI applications can use this INT 2F call to get the OS/2 version):
ENTRY AX = 0x4010
EXIT If OS/2 is running:
AX = 0
BX = OS/2 version (example:BX = 1400 for 2.0)
If OS/2 is not present, AX is unchanged
Get virtual device driver API entry points. DOS or DPMI applications can use this INT 2F call to get the address to call the virtual device driver entry points. If the INT 2F is issued in V86 mode, an address that calls the V86 virtual device driver API handler is returned. If the INT 2F call is issued in protected-mode, an address that corresponds to the protected- mode API handler is returned.
ENTRY AX = 0x4011
DS:(E)SI = pointer to ASCIIZ name registered
with VDHRegisterAPI
EXIT If VDD API handler exists:
ES:DI = address to call to invoke handler
If handler is not registered:
ES:DI = NULL
The DOS or DPMI application can then issue a far call to the address returned to invoke the virtual device driver API handler.
VDHRegisterAPI - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRegisterDMAChannel
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used by virtual device drivers to register with the virtual DMA device driver (VDMA) to get the ownership of a DMA channel.
#include mvdm.h ULONG DMAChannel; /* DMA channel */ PFNDMA DMAHandlerFunc; /* The virtual device driver's DMA-handling routine */ BOOL rc; rc = VDHRegisterDMAChannel(DMAChannel, DMAHandlerFunc);
VDHRegisterDMAChannel - Format
This function is used by virtual device drivers to register with the virtual DMA device driver (VDMA) to get the ownership of a DMA channel.
#include mvdm.h ULONG DMAChannel; /* DMA channel */ PFNDMA DMAHandlerFunc; /* The virtual device driver's DMA-handling routine */ BOOL rc; rc = VDHRegisterDMAChannel(DMAChannel, DMAHandlerFunc);
VDHRegisterDMAChannel Parameter - DMAChannel
DMAChannel(ULONG) DMA channel.
VDHRegisterDMAChannel Parameter - DMAHandlerFunc
DMAHandlerFunc(PFNDMA) The virtual device driver's DMA-handler function.
The interface for the DMA-handler routine is as follows:
BOOL HOOKENTRY (hvdm, iEvent)
ENTRY
HVDM hvdm - DOS session requesting DMA
ULONG iEvent - VDD_DMA_MASKOFF (Start DMA, Event)
VDD_DMA_MASK (Stop DMA, Event)
EXIT
SUCCESS - returns nonzero
If VDD_DMA_MASKOFF,
the virtual DMA device driver will program the DMA
If VDD_DMA_MASK, don't care
FAILURE - returns 0 (zero)
VDHRegisterDMAChannel Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns 1.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHRegisterDMAChannel - Parameters
DMAChannel(ULONG) DMA channel.
DMAHandlerFunc(PFNDMA) The virtual device driver's DMA-handler function.
The interface for the DMA-handler routine is as follows:
BOOL HOOKENTRY (hvdm, iEvent)
ENTRY
HVDM hvdm - DOS session requesting DMA
ULONG iEvent - VDD_DMA_MASKOFF (Start DMA, Event)
VDD_DMA_MASK (Stop DMA, Event)
EXIT
SUCCESS - returns nonzero
If VDD_DMA_MASKOFF,
the virtual DMA device driver will program the DMA
If VDD_DMA_MASK, don't care
FAILURE - returns 0 (zero)
rc(BOOL) - returns
Success If the function is successful, it returns 1.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHRegisterDMAChannel - Purpose
Context Issues: This function can be called only in the initialization context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: In the case of VDD_DMA_MASKOFF, the virtual device driver gets the hardware ownership and unhooks all the ports. If hardware ownership is not available immediately, it blocks the DOS session. On VDD_DMA_MASK, the virtual device driver returns the ownership and hooks back the ports.
If the DOS application programs the hardware handled by a virtual device driver first, and then programs the DMA, this virtual device driver receives ownership of hardware, unhooks all ports on first port access, and arms a timer for a safe period. This is a preventive measure to protect the system from errant I/O to DMA ports. If the timer fires, the virtual device driver releases the hardware. In this case, the virtual device driver does nothing when the virtual DMA device driver later calls with VDD_DMA_MASKOFF .
It is the virtual device driver's responsibility (in DMAHandlerFunc) to handle the unavailability of hardware ownership. This means the virtual device driver must put up the pop-up and suspend (or terminate) the DOS session. The virtual device driver passes the interrupt notification to the virtual DMA device driver before simulating that interrupt to the DOS session, if it owns the hardware.
In between VDD_DMA_MASKOFF and VDD_DMA_MASK events, the virtual DMA device driver always returns the physical DMA state, if the application polls its status or transfer count. This is appropriate because the virtual device driver owns the device during this period. VDD_DMA_MASK event notification takes place before actually masking the register in DMA. VDD_DMA_MASKOFF takes place after masking off the DMA.
DMA Channel 4 is not supported.
VDHRegisterDMAChannel - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRegisterProperty
Select an item:
Format Parameters Return Codes Purpose Glossary
This function registers a virtual device driver property with the DOS Session Manager.
#include mvdm.h
PSZ PropertyName; /* Property name pointer */
PSZ Reserved; /* Must be set to 0 */
ULONG Reserved; /* Must be set to 0 */
VPTYPE PropertyType; /* Property type */
VPORD PropertyOrdinal; /* Property ordinal */
ULONG PropertyFlag; /* Property flag */
PVOID DefaultValue; /* Default value of the property */
PVOID ValidationData; /* Validation data */
PFNVDHRP ValidationFunc; /* Pointer to a virtual device driver property function */
BOOL rc;
rc = VDHRegisterProperty(PropertyName, Reserved,
Reserved, PropertyType, PropertyOrdinal,
PropertyFlag, DefaultValue, ValidationData,
ValidationFunc);
VDHRegisterProperty - Format
This function registers a virtual device driver property with the DOS Session Manager.
#include mvdm.h
PSZ PropertyName; /* Property name pointer */
PSZ Reserved; /* Must be set to 0 */
ULONG Reserved; /* Must be set to 0 */
VPTYPE PropertyType; /* Property type */
VPORD PropertyOrdinal; /* Property ordinal */
ULONG PropertyFlag; /* Property flag */
PVOID DefaultValue; /* Default value of the property */
PVOID ValidationData; /* Validation data */
PFNVDHRP ValidationFunc; /* Pointer to a virtual device driver property function */
BOOL rc;
rc = VDHRegisterProperty(PropertyName, Reserved,
Reserved, PropertyType, PropertyOrdinal,
PropertyFlag, DefaultValue, ValidationData,
ValidationFunc);
VDHRegisterProperty Parameter - PropertyName
PropertyName(PSZ) Pointer to an ASCIIZ string containing the property name . Maximum length is 40 characters.
VDHRegisterProperty Parameter - Reserved
Reserved(PSZ) Must be set to 0 (zero).
VDHRegisterProperty Parameter - Reserved
Reserved(ULONG) Must be set to 0 (zero).
VDHRegisterProperty Parameter - PropertyType
PropertyType(VPTYPE) Property type.
Values are:
VDMP_BOOL 0-Boolean
VDMP_INT 1-Integer. DD size, but only DW is valid
VDMP_ENUM 2-Enumeration
VDMP_STRING 3-ASCIIZ string
VDMP_MLSTR 4-Multi-line string, separated by linefeed (0AH)
VDHRegisterProperty Parameter - PropertyOrdinal
PropertyOrdinal(VPORD) Property ordinal.
Values are:
VDMP_ORD_OTHER 0-Custom virtual device driver property
VDMP_ORD_KERNEL 1-ASCIIZ path of DOS kernel
VDMP_ORD_SHELL 2-ASCIIZ path of DOS_SHELL
VDMP_ORD_RMSIZE 3-Integer size of DOS box (128KB-640KB)
VDMP_ORD_FCB 4-Integer total FCBs
VDMP_ORD_FCB2 5-Integer FCBs immune to close LRUing
VDMP_ORD_BREAK 6-Boolean Break flag
VDMP_ORD_DOSDD 7-Multi-line string DOS_DEVICE
VDMP_ORD_VMBOOT 8-ASCIIZ string virtual machine boot drives
VDMP_ORD_VERSION 10-Multi-line string fake version entries
VDMP_ORD_DOS_UMB 11-Boolean flag. DOS_UMB
VDMP_ORD_DOS_HIGH 12-Boolean flag. DOS_HIGH
VDMP_ORD_LASTDRIVE 13-ASCIIZ DOS_LASTDRIVE
VDMP_ORD_FILES 14-Integer total FILES
VDHRegisterProperty Parameter - PropertyFlag
PropertyFlag(ULONG) Property flag.
Possible value:
VDMP_CREATE Property can be specified only at DOS session creation. Any change to the property after DOS session creation is ignored.
VDHRegisterProperty Parameter - DefaultValue
DefaultValue(PVOID) Default value of the property.
The format of this field depends on the value of PropertyType:
VDMP_BOOL DefaultValue is interpreted as a BOOL (Boolean) value.
VDMP_INT DefaultValue is interpreted as a DD value. Only the low half is used (the high half is ignored) so this is more similar to a DW than a DD.
VDMP_ENUM DefaultValue is interpreted as a pointer to an ASCIIZ string.
VDMP_STRING DefaultValue is interpreted as a pointer to an ASCIIZ string.
VDMP_MLSTR DefaultValue is interpreted as a pointer to an ASCIIZ string.
VDHRegisterProperty Parameter - ValidationData
ValidationData(PVOID) Validation data.
The value of this field depends on the value of PropertyType.
VDMP_BOOL ValidationData is NULL. The user is expected to validate Booleans .
VDMP_INT ValidationData is a pointer to a VPBOUND structure:
VPBOUND Limits for VDMP_INT properties. Note that maximum >minimum must hold, the range of maximum to minimum must be a multiple of step, and step= 1 implies that all values between minimum and maximum are valid:
typedef struct VPBOUND_s {
USHORT min; // minimum allowed value
USHORT max; // maximum allowed value
USHORT step; // increment between values
} VPBOUND;
typedef VPBOUND *PVPBOUND;
VDMP_ENUM ValidationData is a pointer to a set of ASCIIZ strings terminated by a zero byte, which is the allowed set of responses. The Shell uses this to construct a list or combination box for the user to pick from. Empty ("\ 0") strings are not allowed.
VDMP_STRING ValidationData is a DD that is the maximum allowed string length (including the NULL terminator).
VDMP_MLSTR ValidationData is a DD that is the maximum allowed string length (including the NULL terminator).
VDHRegisterProperty Parameter - ValidationFunc
ValidationFunc(PFNVDHRP) Function that validates and accepts changes to this property for a running DOS session. Ignored if VDMP_CREATE is specified in conjunction with VDMP_BOOL, VDMP_INT, or VDMP_ENUM.
The interface for the ValidationFunc is defined as follows:
#define VDHPROP_VALIDATE 0x00000000L #define VDHPROP_SET 0x00000001L ULONG EXPENTRY fnvdhrp (ULONG op, HVDM hvdm, ULONG cb, PSZ pch);
PFNVDHRP is a pointer to a property function of the virtual device driver that performs property setting and validation. This routine is required for any property that does not specify VDMP_CREATE. Set operations can be requested any time after a DOS session is created. The validation operation can be requested at any time, even before a DOS session is created. Validation is requested only for VDMP_STRING and VDMP_MLSTR types because all other types can be validated using the information supplied by VDHRegisterProperty.
Parameter Data Type Description
_________ _________ ___________
op ULONG Operation to perform. See the following
parameter.
hvdm HVDM Handle of DOS session. Undefined if op =
VDHPROP_VALIDATE.
cb ULONG Count of bytes pointed by pch. See the
following parameter.
pch PSZ Pointer to the value set or validate. See the
following parameter.
op Operation to perform (enumeration):
VDHPROP_VALIDATE Validate property for any process. Only called for VDMP_ STRING and VDMP_MLSTR properties.
VDHPROP_SET Set an already validated property for specified hvdm. The return code is ignored.
cb Count of bytes pointed to by pch. Value depends upon PropertyType:
VDMPROP_BOOL Undefined
VDMPROP_INT Undefined
VDMPROP_ENUM Length of ASCIIZ string including NULL terminator
VDMPROP_STRING Length of ASCIIZ string including NULL terminator
VDMPROP_MLSTR Length of ASCIIZ string including NULL terminator
pch Value to set/validate. The format depends on the property type:
VDMPROP_BOOL pch is interpreted as a BOOL (Boolean). Value 0 is FALSE; a nonzero value is TRUE.
VDMPROP_INT pch is interpreted as a DD, and is guaranteed to meet the registered bounds.
VDMPROP_ENUM pch points to an ASCIIZ string, and is guaranteed to be one of the registered enumeration strings.
VDMPROP_STRING pch points to an ASCIIZ string, and is guaranteed to be equal to or less than the registered maximum string length.
VDMPROP_MLSTR pch points to an ASCIIZ string. Multiple lines are separated by a line feed (0x0A). It is guaranteed to be less than or equal to the registered maximum string length.
VDHRegisterProperty Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. A system halt occurs if:
- Any of the pointers (PropertyName, HelpFile, ValidationData, or ValidationFunc) are invalid
*PropertyFlag or PropertyType are invalid
*A VPBOUND structure has invalid contents
*The maximum string length for a VDMP_STRING is less than the length of the default string value
VDHRegisterProperty - Parameters
PropertyName(PSZ) Pointer to an ASCIIZ string containing the property name . Maximum length is 40 characters.
Reserved(PSZ) Must be set to 0 (zero).
Reserved(ULONG) Must be set to 0 (zero).
PropertyType(VPTYPE) Property type.
Values are:
VDMP_BOOL 0-Boolean
VDMP_INT 1-Integer. DD size, but only DW is valid
VDMP_ENUM 2-Enumeration
VDMP_STRING 3-ASCIIZ string
VDMP_MLSTR 4-Multi-line string, separated by linefeed (0AH)
PropertyOrdinal(VPORD) Property ordinal.
Values are:
VDMP_ORD_OTHER 0-Custom virtual device driver property
VDMP_ORD_KERNEL 1-ASCIIZ path of DOS kernel
VDMP_ORD_SHELL 2-ASCIIZ path of DOS_SHELL
VDMP_ORD_RMSIZE 3-Integer size of DOS box (128KB-640KB)
VDMP_ORD_FCB 4-Integer total FCBs
VDMP_ORD_FCB2 5-Integer FCBs immune to close LRUing
VDMP_ORD_BREAK 6-Boolean Break flag
VDMP_ORD_DOSDD 7-Multi-line string DOS_DEVICE
VDMP_ORD_VMBOOT 8-ASCIIZ string virtual machine boot drives
VDMP_ORD_VERSION 10-Multi-line string fake version entries
VDMP_ORD_DOS_UMB 11-Boolean flag. DOS_UMB
VDMP_ORD_DOS_HIGH 12-Boolean flag. DOS_HIGH
VDMP_ORD_LASTDRIVE 13-ASCIIZ DOS_LASTDRIVE
VDMP_ORD_FILES 14-Integer total FILES
PropertyFlag(ULONG) Property flag.
Possible value:
VDMP_CREATE Property can be specified only at DOS session creation. Any change to the property after DOS session creation is ignored.
DefaultValue(PVOID) Default value of the property.
The format of this field depends on the value of PropertyType:
VDMP_BOOL DefaultValue is interpreted as a BOOL (Boolean) value.
VDMP_INT DefaultValue is interpreted as a DD value. Only the low half is used (the high half is ignored) so this is more similar to a DW than a DD.
VDMP_ENUM DefaultValue is interpreted as a pointer to an ASCIIZ string.
VDMP_STRING DefaultValue is interpreted as a pointer to an ASCIIZ string.
VDMP_MLSTR DefaultValue is interpreted as a pointer to an ASCIIZ string.
ValidationData(PVOID) Validation data.
The value of this field depends on the value of PropertyType.
VDMP_BOOL ValidationData is NULL. The user is expected to validate Booleans .
VDMP_INT ValidationData is a pointer to a VPBOUND structure:
VPBOUND Limits for VDMP_INT properties. Note that maximum >minimum must hold, the range of maximum to minimum must be a multiple of step, and step= 1 implies that all values between minimum and maximum are valid:
typedef struct VPBOUND_s {
USHORT min; // minimum allowed value
USHORT max; // maximum allowed value
USHORT step; // increment between values
} VPBOUND;
typedef VPBOUND *PVPBOUND;
VDMP_ENUM ValidationData is a pointer to a set of ASCIIZ strings terminated by a zero byte, which is the allowed set of responses. The Shell uses this to construct a list or combination box for the user to pick from. Empty ("\ 0") strings are not allowed.
VDMP_STRING ValidationData is a DD that is the maximum allowed string length (including the NULL terminator).
VDMP_MLSTR ValidationData is a DD that is the maximum allowed string length (including the NULL terminator).
ValidationFunc(PFNVDHRP) Function that validates and accepts changes to this property for a running DOS session. Ignored if VDMP_CREATE is specified in conjunction with VDMP_BOOL, VDMP_INT, or VDMP_ENUM.
The interface for the ValidationFunc is defined as follows:
#define VDHPROP_VALIDATE 0x00000000L #define VDHPROP_SET 0x00000001L ULONG EXPENTRY fnvdhrp (ULONG op, HVDM hvdm, ULONG cb, PSZ pch);
PFNVDHRP is a pointer to a property function of the virtual device driver that performs property setting and validation. This routine is required for any property that does not specify VDMP_CREATE. Set operations can be requested any time after a DOS session is created. The validation operation can be requested at any time, even before a DOS session is created. Validation is requested only for VDMP_ STRING and VDMP_MLSTR types because all other types can be validated using the information supplied by VDHRegisterProperty.
Parameter Data Type Description
_________ _________ ___________
op ULONG Operation to perform. See the following
parameter.
hvdm HVDM Handle of DOS session. Undefined if op =
VDHPROP_VALIDATE.
cb ULONG Count of bytes pointed by pch. See the
following parameter.
pch PSZ Pointer to the value set or validate. See the
following parameter.
op Operation to perform (enumeration):
VDHPROP_VALIDATE Validate property for any process. Only called for VDMP_ STRING and VDMP_MLSTR properties.
VDHPROP_SET Set an already validated property for specified hvdm. The return code is ignored.
cb Count of bytes pointed to by pch. Value depends upon PropertyType:
VDMPROP_BOOL Undefined
VDMPROP_INT Undefined
VDMPROP_ENUM Length of ASCIIZ string including NULL terminator
VDMPROP_STRING Length of ASCIIZ string including NULL terminator
VDMPROP_MLSTR Length of ASCIIZ string including NULL terminator
pch Value to set/validate. The format depends on the property type:
VDMPROP_BOOL pch is interpreted as a BOOL (Boolean). Value 0 is FALSE; a nonzero value is TRUE.
VDMPROP_INT pch is interpreted as a DD, and is guaranteed to meet the registered bounds.
VDMPROP_ENUM pch points to an ASCIIZ string, and is guaranteed to be one of the registered enumeration strings.
VDMPROP_STRING pch points to an ASCIIZ string, and is guaranteed to be equal to or less than the registered maximum string length.
VDMPROP_MLSTR pch points to an ASCIIZ string. Multiple lines are separated by a line feed (0x0A). It is guaranteed to be less than or equal to the registered maximum string length.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. A system halt occurs if:
- Any of the pointers (PropertyName, HelpFile, ValidationData, or ValidationFunc) are invalid
*PropertyFlag or PropertyType are invalid
*A VPBOUND structure has invalid contents
*The maximum string length for a VDMP_STRING is less than the length of the default string value
VDHRegisterProperty - Purpose
Context Issues: This function can be called only in the initialization context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: VDHQueryProperty is used to obtain the value of a virtual device driver property for a particular DOS session.
VDHRegisterProperty - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRegisterVDD
Select an item:
Format Parameters Return Codes Purpose Glossary
This function registers virtual device driver entry points for use by other virtual device drivers (through VDHOpenVDDand VDHRequestVDD), and by OS/2 applications (through DosOpenVDDand DosRequestVDD).
#include mvdm.h PSZ VDDName; /* Pointer to the name of the virtual device driver */ PFNSYSREQ DosReqFcn; /* Function for use by DosRequestVDD */ PFNDEVREQ VDDReqFcn; /* Function for use by VDHRequestVDD */ BOOL rc; rc = VDHRegisterVDD(VDDName, DosReqFcn, VDDReqFcn);
VDHRegisterVDD - Format
This function registers virtual device driver entry points for use by other virtual device drivers (through VDHOpenVDDand VDHRequestVDD), and by OS/2 applications (through DosOpenVDDand DosRequestVDD).
#include mvdm.h PSZ VDDName; /* Pointer to the name of the virtual device driver */ PFNSYSREQ DosReqFcn; /* Function for use by DosRequestVDD */ PFNDEVREQ VDDReqFcn; /* Function for use by VDHRequestVDD */ BOOL rc; rc = VDHRegisterVDD(VDDName, DosReqFcn, VDDReqFcn);
VDHRegisterVDD Parameter - VDDName
VDDName(PSZ) Pointer to the name of the virtual device driver. Maximum length is MAXLENXDD.
VDHRegisterVDD Parameter - DosReqFcn
DosReqFcn(PFNSYSREQ) Function used by DosRequestVDD. NULL, if none.
The interface for the DosReqFcnis:
RETCODE EXPENTRY DosReqFcn(ulCmd,SGid,nbIn,pReqIn,nbOut,pReqOut)
ENTRY
SGID SGid - Screen Group ID
ULONG ulCmd - Command
ULONG cbIn - Input buffer size
PVOID pReqIn - Input packet
ULONG cbOut - Output buffer size
PVOID pReqOut - Output packet
EXIT
VDDREQ_PASS - DOS session manager calls the next routine
registered under same name
TRUE (nonzero) - Return failure (For APIs, 0 is success)
FALSE (0) - Return the caller success
VDHRegisterVDD Parameter - VDDReqFcn
VDDReqFcn(PFNDEVREQ) Function used by VDHRequestVDD. NULL, if none.
The interface for the VDDReqFcnis:
BOOL EXPENTRY VDDReqFcn(hvdm,ulCmd,pReqIn,pReqOut)
ENTRY
HVDM hvdm - DOS session handle
ULONG ulCmd - Command
PVOID pReqIn - Input packet
PVOID pReqOut - Output packet
EXIT
VDDREQ_PASS - DOS Session Manager calls the next routine
registered under same name
TRUE (nonzero) - Return success (For virtual DevHlp services, 1 is success)
FALSE (0) - Return the caller failure
VDHRegisterVDD Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0. If this function is called with invalid parameters or in an incorrect context, a system halt occurs.
VDHRegisterVDD - Parameters
VDDName(PSZ) Pointer to the name of the virtual device driver. Maximum length is MAXLENXDD.
DosReqFcn(PFNSYSREQ) Function used by DosRequestVDD. NULL, if none.
The interface for the DosReqFcnis:
RETCODE EXPENTRY DosReqFcn(ulCmd,SGid,nbIn,pReqIn,nbOut,pReqOut)
ENTRY
SGID SGid - Screen Group ID
ULONG ulCmd - Command
ULONG cbIn - Input buffer size
PVOID pReqIn - Input packet
ULONG cbOut - Output buffer size
PVOID pReqOut - Output packet
EXIT
VDDREQ_PASS - DOS session manager calls the next routine
registered under same name
TRUE (nonzero) - Return failure (For APIs, 0 is success)
FALSE (0) - Return the caller success
VDDReqFcn(PFNDEVREQ) Function used by VDHRequestVDD. NULL, if none.
The interface for the VDDReqFcnis:
BOOL EXPENTRY VDDReqFcn(hvdm,ulCmd,pReqIn,pReqOut)
ENTRY
HVDM hvdm - DOS session handle
ULONG ulCmd - Command
PVOID pReqIn - Input packet
PVOID pReqOut - Output packet
EXIT
VDDREQ_PASS - DOS Session Manager calls the next routine
registered under same name
TRUE (nonzero) - Return success (For virtual DevHlp services, 1 is success)
FALSE (0) - Return the caller failure
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0. If this function is called with invalid parameters or in an incorrect context, a system halt occurs.
VDHRegisterVDD - Purpose
Context Issues: This function can be called only in the initialization context.
DOS Session Terminations: The virtual device driver must communicate with any virtual device driver or OS/2 clients, to ensure that the resources for the terminating DOS session are freed.
Notes: If a virtual device driver fails in its INIT routine after registering (through VDHRegisterVDD), the deregistration is done automatically at the time the virtual device driver is unloaded. Because two or more virtual device drivers can register the same name (VDDName), the DOS Session Manager calls each virtual device driver's routine in turn, until one of them returns a nonzero value.
Note that the order of the calling sequence is not consistent.
VDHRegisterVDD - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHReleaseCodePageFont
Select an item:
Format Parameters Return Codes Purpose Glossary
This function releases a code page font loaded with VDHGetCodePageFont. If system memory was allocated to hold the specified font, this call will free that memory.
#include mvdm.h PVOID FontPtr; /* Pointer returned by VDHGetCodePageFont */ VDHReleaseCodePageFont(FontPtr);
VDHReleaseCodePageFont - Format
This function releases a code page font loaded with VDHGetCodePageFont. If system memory was allocated to hold the specified font, this call will free that memory.
#include mvdm.h PVOID FontPtr; /* Pointer returned by VDHGetCodePageFont */ VDHReleaseCodePageFont(FontPtr);
VDHReleaseCodePageFont Parameter - FontPtr
FontPtr(PVOID) Pointer returned in FontAddressby VDHGetCodePageFont.
VDHReleaseCodePageFont - Return Value
Success If the function is successful, it returns nothing.
Failure If FontPtris not valid, a system halt occurs.
VDHReleaseCodePageFont - Parameters
FontPtr(PVOID) Pointer returned in FontAddressby VDHGetCodePageFont.
Success If the function is successful, it returns nothing.
Failure If FontPtris not valid, a system halt occurs.
VDHReleaseCodePageFont - Purpose
Context Issues: This function can be called only in the DOS session task context.
DOS Session Terminations: The virtual device driver must call this function for any code page fonts loaded for this DOS session.
VDHReleaseCodePageFont - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHReleaseMutexSem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function releases the ownership of a mutex semaphore. If the request count becomes 0 (zero), the highest priority semaphore is awakened.
#include mvdm.h HVDHSEM MutexSemHandle; /* Handle of the semaphore to be released */ VDHReleaseMutexSem(MutexSemHandle);
VDHReleaseMutexSem - Format
This function releases the ownership of a mutex semaphore. If the request count becomes 0 (zero), the highest priority semaphore is awakened.
#include mvdm.h HVDHSEM MutexSemHandle; /* Handle of the semaphore to be released */ VDHReleaseMutexSem(MutexSemHandle);
VDHReleaseMutexSem Parameter - MutexSemHandle
MutexSemHandle(HVDHSEM) Handle of the semaphore to be released.
VDHReleaseMutexSem - Return Value
Success If the function is successful, it returns nothing and the semaphore in MutexSemHandleis released.
Failure If the virtual device driver that called VDHReleaseMutexSemis not the owner of the semaphore to be released, or if MutexSemHandleinvalid, a system halt occurs.
VDHReleaseMutexSem - Parameters
MutexSemHandle(HVDHSEM) Handle of the semaphore to be released.
Success If the function is successful, it returns nothing and the semaphore in MutexSemHandleis released.
Failure If the virtual device driver that called VDHReleaseMutexSemis not the owner of the semaphore to be released, or if MutexSemHandleinvalid, a system halt occurs.
VDHReleaseMutexSem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHReleaseMutexSem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRemoveFaultHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function removes the page fault handler hook for the specified DOS session page range.
#include mvdm.h
HVDM VDMHandle; /* DOS session handle. 0 = current DOS session */
PVOID StartingAddress; /* Starting linear address */
ULONG Pages; /* Number of pages */
PFAULTHOOK PageFaultHandlerFcnPtr; /* Function supplied to VDHInstallFaultHook */
VDHRemoveFaultHook(VDMHandle, StartingAddress,
Pages, PageFaultHandlerFcnPtr);
VDHRemoveFaultHook - Format
This function removes the page fault handler hook for the specified DOS session page range.
#include mvdm.h
HVDM VDMHandle; /* DOS session handle. 0 = current DOS session */
PVOID StartingAddress; /* Starting linear address */
ULONG Pages; /* Number of pages */
PFAULTHOOK PageFaultHandlerFcnPtr; /* Function supplied to VDHInstallFaultHook */
VDHRemoveFaultHook(VDMHandle, StartingAddress,
Pages, PageFaultHandlerFcnPtr);
VDHRemoveFaultHook Parameter - VDMHandle
VDMHandle(HVDM) DOS session handle. A value of 0 (zero) indicates the current DOS session.
VDHRemoveFaultHook Parameter - StartingAddress
StartingAddress(PVOID) Starting linear address.
VDHRemoveFaultHook Parameter - Pages
Pages(ULONG) Number of pages.
VDHRemoveFaultHook Parameter - PageFaultHandlerFcnPtr
PageFaultHandlerFcnPtr(PFAULTHOOK) Function supplied to VDHInstallFaultHook. This is used to verify that the calling virtual device driver is the one that installed the fault hook.
VDHRemoveFaultHook - Return Value
Success If the function is successful, it returns nothing.
Failure If any of the input parameters are invalid, a system halt occurs.
VDHRemoveFaultHook - Parameters
VDMHandle(HVDM) DOS session handle. A value of 0 (zero) indicates the current DOS session.
StartingAddress(PVOID) Starting linear address.
Pages(ULONG) Number of pages.
PageFaultHandlerFcnPtr(PFAULTHOOK) Function supplied to VDHInstallFaultHook. This is used to verify that the calling virtual device driver is the one that installed the fault hook.
Success If the function is successful, it returns nothing.
Failure If any of the input parameters are invalid, a system halt occurs.
VDHRemoveFaultHook - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: Any fault hooks for the terminating DOS session must be released.
VDHRemoveFaultHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRemoveIOHook
Select an item:
Format Parameters Return Codes Purpose Glossary
This function must be called with StartingPortand NumPortsto remove the I /O hooks for the specified I/O ports. Port hooks cannot be removed for a subset of the range of ports hooked by VDHInstallIOHook.
#include mvdm.h
ULONG Reserved; /* Reserved. Must be set to 0 (zero). */
PORT StartingPort; /* Starting port number */
ULONG NumPorts; /* Number of ports in the range */
PIOH IOPortHook; /* Pointer to installed I/O hook entry */
VDHRemoveIOHook(Reserved, StartingPort, NumPorts,
IOPortHook);
VDHRemoveIOHook - Format
This function must be called with StartingPortand NumPortsto remove the I /O hooks for the specified I/O ports. Port hooks cannot be removed for a subset of the range of ports hooked by VDHInstallIOHook.
#include mvdm.h
ULONG Reserved; /* Reserved. Must be set to 0 (zero). */
PORT StartingPort; /* Starting port number */
ULONG NumPorts; /* Number of ports in the range */
PIOH IOPortHook; /* Pointer to installed I/O hook entry */
VDHRemoveIOHook(Reserved, StartingPort, NumPorts,
IOPortHook);
VDHRemoveIOHook Parameter - Reserved
Reserved(ULONG) Reserved. Must be set to 0.
VDHRemoveIOHook Parameter - StartingPort
StartingPort(PORT) Starting port number.
VDHRemoveIOHook Parameter - NumPorts
NumPorts(ULONG) Number of ports in the range.
VDHRemoveIOHook Parameter - IOPortHook
IOPortHook(PIOH) Pointer to installed I/O hook entry. This parameter is used to verify that the calling virtual device driver is the one that installed the I/O hook.
VDHRemoveIOHook - Return Value
Success If the function was successful, it returns nothing.
Failure If IOPortHookEntryis invalid or if StartingPortor NumPortsare out of range, a system halt occurs.
VDHRemoveIOHook - Parameters
Reserved(ULONG) Reserved. Must be set to 0.
StartingPort(PORT) Starting port number.
NumPorts(ULONG) Number of ports in the range.
IOPortHook(PIOH) Pointer to installed I/O hook entry. This parameter is used to verify that the calling virtual device driver is the one that installed the I/O hook.
Success If the function was successful, it returns nothing.
Failure If IOPortHookEntryis invalid or if StartingPortor NumPortsare out of range, a system halt occurs.
VDHRemoveIOHook - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function. I/O hooks are automatically removed during DOS session termination.
Notes: If the IOPortHookis in instance data, the address passed VDHInstallIOHookmust be the same address passed to VDHRemoveIOHookor VDHSetIOHookState.
VDHRemoveIOHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHReportPeek
Select an item:
Format Parameters Return Codes Purpose Glossary
This function reports DOS session polling activity. A counter of idle polling activity is incremented. If the count exceeds a threshold, the current DOS session is put to sleep for a period.
#include mvdm.h ULONG PeekWeight; /* Value to add to the idle counter */ VDHReportPeek(PeekWeight);
VDHReportPeek - Format
This function reports DOS session polling activity. A counter of idle polling activity is incremented. If the count exceeds a threshold, the current DOS session is put to sleep for a period.
#include mvdm.h ULONG PeekWeight; /* Value to add to the idle counter */ VDHReportPeek(PeekWeight);
VDHReportPeek Parameter - PeekWeight
PeekWeight(ULONG) Value to add to the idle counter.
VDHReportPeek - Return Value
Success If the function is successful, it returns nothing.
Failure If the current process is not a DOS session, a system halt occurs.
VDHReportPeek - Parameters
PeekWeight(ULONG) Value to add to the idle counter.
Success If the function is successful, it returns nothing.
Failure If the current process is not a DOS session, a system halt occurs.
VDHReportPeek - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Any virtual device driver that can detect idle polling activity can call this service to report it. If the sum of peek weights exceeds 64KB in a single VDHGSV_MSECSBOOT clock tick (see VDHQuerySysValue), the DOS session is considered idle. It is the responsibility of the virtual device driver to calibrate its peek weight. This depends on machine speed and the Ring 0 trap overhead time, and therefore cannot be calibrated from measuring peek rate under DOS.
Note that testing the time before the count ensures that new tests begin at the first peek in a time slice. This allows use of a very short test period .
VDHReportPeek - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRequestMutexSem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function requests the ownership of a mutex semaphore. If the semaphore is owned and the caller is not the owner, the thread will block. If the caller is the owner, a request count is incremented. Request calls can be nested. A maximum of 65,535 (64KB) requests are allowed for each semaphore at any one time. Exceeding this limit results in a system halt.
#include mvdm.h HVDHSEM MutexSemHandle; /* Mutex semaphore handle */ ULONG Timeout; /* Timeout (in milliseconds) */ BOOL rc; rc = VDHRequestMutexSem(MutexSemHandle, Timeout);
VDHRequestMutexSem - Format
This function requests the ownership of a mutex semaphore. If the semaphore is owned and the caller is not the owner, the thread will block. If the caller is the owner, a request count is incremented. Request calls can be nested. A maximum of 65,535 (64KB) requests are allowed for each semaphore at any one time. Exceeding this limit results in a system halt.
#include mvdm.h HVDHSEM MutexSemHandle; /* Mutex semaphore handle */ ULONG Timeout; /* Timeout (in milliseconds) */ BOOL rc; rc = VDHRequestMutexSem(MutexSemHandle, Timeout);
VDHRequestMutexSem Parameter - MutexSemHandle
MutexSemHandle(HVDHSEM) Mutex semaphore handle.
VDHRequestMutexSem Parameter - Timeout
Timeout(ULONG) Number of milliseconds to wait before timing out the semaphore.
VDHRequestMutexSem Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns 1.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. An invalid semaphore will result in a system halt. A system halt also occurs if the request count crosses the 64KB limit.
VDHRequestMutexSem - Parameters
MutexSemHandle(HVDHSEM) Mutex semaphore handle.
Timeout(ULONG) Number of milliseconds to wait before timing out the semaphore.
rc(BOOL) - returns
Success If the function is successful, it returns 1.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. An invalid semaphore will result in a system halt. A system halt also occurs if the request count crosses the 64KB limit.
VDHRequestMutexSem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHRequestMutexSem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRequestVDD
Select an item:
Format Parameters Return Codes Purpose Glossary
This function requests an operation of a virtual device driver. This service is also used for communication between two or more virtual device drivers where dynamic linkage between them is not appropriate.
#include mvdm.h
HVDD VDDHandle; /* Virtual device driver handle */
HVDM VDMHandle; /* DOS session handle */
ULONG Command; /* Command requested */
PVOID InputRequestPacket; /* Pointer to the input packet */
PVOID OutputRequestPacket; /* Pointer to the output packet */
BOOL rc;
rc = VDHRequestVDD(VDDHandle, VDMHandle, Command,
InputRequestPacket, OutputRequestPacket);
VDHRequestVDD - Format
This function requests an operation of a virtual device driver. This service is also used for communication between two or more virtual device drivers where dynamic linkage between them is not appropriate.
#include mvdm.h
HVDD VDDHandle; /* Virtual device driver handle */
HVDM VDMHandle; /* DOS session handle */
ULONG Command; /* Command requested */
PVOID InputRequestPacket; /* Pointer to the input packet */
PVOID OutputRequestPacket; /* Pointer to the output packet */
BOOL rc;
rc = VDHRequestVDD(VDDHandle, VDMHandle, Command,
InputRequestPacket, OutputRequestPacket);
VDHRequestVDD Parameter - VDDHandle
VDDHandle(HVDD) Handle to a virtual device driver.
VDHRequestVDD Parameter - VDMHandle
VDMHandle(HVDM) Handle to a DOS session.
VDHRequestVDD Parameter - Command
Command(ULONG) Command requested.
VDHRequestVDD Parameter - InputRequestPacket
InputRequestPacket(PVOID) Pointer to the input packet.
VDHRequestVDD Parameter - OutputRequestPacket
OutputRequestPacket(PVOID) Pointer to the output packet.
VDHRequestVDD Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If VDDHandleor VDMHandleis invalid, a system halt occurs.
VDHRequestVDD - Parameters
VDDHandle(HVDD) Handle to a virtual device driver.
VDMHandle(HVDM) Handle to a DOS session.
Command(ULONG) Command requested.
InputRequestPacket(PVOID) Pointer to the input packet.
OutputRequestPacket(PVOID) Pointer to the output packet.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If VDDHandleor VDMHandleis invalid, a system halt occurs.
VDHRequestVDD - Purpose
Context Issues: This function can be called in the task or the interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Every VDHRequestVDDprocedure registered under the virtual device driver name associated with the given handle is called until one returns a nonzero value. No assumption should be made about the order of the calling sequence.
The virtual device driver worker routine sets the error with VDHSetErrorwhen it returns 0 (zero). If the calling virtual device driver is registered under the same name as the virtual device driver handle, then its entry point is also called. Furthermore, the DOS Session Manager does not prevent any of the called virtual device drivers from issuing another VDHRequestVDD.
VDHRequestVDD - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHReservePages
Select an item:
Format Parameters Return Codes Purpose Glossary
This function reserves a range of linear addresses for later use with VDHMapPagesor VDHAllocPages. A reserved area cannot contain a mixture of pages set by VDHMapPagesand VDHAllocPages, but it can be used successively with either one.
#include mvdm.h PVOID StartingAddress; /* Starting address of the linear memory to reserve */ ULONG NumPages; /* Number of pages to reserve */ BOOL rc; rc = VDHReservePages(StartingAddress, NumPages);
VDHReservePages - Format
This function reserves a range of linear addresses for later use with VDHMapPagesor VDHAllocPages. A reserved area cannot contain a mixture of pages set by VDHMapPagesand VDHAllocPages, but it can be used successively with either one.
#include mvdm.h PVOID StartingAddress; /* Starting address of the linear memory to reserve */ ULONG NumPages; /* Number of pages to reserve */ BOOL rc; rc = VDHReservePages(StartingAddress, NumPages);
VDHReservePages Parameter - StartingAddress
StartingAddress(PVOID) Starting address of the linear memory to reserve. Must be page aligned and must be less than 110000H (1MB + 64KB).
VDHReservePages Parameter - NumPages
NumPages(ULONG) Number of pages to reserve.
VDHReservePages Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value and the pages are reserved for later access.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If StartingAddressor NumPagesis invalid, a system halt occurs.
VDHReservePages - Parameters
StartingAddress(PVOID) Starting address of the linear memory to reserve. Must be page aligned and must be less than 110000H (1MB + 64KB).
NumPages(ULONG) Number of pages to reserve.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value and the pages are reserved for later access.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If StartingAddressor NumPagesis invalid, a system halt occurs.
VDHReservePages - Purpose
Context Issues: This function can be called in the initialization and DOS session-task contexts. In the initialization context, the reservation affects only the global linear memory map. In the DOS session-task context, reservations affect only the local linear memory map.
DOS Session Terminations: There are no DOS session termination implications for this function. The DOS Session Manager will clean up these reservations when the DOS session terminates.
VDHReservePages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHResetEventSem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function resets an event semaphore.
#include mvdm.h HVDHSEM EventSemHandle; /* Handle to the event semaphore to be reset */ VDHResetEventSem(EventSemHandle);
VDHResetEventSem - Format
This function resets an event semaphore.
#include mvdm.h HVDHSEM EventSemHandle; /* Handle to the event semaphore to be reset */ VDHResetEventSem(EventSemHandle);
VDHResetEventSem Parameter - EventSemHandle
EventSemHandle(HVDHSEM) Handle to the event semaphore to be reset.
VDHResetEventSem - Return Value
Success If the function is successful, it returns nothing and the semaphore is reset.
Failure Resetting a semaphore that is invalid or is already reset causes a system halt to occur.
VDHResetEventSem - Parameters
EventSemHandle(HVDHSEM) Handle to the event semaphore to be reset.
Success If the function is successful, it returns nothing and the semaphore is reset.
Failure Resetting a semaphore that is invalid or is already reset causes a system halt to occur.
VDHResetEventSem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHResetEventSem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSeek
Select an item:
Format Parameters Return Codes Purpose Glossary
This function seeks to a specified position within a file previously opened by VDHOpen.
#include mvdm.h HFILE FileHandle; /* Handle to the file */ ULONG NewOffset; /* Offset of the new file-pointer position */ ULONG MoveTypeFlag; /* Type of move (absolute, relative) */ ULONG rc; rc = VDHSeek(FileHandle, NewOffset, MoveTypeFlag);
VDHSeek - Format
This function seeks to a specified position within a file previously opened by VDHOpen.
#include mvdm.h HFILE FileHandle; /* Handle to the file */ ULONG NewOffset; /* Offset of the new file-pointer position */ ULONG MoveTypeFlag; /* Type of move (absolute, relative) */ ULONG rc; rc = VDHSeek(FileHandle, NewOffset, MoveTypeFlag);
VDHSeek Parameter - FileHandle
FileHandle(HFILE) Handle to the file.
VDHSeek Parameter - NewOffset
NewOffset(ULONG) Offset to the new file-pointer position. Depending on the value of MoveTypeFlag, this can be the offset from the beginning of the file, the ending of the file, or the current position of the file-pointer.
VDHSeek Parameter - MoveTypeFlag
MoveTypeFlag(ULONG) Indicates what type of move is being done.
Possible values are:
VDHSK_ABSOLUTE Move file-pointer to a location relative to the beginning of the file
VDHSK_CURRENT_POSITION Move file-pointer relative to its current position
VDHSK_END_OF_FILE Move file-pointer to a location relative to the end of the file
VDHSeek Return Value - rc
rc(ULONG) - returns
Success If the function is successful, it returns the new current absolute position of the file-pointer within the file.
Failure If the function fails, it returns 0FFFFFFFFH. VDHGetErrorshould be called to determine the nature of the problem. If FileHandleis invalid, or if this function is not called in the DOS session-task context, a system halt occurs.
VDHSeek - Parameters
FileHandle(HFILE) Handle to the file.
NewOffset(ULONG) Offset to the new file-pointer position. Depending on the value of MoveTypeFlag, this can be the offset from the beginning of the file, the ending of the file, or the current position of the file-pointer.
MoveTypeFlag(ULONG) Indicates what type of move is being done.
Possible values are:
VDHSK_ABSOLUTE Move file-pointer to a location relative to the beginning of the file
VDHSK_CURRENT_POSITION Move file-pointer relative to its current position
VDHSK_END_OF_FILE Move file-pointer to a location relative to the end of the file
rc(ULONG) - returns
Success If the function is successful, it returns the new current absolute position of the file-pointer within the file.
Failure If the function fails, it returns 0FFFFFFFFH. VDHGetErrorshould be called to determine the nature of the problem. If FileHandleis invalid, or if this function is not called in the DOS session-task context, a system halt occurs.
VDHSeek - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHSeek - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSendVEOI
Select an item:
Format Parameters Return Codes Purpose Glossary
This function sends a virtual End-Of-Interrupt (EOI) signal to the Virtual Programmable Interrupt Controller (VPIC), and clears the in-service state of the IRQ for the calling device. The EOI handler for the IRQ is called, if one exists.
#include mvdm.h HIRQ IRQHandle; /* IRQ handle */ VDHSendVEOI(IRQHandle);
VDHSendVEOI - Format
This function sends a virtual End-Of-Interrupt (EOI) signal to the Virtual Programmable Interrupt Controller (VPIC), and clears the in-service state of the IRQ for the calling device. The EOI handler for the IRQ is called, if one exists.
#include mvdm.h HIRQ IRQHandle; /* IRQ handle */ VDHSendVEOI(IRQHandle);
VDHSendVEOI Parameter - IRQHandle
IRQHandle(HIRQ) IRQ handle.
VDHSendVEOI - Return Value
Success If the function was successful, it returns nothing.
Failure If IRQHandleis invalid, a system halt occurs.
VDHSendVEOI - Parameters
IRQHandle(HIRQ) IRQ handle.
Success If the function was successful, it returns nothing.
Failure If IRQHandleis invalid, a system halt occurs.
VDHSendVEOI - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHSendVEOI - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetDosDevice
Select an item:
Format Parameters Return Codes Purpose Glossary
This function links a DOS device driver into the chain of DOS device drivers for a DOS session.
#include mvdm.h VPDOSDDTYPE vpDosDD; /* V86 FAR address of the DOS device driver header */ BOOL rc; rc = VDHSetDosDevice(vpDosDD);
VDHSetDosDevice - Format
This function links a DOS device driver into the chain of DOS device drivers for a DOS session.
#include mvdm.h VPDOSDDTYPE vpDosDD; /* V86 FAR address of the DOS device driver header */ BOOL rc; rc = VDHSetDosDevice(vpDosDD);
VDHSetDosDevice Parameter - vpDosDD
vpDosDD(VPDOSDDTYPE) V86 FAR address of the DOS device driver header. This header (and any headers chained to it) are entered into the DOS device driver list for this DOS session.
VDHSetDosDevice Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero).
VDHSetDosDevice - Parameters
vpDosDD(VPDOSDDTYPE) V86 FAR address of the DOS device driver header. This header (and any headers chained to it) are entered into the DOS device driver list for this DOS session.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero).
VDHSetDosDevice - Purpose
Context Issues: This function can be called only in the DOS session-task context (DOS session creation only).
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHSetDosDevice - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetError
Select an item:
Format Parameters Return Codes Purpose Glossary
This function sets the error code for return by VDHGetError.
#include mvdm.h ULONG ErrorCode; /* Error code to set */ VDHSetError(ErrorCode);
VDHSetError - Format
This function sets the error code for return by VDHGetError.
#include mvdm.h ULONG ErrorCode; /* Error code to set */ VDHSetError(ErrorCode);
VDHSetError Parameter - ErrorCode
ErrorCode(ULONG) Error code to set for VDHGetError.
VDHSetError - Return Value
None.
VDHSetError - Parameters
ErrorCode(ULONG) Error code to set for VDHGetError.
None.
VDHSetError - Purpose
Context Issues: This function can be called in any context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This function is intended for use by any virtual device driver that offers dynamic link services to other virtual device drivers. Most of the base errors are defined in BSEERR.INC. Where possible, these definitions are used when returning errors.
VDHSetError - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetFlags
Select an item:
Format Parameters Return Codes Purpose Glossary
This function sets the DOS session's Flags Register to specified values.
#include mvdm.h ULONG FlagValue; /* DOS session flag value */ VDHSetFlags(FlagValue);
VDHSetFlags - Format
This function sets the DOS session's Flags Register to specified values.
#include mvdm.h ULONG FlagValue; /* DOS session flag value */ VDHSetFlags(FlagValue);
VDHSetFlags Parameter - FlagValue
FlagValue(ULONG) DOS session flag value that sets the flag register of the DOS session.
VDHSetFlags - Return Value
None.
VDHSetFlags - Parameters
FlagValue(ULONG) DOS session flag value that sets the flag register of the DOS session.
None.
VDHSetFlags - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Virtual device drivers must use this interface instead of the client register frame pointer to change the DOS session's flags. Changes to the interrupt flag and the I/O Privilege Level (IOPL) field must be under the control of 8086 emulation so that VDHArmSTIHookworks correctly.
Nested Task (NT) and Resume Flag (RF) flags are cleared, the virtual 8086 Mode (VM) flag is set, and the IOPL field is left unchanged. This function does not take effect until the operating system returns to V86 mode.
VDHSetFlags - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetIOHookState
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used to enable and disable I/O port trapping for a range of ports.
#include mvdm.h
ULONG Reserved; /* Reserved. Must be set to 0 */
PORT StartingPort; /* Starting port number */
ULONG NumPorts; /* Number of ports in the range */
PIOH IOPortHook; /* Pointer used to install I/O hooks */
BOOL EnableFlag; /* FLag for setting I/O hooks */
VDHSetIOHookState(Reserved, StartingPort,
NumPorts, IOPortHook, EnableFlag);
VDHSetIOHookState - Format
This function is used to enable and disable I/O port trapping for a range of ports.
#include mvdm.h
ULONG Reserved; /* Reserved. Must be set to 0 */
PORT StartingPort; /* Starting port number */
ULONG NumPorts; /* Number of ports in the range */
PIOH IOPortHook; /* Pointer used to install I/O hooks */
BOOL EnableFlag; /* FLag for setting I/O hooks */
VDHSetIOHookState(Reserved, StartingPort,
NumPorts, IOPortHook, EnableFlag);
VDHSetIOHookState Parameter - Reserved
Reserved(ULONG) Reserved. Must be set to 0 (zero).
VDHSetIOHookState Parameter - StartingPort
StartingPort(PORT) Starting port number.
VDHSetIOHookState Parameter - NumPorts
NumPorts(ULONG) Number of ports in the range.
VDHSetIOHookState Parameter - IOPortHook
IOPortHook(PIOH) Pointer used to install I/O hooks. This is used to verify that the calling virtual device driver is the one that installed the I/O hooks.
VDHSetIOHookState Parameter - EnableFlag
EnableFlag(BOOL) Flag for setting I/O hooks.
TRUE (Non-zero). Enable I/O hooks.
FALSE (0). Disable I/O hooks.
VDHSetIOHookState - Return Value
Success If the function was successful, it returns nothing.
Failure If IOPortHookis invalid, or if StartingPortor NumPortsare out of range, or if StartingPortand NumPortsoverlap a range of ports previously marked as VDHIIH_ALWAYS_TRAPby VDHInstallIOHook, a system halt occurs.
VDHSetIOHookState - Parameters
Reserved(ULONG) Reserved. Must be set to 0 (zero).
StartingPort(PORT) Starting port number.
NumPorts(ULONG) Number of ports in the range.
IOPortHook(PIOH) Pointer used to install I/O hooks. This is used to verify that the calling virtual device driver is the one that installed the I/O hooks.
EnableFlag(BOOL) Flag for setting I/O hooks.
TRUE (Non-zero). Enable I/O hooks.
FALSE (0). Disable I/O hooks.
Success If the function was successful, it returns nothing.
Failure If IOPortHookis invalid, or if StartingPortor NumPortsare out of range, or if StartingPortand NumPortsoverlap a range of ports previously marked as VDHIIH_ALWAYS_TRAPby VDHInstallIOHook, a system halt occurs.
VDHSetIOHookState - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: If the IOPortHookis in instance data, the address passed to VDHInstallIOHookmust be the same address passed to VDHRemoveIOHookor VDHSetIOHookState. When trapping is enabled, the I/O port hooks for the specified range get control when a DOS session does I/O to that range. When trapping is disabled, DOS session I/O goes directly to the physical hardware ports. None of the ports in the range can be marked as VDHIIH_ ALWAYS_TRAP by VDHInstallIOHook.
VDHSetIOHookState - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetPriority
Select an item:
Format Parameters Return Codes Purpose Glossary
This function adjusts a DOS session's scheduler priority class and level. Priority levels within each priority class range from 0-31.
#include mvdm.h
HVDM VDMHandle; /* Handle to the DOS session with the priority to change */
ULONG ActionClassFlag; /* Dual purpose flag, Action and Class */
LONG NewPriority; /* Change from the DOS session's previous priority level */
VDHSetPriority(VDMHandle, ActionClassFlag,
NewPriority);
VDHSetPriority - Format
This function adjusts a DOS session's scheduler priority class and level. Priority levels within each priority class range from 0-31.
#include mvdm.h
HVDM VDMHandle; /* Handle to the DOS session with the priority to change */
ULONG ActionClassFlag; /* Dual purpose flag, Action and Class */
LONG NewPriority; /* Change from the DOS session's previous priority level */
VDHSetPriority(VDMHandle, ActionClassFlag,
NewPriority);
VDHSetPriority Parameter - VDMHandle
VDMHandle(HVDM) Handle to the DOS session with the priority to change.
VDHSetPriority Parameter - ActionClassFlag
ActionClassFlag(ULONG) A dual-purpose flag.
The Classcomponent of ActionClassFlagindicates the class to which the DOS session should be changed. The Actioncomponent of the ActionClassFlagallows the virtual device driver to manage when the priority is changed, and when to start, end, or continue use of the class. See "Notes" under Purpose.
The value of the Classcomponent can be one of the following:
VDHSP_TIME_CRITICAL Highest priority
VDHSP_SERVER Highest priority
VDHSP_REGULAR Highest priority
VDHSP_IDLE Lowest priority
VDHSP_NO_CHANGE Do not change the DOS session's class
The value of the Actioncomponent can be one of the following:
VDHSP_START_USE Start use of a class
VDHSP_CONTINUE_USE Continue use of a class
VDHSP_END_USE End use of a class
VDHSP_DEFAULT_ACTION If no action is specified, the default class is changed
VDHSetPriority Parameter - NewPriority
NewPriority(LONG) Change from the DOS session's previous priority level.
VDHSetPriority - Return Value
Success If the function is successful, it returns nothing.
Failure If VDMHandleor ActionClassFlagare invalid, a system halt occurs.
VDHSetPriority - Parameters
VDMHandle(HVDM) Handle to the DOS session with the priority to change.
ActionClassFlag(ULONG) A dual-purpose flag.
The Classcomponent of ActionClassFlagindicates the class to which the DOS session should be changed. The Actioncomponent of the ActionClassFlagallows the virtual device driver to manage when the priority is changed, and when to start, end, or continue use of the class. See "Notes" under Purpose.
The value of the Classcomponent can be one of the following:
VDHSP_TIME_CRITICAL Highest priority
VDHSP_SERVER Highest priority
VDHSP_REGULAR Highest priority
VDHSP_IDLE Lowest priority
VDHSP_NO_CHANGE Do not change the DOS session's class
The value of the Actioncomponent can be one of the following:
VDHSP_START_USE Start use of a class
VDHSP_CONTINUE_USE Continue use of a class
VDHSP_END_USE End use of a class
VDHSP_DEFAULT_ACTION If no action is specified, the default class is changed
NewPriority(LONG) Change from the DOS session's previous priority level.
Success If the function is successful, it returns nothing.
Failure If VDMHandleor ActionClassFlagare invalid, a system halt occurs.
VDHSetPriority - Purpose
Context Issues: This function can be called in the task or interrupt contexts.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: A count of the current users is maintained at each class. The actual priority class in effect at any time is always the highest priority class with current declared users. When there are no declared users, the default class is used. Changes to a class other than the effective class are made to saved values. These changes take effect when the class becomes the effective class.
The caller must signal when it begins use of the class, when it makes changes within the class, and when it finishes with the class. The typical user would make one or more changes to priority at a particular class, and finish the series of changes at the class. The virtual device driver uses the VDHSP_START_USE and VDHSP_END_USE flags at the first and last calls within the class, and the VDHSP_CONTINUE_USE flag for changes in between.
The default class is normally VDHSP_REGULAR unless the class or NewPriorityis changed without declaring a user (that is, without specifying a start, continue, or end action flag). This allows a user interface to adjust the default priority of a DOS session.
VDHSetPriority - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetVIRR
Select an item:
Format Parameters Return Codes Purpose Glossary
This function sets the Virtual Interrupt Request Register (VIRR) in the Virtual Programmable Interrupt Controller (VPIC) of the specified DOS session for the IRQ specified. This causes an interrupt to be simulated to the DOS session.
#include mvdm.h HVDM VDMHandle; /* DOS session handle */ HIRQ IRQHandle; /* Handle from VDHOpenVIRQ */ VDHSetVIRR(VDMHandle, IRQHandle);
VDHSetVIRR - Format
This function sets the Virtual Interrupt Request Register (VIRR) in the Virtual Programmable Interrupt Controller (VPIC) of the specified DOS session for the IRQ specified. This causes an interrupt to be simulated to the DOS session.
#include mvdm.h HVDM VDMHandle; /* DOS session handle */ HIRQ IRQHandle; /* Handle from VDHOpenVIRQ */ VDHSetVIRR(VDMHandle, IRQHandle);
VDHSetVIRR Parameter - VDMHandle
VDMHandle(HVDM) DOS session handle. A value of 0 (zero) indicates the current DOS session.
VDHSetVIRR Parameter - IRQHandle
IRQHandle(HIRQ) IRQ handle from VDHOpenVIRQ.
VDHSetVIRR - Return Value
Success If the function was successful, it returns nothing.
Failure If either of the parameters is invalid, a system halt occurs.
VDHSetVIRR - Parameters
VDMHandle(HVDM) DOS session handle. A value of 0 (zero) indicates the current DOS session.
IRQHandle(HIRQ) IRQ handle from VDHOpenVIRQ.
Success If the function was successful, it returns nothing.
Failure If either of the parameters is invalid, a system halt occurs.
VDHSetVIRR - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: If the interrupt request has not been cleared when the DOS session issues an End-Of-Interrupt (EOI), another interrupt will be simulated to the DOS session.
VDHSetVIRR - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetVPMExcept
Select an item:
Format Parameters Return Codes Purpose Glossary
This function sets the current value in the protected-mode exception table.
#include mvdm.h
ULONG Vector; /* Interrupt vector number */
FPFN HandlerAddress; /* Far32 handler address */
BYTE Flag; /* Flag indicating exception handler */
BOOL rc;
rc = VDHSetVPMExcept(Vector, HandlerAddress,
Flag);
VDHSetVPMExcept - Format
This function sets the current value in the protected-mode exception table.
#include mvdm.h
ULONG Vector; /* Interrupt vector number */
FPFN HandlerAddress; /* Far32 handler address */
BYTE Flag; /* Flag indicating exception handler */
BOOL rc;
rc = VDHSetVPMExcept(Vector, HandlerAddress,
Flag);
VDHSetVPMExcept Parameter - Vector
Vector(ULONG) Interrupt vector number.
VDHSetVPMExcept Parameter - HandlerAddress
HandlerAddress(FPFN) Far32 handler address.
VDHSetVPMExcept Parameter - Flag
Flag(BYTE) Flag indicating the kind of exception handler being registered.
Possible value:
VPMXCPT32 A 32-bit handler is being registered.
VDHSetVPMExcept Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero).
VDHSetVPMExcept - Parameters
Vector(ULONG) Interrupt vector number.
HandlerAddress(FPFN) Far32 handler address.
Flag(BYTE) Flag indicating the kind of exception handler being registered.
Possible value:
VPMXCPT32 A 32-bit handler is being registered.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero).
VDHSetVPMExcept - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: There must be a DPMI client running in the DOS session before calling this function.
VDHSetVPMExcept - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetVPMIntVector
Select an item:
Format Parameters Return Codes Purpose Glossary
This function sets the application Ring 3 handler in the protected-mode interrupt chain. This is used only for DOS Protect Mode Interface (DPMI) support.
#include mvdm.h
ULONG Vector; /* Interrupt vector number */
FPFN HandlerAddress; /* Far32 handler address */
BYTE Flag; /* Flag. */
BOOL rc;
rc = VDHSetVPMIntVector(Vector, HandlerAddress,
Flag);
VDHSetVPMIntVector - Format
This function sets the application Ring 3 handler in the protected-mode interrupt chain. This is used only for DOS Protect Mode Interface (DPMI) support.
#include mvdm.h
ULONG Vector; /* Interrupt vector number */
FPFN HandlerAddress; /* Far32 handler address */
BYTE Flag; /* Flag. */
BOOL rc;
rc = VDHSetVPMIntVector(Vector, HandlerAddress,
Flag);
VDHSetVPMIntVector Parameter - Vector
Vector(ULONG) Interrupt vector number.
VDHSetVPMIntVector Parameter - HandlerAddress
HandlerAddress(FPFN) Far32 handler address.
VDHSetVPMIntVector Parameter - Flag
Flag(BYTE) Flag.
VDHSetVPMIntVector Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero).
VDHSetVPMIntVector - Parameters
Vector(ULONG) Interrupt vector number.
HandlerAddress(FPFN) Far32 handler address.
Flag(BYTE) Flag.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero).
VDHSetVPMIntVector - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: There must be a DPMI client running in the DOS session before calling this function.
VDHSetVPMIntVector - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSwitchToVPM
Select an item:
Format Parameters Return Codes Purpose Glossary
This function switches the current DOS session into protected mode. This assumes that the appropriate initializations have already been performed.
#include mvdm.h VOID ; VDHSwitchToVPM();
VDHSwitchToVPM - Format
This function switches the current DOS session into protected mode. This assumes that the appropriate initializations have already been performed.
#include mvdm.h VOID ; VDHSwitchToVPM();
VDHSwitchToVPM Parameter -
None.
VDHSwitchToVPM - Return Value
None.
VDHSwitchToVPM - Parameters
None.
None.
VDHSwitchToVPM - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHSwitchToVPM - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSwitchToV86
Select an item:
Format Parameters Return Codes Purpose Glossary
This function switches the current DOS session to V86 mode.
#include mvdm.h VOID ; VDHSwitchToV86();
VDHSwitchToV86 - Format
This function switches the current DOS session to V86 mode.
#include mvdm.h VOID ; VDHSwitchToV86();
VDHSwitchToV86 Parameter -
None.
VDHSwitchToV86 - Return Value
None.
VDHSwitchToV86 - Parameters
None.
None.
VDHSwitchToV86 - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHSwitchToV86 - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHThawVDM
Select an item:
Format Parameters Return Codes Purpose Glossary
This function reverses the effect of VDHFreezeVDM. The specified DOS session is allowed to run when the freeze count becomes 0 (zero).
#include mvdm.h HVDM VDMHandle; /* Handle to the DOS session to thaw */ VDHThawVDM(VDMHandle);
VDHThawVDM - Format
This function reverses the effect of VDHFreezeVDM. The specified DOS session is allowed to run when the freeze count becomes 0 (zero).
#include mvdm.h HVDM VDMHandle; /* Handle to the DOS session to thaw */ VDHThawVDM(VDMHandle);
VDHThawVDM Parameter - VDMHandle
VDMHandle(HVDM) Handle to the DOS session to allow to execute (thaw).
VDHThawVDM - Return Value
Success If the function is successful, it returns nothing. The freeze count for the DOS session is decremented.
Failure If VDMHandleis an invalid handle, a system halt occurs.
VDHThawVDM - Parameters
VDMHandle(HVDM) Handle to the DOS session to allow to execute (thaw).
Success If the function is successful, it returns nothing. The freeze count for the DOS session is decremented.
Failure If VDMHandleis an invalid handle, a system halt occurs.
VDHThawVDM - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This function does nothing if called on behalf of a DOS session that is not frozen. See VDHFreezeVDMfor a full discussion of freeze counting.
VDHThawVDM - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHUnlockMem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function reverses the effect of VDHLockMem, unlocking a previously locked area of memory.
#include mvdm.h HLOCK LockHandle; /* Lock handle from VDHLockMem */ VDHUnlockMem(LockHandle);
VDHUnlockMem - Format
This function reverses the effect of VDHLockMem, unlocking a previously locked area of memory.
#include mvdm.h HLOCK LockHandle; /* Lock handle from VDHLockMem */ VDHUnlockMem(LockHandle);
VDHUnlockMem Parameter - LockHandle
LockHandle(HLOCK) Lock handle of a locked memory area. Originally obtained from VDHLockMem.
VDHUnlockMem - Return Value
Success If the function is successful, it returns nothing.
Failure An invalid lock handle causes a system halt to occur.
VDHUnlockMem - Parameters
LockHandle(HLOCK) Lock handle of a locked memory area. Originally obtained from VDHLockMem.
Success If the function is successful, it returns nothing.
Failure An invalid lock handle causes a system halt to occur.
VDHUnlockMem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Because lock handles are global, this function can be made in any task context.
VDHUnlockMem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHUnreservePages
Select an item:
Format Parameters Return Codes Purpose Glossary
This function unreserves pages that were previously reserved with VDHReservePages. The starting address and size must be identical to the previous corresponding call to VDHReservePages. Note that any mapping made earlier on this region is unmapped before calling this function.
#include mvdm.h PVOID StartingAddress; /* Starting address of the region to unreserve */ ULONG NumPages; /* Size of the region to unreserve, in pages */ VDHUnreservePages(StartingAddress, NumPages);
VDHUnreservePages - Format
This function unreserves pages that were previously reserved with VDHReservePages. The starting address and size must be identical to the previous corresponding call to VDHReservePages. Note that any mapping made earlier on this region is unmapped before calling this function.
#include mvdm.h PVOID StartingAddress; /* Starting address of the region to unreserve */ ULONG NumPages; /* Size of the region to unreserve, in pages */ VDHUnreservePages(StartingAddress, NumPages);
VDHUnreservePages Parameter - StartingAddress
StartingAddress(PVOID) Starting address of the region to unreserve. Must be less than 110000H (1MB+64KB) and must be page-aligned. In addition, StartingAddressmust match a previous VDHReservePagescall.
VDHUnreservePages Parameter - NumPages
NumPages(ULONG) Size, in pages, of the region to unreserve. Must match the corresponding parameter to a previous call to VDHReservePages.
VDHUnreservePages - Return Value
Success If the function is successful, it returns nothing.
Failure If StartingAddressor NumPagesis invalid, or if they were not used together in an earlier call to VDHReservePages, a system halt occurs.
VDHUnreservePages - Parameters
StartingAddress(PVOID) Starting address of the region to unreserve. Must be less than 110000H (1MB+64KB) and must be page-aligned. In addition, StartingAddressmust match a previous VDHReservePagescall.
NumPages(ULONG) Size, in pages, of the region to unreserve. Must match the corresponding parameter to a previous call to VDHReservePages.
Success If the function is successful, it returns nothing.
Failure If StartingAddressor NumPagesis invalid, or if they were not used together in an earlier call to VDHReservePages, a system halt occurs.
VDHUnreservePages - Purpose
Context Issues: This function can be called in the initialization or DOS session-task context (DOS session creation). In the initialization context, memory can be unreserved only from the global linear memory map. In the DOS session-task context, memory can be unreserved only from the local linear memory map.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: StartingAddressmust be less than 110000H(1MB+64KB) and must be page -aligned. Additionally, StartingAddressmust match a previous call to VDHReservePages. NumPagesmust match the corresponding parameter to a previous call to VDHReservePages.
VDHUnreservePages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHWaitEventSem
Select an item:
Format Parameters Return Codes Purpose Glossary
This function is used to wait on an event semaphore. If the semaphore is posted, it will return immediately.
#include mvdm.h HVDHSEM EventSemHandle; /* Event semaphore handle */ ULONG Timeout; /* Timeout (in milliseconds) */ BOOL rc; rc = VDHWaitEventSem(EventSemHandle, Timeout);
VDHWaitEventSem - Format
This function is used to wait on an event semaphore. If the semaphore is posted, it will return immediately.
#include mvdm.h HVDHSEM EventSemHandle; /* Event semaphore handle */ ULONG Timeout; /* Timeout (in milliseconds) */ BOOL rc; rc = VDHWaitEventSem(EventSemHandle, Timeout);
VDHWaitEventSem Parameter - EventSemHandle
EventSemHandle(HVDHSEM) Event semaphore handle.
VDHWaitEventSem Parameter - Timeout
Timeout(ULONG) Number of milliseconds to wait before timing out.
VDHWaitEventSem Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns 1 (one).
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If EventSemHandleis invalid , a system halt occurs.
VDHWaitEventSem - Parameters
EventSemHandle(HVDHSEM) Event semaphore handle.
Timeout(ULONG) Number of milliseconds to wait before timing out.
rc(BOOL) - returns
Success If the function is successful, it returns 1 (one).
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If EventSemHandleis invalid , a system halt occurs.
VDHWaitEventSem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function. If Timeoutis 0 (zero), the caller will not block; however, ERROR_TIMEOUT is returned. If Timeoutis -1, the caller is blocked until the semaphore is posted. Otherwise, the caller blocks for the time specified (in milliseconds) in Timeout.
VDHWaitEventSem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHWaitVIRRs
Select an item:
Format Parameters Return Codes Purpose Glossary
This function waits until any virtual interrupt is simulated to the current DOS session.
#include mvdm.h HHOOK PostInFcnHook; /* Hook handle */ BOOL rc; rc = VDHWaitVIRRs(PostInFcnHook);
VDHWaitVIRRs - Format
This function waits until any virtual interrupt is simulated to the current DOS session.
#include mvdm.h HHOOK PostInFcnHook; /* Hook handle */ BOOL rc; rc = VDHWaitVIRRs(PostInFcnHook);
VDHWaitVIRRs Parameter - PostInFcnHook
PostInFcnHook(HHOOK) Hook handle of a routine that is to be called after interrupts are simulated.
VDHWaitVIRRs Return Value - rc
rc(BOOL) - returns
Success The function returns a nonzero value, if it woke up because of a simulated interrupt. If it woke up because of a VDHWakeVIRRscall, the function returns 0 (zero).
Failure If the function fails, it returns nothing.
VDHWaitVIRRs - Parameters
PostInFcnHook(HHOOK) Hook handle of a routine that is to be called after interrupts are simulated.
rc(BOOL) - returns
Success The function returns a nonzero value, if it woke up because of a simulated interrupt. If it woke up because of a VDHWakeVIRRscall, the function returns 0 (zero).
Failure If the function fails, it returns nothing.
VDHWaitVIRRs - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: The hook handle must be allocated as a VDH_WAITVIRRS_HOOK type. This function is intended for virtual device drivers that need to simulate a spin loop without stopping virtual interrupt simulation. This allows the virtual device driver to be compatible with DOS but avoid wasting CPU time in a spin loop.
The DOS session's interrupts must be enabled, using VDHSetFlags, before this service is used.
Generally, the virtual device driver will be in a loop when calling this function. When it returns a nonzero value, the virtual device driver returns to V86 mode so that the interrupt can be simulated. The hook function passed to this service is executed after all interrupts are simulated. When this function returns 0 (zero), it is because some other portion of the virtual device driver (likely in response to a physical hardware interrupt) has determined that the DOS session no longer needs to spin. The virtual device driver exits the loop at this point.
The virtual keyboard device driver behaves in this manner in order to emulate the ROM BIOS Read Keyboard function (INT 16H, AH=00) without using excessive CPU time, by allowing the ROM BIOS to spin out in V86 mode, or stopping simulated interrupts by performing a VDHWaitEventSem.
VDHWaitVIRRs - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHWakeIdle
Select an item:
Format Parameters Return Codes Purpose Glossary
This function notes that the DOS session is busy (doing useful work). If the DOS session is currently sleeping or running at a lower priority because of the polling activities, the DOS session is awakened, its priority is restored, and it is no longer considered idle.
#include mvdm.h HVDM VDMHandle; /* Handle to the DOS session to wake up */ VDHWakeIdle(VDMHandle);
VDHWakeIdle - Format
This function notes that the DOS session is busy (doing useful work). If the DOS session is currently sleeping or running at a lower priority because of the polling activities, the DOS session is awakened, its priority is restored, and it is no longer considered idle.
#include mvdm.h HVDM VDMHandle; /* Handle to the DOS session to wake up */ VDHWakeIdle(VDMHandle);
VDHWakeIdle Parameter - VDMHandle
VDMHandle(HVDM) Handle to the DOS session to be awakened.
VDHWakeIdle - Return Value
None.
VDHWakeIdle - Parameters
VDMHandle(HVDM) Handle to the DOS session to be awakened.
None.
VDHWakeIdle - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHWakeIdle - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHWakeVIRRs
Select an item:
Format Parameters Return Codes Purpose Glossary
This function wakes up a DOS session that is waiting with the VDHWaitVIRRsservice. See VDHWaitVIRRsfor a full description of the use of this function.
#include mvdm.h HVDM VDMHandle; /* Handle of the DOS session to wake up */ VDHWakeVIRRs(VDMHandle);
VDHWakeVIRRs - Format
This function wakes up a DOS session that is waiting with the VDHWaitVIRRsservice. See VDHWaitVIRRsfor a full description of the use of this function.
#include mvdm.h HVDM VDMHandle; /* Handle of the DOS session to wake up */ VDHWakeVIRRs(VDMHandle);
VDHWakeVIRRs Parameter - VDMHandle
VDMHandle(HVDM) Handle of the DOS session to be awakened.
VDHWakeVIRRs - Return Value
Success If the function was successful, it returns nothing.
Failure If VDMHandleis invalid, a system halt occurs.
VDHWakeVIRRs - Parameters
VDMHandle(HVDM) Handle of the DOS session to be awakened.
Success If the function was successful, it returns nothing.
Failure If VDMHandleis invalid, a system halt occurs.
VDHWakeVIRRs - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Use with caution because it wakes up every virtual device driver that is waiting on a VDHWaitVIRRs.
VDHWakeVIRRs - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHWrite
Select an item:
Format Parameters Return Codes Purpose Glossary
This function writes bytes to a file or device previously opened by VDHOpen .
#include mvdm.h
HFILE FileHandle; /* Handle to the file or device to write to */
PVOID WriteBufferPtr; /* Pointer to the buffer to write */
ULONG NumBytes; /* Number of bytes to write */
ULONG rc;
rc = VDHWrite(FileHandle, WriteBufferPtr,
NumBytes);
VDHWrite - Format
This function writes bytes to a file or device previously opened by VDHOpen .
#include mvdm.h
HFILE FileHandle; /* Handle to the file or device to write to */
PVOID WriteBufferPtr; /* Pointer to the buffer to write */
ULONG NumBytes; /* Number of bytes to write */
ULONG rc;
rc = VDHWrite(FileHandle, WriteBufferPtr,
NumBytes);
VDHWrite Parameter - FileHandle
FileHandle(HFILE) Handle to the file or device to write to.
VDHWrite Parameter - WriteBufferPtr
WriteBufferPtr(PVOID) Pointer to the buffer to write.
VDHWrite Parameter - NumBytes
NumBytes(ULONG) Number of bytes to write.
VDHWrite Return Value - rc
rc(ULONG) - returns
Success If the function is successful, it returns a count of the bytes written. This can be equal to 0 (zero).
Failure If the function fails, it returns 0FFFFFFFFH. VDHGetErrorshould be called to determine the nature of the problem. If FileHandleis invalid, or this function is called in any context except DOS session-task, a system halt occurs.
VDHWrite - Parameters
FileHandle(HFILE) Handle to the file or device to write to.
WriteBufferPtr(PVOID) Pointer to the buffer to write.
NumBytes(ULONG) Number of bytes to write.
rc(ULONG) - returns
Success If the function is successful, it returns a count of the bytes written. This can be equal to 0 (zero).
Failure If the function fails, it returns 0FFFFFFFFH. VDHGetErrorshould be called to determine the nature of the problem. If FileHandleis invalid, or this function is called in any context except DOS session-task, a system halt occurs.
VDHWrite - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHWrite - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHWriteUBuf
Select an item:
Format Parameters Return Codes Purpose Glossary
This function writes to protected-mode address space as if access were done at Ring 3. This means checking for supervisor and read-only faults, and trapping any other faults. All faults are passed on to the DOS session application handler through VDHRaiseException.
#include mvdm.h
PVOID SourceBuffer; /* Source buffer from which to copy */
ULONG ByteCount; /* Count of bytes */
SEL Selector; /* Application selector */
PULONG OffsetPointer; /* Address of the variable containing the offset */
ULONG Flag; /* Flag for checking controls */
BOOL rc;
rc = VDHWriteUBuf(SourceBuffer, ByteCount,
Selector, OffsetPointer, Flag);
VDHWriteUBuf - Format
This function writes to protected-mode address space as if access were done at Ring 3. This means checking for supervisor and read-only faults, and trapping any other faults. All faults are passed on to the DOS session application handler through VDHRaiseException.
#include mvdm.h
PVOID SourceBuffer; /* Source buffer from which to copy */
ULONG ByteCount; /* Count of bytes */
SEL Selector; /* Application selector */
PULONG OffsetPointer; /* Address of the variable containing the offset */
ULONG Flag; /* Flag for checking controls */
BOOL rc;
rc = VDHWriteUBuf(SourceBuffer, ByteCount,
Selector, OffsetPointer, Flag);
VDHWriteUBuf Parameter - SourceBuffer
SourceBuffer(PVOID) Source buffer from which to copy.
VDHWriteUBuf Parameter - ByteCount
ByteCount(ULONG) Count of bytes.
VDHWriteUBuf Parameter - Selector
Selector(SEL) Application selector.
VDHWriteUBuf Parameter - OffsetPointer
OffsetPointer(PULONG) Address of the variable containing the offset for the start of the write.
VDHWriteUBuf Parameter - Flag
Flag(ULONG) Checking control.
Possible values are:
VPM_PROT_READ Check for read.
VPM_PROT_WRITE Check for write.
VPM_FAULT_IF_SU_SET Fault, if supervisor pages.
VPM_FAULT_IF_RO Fault, if writing to read-only descriptor.
VPM_SEL_PRESENT Caller knows descriptor is present.
VPM_SEL_WRITEABLE Caller knows descriptor is writable.
VPM_SEL_IS_SS Selector is client's stack.
VPM_XCPTRET_ALT After exception, return to alternate mode. For example, if the client was in protected mode when the service was called, return in V86 mode after the exception is handled.
VDHWriteUBuf Return Value - rc
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero) if there is a bad address reference, which causes a fault. In such a case, OffsetPointeris updated with the address of the fault. For Selector Faults, OffsetPointerremains unchanged.
VDHWriteUBuf - Parameters
SourceBuffer(PVOID) Source buffer from which to copy.
ByteCount(ULONG) Count of bytes.
Selector(SEL) Application selector.
OffsetPointer(PULONG) Address of the variable containing the offset for the start of the write.
Flag(ULONG) Checking control.
Possible values are:
VPM_PROT_READ Check for read.
VPM_PROT_WRITE Check for write.
VPM_FAULT_IF_SU_SET Fault, if supervisor pages.
VPM_FAULT_IF_RO Fault, if writing to read-only descriptor.
VPM_SEL_PRESENT Caller knows descriptor is present.
VPM_SEL_WRITEABLE Caller knows descriptor is writable.
VPM_SEL_IS_SS Selector is client's stack.
VPM_XCPTRET_ALT After exception, return to alternate mode. For example, if the client was in protected mode when the service was called, return in V86 mode after the exception is handled.
rc(BOOL) - returns
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero) if there is a bad address reference, which causes a fault. In such a case, OffsetPointeris updated with the address of the fault. For Selector Faults, OffsetPointerremains unchanged.
VDHWriteUBuf - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: When the routine fails, the caller must clean up and exit so that the exception can be simulated to the user.
VDHWriteUBuf - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHYield
Select an item:
Format Parameters Return Codes Purpose Glossary
This function yields the processor to any other thread of equal or higher priority.
#include mvdm.h BOOL OptionFlag; /* Yield options */ VDHYield(OptionFlag);
VDHYield - Format
This function yields the processor to any other thread of equal or higher priority.
#include mvdm.h BOOL OptionFlag; /* Yield options */ VDHYield(OptionFlag);
VDHYield Parameter - OptionFlag
OptionFlag(BOOL) Yield options.
Possible value:
VDH_YIELD_TIME_CRITICAL Yield only to time-critical threads.
VDHYield - Return Value
None.
VDHYield - Parameters
OptionFlag(BOOL) Yield options.
Possible value:
VDH_YIELD_TIME_CRITICAL Yield only to time-critical threads.
None.
VDHYield - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: If OptionFlagis VDH_YIELD_TIME_CRITICAL, and no time-critical thread is able to run, the caller keeps the CPU.
VDHYield - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
OS/2 Version Compatibility Considerations
The following table lists information that has been added to or changed in this documentation since the availability of OS/2 Warp, Version 3. When writing a device driver, you will want to take into consideration these particular changes, which may affect the downward compatibility of these items.
/--------------------------------------------------------------\ |Item Added or |Date Item Added or |Compatibility of | |Changed |Changed |Addition or Change | |--------------------+--------------------+--------------------| |Advanced OS/2 |November 1995 |OS/2 Warp, Version 3| |Joystick Device | |and higher | |Driver | | | \--------------------------------------------------------------/
Assembler Language Syntax
This appendix categorizes the assembler language versions of all virtual DevHlp services in following list and in subsequent sections. These APIs are counterparts of the C language services listed in C Language Virtual DevHlp Services.
A detailed description of each function follows the Virtual DevHlp Services by Category.
Function Type
VDHAllocBlockbyte-granular memory management service
VDHAllocDMABufferDMA service
VDHAllocDOSMembyte-granular memory management service
VDHAllocHookhook management service
VDHAllocMembyte-granular memory management service
VDHAllocPagespage-granular memory management service
VDHArmBPHookhook management service
VDHArmContextHookhook management service
VDHArmReturnHookhook management service
VDHArmSTIHookhook management service
VDHArmTimerHooktimer service
VDHArmVPMBPHookDPMI service
VDHBeginUseVPMStackDPMI service
VDHCallOutDMADMA service
VDHChangeVPMIFDPMI service
VDHCheckPagePermDPMI service
VDHCheckVPMIntVectorDPMI service
VDHClearVIRRvirtual interrupt service
VDHClosefile or device I/O service
VDHCloseVDDinter-device communication service
VDHCloseVIRQvirtual interrupt service
VDHCopyMembyte-granular memory management service
VDHCreateBlockPoolbyte-granular memory management service
VDHCreateSelGDT selector service
VDHCreateSemsemaphore service
VDHDecodePropertyDOS settings service
VDHDestroyBlockPoolbyte-granular memory management service
VDHDestroySelGDT selector service
VDHDestroySemsemaphore service
VDHDevBeepmiscellaneous virtual DevHlp service
VDHDevIOCtlfile or device I/O service
VDHDisarmTimerHooktimer service
VDHEndUseVPMStackDPMI service
VDHEnumerateVDMsmiscellaneous virtual DevHlp service
VDHExchangeMembyte-granular memory management service
VDHFindFreePagespage-granular memory management service
VDHFreeBlockbyte-granular memory management service
VDHFreeDMABufferDMA service
VDHFreeHookhook management service
VDHFreeMembyte-granular memory management service
VDHFreePagespage-granular memory management service
VDHFreezeVDMDOS session control service
VDHGetCodePageFontmiscellaneous virtual DevHlp service
VDHGetDirtyPageInfopage-granular memory management service
VDHGetErrormiscellaneous virtual DevHlp service
VDHGetFlagsmiscellaneous virtual DevHlp service
VDHGetSelBaseDPMI service
VDHGetVPMExceptDPMI service
VDHGetVPMIntVectorDPMI service
VDHHaltSystemDOS session control service
VDHHandleFromPIDmiscellaneous virtual DevHlp service
VDHHandleFromSGIDmiscellaneous virtual DevHlp service
VDHInstallFaultHookpage-granular memory management service
VDHInstallIntHookhook management service
VDHInstallIOHookhook management service
VDHInstallUserHookhook management service
VDHIsVDMFrozenDOS session control service
VDHKillVDMDOS session control service
VDHLockMemmemory-locking memory management service
VDHMapPagespage-granular memory management service
VDHOpenfile or device I/O service
VDHOpenPDDinter-device communication service
VDHOpenVDDinter-device communication service
VDHOpenVIRQvirtual interrupt service
VDHPhysicalDiskfile or device I/O service
VDHPopIntv8086 stack manipulation service
VDHPopRegsv8086 stack manipulation service
VDHPopStackv8086 stack manipulation service
VDHPopupmiscellaneous virtual DevHlp service
VDHPostEventSemsemaphore service
VDHPrintCloseparallel port and printer service
VDHPushFarCallv8086 stack manipulation service
VDHPushIntv8086 stack manipulation service
VDHPushRegsv8086 stack manipulation service
VDHPushStackv8086 stack manipulation service
VDHPutSysValuemiscellaneous virtual DevHlp service
VDHQueryFreePagespage-granular memory management service
VDHQueryHookDatahook management service
VDHQueryLinmiscellaneous virtual DevHlp service
VDHQueryKeyShiftkeyboard service
VDHQueryPropertyDOS settings service
VDHQuerySelGDT selector service
VDHQuerySemsemaphore service
VDHQuerySysValuemiscellaneous virtual DevHlp service
VDHQueryVIRQvirtual interrupt service
VDHRaiseExceptionDPMI service
VDHReadfile or device I/O service
VDHReadUBufDPMI service
VDHReallocPagespage-granular memory management service
VDHRegisterAPIRegister API handler
VDHRegisterDMAChannelDMA service
VDHRegisterPropertyDOS settings service
VDHRegisterVDDinter-device communication service
VDHReleaseCodePageFontmiscellaneous virtual DevHlp service
VDHReleaseMutexSemsemaphore service
VDHRemoveFaultHookpage-granular memory management service
VDHRemoveIOHookhook management service
VDHReportPeekidle DOS application management service
VDHRequestMutexSemsemaphore service
VDHRequestVDDinter-device communication service
VDHReservePagespage-granular memory management service
VDHResetEventSemsemaphore service
VDHSeekfile or device I/O service
VDHSendVEOIvirtual interrupt service
VDHSetDosDevicemiscellaneous virtual DevHlp service
VDHSetErrormiscellaneous virtual DevHlp service
VDHSetFlagsmiscellaneous virtual DevHlp service
VDHSetIOHookStatehook management service
VDHSetPriorityDOS session control service
VDHSetVIRRvirtual interrupt service
VDHSetVPMExceptDPMI service
VDHSetVPMIntVectorDPMI service
VDHSwitchToVPMDPMI service
VDHSwitchToV86DPMI service
VDHThawVDMDOS session control service
VDHUnlockMemmemory-locking memory management service
VDHUnreservePagespage-granular memory management service
VDHWaitEventSemsemaphore service
VDHWaitVIRRsvirtual interrupt service
VDHWakeIdleidle DOS application management service
VDHWakeVIRRsvirtual interrupt service
VDHWritefile or device I/O service
VDHWriteUBufDPMI service
VDHYieldDOS session control service
Virtual DevHlp Services by Category
Virtual DevHlp services can be divided into categories based on the type of service the virtual DevHlp provides. These categories are:
DMA Services
Function Type
VDHAllocDMABufferAllocate DMA buffer
VDHCallOutDMACall virtual DMA device driver
VDHFreeDMABufferFree DMA buffer
VDHRegisterDMAChannelRegister DMA channel
DOS Session Control Services
Function Type
VDHFreezeVDMFreeze DOS session
VDHHaltSystemCause system halt
VDHIsVDMFrozenDetermine if DOS session is frozen
VDHKillVDMTerminate DOS session
VDHSetPriorityAdjust DOS session scheduler priority
VDHThawVDMAllow frozen DOS session to resume executing
VDHYieldYield the processor.
DOS Settings Services
Function Type
VDHDecodePropertyDecode property string
VDHQueryPropertyQuery virtual device driver property value
VDHRegisterPropertyRegister virtual device driver property
DPMI Services
Function Type
VDHArmVPMBPHookObtain address of DOS session protected-mode breakpoint
VDHBeginUseVPMStackBegin using DOS session protected-mode stack
VDHChangeVPMIFChange virtual Interrupt Flag (IF)
VDHCheckPagePermCheck Ring 3 page permissions
VDHCheckVPMIntVectorDetermine if DOS session protected-mode handler exists
VDHEndUseVPMStackEnd use of DOS session protected-mode stack
VDHGetSelBaseGet flat base address
VDHGetVPMExceptGet DOS session protected-mode exception vector
VDHGetVPMIntVectorReturn DOS session protected-mode interrupt vector
VDHRaiseExceptionRaise an exception to a DOS session
VDHReadUBufRead from protected-mode address space
VDHSetVPMExceptSet DOS session protected-mode exception vector
VDHSetVPMIntVectorSet DOS session protected-mode interrupt vector
VDHSwitchToVPMSwitch DOS session to protected mode
VDHSwitchToV86Switch DOS session to V86 mode
VDHWriteUBufWrite to protected-mode address space
Note:"VPM", as found in the function names above, stands for Virtual Protected Mode.
File or Device I/O Services
Function Type
VDHCloseClose a file handle
VDHDevIOCtlIssue device-specific commands
VDHOpenOpen a file or device
VDHPhysicalDiskGet information about partitionable disks
VDHReadRead bytes from file or device
VDHSeekMove read or write file pointer for a handle
VDHWriteWrite bytes to file or device
GDT Selector Services
Function Type
VDHCreateSelCreate GDT selector to map a linear range
VDHDestroySelDestroy GDT selector
VDHQuerySelGet selector for data or stack address
Hook Management Services
Function Type
VDHAllocHookAllocate hooks needed for interrupt simulation
VDHArmBPHookObtain address of V86 breakpoint
VDHArmContextHookSet local or global context hook
VDHArmReturnHookSet handler to receive control
VDHArmSTIHookSet handler to receive control
VDHFreeHookDisarm and free hook
VDHInstallIntHookSet handler for V86 interrupt
VDHInstallIOHookInstall I/O port hooks
VDHInstallUserHookInstall handler for DOS session event
VDHQueryHookDataReturns pointer to hook reference data
VDHRemoveIOHookRemove hooks for PIC I/O ports
VDHSetIOHookStateEnable/disable I/O port trapping
Idle DOS Application Management Services
Function Type
VDHReportPeekReport DOS session polling activity
VDHWakeIdleWake up DOS session
Note:The services above indicate when a DOS application appears to be idle, and when activity exists that could make the DOS application busy.
Inter-Device Communication Services
DevHlp services
Function Type
VDHCloseVDDClose virtual device driver
VDHOpenPDDOpen physical device driver
VDHOpenVDDOpen virtual device driver
VDHRegisterVDDRegister virtual device driver entry points
VDHRequestVDDIssue request for virtual device driver operation
Keyboard Services
Function Type
VDHQueryKeyShiftQuery keyboard shift state
Memory Management Services
There are three sub-categories of the memory management virtual DevHlp services. The first two are used for the granularity of the memory allocation unit, the third category is used for memory-locking services.
Byte-Granular Memory Management Services
Function Type
VDHAllocBlockAllocate block from memory block pool
VDHAllocDOSMemAllocate block of memory from DOS area
VDHAllocMemAllocate small amount of memory
VDHCopyMemCopy from one linear memory address to another
VDHCreateBlockPoolCreate memory block pool
VDHDestroyBlockPoolDestroy memory block pool
VDHExchangeMemExchange contents of two linear memory regions
VDHFreeBlockFree block of memory
VDHFreeMemFree memory
Page-Granular Memory Management Services
Function Type
VDHAllocPagesAllocate page-aligned memory object
VDHFindFreePagesFind largest available linear memory
VDHFreePagesFree memory object
VDHGetDirtyPageInfoReturn status of dirty bits
VDHInstallFaultHookInstall page fault handler
VDHMapPagesMap specified linear address
VDHQueryFreePagesReturn amount of free virtual memory
VDHReallocPagesReallocate memory object
VDHRemoveFaultHookRemove page fault handler
VDHReservePagesReserve range of linear addresses
VDHUnreservePagesUnreserve range of linear addresses
Memory-Locking Memory Management Services
Function Type
VDHLockMemVerify access or lock memory
VDHUnlockMemRelease memory lock
Note:The services above allow virtual device drivers to allocate, free, reallocate, and lock memory for global, per-DOS session, page-granular, or byte-granular objects.
Four types of mappings are supported:
- Mapping to a physical address
*Mapping to another linear address
*Mapping to black holes (don't care) pages
*Mapping to invalid (unmapped) pages
Note:Virtual device drivers can also request smaller memory allocations from the kernel heap, which is global and fixed. Small, fixed size block services are available to speed up frequent allocations and freeing of memory. For a particular block size, a pool of blocks is maintained and the requirements are met by taking off a block from the block pool.
Miscellaneous Virtual DevHlp Services
Function Type
VDHDevBeepDevice beep virtual DevHlp service
VDHEnumerateVDMsRun worker function for each DOS session
VDHGetCodePageFontReturn information of DOS session code page font
VDHGetErrorGet error code from last virtual DevHlp service
VDHGetFlagsGet DOS Session's EFLAGS Register
VDHHandleFromPIDGet handle for given Process ID
VDHHandleFromSGIDGet DOS session handle from Screen Group ID
VDHPopupDisplay message
VDHPutSysValueSet system value
VDHQueryLinGet linear address for Far16 address
VDHQuerySysValueQuery system value
VDHRegisterAPIRegister API handler
VDHReleaseCodePageFontRelease code page font
VDHSetDosDeviceRegister/install DOS device driver
VDHSetErrorSet error code
VDHSetFlagsSet DOS session flags register
Parallel Port and Printer Services
Function Type
VDHPrintCloseFlush and close open printers for DOS session
Semaphore Services
Function Type
VDHCreateSemCreate event or mutex semaphore
VDHDestroySemDestroy semaphore
VDHPostEventSemPost event semaphore
VDHQuerySemQuery semaphore state
VDHReleaseMutexSemRelease mutex semaphore
VDHRequestMutexSemRequest mutex semaphore
VDHResetEventSemReset event semaphore
VDHWaitEventSemWait on event semaphore
Note:These semaphore services above are used for synchronizing with an OS /2 process. Virtual device drivers must be careful not to block ( VDHRequestMutexSem/VDHWaitEventSem) in the context of a DOS session task; otherwise, that task will receive no more simulated hardware interrupts until it becomes unblocked.
Timer Services
Function Type
VDHArmTimerHookSet timer service/handler
VDHDisarmTimerHookCancel timer service
Virtual Interrupt Services
Function Type
VDHClearVIRRClear virtual IRR
VDHCloseVIRQDeregister IRQ handler
VDHOpenVIRQRegister IRQ handler
VDHQueryVIRQQuery IRQ status on a DOS session
VDHSendVEOISend virtual EOI to VPIC
VDHSetVIRRSet virtual interrupt request register (IRR)
VDHWaitVIRRsWait until interrupt is simulated
VDHWakeVIRRsWake up DOS session
V8086 Stack Manipulation Services
Function Type
VDHPopIntRemove IRET frame from client DOS session stack
VDHPopRegsPop client DOS session registers from client stack
VDHPopStackPop data off client stack
VDHPushFarCallSimulate FAR call to V86 code
VDHPushIntTransfer control to V86 interrupt handler
VDHPushRegsPush client DOS session registers onto client stack
VDHPushStackPush data onto client stack
VDHAllocBlock
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function allocates a block from the specified memory block pool. This block is allocated from fixed or swappable memory, depending on the value of the OptionFlag flag when the block is created with VDHCreateBlockPool. */ include mvdm.inc EXTERN VDHAllocBlock:NEAR SourceBlockPool DD ? ; Handle to a memory block pool PUSH SourceBlockPool ; Push SourceBlockPool CALL VDHAllocBlock ; Call the function
VDHAllocBlock - Format
/* This function allocates a block from the specified memory block pool. This block is allocated from fixed or swappable memory, depending on the value of the OptionFlag flag when the block is created with VDHCreateBlockPool. */ include mvdm.inc EXTERN VDHAllocBlock:NEAR SourceBlockPool DD ? ; Handle to a memory block pool PUSH SourceBlockPool ; Push SourceBlockPool CALL VDHAllocBlock ; Call the function
VDHAllocBlock Parameter - SourceBlockPool
SourceBlockPool(DD) Handle to the pool of memory blocks from which to allocate a memory block.
VDHAllocBlock Return Value - rc
Success If the function is successful, it returns the address of the allocated memory block.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. Note that passing an invalid memory block handle causes a system halt to occur.
VDHAllocBlock - Parameters
SourceBlockPool(DD) Handle to the pool of memory blocks from which to allocate a memory block.
VDHAllocBlock - Purpose
Context Issues: This function can be called in the initialization or task context.
DOS Session Terminations: Any blocks allocated by a virtual device driver for use by the terminating DOS session are freed by using VDHFreeBlock. Any block pools created for the DOS session should also be freed.
VDHAllocBlock - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHAllocDMABuffer
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function allocates a DMA buffer . * / include mvdm . inc EXTERN VDHAllocDMABuffer : NEAR RequestSize DD ? ; Request size Align64kFlag DD ? ; Alignment flag PhysAddrPtr DD ? ; Location to store the physical address returned PUSH RequestSize ; Push RequestSize PUSH Align64kFlag ; Push Align64kFlag PUSH PhysAddrPtr ; Push PhysAddrPtr CALL VDHAllocDMABuffer ; Call the function
VDHAllocDMABuffer - Format
/* This function allocates a DMA buffer . * / include mvdm . inc EXTERN VDHAllocDMABuffer : NEAR RequestSize DD ? ; Request size Align64kFlag DD ? ; Alignment flag PhysAddrPtr DD ? ; Location to store the physical address returned PUSH RequestSize ; Push RequestSize PUSH Align64kFlag ; Push Align64kFlag PUSH PhysAddrPtr ; Push PhysAddrPtr CALL VDHAllocDMABuffer ; Call the function
VDHAllocDMABuffer Parameter - RequestSize
RequestSize(DD) Request Size.
If the Align64kFlag=1, RequestSizeis always less than or equal to 64KB. If the Align64kFlag=0, RequestSizeis always less than or equal to 128KB.
VDHAllocDMABuffer Parameter - Align64kFlag
Align64kFlag(DD) Alignment flag.
If Align64kFlag=1, the buffer is at a 64KB alignment in physical memory. If Align64kFlag=0, the buffer is at a 128KB alignment in physical memory.
VDHAllocDMABuffer Parameter - PhysAddrPtr
PhysAddrPtr(DD) Location where VDHAllocDMABufferreturns the physical address of the allocation.
VDHAllocDMABuffer Return Value - rc
Success If the function is successful, it returns the linear address of allocation (system memory).
Failure If the function fails, it returns -1. VDHGetErrorshould be called to determine the nature of the problem.
VDHAllocDMABuffer - Parameters
RequestSize(DD) Request Size.
If the Align64kFlag=1, RequestSizeis always less than or equal to 64KB. If the Align64kFlag=0, RequestSizeis always less than or equal to 128KB.
Align64kFlag(DD) Alignment flag.
If Align64kFlag=1, the buffer is at a 64KB alignment in physical memory. If Align64kFlag=0, the buffer is at a 128KB alignment in physical memory.
PhysAddrPtr(DD) Location where VDHAllocDMABufferreturns the physical address of the allocation.
VDHAllocDMABuffer - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: The virtual device driver frees the buffer by using VDHFreeDMABufferat DOS session termination.
Notes: Physical memory is allocated resident and contiguous, and is always in the first 16MB. The Linear Memory range comes from the system arena. The contents of the returned buffer are not important; that is, the buffer is not zero-filled.
VDHAllocDMABuffer - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHAllocDOSMem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function allocates a block of memory from the DOS memory area . Allocations start at 0 bytes and go to 256KB . * / include mvdm . inc EXTERN VDHAllocDOSMem : NEAR BlockSize DD ? ; Size of the desired memory block ( in bytes ) PUSH BlockSize ; Push BlockSize CALL VDHAllocDOSMem ; Call the function
VDHAllocDOSMem - Format
/* This function allocates a block of memory from the DOS memory area . Allocations start at 0 bytes and go to 256KB . * / include mvdm . inc EXTERN VDHAllocDOSMem : NEAR BlockSize DD ? ; Size of the desired memory block ( in bytes ) PUSH BlockSize ; Push BlockSize CALL VDHAllocDOSMem ; Call the function
VDHAllocDOSMem Parameter - BlockSize
BlockSize(DD) Size of the desired memory block; the number of bytes to allocate.
VDHAllocDOSMem Return Value - rc
Success If the function is successful, it returns the address of the allocated memory block.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. If BlockSize= 0, or if the function is called in an invalid context (see "Context Issues" below), a system halt occurs.
VDHAllocDOSMem - Parameters
BlockSize(DD) Size of the desired memory block; the number of bytes to allocate.
VDHAllocDOSMem - Purpose
Context Issues: This function can be called only in the DOS session-task context (DOS session creation).
DOS Session Terminations: There are no DOS session termination implications for this function. The DOS Session Manager frees this memory.
Notes: There is no way to free memory taken from the DOS heap. If there is no free memory in the DOS memory area, the allocation fails. Allocations always start on paragraph (16-byte) boundaries.
VDHAllocDOSMem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHAllocHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is used to allocate a hook handle for the arm hook services : Context , STI , Return , Timer , and BP ( breakpoint ) . * / include mvdm . inc EXTERN VDHAllocHook : NEAR HookType DD ? ; Hook type ArmHookFcn DD ? ; Arm hook function RefDataSize DD ? ; Size of the reference data PUSH HookType ; Push HookType PUSH ArmHookFcn ; Push ArmHookFcn PUSH RefDataSize ; Push RefDataSize CALL VDHAllocHook ; Call the function
VDHAllocHook - Format
/* This function is used to allocate a hook handle for the arm hook services : Context , STI , Return , Timer , and BP ( breakpoint ) . * / include mvdm . inc EXTERN VDHAllocHook : NEAR HookType DD ? ; Hook type ArmHookFcn DD ? ; Arm hook function RefDataSize DD ? ; Size of the reference data PUSH HookType ; Push HookType PUSH ArmHookFcn ; Push ArmHookFcn PUSH RefDataSize ; Push RefDataSize CALL VDHAllocHook ; Call the function
VDHAllocHook Parameter - HookType
HookType(DD) Hook type.
Possible values are:
VDH_CONTEXT_HOOK VDHArmContextHook
VDH_STI_HOOK VDHArmSTIHook
VDH_RETURN_HOOK VDHArmReturnHook
VDH_TIMER_HOOK VDHArmTimerHook
VDH_BP_HOOK VDHArmBPHook
VDHAllocHook Parameter - ArmHookFcn
ArmHookFcn(DD) Arm hook function.
VDHAllocHook Parameter - RefDataSize
RefDataSize(DD) Size of the reference data.
VDHAllocHook Return Value - rc
Success If the function is successful, it returns a hook handle, which is used in the Arm services.
Failure If there is an error, the function returns NULL. VDHGetErrorshould be called to determine the nature of the problem. If HookTypeor ArmHookFcnis invalid, a system halt occurs.
VDHAllocHook - Parameters
HookType(DD) Hook type.
Possible values are:
VDH_CONTEXT_HOOK VDHArmContextHook
VDH_STI_HOOK VDHArmSTIHook
VDH_RETURN_HOOK VDHArmReturnHook
VDH_TIMER_HOOK VDHArmTimerHook
VDH_BP_HOOK VDHArmBPHook
ArmHookFcn(DD) Arm hook function.
RefDataSize(DD) Size of the reference data.
VDHAllocHook - Purpose
Context Issues: This function can be called in the initialization or DOS session-task context. However, VDH_RETURN_HOOK and VDH_BP_HOOK require the DOS session-task context.
DOS Session Terminations: During initialization time, hooks are allocated globally; that is, they are not associated with a DOS session process. These hooks are not automatically freed when a DOS session terminates. During DOS session creation time or thereafter, allocated hooks are associated with the current DOS session, and are freed when that DOS session terminates.
Notes: Use VDHQueryHookDatato get a pointer to any reference data allocated.
VDHAllocHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHAllocMem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function allocates a small amount of memory on a LONG / DWORD boundary . The memory is allocated from the system area , so the address is valid in all process contexts . * / include mvdm . inc EXTERN VDHAllocMem : NEAR NumBytes DD ? OptionFlag DD ? ; Number of bytes to allocate PUSH NumBytes ; Push NumBytes PUSH OptionFlag ; Push OptionFlag CALL VDHAllocMem ; Call the function
VDHAllocMem - Format
/* This function allocates a small amount of memory on a LONG / DWORD boundary . The memory is allocated from the system area , so the address is valid in all process contexts . * / include mvdm . inc EXTERN VDHAllocMem : NEAR NumBytes DD ? OptionFlag DD ? ; Number of bytes to allocate PUSH NumBytes ; Push NumBytes PUSH OptionFlag ; Push OptionFlag CALL VDHAllocMem ; Call the function
VDHAllocMem Parameter - NumBytes
NumBytes(DD) Number of bytes to allocate.
VDHAllocMem Parameter - OptionFlag
OptionFlag(DD) Bit flag describing the allocation options.
Possible value:
VDHAM_SWAPPABLE Allocate memory from the swappable heap. Otherwise, memory is allocated from the fixed heap and can be accessed at hardware interrupt time.
VDHAllocMem Return Value - rc
Success If the function is successful, it returns the address of the allocated space.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. If either NumBytesor OptionFlagis invalid, a system halt occurs.
VDHAllocMem - Parameters
NumBytes(DD) Number of bytes to allocate.
OptionFlag(DD) Bit flag describing the allocation options.
Possible value:
VDHAM_SWAPPABLE Allocate memory from the swappable heap. Otherwise, memory is allocated from the fixed heap and can be accessed at hardware interrupt time.
VDHAllocMem - Purpose
Context Issues: This function can be called in the initialization or task context.
DOS Session Terminations: All memory allocated by a virtual device driver for use by the terminating DOS session is freed by using VDHFreeMem.
Notes: Allocations larger than one page are performed by using VDHAllocPages. To access the allocated memory at hardware interrupt time, be sure to allocate memory from the fixed heap.
VDHAllocMem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHAllocPages
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function allocates a page - aligned , page - granular memory object . * / include mvdm . inc EXTERN VDHAllocPages : NEAR StartingAddress DD ? ; A specific linear address NumPages DD ? ; The number of pages to allocate OptionFlag DD ? ; Allocation options bit - flag PUSH StartingAddress ; Push StartingAddress PUSH NumPages ; Push NumPages PUSH OptionFlag ; Push OptionFlag CALL VDHAllocPages ; Call the function
VDHAllocPages - Format
/* This function allocates a page - aligned , page - granular memory object . * / include mvdm . inc EXTERN VDHAllocPages : NEAR StartingAddress DD ? ; A specific linear address NumPages DD ? ; The number of pages to allocate OptionFlag DD ? ; Allocation options bit - flag PUSH StartingAddress ; Push StartingAddress PUSH NumPages ; Push NumPages PUSH OptionFlag ; Push OptionFlag CALL VDHAllocPages ; Call the function
VDHAllocPages Parameter - StartingAddress
StartingAddress(DD) A specific address used with the available options ( see Option Flag).
VDHAllocPages Parameter - NumPages
NumPages(DD) Number of pages of linear memory to allocate.
VDHAllocPages Parameter - OptionFlag
OptionFlag(DD) Bit flag indicating choices in allocation options.
This flag can take one or more of the following values:
VDHAP_SPECIFIC VDHAllocPagesattempts to allocate pages starting at the linear address, StartingAddress. Otherwise, an arbitrary linear address is selected.
VDHAP_SYSTEM The linear address is allocated from the system (global) area, essentially allocating global memory. Otherwise, it is allocated from the private area of this process.
VDHAP_FIXED The allocated memory is fixed. Otherwise, the memory is swappable. This flag cannot be used if VDHAP_PHYSICAL is specified.
VDHAP_PHYSICAL The allocated linear address range maps the physical address range, starting at StartingAddress. Otherwise, an arbitrary physical page is assigned. Note that this flag cannot be used if VDHAP_FIXED is specified .
VDHAllocPages Return Value - rc
Success If the function is successful, it returns the address of the allocated memory.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. If the OptionFlagflag is invalid, a system halt occurs.
VDHAllocPages - Parameters
StartingAddress(DD) A specific address used with the available options ( see Option Flag).
NumPages(DD) Number of pages of linear memory to allocate.
OptionFlag(DD) Bit flag indicating choices in allocation options.
This flag can take one or more of the following values:
VDHAP_SPECIFIC VDHAllocPagesattempts to allocate pages starting at the linear address, StartingAddress. Otherwise, an arbitrary linear address is selected.
VDHAP_SYSTEM The linear address is allocated from the system (global) area, essentially allocating global memory. Otherwise, it is allocated from the private area of this process.
VDHAP_FIXED The allocated memory is fixed. Otherwise, the memory is swappable. This flag cannot be used if VDHAP_PHYSICAL is specified.
VDHAP_PHYSICAL The allocated linear address range maps the physical address range, starting at StartingAddress. Otherwise, an arbitrary physical page is assigned. Note that this flag cannot be used if VDHAP_FIXED is specified .
VDHAllocPages - Purpose
Context Issues: This function can be called in the initialization or task context. If called in the initialization context, VDHAP_SYSTEM must be specified. If called in the OS/2 task context, VDHAP_SYSTEM must also be specified.
DOS Session Terminations: Any allocations that are not in the terminating DOS sessions private area must be released by using VDHFreePages.
Notes: When an allocation made with VDHAllocPagesis shrunk by VDHReallocPages, the linear range between the end of the allocation and the original end of the allocation remains available for object growth without movement. Regardless of VDHReallocPagesactivity, all pages in the allocation retain the same properties (that is fixed, system, and physical) .
VDHAllocPages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHArmBPHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function obtains the address of the V86 breakpoint allocated by a previous call to VDHAllocHook with the VDH _ BP _ HOOK flag . * / include mvdm . inc EXTERN VDHArmBPHook : NEAR HookHandle DD ? ; Hook handle PUSH HookHandle ; Push HookHandle CALL VDHArmBPHook ; Call the function
VDHArmBPHook - Format
/* This function obtains the address of the V86 breakpoint allocated by a previous call to VDHAllocHook with the VDH _ BP _ HOOK flag . * / include mvdm . inc EXTERN VDHArmBPHook : NEAR HookHandle DD ? ; Hook handle PUSH HookHandle ; Push HookHandle CALL VDHArmBPHook ; Call the function
VDHArmBPHook Parameter - HookHandle
HookHandle(DD) Hook handle allocated with VDHAllocHook.
Hook routine interface:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - p - Pointer to hook-specific reference data ; [ESP + 4] - pcrf - Pointer to client register frame ; EXIT None ; ; CONTEXT DOS session-task
VDHArmBPHook Return Value - rc
Success If the function is successful, it returns a V86 breakpoint address.
Failure If HookHandleis invalid, a system halt occurs.
VDHArmBPHook - Parameters
HookHandle(DD) Hook handle allocated with VDHAllocHook.
Hook routine interface:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - p - Pointer to hook-specific reference data ; [ESP + 4] - pcrf - Pointer to client register frame ; EXIT None ; ; CONTEXT DOS session-task
VDHArmBPHook - Purpose
Context Issues: This function can be called only in the task context, and needs to be called only at DOS session creation time.
DOS Session Terminations: There are no DOS session termination implications for this function. BP (breakpoint) hooks are automatically removed during DOS session termination.
Notes: This VDH service provides a raw breakpoint service. Upon entry to the arm hook function, the client's CS:IP is randomly set. Therefore, it is crucial that this function set the CS:IP to a valid address. Typically, the CS:IP is retrieved from the client's stack through use of VDHPopStack. This is a low-level service. Appropriate care should be exercised to ensure that the client's CS:IP and stack remain valid.
Unlike other hooks, breakpoint hooks are armed until explicitly disarmed by a call to VDHFreeHook. When the V86 breakpoint address is called from V86 mode, the hook function is called. Any changes made to the client register frame cause the corresponding registers to take on these values upon return to V86 mode. The pparameter in the hook routine points to the cbRefDatabytes of data allocated by VDHAllocHook.
VDHArmBPHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHArmContextHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is used to get to a task - time context from interrupt time when an interrupt is simulated . This service adds a handler to the list of routines called the next time the task context is entered ( global context ) , or the next time a specific DOS session - task context is reached ( local context ) . This is done only once ; the handler is removed from the list after it is executed . * / include mvdm . inc EXTERN VDHArmContextHook : NEAR HookHandle DD ? ; Hook handle allocated with VDHAllocHook VDMHandle DD ? ; DOS session handle PUSH HookHandle ; Push HookHandle PUSH VDMHandle ; Push VDMHandle CALL VDHArmContextHook ; Call the function
VDHArmContextHook - Format
/* This function is used to get to a task - time context from interrupt time when an interrupt is simulated . This service adds a handler to the list of routines called the next time the task context is entered ( global context ) , or the next time a specific DOS session - task context is reached ( local context ) . This is done only once ; the handler is removed from the list after it is executed . * / include mvdm . inc EXTERN VDHArmContextHook : NEAR HookHandle DD ? ; Hook handle allocated with VDHAllocHook VDMHandle DD ? ; DOS session handle PUSH HookHandle ; Push HookHandle PUSH VDMHandle ; Push VDMHandle CALL VDHArmContextHook ; Call the function
VDHArmContextHook Parameter - HookHandle
HookHandle(DD) Hook handle allocated with VDHAllocHook.
VDHArmContextHook Parameter - VDMHandle
VDMHandle(DD) DOS session handle. A value of -1 indicates a global context .
Hook routine interface:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - pRefData - Pointer to reference data ; [ESP + 4] - pcrf - Pointer to client register frame ; EXIT None ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT Task (global) or DOS session-task (local) ; NOTE pcrf is valid only for local context hook handlers
VDHArmContextHook Return Value - rc
Success If the function was successful, it returns nothing.
Failure If HookHandleor VDMHandleis invalid, or if the hook is already armed, a system halt occurs.
VDHArmContextHook - Parameters
HookHandle(DD) Hook handle allocated with VDHAllocHook.
VDMHandle(DD) DOS session handle. A value of -1 indicates a global context .
Hook routine interface:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - pRefData - Pointer to reference data ; [ESP + 4] - pcrf - Pointer to client register frame ; EXIT None ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT Task (global) or DOS session-task (local) ; NOTE pcrf is valid only for local context hook handlers
VDHArmContextHook - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: Any context hooks allocated in the context of the terminating DOS session are deallocated by the DOS Session Manager.
Notes: After calling this routine, the caller is guaranteed that the context hook will be executed before any user-space code (global context) or any V86 code in the specified DOS session (local context).
VDHArmContextHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHArmReturnHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function sets a service to receive control when an Interrupt Return ( IRET ) or Far Return ( RETF ) instruction is executed in V86 mode or when VDHPopInt is executed . * / include mvdm . inc EXTERN VDHArmReturnHook : NEAR HookHandle DD ? ; Hook handle RetHookType DD ? ; Return hook type PUSH HookHandle ; Push HookHandle PUSH RetHookType ; Push RetHookType CALL VDHArmReturnHook ; Call the function
VDHArmReturnHook - Format
/* This function sets a service to receive control when an Interrupt Return ( IRET ) or Far Return ( RETF ) instruction is executed in V86 mode or when VDHPopInt is executed . * / include mvdm . inc EXTERN VDHArmReturnHook : NEAR HookHandle DD ? ; Hook handle RetHookType DD ? ; Return hook type PUSH HookHandle ; Push HookHandle PUSH RetHookType ; Push RetHookType CALL VDHArmReturnHook ; Call the function
VDHArmReturnHook Parameter - HookHandle
HookHandle(DD) Hook handles the routine to get control on an IRET/RETF. Allocated with VDHAllocHook.
VDHArmReturnHook Parameter - RetHookType
RetHookType(DD) Return hook type.
Possible values are:
VDHARH_NORMAL_IRET
VDHARH_NORMAL_RET
VDHARH_RECURSIVE_IRET
VDHARH_RECURSIVE_RET
VDHARH_CSEIP_HOOK
VDHARH_RECURSIVE_CSEIP_HOOK
Hook routine interface:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - pRefData - Pointer to reference data ; [ESP + 4] - pcrf - Pointer to client register frame ; EXIT None ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS session-task
VDHArmReturnHook Return Value - rc
Success If the function was successful it returns a nonzero value.
Failure If VDHARH_NORMAL_x is already armed, the function returns 0. If HookHandleis invalid, a system halt occurs.
VDHArmReturnHook - Parameters
HookHandle(DD) Hook handles the routine to get control on an IRET/RETF. Allocated with VDHAllocHook.
RetHookType(DD) Return hook type.
Possible values are:
VDHARH_NORMAL_IRET
VDHARH_NORMAL_RET
VDHARH_RECURSIVE_IRET
VDHARH_RECURSIVE_RET
VDHARH_CSEIP_HOOK
VDHARH_RECURSIVE_CSEIP_HOOK
Hook routine interface:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - pRefData - Pointer to reference data ; [ESP + 4] - pcrf - Pointer to client register frame ; EXIT None ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS session-task
VDHArmReturnHook - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: Any return hooks allocated in the context of the terminating DOS session are deallocated automatically by the DOS Session Manager.
Notes: The VDHARH_NORMAL_RET and VDHARH_RECURSIVE_RET return hook types can be made only after VDHPushFarCallhas been called, but before returning to V86 mode. The return hook types, VDHARH_NORMAL_IRET and VDHARH_RECURSIVE_ IRET, can be made only in the following contexts:
- Within a software interrupt handler set by VDHInstallIntHook
*After VDHPushInthas been called, but before returning to V86 mode
The VDHARH_RECURSIVE_x return types push two extra WORDs on the client's stack before the IRET or RET frame. VDHARH_CSEIP_HOOK and VDHARH_RECURSIVE_ CSEIP_HOOK are meant to be used before a VDHPushIntor VDHPushFarCall, as it is more efficient to do this type of return hook first. Only the normal and recursive CS:EIP hooks will work in DOS session protected mode.
VDHArmReturnHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHArmSTIHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function sets a handler to receive control when the current DOS session enables simulated interrupts . This handler is called only once . If interrupts are already enabled in the DOS session , the handler is called immediately . * / include mvdm . inc EXTERN VDHArmSTIHook : NEAR HookHandle DD ? ; Hook handle allocated with VDHAllocHook VDMHandle DD ? ; DOS session handle PUSH HookHandle ; Push HookHandle PUSH VDMHandle ; Push VDMHandle CALL VDHArmSTIHook ; Call the function
VDHArmSTIHook - Format
/* This function sets a handler to receive control when the current DOS session enables simulated interrupts . This handler is called only once . If interrupts are already enabled in the DOS session , the handler is called immediately . * / include mvdm . inc EXTERN VDHArmSTIHook : NEAR HookHandle DD ? ; Hook handle allocated with VDHAllocHook VDMHandle DD ? ; DOS session handle PUSH HookHandle ; Push HookHandle PUSH VDMHandle ; Push VDMHandle CALL VDHArmSTIHook ; Call the function
VDHArmSTIHook Parameter - HookHandle
HookHandle(DD) Hook handle allocated with VDHAllocHook.
VDHArmSTIHook Parameter - VDMHandle
VDMHandle(DD) DOS session handle.
Hook routine interface:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - pRefData - Pointer to reference data ; [ESP + 4] - pcrf - Pointer to client register frame ; EXIT None ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS session-task
VDHArmSTIHook Return Value - rc
Success If the function was successful, it returns nothing.
Failure If either HookHandleor VDMHandleis invalid, or if the hook is already armed, a system halt occurs.
VDHArmSTIHook - Parameters
HookHandle(DD) Hook handle allocated with VDHAllocHook.
VDMHandle(DD) DOS session handle.
Hook routine interface:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - pRefData - Pointer to reference data ; [ESP + 4] - pcrf - Pointer to client register frame ; EXIT None ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS session-task
VDHArmSTIHook - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: Any STI hooks allocated in the context of the terminating DOS session are deallocated automatically by the DOS Session Manager.
Notes: Interrupt re-enabling detection is performed when the DOS session runs with IOPL = 0. This causes any instructions that might modify the interrupt flag to fault.
VDHArmSTIHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHArmTimerHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function sets a timer handler to be called after a specified period of time has elapsed . The handler is called only once . * / include mvdm . inc EXTERN VDHArmTimerHook : NEAR HookHandle DD ? ; Timer hook handle Duration DD ? ; Duration of the timeout in milliseconds VDMHandle DD ? ; DOS session handle PUSH HookHandle ; Push HookHandle PUSH Duration ; Push Duration PUSH VDMHandle ; Push VDMHandle CALL VDHArmTimerHook ; Call the function
VDHArmTimerHook - Format
/* This function sets a timer handler to be called after a specified period of time has elapsed . The handler is called only once . * / include mvdm . inc EXTERN VDHArmTimerHook : NEAR HookHandle DD ? ; Timer hook handle Duration DD ? ; Duration of the timeout in milliseconds VDMHandle DD ? ; DOS session handle PUSH HookHandle ; Push HookHandle PUSH Duration ; Push Duration PUSH VDMHandle ; Push VDMHandle CALL VDHArmTimerHook ; Call the function
VDHArmTimerHook Parameter - HookHandle
HookHandle(DD) Timer hook handle.
VDHArmTimerHook Parameter - Duration
Duration(DD) Timer duration in milliseconds.
VDHArmTimerHook Parameter - VDMHandle
VDMHandle(DD) DOS session handle.
Possible values are:
DOS Session Handle or 0 When the specified time duration expires, a local context hook is automatically armed by using the specified HookHandle.
VDH_TIMER_GLOBAL_CONTEXT When the specified time duration expires, a global context hook is automatically armed by using the specified HookHandle.
VDH_TIMER_INTERRUPT_HOOK When the specified time duration expires, the timer hook specified by HookHandleis called at interrupt time.
Hook routine interface:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - pRefData - Pointer to reference data ; EXIT None ; ; CONTEXT Interrupt
VDHArmTimerHook Return Value - rc
Success If the function is successful, it returns nothing.
Failure If either Durationor HookHandleis invalid or the hook is already armed, a system halt occurs.
VDHArmTimerHook - Parameters
HookHandle(DD) Timer hook handle.
Duration(DD) Timer duration in milliseconds.
VDMHandle(DD) DOS session handle.
Possible values are:
DOS Session Handle or 0 When the specified time duration expires, a local context hook is automatically armed by using the specified HookHandle.
VDH_TIMER_GLOBAL_CONTEXT When the specified time duration expires, a global context hook is automatically armed by using the specified HookHandle.
VDH_TIMER_INTERRUPT_HOOK When the specified time duration expires, the timer hook specified by HookHandleis called at interrupt time.
Hook routine interface:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - pRefData - Pointer to reference data ; EXIT None ; ; CONTEXT Interrupt
VDHArmTimerHook - Purpose
Context Issues: This function can be called in the initialization, task, or interrupt context.
DOS Session Terminations: Any timer hooks allocated in the context of the terminating DOS session are deallocated automatically by the DOS Session Manager at DOS session termination.
Notes: If type VDH_TIMER_INTERRUPT_HOOK, the timer handler cannot block since it executes at physical interrupt time.
VDHArmTimerHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHArmVPMBPHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function obtains the address of the DOS session ' s protected - mode breakpoint allocated by a previous call to VDHAllocHook with the VDH _ BP _ HOOK flag . * / include mvdm . inc EXTERN VDHArmVPMBPHook : NEAR HookHandle DD ? ; Hook handle allocated with VDHAllocHook PUSH HookHandle ; Push HookHandle CALL VDHArmVPMBPHook ; Call the function
VDHArmVPMBPHook - Format
/* This function obtains the address of the DOS session ' s protected - mode breakpoint allocated by a previous call to VDHAllocHook with the VDH _ BP _ HOOK flag . * / include mvdm . inc EXTERN VDHArmVPMBPHook : NEAR HookHandle DD ? ; Hook handle allocated with VDHAllocHook PUSH HookHandle ; Push HookHandle CALL VDHArmVPMBPHook ; Call the function
VDHArmVPMBPHook Parameter - HookHandle
HookHandle(DD) Hook handle allocated with VDHAllocHook.
The hook routine interface:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - pRefData - Pointer to hook-specific reference data ; [ESP + 4] - pcrf - Pointer to client register frame ; ; EXIT None ; ; CONTEXT DOS session-task
VDHArmVPMBPHook Return Value - rc
Success If the function is successful, it returns a DOS session protected- mode breakpoint address.
Failure If HookHandleis invalid, a system halt occurs.
VDHArmVPMBPHook - Parameters
HookHandle(DD) Hook handle allocated with VDHAllocHook.
The hook routine interface:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - pRefData - Pointer to hook-specific reference data ; [ESP + 4] - pcrf - Pointer to client register frame ; ; EXIT None ; ; CONTEXT DOS session-task
VDHArmVPMBPHook - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Unlike other hooks, breakpoint hooks are armed until explicitly disarmed by a call to VDHFreeHook. When the breakpoint address is executed from DOS session protected mode, the hook function is called. Any changes made to the client register frame cause the corresponding registers to take on these values after returning to the DOS session. The pparameter in the hook routine points to the RefDataSizebytes of data allocated by VDHAllocHook.
VDHArmVPMBPHookprovides a raw breakpoint service. On entry to the arm hook function, the client's CS:EIP is randomly set. It is therefore crucial that the virtual device driver's hook handler sets the CS:EIP to a valid address . Typically, the CS:EIP is retrieved from the client's stack through the use of VDHPopStack, which is a low-level service. Appropriate care should be exercised to ensure that the client's CS:EIP and stack remain valid.
The breakpoint address returned will be valid for all DPMI clients within the DOS session. The breakpoint address may be placed in the DPMI application's IDT (see VDHSetVPMIntVector), but will have to be rehooked each time a DPMI task starts (see VDHInstallUserHook).
There must be a protected-mode DPMI client running in the DOS session before calling this function.
VDHArmVPMBPHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHBeginUseVPMStack
Select an item:
Format Parameters Return Codes Purpose Glossary
/*
This function is used to switch to the DOS session ' s protected - mode
stack for hardware interrupts , exceptions , and so forth .
This service
can be called repeatedly , but only the first call will switch stacks .
Subsequent calls increment use , count but remain on the VPM stack .
* /
include mvdm . inc
EXTERN VDHBeginUseVPMStack : NEAR
DD ?
PUSH ; Push
CALL VDHBeginUseVPMStack ; Call the function
VDHBeginUseVPMStack - Format
/*
This function is used to switch to the DOS session ' s protected - mode
stack for hardware interrupts , exceptions , and so forth .
This service
can be called repeatedly , but only the first call will switch stacks .
Subsequent calls increment use , count but remain on the VPM stack .
* /
include mvdm . inc
EXTERN VDHBeginUseVPMStack : NEAR
DD ?
PUSH ; Push
CALL VDHBeginUseVPMStack ; Call the function
VDHBeginUseVPMStack Parameter -
(DD) None.
VDHBeginUseVPMStack Return Value -
None.
VDHBeginUseVPMStack - Parameters
(DD) None.
VDHBeginUseVPMStack - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: There must be a DPMI client running in the DOS session before calling this function.
VDHBeginUseVPMStack - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCallOutDMA
Select an item:
Format Parameters Return Codes Purpose Glossary
/*
This function is used by the
virtual DMA device driver ( VDMA ) to check how much DMA transfer has
been completed , and to copy the contents from the temporary buffer to
the DOS area .
If a virtual device driver owns a DMA channel , it must call
the virtual DMA device driver for those interrupts that occur when a
DMA request is pending on that channel .
This service also indicates when the DOS session is done with
the channel so that the channel can be given to another waiting DOS session .
* /
include mvdm . inc
EXTERN VDHCallOutDMA : NEAR
DD ?
PUSH ; Push
CALL VDHCallOutDMA ; Call the function
VDHCallOutDMA - Format
/*
This function is used by the
virtual DMA device driver ( VDMA ) to check how much DMA transfer has
been completed , and to copy the contents from the temporary buffer to
the DOS area .
If a virtual device driver owns a DMA channel , it must call
the virtual DMA device driver for those interrupts that occur when a
DMA request is pending on that channel .
This service also indicates when the DOS session is done with
the channel so that the channel can be given to another waiting DOS session .
* /
include mvdm . inc
EXTERN VDHCallOutDMA : NEAR
DD ?
PUSH ; Push
CALL VDHCallOutDMA ; Call the function
VDHCallOutDMA Parameter -
(DD) None.
VDHCallOutDMA Return Value -
None.
VDHCallOutDMA - Parameters
(DD) None.
VDHCallOutDMA - Purpose
Context Issues: This function can be called in any context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHCallOutDMA - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHChangeVPMIF
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function changes the virtual Interrupt Flag ( IF ) that enables or disables protected - mode interrupts . This change is reflected in a bit in the flVDMStatus kernel variable ( see " Notes " under Purpose ) . If the STI hooks are waiting and interrupts are enabled , the hooks are called . * / include mvdm . inc EXTERN VDHChangeVPMIF : NEAR SetIFFlag DD ? ; Indicates whether to turn the IF flag on or off PUSH SetIFFlag ; Push SetIFFlag CALL VDHChangeVPMIF ; Call the function
VDHChangeVPMIF - Format
/* This function changes the virtual Interrupt Flag ( IF ) that enables or disables protected - mode interrupts . This change is reflected in a bit in the flVDMStatus kernel variable ( see " Notes " under Purpose ) . If the STI hooks are waiting and interrupts are enabled , the hooks are called . * / include mvdm . inc EXTERN VDHChangeVPMIF : NEAR SetIFFlag DD ? ; Indicates whether to turn the IF flag on or off PUSH SetIFFlag ; Push SetIFFlag CALL VDHChangeVPMIF ; Call the function
VDHChangeVPMIF Parameter - SetIFFlag
SetIFFlag(DD) Indicates whether to turn the IF flag ON or OFF. If nonzero, set IF flag to 1 (one). If zero, set IF flag to 0 (zero).
VDHChangeVPMIF Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure Not applicable to this function.
VDHChangeVPMIF - Parameters
SetIFFlag(DD) Indicates whether to turn the IF flag ON or OFF. If nonzero, set IF flag to 1 (one). If zero, set IF flag to 0 (zero).
VDHChangeVPMIF - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: The flVDMStatuskernel variable is exported from the kernel. Any virtual device driver can refer to it directly. flVDMStatusis a DD-sized variable that contains various DOS session status flags relating to protected mode and the DOS Protected Mode Interface (DPMI).
The flVDMStatusflags indicate:
- DPMI was initialized (protected mode was enabled)
*16-bit or 32-bit
*The current execution mode (V86 or protected)
These flags and their values are:
VDM_STATUS_VPM_32 0x00000001 /* 32-bit DPMI application */ VDM_STATUS_VPM_APP 0x00000002 /* DPMI application started */ VDM_STATUS_VPM_EXEC 0x00000004 /* In DOS session protected mode*/ VDM_STATUS_VPM_IF_FLAG 0x00000010 /* Virtual IF flag */ VDM_STATUS_VPM_PERM 0x00000080 /* Protected mode allowed? */ VDM_STATUS_VPM_XDOS 0x00000100 /* DOS API extension active? */
VDHChangeVPMIF - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCheckPagePerm
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function checks Ring 3 page permissions for a range of pages . This service fails if a Ring 3 client faults on any of the pages that have been checked . * / include mvdm . inc EXTERN VDHCheckPagePerm : NEAR BasePage DD ? ; Base virtual page number Reserved DD ? ; Reserved ; must be set to zero NumPages DD ? ; Number of pages to verify Flag DD ? ; Flag PUSH BasePage ; Push BasePage PUSH Reserved ; Push Reserved PUSH NumPages ; Push NumPages PUSH Flag ; Push Flag CALL VDHCheckPagePerm ; Call the function
VDHCheckPagePerm - Format
/* This function checks Ring 3 page permissions for a range of pages . This service fails if a Ring 3 client faults on any of the pages that have been checked . * / include mvdm . inc EXTERN VDHCheckPagePerm : NEAR BasePage DD ? ; Base virtual page number Reserved DD ? ; Reserved ; must be set to zero NumPages DD ? ; Number of pages to verify Flag DD ? ; Flag PUSH BasePage ; Push BasePage PUSH Reserved ; Push Reserved PUSH NumPages ; Push NumPages PUSH Flag ; Push Flag CALL VDHCheckPagePerm ; Call the function
VDHCheckPagePerm Parameter - BasePage
BasePage(DD) Base virtual page number.
VDHCheckPagePerm Parameter - Reserved
Reserved(DD) Reserved. Must be set to 0.
VDHCheckPagePerm Parameter - NumPages
NumPages(DD) Number of pages to verify.
VDHCheckPagePerm Parameter - Flag
Flag(DD) Values are:
VPMPG_U Are the pages user-accessible?
VPMPG_W Are the pages writable?
VPMPG_R Are the pages readable (valid)?
VPMPG_X Are the pages executable?
VDHCheckPagePerm Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0.
VDHCheckPagePerm - Parameters
BasePage(DD) Base virtual page number.
Reserved(DD) Reserved. Must be set to 0.
NumPages(DD) Number of pages to verify.
Flag(DD) Values are:
VPMPG_U Are the pages user-accessible?
VPMPG_W Are the pages writable?
VPMPG_R Are the pages readable (valid)?
VPMPG_X Are the pages executable?
VDHCheckPagePerm - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHCheckPagePerm - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCheckVPMIntVector
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function returns a nonzero value if the application protected - mode interrupt vector is set . * / include mvdm . inc EXTERN VDHCheckVPMIntVector : NEAR Vector DD ? ; Interrupt vector number PUSH Vector ; Push Vector CALL VDHCheckVPMIntVecto ; Call the function
VDHCheckVPMIntVector - Format
/* This function returns a nonzero value if the application protected - mode interrupt vector is set . * / include mvdm . inc EXTERN VDHCheckVPMIntVector : NEAR Vector DD ? ; Interrupt vector number PUSH Vector ; Push Vector CALL VDHCheckVPMIntVecto ; Call the function
VDHCheckVPMIntVector Parameter - Vector
Vector(DD) Interrupt vector number.
VDHCheckVPMIntVector Return Value - rc
Success If the function is successful it returns a nonzero value.
Failure If there is no user-registered interrupt handler for the interrupt in Vector, the function returns 0 (zero).
VDHCheckVPMIntVector - Parameters
Vector(DD) Interrupt vector number.
VDHCheckVPMIntVector - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: There must be a DPMI client running in the DOS session before calling this function.
VDHCheckVPMIntVector - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHClearVIRR
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function clears the virtual Interrupt Request Register ( IRR ) in the Virtual Programmable Interrupt Controller ( VPIC ) of the specified DOS session for the IRQ specified . The simulation of interrupts to the specified DOS session is stopped on this IRQ level . * / include mvdm . inc EXTERN VDHClearVIRR : NEAR VDMHandle DD ? ; DOS session handle IRQHandle DD ? ; IRQ handle from VDHOpenVIRQ PUSH VDMHandle ; Push VDMHandle PUSH IRQHandle ; Push IRQHandle CALL VDHClearVIRR ; Call the function
VDHClearVIRR - Format
/* This function clears the virtual Interrupt Request Register ( IRR ) in the Virtual Programmable Interrupt Controller ( VPIC ) of the specified DOS session for the IRQ specified . The simulation of interrupts to the specified DOS session is stopped on this IRQ level . * / include mvdm . inc EXTERN VDHClearVIRR : NEAR VDMHandle DD ? ; DOS session handle IRQHandle DD ? ; IRQ handle from VDHOpenVIRQ PUSH VDMHandle ; Push VDMHandle PUSH IRQHandle ; Push IRQHandle CALL VDHClearVIRR ; Call the function
VDHClearVIRR Parameter - VDMHandle
VDMHandle(DD) DOS session handle. A value of 0 (zero) indicates the current DOS session.
VDHClearVIRR Parameter - IRQHandle
IRQHandle(DD) IRQ handle from VDHOpenVIRQ.
VDHClearVIRR Return Value - rc
Success If the function was successful, it returns nothing.
Failure If either of the parameters is invalid, a system halt occurs.
VDHClearVIRR - Parameters
VDMHandle(DD) DOS session handle. A value of 0 (zero) indicates the current DOS session.
IRQHandle(DD) IRQ handle from VDHOpenVIRQ.
VDHClearVIRR - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHClearVIRR - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHClose
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function closes a file or device that was opened with VDHOpen . * / include mvdm . inc EXTERN VDHClose : NEAR FileHandle DW ? ; Handle to the file or device to close PUSH FileHandle ; Push FileHandle CALL VDHClose ; Call the function
VDHClose - Format
/* This function closes a file or device that was opened with VDHOpen . * / include mvdm . inc EXTERN VDHClose : NEAR FileHandle DW ? ; Handle to the file or device to close PUSH FileHandle ; Push FileHandle CALL VDHClose ; Call the function
VDHClose Parameter - FileHandle
FileHandle(DW) Handle (from VDHOpen) to the file or device to close.
VDHClose Return Value - rc
Success If the function is successful, it returns nothing.
Failure If FileHandleis invalid or if the DOS session is not in the DOS session-task context, a system halt occurs.
VDHClose - Parameters
FileHandle(DW) Handle (from VDHOpen) to the file or device to close.
VDHClose - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: Any handles opened by the virtual device driver for the terminating DOS session must be closed.
VDHClose - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCloseVDD
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function closes a virtual device driver / virtual device driver ( VDD / VDD ) Inter - Device - Driver Communication ( IDC ) session that was opened with VDHOpenVDD . * / include mvdm . inc EXTERN VDHCloseVDD : NEAR VDDHandle DD ? ; Handle to the file or device to close PUSH VDDHandle ; Push VDDHandle CALL VDHCloseVDD ; Call the function
VDHCloseVDD - Format
/* This function closes a virtual device driver / virtual device driver ( VDD / VDD ) Inter - Device - Driver Communication ( IDC ) session that was opened with VDHOpenVDD . * / include mvdm . inc EXTERN VDHCloseVDD : NEAR VDDHandle DD ? ; Handle to the file or device to close PUSH VDDHandle ; Push VDDHandle CALL VDHCloseVDD ; Call the function
VDHCloseVDD Parameter - VDDHandle
VDDHandle(DD) Handle (from VDHOpenVDD) to the virtual device driver to close.
VDHCloseVDD Return Value - rc
Success If the function is successful, it returns nothing.
Failure If VDMHandleis invalid, a system halt occurs.
VDHCloseVDD - Parameters
VDDHandle(DD) Handle (from VDHOpenVDD) to the virtual device driver to close.
VDHCloseVDD - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: If a virtual device driver has a VDD/VDD session for a particular DOS session, that session is closed when the DOS session terminates.
Notes: This service is used to close the type of VDD/VDD connections, which are temporary or are on a per-DOS session basis.
VDHCloseVDD - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCloseVIRQ
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function closes the virtual IRQ handle passed to it . * / include mvdm . inc EXTERN VDHCloseVIRQ : NEAR IRQHandl DD ? ; Handle of the virtual device driver to close PUSH IRQHandl ; Push IRQHandl CALL VDHCloseVIRQ ; Call the function
VDHCloseVIRQ - Format
/* This function closes the virtual IRQ handle passed to it . * / include mvdm . inc EXTERN VDHCloseVIRQ : NEAR IRQHandl DD ? ; Handle of the virtual device driver to close PUSH IRQHandl ; Push IRQHandl CALL VDHCloseVIRQ ; Call the function
VDHCloseVIRQ Parameter - IRQHandl
IRQHandl(DD) Handle to the IRQ (from VDHOpenVIRQ) to close.
VDHCloseVIRQ Return Value - rc
Success If the function was successful, it returns nothing.
Failure If IRQHandleis invalid, a system halt occurs.
VDHCloseVIRQ - Parameters
IRQHandl(DD) Handle to the IRQ (from VDHOpenVIRQ) to close.
VDHCloseVIRQ - Purpose
Context Issues: This function can be called only in the initialization context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHCloseVIRQ - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCopyMem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function copies memory from one user linear address to another . * / include mvdm . inc EXTERN VDHCopyMem : NEAR Source DD ? ; Address of the data to copy Destination DD ? ; Address to copy the data to NumBytes DD ? ; Number of bytes to copy PUSH Source ; Push Source PUSH Destination ; Push Destination PUSH NumBytes ; Push NumBytes CALL VDHCopyMem ; Call the function
VDHCopyMem - Format
/* This function copies memory from one user linear address to another . * / include mvdm . inc EXTERN VDHCopyMem : NEAR Source DD ? ; Address of the data to copy Destination DD ? ; Address to copy the data to NumBytes DD ? ; Number of bytes to copy PUSH Source ; Push Source PUSH Destination ; Push Destination PUSH NumBytes ; Push NumBytes CALL VDHCopyMem ; Call the function
VDHCopyMem Parameter - Source
Source(DD) Address of the source data to be copied.
VDHCopyMem Parameter - Destination
Destination(DD) Address to which the data is to be copied.
VDHCopyMem Parameter - NumBytes
NumBytes(DD) Number of bytes to copy.
VDHCopyMem Return Value - rc
Success If the function is successful, it returns nothing.
Failure If NumBytesis 0 (zero), a system halt occurs.
VDHCopyMem - Parameters
Source(DD) Address of the source data to be copied.
Destination(DD) Address to which the data is to be copied.
NumBytes(DD) Number of bytes to copy.
VDHCopyMem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Protection faults are handled as if a user application had performed the access. Therefore, writing to an invalid page causes a virtual device driver page fault handler to gain control. If there is no virtual device driver fault handler, a "don't care" page is mapped in at the faulting linear address.
Note that touching invalid pages is allowed only in the context of the DOS session. A virtual device driver cannot touch invalid pages through the HVDM (DOS session Handle) alias region if it is not in the context of that DOS session. A virtual device driver that violates this rule causes a system halt.
This function yields the CPU if it is necessary to ensure that the thread dispatch latency limit is not exceeded. This function also supports overlapping linear regions. However, the results are undefined when copying between regions with aliases (through VDHMapPages) to the same physical page.
If necessary, VDHLockMemis used to ensure that the status of the source and destination linear ranges does not change. This is required only if the source and destination ranges are in private DOS session memory (accessed through the HVDM), and the call to VDHCopyMemis made in the context of some other process.
VDHCopyMem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCreateBlockPool
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function creates a pool of memory blocks of a specified size . The blocks are allocated from the system area so that the block addresses are valid in all process contexts . * / include mvdm . inc EXTERN VDHCreateBlockPool : NEAR BlockSize DD ? ; Size of block to initialize ( in bytes ) OptionFlag DD ? ; Allocation options bit flag PUSH BlockSize ; Push BlockSize PUSH OptionFlag ; Push OptionFlag CALL VDHCreateBlockPool ; Call the function
VDHCreateBlockPool - Format
/* This function creates a pool of memory blocks of a specified size . The blocks are allocated from the system area so that the block addresses are valid in all process contexts . * / include mvdm . inc EXTERN VDHCreateBlockPool : NEAR BlockSize DD ? ; Size of block to initialize ( in bytes ) OptionFlag DD ? ; Allocation options bit flag PUSH BlockSize ; Push BlockSize PUSH OptionFlag ; Push OptionFlag CALL VDHCreateBlockPool ; Call the function
VDHCreateBlockPool Parameter - BlockSize
BlockSize(DD) Size of block to initialize (in bytes).
VDHCreateBlockPool Parameter - OptionFlag
OptionFlag(DD) Allocation options bit flag. Possible value:
VDHCBP_SWAPPABLE Blocks are allocated from the swappable heap. Otherwise, blocks are allocated from the fixed heap and can be accessed at hardware interrupt time.
VDHCreateBlockPool Return Value - rc
Success If the function is successful, it returns a handle to the pool of memory blocks.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If OptionFlagis invalid, or if BlockSizeis equal to 0 (zero), a system halt occurs.
VDHCreateBlockPool - Parameters
BlockSize(DD) Size of block to initialize (in bytes).
OptionFlag(DD) Allocation options bit flag. Possible value:
VDHCBP_SWAPPABLE Blocks are allocated from the swappable heap. Otherwise, blocks are allocated from the fixed heap and can be accessed at hardware interrupt time.
VDHCreateBlockPool - Purpose
Context Issues: This function can be called in the initialization or task context.
DOS Session Terminations: Any block pools allocated by a virtual device driver for use by the terminating DOS session is freed by using VDHDestroyBlockPool.
VDHCreateBlockPool - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCreateSel
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function creates a GDT selector that maps a linear range . This service is used to create a 16 : 16 pointer , which is passed to a 16 - bit physical device driver . * / include mvdm . inc EXTERN VDHCreateSel : NEAR LinearAddress DD ? ; Linear address of the start of the buffer BufferSize DD ? ; Size of the buffer in bytes PUSH LinearAddress ; Push LinearAddress PUSH BufferSize ; Push BufferSize CALL VDHCreateSel ; Call the function
VDHCreateSel - Format
/* This function creates a GDT selector that maps a linear range . This service is used to create a 16 : 16 pointer , which is passed to a 16 - bit physical device driver . * / include mvdm . inc EXTERN VDHCreateSel : NEAR LinearAddress DD ? ; Linear address of the start of the buffer BufferSize DD ? ; Size of the buffer in bytes PUSH LinearAddress ; Push LinearAddress PUSH BufferSize ; Push BufferSize CALL VDHCreateSel ; Call the function
VDHCreateSel Parameter - LinearAddress
LinearAddress(DD) Linear address of the beginning of the buffer.
VDHCreateSel Parameter - BufferSize
BufferSize(DD) Size of the buffer in bytes. The expected range is 0-65535 with 0 interpreted as 65536.
VDHCreateSel Return Value - rc
Success If the function is successful, it returns a nonzero selector value such that SELECTOR:0 points to the first byte of the linear range.
Failure If BufferSizeis greater than 65535 or if there are no more selectors available, a system halt occurs.
VDHCreateSel - Parameters
LinearAddress(DD) Linear address of the beginning of the buffer.
BufferSize(DD) Size of the buffer in bytes. The expected range is 0-65535 with 0 interpreted as 65536.
VDHCreateSel - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: Any selectors created to map memory in the terminating DOS session must be destroyed with VDHDestroySel. The virtual device driver must ensure that any physical device driver that was given these selectors is finished with them.
Notes: The linear address must be in system memory. To create a 16:16 pointer to a DOS session address (in the 0 to 1MB+64KB range), use the HVDM (DOS session handle) alias linear address. VDHDestroySelmust be called when finished with this pointer.
VDHCreateSel - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHCreateSem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is used to create an event or mutex semaphore . * / include mvdm . inc EXTERN VDHCreateSem : NEAR SemHandlePointer DD ? ; Semaphore handle address SemType DD ? ; Type of semaphore of create PUSH SemHandlePointer ; Push SemHandlePointer PUSH SemType ; Push SemType CALL VDHCreateSem ; Call the function
VDHCreateSem - Format
/* This function is used to create an event or mutex semaphore . * / include mvdm . inc EXTERN VDHCreateSem : NEAR SemHandlePointer DD ? ; Semaphore handle address SemType DD ? ; Type of semaphore of create PUSH SemHandlePointer ; Push SemHandlePointer PUSH SemType ; Push SemType CALL VDHCreateSem ; Call the function
VDHCreateSem Parameter - SemHandlePointer
SemHandlePointer(DD) Semaphore handle address.
VDHCreateSem Parameter - SemType
SemType(DD) Type of semaphore to create.
Values are:
VDH_EVENTSEM Event semaphore
VDH_MUTEXSEM Mutex semaphore
VDHCreateSem Return Value - rc
Success If the function is successful, it returns a nonzero value and places a handle to the semaphore in SemHandlePointer.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. An invalid semaphore type causes a system halt to occur.
VDHCreateSem - Parameters
SemHandlePointer(DD) Semaphore handle address.
SemType(DD) Type of semaphore to create.
Values are:
VDH_EVENTSEM Event semaphore
VDH_MUTEXSEM Mutex semaphore
VDHCreateSem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: These semaphores are global and are not attached to a specific DOS session. If a virtual device driver maintains semaphores on a per-DOS session basis, it destroys the semaphores by using VDHDestroySemwhen the DOS session they are associated with is terminated.
VDHCreateSem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHDecodeProperty
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function decodes the specified format of a property string. (See Notes) */ include mvdm.inc EXTERN VDHDecodeProperty:NEAR ppProperty DD ? ; Pointer to a pointer to property string StartNumberPtr DD ? ; Location to return the starting number EndNumberPtr DD ? ; Location to return the ending number BaseFlag DD ? ; Flag indicating the numeric base to use PUSH ppProperty ; Push ppProperty PUSH StartNumberPtr ; Push StartNumberPtr PUSH EndNumberPtr ; Push EndNumberPtr PUSH BaseFlag ; Push BaseFlag CALL VDHDecodeProperty ; Call the function
VDHDecodeProperty - Format
/* This function decodes the specified format of a property string. (See Notes) */ include mvdm.inc EXTERN VDHDecodeProperty:NEAR ppProperty DD ? ; Pointer to a pointer to property string StartNumberPtr DD ? ; Location to return the starting number EndNumberPtr DD ? ; Location to return the ending number BaseFlag DD ? ; Flag indicating the numeric base to use PUSH ppProperty ; Push ppProperty PUSH StartNumberPtr ; Push StartNumberPtr PUSH EndNumberPtr ; Push EndNumberPtr PUSH BaseFlag ; Push BaseFlag CALL VDHDecodeProperty ; Call the function
VDHDecodeProperty Parameter - ppProperty
ppProperty(DD) A pointer to a pointer to the property string to be decoded .
VDHDecodeProperty Parameter - StartNumberPtr
StartNumberPtr(DD) Location for storing the returned starting number.
VDHDecodeProperty Parameter - EndNumberPtr
EndNumberPtr(DD) Location for storing the returned ending number.
VDHDecodeProperty Parameter - BaseFlag
BaseFlag(DD) Flag indicating which numeric base to use:
VDH_DP_DECIMAL Decimal
VDH_DP_HEX Hex
VDHDecodeProperty Return Value - rc
Success If the function is successful, it returns a nonzero value and the ppPropertypointer is modified to point to the next range in the property string. StartNumberPtrand EndNumberPtrwill have the range values. ppPropertyis returned NULL after processing the last range.
Failure If the function fails, it returns 0, indicating an invalid parameter. If BaseFlagcontains an invalid value or if ppPropertyis NULL, a system halt occurs.
VDHDecodeProperty - Parameters
ppProperty(DD) A pointer to a pointer to the property string to be decoded .
StartNumberPtr(DD) Location for storing the returned starting number.
EndNumberPtr(DD) Location for storing the returned ending number.
BaseFlag(DD) Flag indicating which numeric base to use:
VDH_DP_DECIMAL Decimal
VDH_DP_HEX Hex
VDHDecodeProperty - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: If a single value is found, EndNumberPtris a -1. All the numbers are decoded in the specified base. A negative sign is used only as range delimiter. Numbers cannot have more than eight digits or a failure is returned. If this service returns Failure, it is still possible that the contents of StartNumberPtror EndNumberPtrmight have changed.
Because pointers passed are from a virtual device driver (not a user), there is no verification of addresses. Bad pointers result in page faults.
This function decodes the specified format of a property string as shown below:
String Syntax = "N1-N2,N3-N4,N5,N6-N7,..."
Notice that Nxare valid numbers in a specified base.
VDHDecodeProperty - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHDestroyBlockPool
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function releases a memory block pool . * / include mvdm . inc EXTERN VDHDestroyBlockPool : NEAR PoolHandle DD ? ; Handle to the memory block pool to release PUSH PoolHandle ; Push PoolHandle CALL VDHDestroyBlockPool ; Call the function
VDHDestroyBlockPool - Format
/* This function releases a memory block pool . * / include mvdm . inc EXTERN VDHDestroyBlockPool : NEAR PoolHandle DD ? ; Handle to the memory block pool to release PUSH PoolHandle ; Push PoolHandle CALL VDHDestroyBlockPool ; Call the function
VDHDestroyBlockPool Parameter - PoolHandle
PoolHandle(DD) Handle to the memory block pool to release.
VDHDestroyBlockPool Return Value - rc
Success If the function was successful, it returns nothing.
Failure An invalid memory block pool handle causes a system halt to occur.
VDHDestroyBlockPool - Parameters
PoolHandle(DD) Handle to the memory block pool to release.
VDHDestroyBlockPool - Purpose
Context Issues: This function can be called in the initialization or task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHDestroyBlockPool - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHDestroySel
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function destroys a GDT selector created by VDHCreateSel . * / include mvdm . inc EXTERN VDHDestroySel : NEAR GDTSelector DW ? ; GDT selector to destroy PUSH GDTSelector ; Push GDTSelector CALL VDHDestroySel ; Call the function
VDHDestroySel - Format
/* This function destroys a GDT selector created by VDHCreateSel . * / include mvdm . inc EXTERN VDHDestroySel : NEAR GDTSelector DW ? ; GDT selector to destroy PUSH GDTSelector ; Push GDTSelector CALL VDHDestroySel ; Call the function
VDHDestroySel Parameter - GDTSelector
GDTSelector(DW) GDT selector to be destroyed.
VDHDestroySel Return Value - rc
Success If the function is successful, it returns nothing.
Failure If GDTSelectorwas not created by VDHCreateSel, a system halt occurs.
VDHDestroySel - Parameters
GDTSelector(DW) GDT selector to be destroyed.
VDHDestroySel - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: All selectors created with VDHCreateSelthat map the terminating DOS session must be destroyed.
VDHDestroySel - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHDestroySem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function destroys a semaphore previously created with VDHCreateSem . The semaphore must be posted or unowned before calling this service . * / include mvdm . inc EXTERN VDHDestroySem : NEAR SemHandle DD ? ; Semaphore handle to destroy PUSH SemHandle ; Push SemHandle CALL VDHDestroySem ; Call the function
VDHDestroySem - Format
/* This function destroys a semaphore previously created with VDHCreateSem . The semaphore must be posted or unowned before calling this service . * / include mvdm . inc EXTERN VDHDestroySem : NEAR SemHandle DD ? ; Semaphore handle to destroy PUSH SemHandle ; Push SemHandle CALL VDHDestroySem ; Call the function
VDHDestroySem Parameter - SemHandle
SemHandle(DD) Handle of the semaphore to destroy.
VDHDestroySem Return Value - rc
Success If the function is successful, it returns nothing.
Failure If SemHandleis invalid or if the semaphore is reset or owned, a system halt occurs.
VDHDestroySem - Parameters
SemHandle(DD) Handle of the semaphore to destroy.
VDHDestroySem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHDestroySem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHDevBeep
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function performs the preempt beep request on behalf of the requesting virtual device driver . * / include mvdm . inc EXTERN VDHDevBeep : NEAR Frequency DD ? ; Frequency of the beep in hertz Duration DD ? ; Duration of the beep in milliseconds PUSH Frequency ; Push Frequency PUSH Duration ; Push Duration CALL VDHDevBeep ; Call the function
VDHDevBeep - Format
/* This function performs the preempt beep request on behalf of the requesting virtual device driver . * / include mvdm . inc EXTERN VDHDevBeep : NEAR Frequency DD ? ; Frequency of the beep in hertz Duration DD ? ; Duration of the beep in milliseconds PUSH Frequency ; Push Frequency PUSH Duration ; Push Duration CALL VDHDevBeep ; Call the function
VDHDevBeep Parameter - Frequency
Frequency(DD) Frequency of the beep in hertz.
VDHDevBeep Parameter - Duration
Duration(DD) Duration of the beep in milliseconds.
VDHDevBeep Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0.
VDHDevBeep - Parameters
Frequency(DD) Frequency of the beep in hertz.
Duration(DD) Duration of the beep in milliseconds.
VDHDevBeep - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHDevBeep - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHDevIOCtl
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function allows a virtual device driver to send device - specific commands to a physical device driver through the generic IOCtl interface . The parameters and error return codes are identical to the ones found in the DosDevIOCtl API . Refer to the OS / 2 Control Program Programming Reference for a complete description of each DosDevIOCtl API parameter . * / include mvdm . inc EXTERN VDHDevIOCtl : NEAR DevHandle DW ? ; Device handle returned by VDHOpen or VDHPhysicalDisk Category DD ? ; Category of function performed Function DD ? ; Function within category performed ParmList DD ? ; Pointer to command - specific input parameter area ParmLengthMax DD ? ; Maximum size of input parameter area , in bytes ParmLengthInOut DD ? ; Pointer to length of the parameters passed , in bytes DataArea DD ? ; Pointer to the data area DataLengthMax DD ? ; Maximum size of the parameters passed , in bytes DataLengthInOut DD ? ; Pointer to length of the parameters passed , in bytes PUSH DevHandle ; Push DevHandle PUSH Category ; Push Category PUSH Function ; Push Function PUSH ParmList ; Push ParmList PUSH ParmLengthMax ; Push ParmLengthMax PUSH ParmLengthInOut ; Push ParmLengthInOut PUSH DataArea ; Push DataArea PUSH DataLengthMax ; Push DataLengthMax PUSH DataLengthInOut ; Push DataLengthInOut CALL VDHDevIOCtl ; Call the function
VDHDevIOCtl - Format
/* This function allows a virtual device driver to send device - specific commands to a physical device driver through the generic IOCtl interface . The parameters and error return codes are identical to the ones found in the DosDevIOCtl API . Refer to the OS / 2 Control Program Programming Reference for a complete description of each DosDevIOCtl API parameter . * / include mvdm . inc EXTERN VDHDevIOCtl : NEAR DevHandle DW ? ; Device handle returned by VDHOpen or VDHPhysicalDisk Category DD ? ; Category of function performed Function DD ? ; Function within category performed ParmList DD ? ; Pointer to command - specific input parameter area ParmLengthMax DD ? ; Maximum size of input parameter area , in bytes ParmLengthInOut DD ? ; Pointer to length of the parameters passed , in bytes DataArea DD ? ; Pointer to the data area DataLengthMax DD ? ; Maximum size of the parameters passed , in bytes DataLengthInOut DD ? ; Pointer to length of the parameters passed , in bytes PUSH DevHandle ; Push DevHandle PUSH Category ; Push Category PUSH Function ; Push Function PUSH ParmList ; Push ParmList PUSH ParmLengthMax ; Push ParmLengthMax PUSH ParmLengthInOut ; Push ParmLengthInOut PUSH DataArea ; Push DataArea PUSH DataLengthMax ; Push DataLengthMax PUSH DataLengthInOut ; Push DataLengthInOut CALL VDHDevIOCtl ; Call the function
VDHDevIOCtl Parameter - DevHandle
DevHandle(DW) Device handle returned by VDHOpenor VDHPhysicalDisk.
VDHDevIOCtl Parameter - Category
Category(DD) Category of function performed.
VDHDevIOCtl Parameter - Function
Function(DD) Function within category performed.
VDHDevIOCtl Parameter - ParmList
ParmList(DD) Pointer to the command-specific input parameter area.
VDHDevIOCtl Parameter - ParmLengthMax
ParmLengthMax(DD) Maximum size of the application input parameter area, in bytes. ParmLengthInOutcan be longer than this on input, but not on output.
VDHDevIOCtl Parameter - ParmLengthInOut
ParmLengthInOut(DD) Pointer to the length (in bytes) of the parameters passed by the caller in ParmList.
VDHDevIOCtl Parameter - DataArea
DataArea(DD) Pointer to the data area.
VDHDevIOCtl Parameter - DataLengthMax
DataLengthMax(DD) Maximum size of the application data area, in bytes.
VDHDevIOCtl Parameter - DataLengthInOut
DataLengthInOut(DD) Pointer to the length (in bytes) of the parameters passed by the caller in ParmList. ParmLengthInOutcan be longer than this on input, but not on output.
VDHDevIOCtl Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. VDHGetErrorcan return the following errors:
ERROR_INVALID_HANDLE
ERROR_INVALID_FUNCTION
ERROR_INVALID_CATEGORY
ERROR_INVALID_DRIVE
ERROR_INVALID_PARAMETER.
If the function is called when not at DOS session-task time, a system halt occurs.
VDHDevIOCtl - Parameters
DevHandle(DW) Device handle returned by VDHOpenor VDHPhysicalDisk.
Category(DD) Category of function performed.
Function(DD) Function within category performed.
ParmList(DD) Pointer to the command-specific input parameter area.
ParmLengthMax(DD) Maximum size of the application input parameter area, in bytes. ParmLengthInOutcan be longer than this on input, but not on output.
ParmLengthInOut(DD) Pointer to the length (in bytes) of the parameters passed by the caller in ParmList.
DataArea(DD) Pointer to the data area.
DataLengthMax(DD) Maximum size of the application data area, in bytes.
DataLengthInOut(DD) Pointer to the length (in bytes) of the parameters passed by the caller in ParmList. ParmLengthInOutcan be longer than this on input, but not on output.
VDHDevIOCtl - Purpose
Context Issues: This function can be called only in the DOS session task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Addresses (pointers) inside device-specific Data or Parameter Packets are not translated.
VDHDevIOCtl - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHDisarmTimerHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function cancels a timer that was installed by VDHArmTimerHook before the handler was called . * / include mvdm . inc EXTERN VDHDisarmTimerHook : NEAR TimerHook DD ? ; Handle to the timer hook to disarm PUSH TimerHook ; Push TimerHook CALL VDHDisarmTimerHook ; Call the function
VDHDisarmTimerHook - Format
/* This function cancels a timer that was installed by VDHArmTimerHook before the handler was called . * / include mvdm . inc EXTERN VDHDisarmTimerHook : NEAR TimerHook DD ? ; Handle to the timer hook to disarm PUSH TimerHook ; Push TimerHook CALL VDHDisarmTimerHook ; Call the function
VDHDisarmTimerHook Parameter - TimerHook
TimerHook(DD) Handle to the timer hook to disarm.
VDHDisarmTimerHook Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If TimerHookis invalid, a system halt occurs.
VDHDisarmTimerHook - Parameters
TimerHook(DD) Handle to the timer hook to disarm.
VDHDisarmTimerHook - Purpose
Context Issues: This function can be called in the initialization, task, or interrupt context.
DOS Session Terminations: Any timer hooks allocated in the context of the terminating DOS session are deallocated automatically by the DOS Session Manager at DOS session termination.
VDHDisarmTimerHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHEndUseVPMStack
Select an item:
Format Parameters Return Codes Purpose Glossary
/*
This function must be called once with every call made to
VDHBeginUseVPMStack .
It switches back to the original DOS session protected - mode stack when
the use count goes to zero .
* /
include mvdm . inc
EXTERN VDHEndUseVPMStack : NEAR
DD ?
PUSH ; Push
CALL VDHEndUseVPMStack ; Call the function
VDHEndUseVPMStack - Format
/*
This function must be called once with every call made to
VDHBeginUseVPMStack .
It switches back to the original DOS session protected - mode stack when
the use count goes to zero .
* /
include mvdm . inc
EXTERN VDHEndUseVPMStack : NEAR
DD ?
PUSH ; Push
CALL VDHEndUseVPMStack ; Call the function
VDHEndUseVPMStack Parameter -
(DD) None.
VDHEndUseVPMStack Return Value -
None.
VDHEndUseVPMStack - Parameters
(DD) None.
VDHEndUseVPMStack - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: There must be a DPMI client running in the DOS session before calling this function.
VDHEndUseVPMStack - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHEnumerateVDMs
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is used to run a worker function for each DOS session in the system . The worker function can stop the enumeration by returning 0 . * / include mvdm . inc EXTERN VDHEnumerateVDMs : NEAR WorkerFcn DD ? ; Worker function FcnData DD ? ; Function - specific data to be passed each call PUSH WorkerFcn ; Push WorkerFcn PUSH FcnData ; Push FcnData CALL VDHEnumerateVDMs ; Call the function
VDHEnumerateVDMs - Format
/* This function is used to run a worker function for each DOS session in the system . The worker function can stop the enumeration by returning 0 . * / include mvdm . inc EXTERN VDHEnumerateVDMs : NEAR WorkerFcn DD ? ; Worker function FcnData DD ? ; Function - specific data to be passed each call PUSH WorkerFcn ; Push WorkerFcn PUSH FcnData ; Push FcnData CALL VDHEnumerateVDMs ; Call the function
VDHEnumerateVDMs Parameter - WorkerFcn
WorkerFcn(DD) Worker function, the routine that does the work.
The worker function uses the following interface:
EnumHook PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - hVDM - Handle to DOS session ; [ESP + 4] - ulData - Function-specific data ; EXIT SUCCESS - Return a non-zero value in EAX, enumeration continues ; FAILURE - Return 0 in EAX, stop enumeration
VDHEnumerateVDMs Parameter - FcnData
FcnData(DD) Function-specific data to be passed each call.
VDHEnumerateVDMs Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 indicating that a worker function stopped the enumeration.
VDHEnumerateVDMs - Parameters
WorkerFcn(DD) Worker function, the routine that does the work.
The worker function uses the following interface:
EnumHook PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - hVDM - Handle to DOS session ; [ESP + 4] - ulData - Function-specific data ; EXIT SUCCESS - Return a non-zero value in EAX, enumeration continues ; FAILURE - Return 0 in EAX, stop enumeration
FcnData(DD) Function-specific data to be passed each call.
VDHEnumerateVDMs - Purpose
Context Issues: This function can be called in the task and interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHEnumerateVDMs - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHExchangeMem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function exchanges the contents of two regions of linear address space . Overlapping regions are not supported . * / include mvdm . inc EXTERN VDHExchangeMem : NEAR Source DD ? ; Source data address Destination DD ? ; Destination address NumBytes DD ? ; Number of bytes to be exchanged PUSH Source ; Push Source PUSH Destination ; Push Destination PUSH NumBytes ; Push NumBytes CALL VDHExchangeMem ; Call the function
VDHExchangeMem - Format
/* This function exchanges the contents of two regions of linear address space . Overlapping regions are not supported . * / include mvdm . inc EXTERN VDHExchangeMem : NEAR Source DD ? ; Source data address Destination DD ? ; Destination address NumBytes DD ? ; Number of bytes to be exchanged PUSH Source ; Push Source PUSH Destination ; Push Destination PUSH NumBytes ; Push NumBytes CALL VDHExchangeMem ; Call the function
VDHExchangeMem Parameter - Source
Source(DD) Address of the source data.
VDHExchangeMem Parameter - Destination
Destination(DD) Address of the target region.
VDHExchangeMem Parameter - NumBytes
NumBytes(DD) Number of bytes to exchange.
VDHExchangeMem Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHExchangeMem - Parameters
Source(DD) Address of the source data.
Destination(DD) Address of the target region.
NumBytes(DD) Number of bytes to exchange.
VDHExchangeMem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This function fails if the two memory regions to be exchanged overlap. Protection faults are handled as if a user application had performed the access. Therefore, writing to read-only pages or invalid page -table entries causes a virtual device driver page fault handler to gain control or causes the default behavior (that is, DOS session termination). This function also yields the CPU, if it is necessary to ensure that the thread dispatch latency limit is not exceeded.
VDHExchangeMem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHFindFreePages
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function starts at a specified linear address and searches linear memory ( up to a specified limit ) for the largest free linear memory block . The address and size of the largest region found are returned . * / include mvdm . inc EXTERN VDHFindFreePages : NEAR StartAddress DD ? ; Starting address Pages DD ? ; Size of the range ( in pages ) PUSH StartAddress ; Push StartAddress PUSH Pages ; Push Pages CALL VDHFindFreePages ; Call the function
VDHFindFreePages - Format
/* This function starts at a specified linear address and searches linear memory ( up to a specified limit ) for the largest free linear memory block . The address and size of the largest region found are returned . * / include mvdm . inc EXTERN VDHFindFreePages : NEAR StartAddress DD ? ; Starting address Pages DD ? ; Size of the range ( in pages ) PUSH StartAddress ; Push StartAddress PUSH Pages ; Push Pages CALL VDHFindFreePages ; Call the function
VDHFindFreePages Parameter - StartAddress
StartAddress(DD) Starting address of the linear memory range to be searched. Must be page-aligned and between 0 and 110000H (1MB+64KB).
VDHFindFreePages Parameter - Pages
Pages(DD) On input: The size of the linear memory range to search, in pages.
On output: The size of the region found, in pages.
VDHFindFreePages Return Value - rc
Success If the function is successful, it returns the address of the region found and sets Pagesto the size of the region found (in pages).
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHFindFreePages - Parameters
StartAddress(DD) Starting address of the linear memory range to be searched. Must be page-aligned and between 0 and 110000H (1MB+64KB).
Pages(DD) On input: The size of the linear memory range to search, in pages.
On output: The size of the region found, in pages.
VDHFindFreePages - Purpose
Context Issues: This function can be called in the initialization context where it searches only the global linear map. This function can also be called in DOS session-task context (DOS session creation only), where it searches only the DOS session's private linear map.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHFindFreePages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHFreeBlock
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function releases a memory block previously allocated by VDHAllocBlock . The memory block is returned to the user ' s memory block pool for reuse . * / include mvdm . inc EXTERN VDHFreeBlock : NEAR PoolHandle DD ? ; Handle to a memory block pool BlockToFree DD ? ; Address of the memory block to free PUSH PoolHandle ; Push PoolHandle PUSH BlockToFree ; Push BlockToFree CALL VDHFreeBlock ; Call the function
VDHFreeBlock - Format
/* This function releases a memory block previously allocated by VDHAllocBlock . The memory block is returned to the user ' s memory block pool for reuse . * / include mvdm . inc EXTERN VDHFreeBlock : NEAR PoolHandle DD ? ; Handle to a memory block pool BlockToFree DD ? ; Address of the memory block to free PUSH PoolHandle ; Push PoolHandle PUSH BlockToFree ; Push BlockToFree CALL VDHFreeBlock ; Call the function
VDHFreeBlock Parameter - PoolHandle
PoolHandle(DD) Handle (from VDHCreateBlockPool) to the pool of memory blocks that contains the memory block to free.
VDHFreeBlock Parameter - BlockToFree
BlockToFree(DD) Address of the memory block to free.
VDHFreeBlock Return Value - rc
Success If the function is successful, it returns nothing.
Failure If BlockPoolis not a valid handle to a memory block pool, or if BlockToFreeis not a block allocated from the BlockPoolmemory block pool, a system halt occurs.
VDHFreeBlock - Parameters
PoolHandle(DD) Handle (from VDHCreateBlockPool) to the pool of memory blocks that contains the memory block to free.
BlockToFree(DD) Address of the memory block to free.
VDHFreeBlock - Purpose
Context Issues: This function can be called in the initialization or task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: The only way to reclaim memory for freed blocks is to call VDHDestroyBlockPool.
VDHFreeBlock - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHFreeDMABuffer
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function frees a DMA buffer previously allocated by VDHAllocDMABuffer . * / include mvdm . inc EXTERN VDHFreeDMABuffer : NEAR LinearAddress DD ? ; Starting linear address of the DMA buffer PUSH LinearAddress ; Push LinearAddress CALL VDHFreeDMABuffer ; Call the function
VDHFreeDMABuffer - Format
/* This function frees a DMA buffer previously allocated by VDHAllocDMABuffer . * / include mvdm . inc EXTERN VDHFreeDMABuffer : NEAR LinearAddress DD ? ; Starting linear address of the DMA buffer PUSH LinearAddress ; Push LinearAddress CALL VDHFreeDMABuffer ; Call the function
VDHFreeDMABuffer Parameter - LinearAddress
LinearAddress(DD) Starting linear address of the DMA buffer.
VDHFreeDMABuffer Return Value - rc
Success If the function is successful, it returns nothing.
Failure If LinearAddressis invalid, a system halt occurs.
VDHFreeDMABuffer - Parameters
LinearAddress(DD) Starting linear address of the DMA buffer.
VDHFreeDMABuffer - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHFreeDMABuffer - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHFreeHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function disarms and frees a hook . * / include mvdm . inc EXTERN VDHFreeHook : NEAR HookHandle DD ? ; Hook handle from VDHAllocHook PUSH HookHandle ; Push HookHandle CALL VDHFreeHook ; Call the function
VDHFreeHook - Format
/* This function disarms and frees a hook . * / include mvdm . inc EXTERN VDHFreeHook : NEAR HookHandle DD ? ; Hook handle from VDHAllocHook PUSH HookHandle ; Push HookHandle CALL VDHFreeHook ; Call the function
VDHFreeHook Parameter - HookHandle
HookHandle(DD) Hook handle (from VDHAllocHook) for the hook to free.
VDHFreeHook Return Value - rc
Success If the function is successful, it returns nothing.
Failure If HookHandleis invalid, a system halt occurs.
VDHFreeHook - Parameters
HookHandle(DD) Hook handle (from VDHAllocHook) for the hook to free.
VDHFreeHook - Purpose
Context Issues: This function can be called in the initialization or DOS session-task context.
DOS Session Terminations: Any context hooks allocated in the context of the terminating DOS session are deallocated automatically by the DOS Session Manager.
VDHFreeHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHFreeMem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function frees memory that was previously allocated by VDHAllocMem . * / include mvdm . inc EXTERN VDHFreeMem : NEAR MemAddress DD ? ; Address of the memory block to free PUSH MemAddress ; Push MemAddress CALL VDHFreeMem ; Call the function
VDHFreeMem - Format
/* This function frees memory that was previously allocated by VDHAllocMem . * / include mvdm . inc EXTERN VDHFreeMem : NEAR MemAddress DD ? ; Address of the memory block to free PUSH MemAddress ; Push MemAddress CALL VDHFreeMem ; Call the function
VDHFreeMem Parameter - MemAddress
MemAddress(DD) Address of the memory block to be freed. Pointer is originally obtained from VDHAllocMem.
VDHFreeMem Return Value - rc
Success If the function is successful, it returns nothing.
Failure If MemAddressis not an address pointer allocated by VDHAllocMem, a system halt occurs.
VDHFreeMem - Parameters
MemAddress(DD) Address of the memory block to be freed. Pointer is originally obtained from VDHAllocMem.
VDHFreeMem - Purpose
Context Issues: This function can be called in the initialization or task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHFreeMem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHFreePages
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function frees a memory object . All the memory associated with the memory object is released . * / include mvdm . inc EXTERN VDHFreePages : NEAR ObjectAddress DD ? ; Address of the memory object to free PUSH ObjectAddress ; Push ObjectAddress CALL VDHFreePages ; Call the function
VDHFreePages - Format
/* This function frees a memory object . All the memory associated with the memory object is released . * / include mvdm . inc EXTERN VDHFreePages : NEAR ObjectAddress DD ? ; Address of the memory object to free PUSH ObjectAddress ; Push ObjectAddress CALL VDHFreePages ; Call the function
VDHFreePages Parameter - ObjectAddress
ObjectAddress(DD) Address of the memory object to free.
VDHFreePages Return Value - rc
Success If the function is successful, it returns nothing.
Failure If ObjectAddresswas not allocated by VDHAllocPagesor VDHReallocPages, a system halt occurs.
VDHFreePages - Parameters
ObjectAddress(DD) Address of the memory object to free.
VDHFreePages - Purpose
Context Issues: This function can be called in the initialization or task context. At initialization time, only global memory can be freed.
DOS Session Terminations: Any allocations made in the terminating DOS session's private area, or on behalf of the terminating DOS session, must be released by using VDHFreePages.
Notes: This function succeeds only if the linear range specified was allocated by a previous call to VDHAllocPagesor VDHReallocPages. Freeing a memory region that was not allocated causes an internal error (a probable system halt).
If the region, starting at ObjectAddress, has been broken into two or more regions by calls to VDHMapPages, then VDHFreePagesis not used.
VDHFreePages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHFreezeVDM
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function freezes a DOS session , which prevents it from executing . The specified DOS session is not allowed to execute any V86 - mode code until VDHThawVDM is called . This freeze occurs when the specified DOS session leaves kernel mode . The DOS session does not execute any V86 - mode code from the time VDHFreezeVDM is called until the matching VDHThawVDM is called . * / include mvdm . inc EXTERN VDHFreezeVDM : NEAR VDMHandle DD ? ; Handle to the DOS session to freeze PUSH VDMHandle ; Push VDMHandle CALL VDHFreezeVDM ; Call the function
VDHFreezeVDM - Format
/* This function freezes a DOS session , which prevents it from executing . The specified DOS session is not allowed to execute any V86 - mode code until VDHThawVDM is called . This freeze occurs when the specified DOS session leaves kernel mode . The DOS session does not execute any V86 - mode code from the time VDHFreezeVDM is called until the matching VDHThawVDM is called . * / include mvdm . inc EXTERN VDHFreezeVDM : NEAR VDMHandle DD ? ; Handle to the DOS session to freeze PUSH VDMHandle ; Push VDMHandle CALL VDHFreezeVDM ; Call the function
VDHFreezeVDM Parameter - VDMHandle
VDMHandle(DD) Handle to the DOS session to freeze.
VDHFreezeVDM Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If VDMHandleis not a valid DOS session handle, a system halt occurs.
VDHFreezeVDM - Parameters
VDMHandle(DD) Handle to the DOS session to freeze.
VDHFreezeVDM - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: The DOS Session Manager thaws a frozen DOS session prior to calling any VDM_TERMINATE user hooks.
Notes: Each DOS session has a freeze count. This count starts at zero when the DOS session is created. Each VDHFreezeVDMcall adds one to this count. Each VDHThawVDMcall subtracts one from this count. The DOS session is frozen when the freeze count is 1 (one) or greater. The DOS session is thawed when the freeze count is 0 (zero). This allows multiple virtual device drivers to perform freeze and thaw operations without inadvertently causing the DOS session to run. If this count exceeds MAX_FREEZE_COUNT, VDHFreezeVDMreturns VDHERR_FROZEN_LIMIT.
VDHFreezeVDM - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHGetCodePageFont
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function returns the address of the code page font information , if code page support is active and a font is available for the given character cell dimensions . * / include mvdm . inc EXTERN VDHGetCodePageFont : NEAR CellWidth DD ? ; Width of character cells , in pels CellHeight DD ? ; Height of character cells , in pels FontAddress DD ? ; Address where font table addresses will be copied PUSH CellWidth ; Push CellWidth PUSH CellHeight ; Push CellHeight PUSH FontAddress ; Push FontAddress CALL VDHGetCodePageFont ; Call the function
VDHGetCodePageFont - Format
/* This function returns the address of the code page font information , if code page support is active and a font is available for the given character cell dimensions . * / include mvdm . inc EXTERN VDHGetCodePageFont : NEAR CellWidth DD ? ; Width of character cells , in pels CellHeight DD ? ; Height of character cells , in pels FontAddress DD ? ; Address where font table addresses will be copied PUSH CellWidth ; Push CellWidth PUSH CellHeight ; Push CellHeight PUSH FontAddress ; Push FontAddress CALL VDHGetCodePageFont ; Call the function
VDHGetCodePageFont Parameter - CellWidth
CellWidth(DD) Width of character cells, measured in pels.
VDHGetCodePageFont Parameter - CellHeight
CellHeight(DD) Height of character cells, measured in pels.
VDHGetCodePageFont Parameter - FontAddress
FontAddress(DD) Address to which font table addresses will be copied.
VDHGetCodePageFont Return Value - rc
Success If the function is successful, it returns the size of the font table in bytes.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHGetCodePageFont - Parameters
CellWidth(DD) Width of character cells, measured in pels.
CellHeight(DD) Height of character cells, measured in pels.
FontAddress(DD) Address to which font table addresses will be copied.
VDHGetCodePageFont - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: If this function was called on behalf of the terminating DOS session, VDHReleaseCodePageFontmust be called to release the fonts.
Notes: System memory can be allocated to hold the font, especially if it is a merged font (that is, merged from two separate font tables). When the virtual device driver is finished with the font, it must call VDHReleaseCodePageFont.
VDHGetCodePageFont - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHGetDirtyPageInfo
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function returns a bit vector for the dirty pages of a specified DOS session for a specified range of pages . The dirty bits for the range are reset . * / include mvdm . inc EXTERN VDHGetDirtyPageInfo : NEAR VDMHandle DD ? ; Handle to the DOS session that owns the object StartingAddress DD ? ; Address to start the scan PageRange DD ? ; Range of pages to scan PUSH VDMHandle ; Push VDMHandle PUSH StartingAddress ; Push StartingAddress PUSH PageRange ; Push PageRange CALL VDHGetDirtyPageInfo ; Call the function
VDHGetDirtyPageInfo - Format
/* This function returns a bit vector for the dirty pages of a specified DOS session for a specified range of pages . The dirty bits for the range are reset . * / include mvdm . inc EXTERN VDHGetDirtyPageInfo : NEAR VDMHandle DD ? ; Handle to the DOS session that owns the object StartingAddress DD ? ; Address to start the scan PageRange DD ? ; Range of pages to scan PUSH VDMHandle ; Push VDMHandle PUSH StartingAddress ; Push StartingAddress PUSH PageRange ; Push PageRange CALL VDHGetDirtyPageInfo ; Call the function
VDHGetDirtyPageInfo Parameter - VDMHandle
VDMHandle(DD) Handle to the DOS session that owns the object. A 0 (zero) value indicates the current DOS session.
VDHGetDirtyPageInfo Parameter - StartingAddress
StartingAddress(DD) Starting address of the range of pages to scan.
VDHGetDirtyPageInfo Parameter - PageRange
PageRange(DD) Range (number of pages) to scan. Maximum allowed is 32.
VDHGetDirtyPageInfo Return Value - rc
Success If the function is successful, it returns the bit vector. The low- order bit (that is, bit 0, the rightmost bit) is the dirty bit for the first page scanned. Bit 1 (from the right) is the dirty bit for the next page, and so forth for all the pages scanned.
Failure If any of the input parameters are invalid, a system halt occurs.
VDHGetDirtyPageInfo - Parameters
VDMHandle(DD) Handle to the DOS session that owns the object. A 0 (zero) value indicates the current DOS session.
StartingAddress(DD) Starting address of the range of pages to scan.
PageRange(DD) Range (number of pages) to scan. Maximum allowed is 32.
VDHGetDirtyPageInfo - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: The virtual dirty bits remain set until cleared by this function, regardless of the swapping activity that has occurred. The actual dirty bits in the page tables are reset whenever a page is swapped to the swap device and brought back into memory. This function is valid only for linear addresses up to 110000H (1MB+64KB) in a DOS session.
VDHGetDirtyPageInfo - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHGetError
Select an item:
Format Parameters Return Codes Purpose Glossary
/*
This function returns the error code from the last virtual DevHlp
service called .
* /
include mvdm . inc
EXTERN VDHGetError : NEAR
DD ?
PUSH ; Push
CALL VDHGet ; Call the function
VDHGetError - Format
/*
This function returns the error code from the last virtual DevHlp
service called .
* /
include mvdm . inc
EXTERN VDHGetError : NEAR
DD ?
PUSH ; Push
CALL VDHGet ; Call the function
VDHGetError Parameter -
(DD) None.
VDHGetError Return Value - rc
Success If the function is successful, it returns the error code.
Failure If the function fails, it returns 0, indicating that the last virtual DevHlp call did not have an error.
VDHGetError - Parameters
(DD) None.
VDHGetError - Purpose
Context Issues: This function can be called in any context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: The return value is guaranteed to be valid as long as the virtual device driver does not block or yield between the virtual DevHlp service that failed and the call to VDHGetError. VDHGetErrorand VDHSetErrorwork at hardware interrupt time. Each level of interrupt nesting (where task time is Level 0) has a separate error code variable.
VDHGetError - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHGetFlags
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function gets the DOS session ' s EFlags Register . * / include mvdm . inc EXTERN VDHGetFlags : NEAR ulFlagsAddr DD ? ; DOS session flag address . PUSH ulFlagsAddr ; Push ulFlagsAddr CALL VDHGetFlags ; Call the function
VDHGetFlags - Format
/* This function gets the DOS session ' s EFlags Register . * / include mvdm . inc EXTERN VDHGetFlags : NEAR ulFlagsAddr DD ? ; DOS session flag address . PUSH ulFlagsAddr ; Push ulFlagsAddr CALL VDHGetFlags ; Call the function
VDHGetFlags Parameter - ulFlagsAddr
ulFlagsAddr(DD) Address of the ULONG in which the EFLAGs value is to be returned.
VDHGetFlags Return Value -
None.
VDHGetFlags - Parameters
ulFlagsAddr(DD) Address of the ULONG in which the EFLAGs value is to be returned.
VDHGetFlags - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Virtual device drivers must use this interface instead of the client register frame pointer to change the DOS session's flags. Changes to the interrupt flag and the I/O Privilege Level (IOPL) field must be under the control of 8086 emulation so that VDHArmSTIHookworks correctly.
Getting the Interrupt Flag (IF) must be under 8086 emulation control due to virtual mode extensions and DPMI.
VDHGetFlags - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHGetSelBase
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function returns the base address for a Local Descriptor Table ( LDT ) selector . * / include mvdm . inc EXTERN VDHGetSelBase : NEAR Selector DW ? ; LDT selector pBasePointer DD ? ; Pointer for returned address PUSH Selector ; Push Selector PUSH pBasePointer ; Push pBasePointer CALL VDHGetSelBase ; Call the function
VDHGetSelBase - Format
/* This function returns the base address for a Local Descriptor Table ( LDT ) selector . * / include mvdm . inc EXTERN VDHGetSelBase : NEAR Selector DW ? ; LDT selector pBasePointer DD ? ; Pointer for returned address PUSH Selector ; Push Selector PUSH pBasePointer ; Push pBasePointer CALL VDHGetSelBase ; Call the function
VDHGetSelBase Parameter - Selector
Selector(DW) LDT Selector.
VDHGetSelBase Parameter - pBasePointer
pBasePointer(DD) Pointer for returned address.
VDHGetSelBase Return Value - rc
Success If the function is successful, it returns a nonzero value. The base address is returned in the variable pointed to by pBasePointer.
Failure If the function fails, it returns 0 (zero).
VDHGetSelBase - Parameters
Selector(DW) LDT Selector.
pBasePointer(DD) Pointer for returned address.
VDHGetSelBase - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Error checking is performed only to ensure that the selector is allocated.
VDHGetSelBase - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHGetVPMExcept
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function gets the current value from the protected - mode exception table . * / include mvdm . inc EXTERN VDHGetVPMExcept : NEAR Vector DD ? ; Exception vector number pHandlerAddressPointer DD ? ; Pointer to put handler address pFlag DD ? ; Pointer to a flag variable PUSH Vector ; Push Vector PUSH pHandlerAddressPointer ; Push pHandlerAddressPointer PUSH pFlag ; Push pFlag CALL VDHGetVPMExcept ; Call the function
VDHGetVPMExcept - Format
/* This function gets the current value from the protected - mode exception table . * / include mvdm . inc EXTERN VDHGetVPMExcept : NEAR Vector DD ? ; Exception vector number pHandlerAddressPointer DD ? ; Pointer to put handler address pFlag DD ? ; Pointer to a flag variable PUSH Vector ; Push Vector PUSH pHandlerAddressPointer ; Push pHandlerAddressPointer PUSH pFlag ; Push pFlag CALL VDHGetVPMExcept ; Call the function
VDHGetVPMExcept Parameter - Vector
Vector(DD) Exception vector number (0-1FH).
VDHGetVPMExcept Parameter - pHandlerAddressPointer
pHandlerAddressPointer(DD) Pointer to put handler address.
VDHGetVPMExcept Parameter - pFlag
pFlag(DD) Pointer to a flag variable for returning the flag value. Possible values are:
VPMXCPT32 A 32-bit handler was registered.
VPMXCPT_REFLECT The exception is reflected back to a V86-mode handler.
VDHGetVPMExcept Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0.
VDHGetVPMExcept - Parameters
Vector(DD) Exception vector number (0-1FH).
pHandlerAddressPointer(DD) Pointer to put handler address.
pFlag(DD) Pointer to a flag variable for returning the flag value. Possible values are:
VPMXCPT32 A 32-bit handler was registered.
VPMXCPT_REFLECT The exception is reflected back to a V86-mode handler.
VDHGetVPMExcept - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: There must be a DPMI client running in the DOS session before calling this function.
VDHGetVPMExcept - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHGetVPMIntVector
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function gets the application Ring 3 protected - mode interrupt handler . This service is used only for DOS Protected - Mode Interface ( DPMI ) support . * / include mvdm . inc EXTERN VDHGetVPMIntVector : NEAR Vector DD ? ; Interrupt vector number HandlerAddressPointer DD ? ; Pointer for return of handler address PUSH Vector ; Push Vector PUSH HandlerAddressPointer ; Push HandlerAddressPointer CALL VDHGetVPMIntVector ; Call the function
VDHGetVPMIntVector - Format
/* This function gets the application Ring 3 protected - mode interrupt handler . This service is used only for DOS Protected - Mode Interface ( DPMI ) support . * / include mvdm . inc EXTERN VDHGetVPMIntVector : NEAR Vector DD ? ; Interrupt vector number HandlerAddressPointer DD ? ; Pointer for return of handler address PUSH Vector ; Push Vector PUSH HandlerAddressPointer ; Push HandlerAddressPointer CALL VDHGetVPMIntVector ; Call the function
VDHGetVPMIntVector Parameter - Vector
Vector(DD) Interrupt vector number.
VDHGetVPMIntVector Parameter - HandlerAddressPointer
HandlerAddressPointer(DD) Pointer for return of the handler address.
VDHGetVPMIntVector Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0.
VDHGetVPMIntVector - Parameters
Vector(DD) Interrupt vector number.
HandlerAddressPointer(DD) Pointer for return of the handler address.
VDHGetVPMIntVector - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Note:There must be a DPMI client in the DOS session before calling this function.
VDHGetVPMIntVector - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHHaltSystem
Select an item:
Format Parameters Return Codes Purpose Glossary
/*
This function causes a system halt .
* /
include mvdm . inc
EXTERN VDHHaltSystem : NEAR
DD ?
PUSH ; Push
CALL VDHHaltSystem ; Call the function
VDHHaltSystem - Format
/*
This function causes a system halt .
* /
include mvdm . inc
EXTERN VDHHaltSystem : NEAR
DD ?
PUSH ; Push
CALL VDHHaltSystem ; Call the function
VDHHaltSystem Parameter -
(DD) None.
VDHHaltSystem Return Value -
None.
VDHHaltSystem - Parameters
(DD) None.
VDHHaltSystem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Calling VDHHaltSystemis an extremely drastic action. Calling VDHPopupand VDHKillVDMis the preferred method for handling a problem. VDHHaltSystemis used only if the virtual device driver is certain that the entire multiple DOS session environment is inoperable. In general, this function is used only by a base virtual device driver (for example, the virtual video device driver or virtual keyboard device driver), whose absence would render the multiple DOS session environment unusable. VDHPopupis called prior to VDHHaltSystemto tell the user what has happened.
VDHHaltSystem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHHandleFromPID
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function returns the DOS session handle for a given Process ID . * / include mvdm . inc EXTERN VDHHandleFromPID : NEAR ProcessID DW ? ; A DOS session process ID PUSH ProcessID ; Push ProcessID CALL VDHHandleFromPID ; Call the function
VDHHandleFromPID - Format
/* This function returns the DOS session handle for a given Process ID . * / include mvdm . inc EXTERN VDHHandleFromPID : NEAR ProcessID DW ? ; A DOS session process ID PUSH ProcessID ; Push ProcessID CALL VDHHandleFromPID ; Call the function
VDHHandleFromPID Parameter - ProcessID
ProcessID(DW) A DOS session Process ID.
VDHHandleFromPID Return Value - rc
Success If the function is successful, it returns the DOS session handle for the Process ID.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHHandleFromPID - Parameters
ProcessID(DW) A DOS session Process ID.
VDHHandleFromPID - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHHandleFromPID - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHHandleFromSGID
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function determines the DOS session handle given the Screen Group ID . * / include mvdm . inc EXTERN VDHHandleFromSGID : NEAR ScreenGroupID DW ? ; Screen Group ID PUSH ScreenGroupID ; Push ScreenGroupID CALL VDHHandleFromSGID ; Call the function
VDHHandleFromSGID - Format
/* This function determines the DOS session handle given the Screen Group ID . * / include mvdm . inc EXTERN VDHHandleFromSGID : NEAR ScreenGroupID DW ? ; Screen Group ID PUSH ScreenGroupID ; Push ScreenGroupID CALL VDHHandleFromSGID ; Call the function
VDHHandleFromSGID Parameter - ScreenGroupID
ScreenGroupID(DW) Screen Group ID.
VDHHandleFromSGID Return Value - rc
Success If the function is successful, it returns a handle to the DOS session that was given the Screen Group ID.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHHandleFromSGID - Parameters
ScreenGroupID(DW) Screen Group ID.
VDHHandleFromSGID - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHHandleFromSGID - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHInstallFaultHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function sets a page fault handler for a region of linear address space . The page fault handler receives control when a DOS session touches a page in a reserved region that was invalidated by VDHMapPages . The handler does not get control if the page was indicated " not present " by the Page Manager . * / include mvdm . inc EXTERN VDHInstallFaultHook : NEAR VDMHandle DD ? ; DOS session handle ; 0 = current DOS session StartingAddress DD ? ; Starting linear address Pages DD ? ; Number of pages PageFaultHandlerFcnPtr DD ? ; Page fault handler function OptionFlag DD ? ; Options bit flag PUSH VDMHandle ; Push VDMHandle PUSH StartingAddress ; Push StartingAddress PUSH Pages ; Push Pages PUSH PageFaultHandlerFcnPtr ; Push PageFaultHandlerFcnPtr PUSH OptionFlag ; Push OptionFlag CALL VDHInstallFaultHook ; Call the function
VDHInstallFaultHook - Format
/* This function sets a page fault handler for a region of linear address space . The page fault handler receives control when a DOS session touches a page in a reserved region that was invalidated by VDHMapPages . The handler does not get control if the page was indicated " not present " by the Page Manager . * / include mvdm . inc EXTERN VDHInstallFaultHook : NEAR VDMHandle DD ? ; DOS session handle ; 0 = current DOS session StartingAddress DD ? ; Starting linear address Pages DD ? ; Number of pages PageFaultHandlerFcnPtr DD ? ; Page fault handler function OptionFlag DD ? ; Options bit flag PUSH VDMHandle ; Push VDMHandle PUSH StartingAddress ; Push StartingAddress PUSH Pages ; Push Pages PUSH PageFaultHandlerFcnPtr ; Push PageFaultHandlerFcnPtr PUSH OptionFlag ; Push OptionFlag CALL VDHInstallFaultHook ; Call the function
VDHInstallFaultHook Parameter - VDMHandle
VDMHandle(DD) DOS session handle. If the parameter contains a 0 (zero), use the currently active DOS session.
VDHInstallFaultHook Parameter - StartingAddress
StartingAddress(DD) Starting linear address.
VDHInstallFaultHook Parameter - Pages
Pages(DD) Number of pages.
VDHInstallFaultHook Parameter - PageFaultHandlerFcnPtr
PageFaultHandlerFcnPtr(DD) Page fault handler function.
The PageFaultHandlerFcnPtr function pointer contains the address of a function with the following interface:
PageFaultHandler PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - pVDM - Address of the page in which fault occurred ; EXIT None ; ; CONTEXT DOS session-task
VDHInstallFaultHook Parameter - OptionFlag
OptionFlag(DD) Options bit flag.
Possible value:
VDHIFH_ADDR If set, pVDM is a byte-granular address. Otherwise, pVDM is a page-granular address.
VDHInstallFaultHook Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetError should be called to determine the nature of the problem. If any of the input parameters are invalid, a system halt occurs.
VDHInstallFaultHook - Parameters
VDMHandle(DD) DOS session handle. If the parameter contains a 0 (zero), use the currently active DOS session.
StartingAddress(DD) Starting linear address.
Pages(DD) Number of pages.
PageFaultHandlerFcnPtr(DD) Page fault handler function.
The PageFaultHandlerFcnPtr function pointer contains the address of a function with the following interface:
PageFaultHandler PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - pVDM - Address of the page in which fault occurred ; EXIT None ; ; CONTEXT DOS session-task
OptionFlag(DD) Options bit flag.
Possible value:
VDHIFH_ADDR If set, pVDM is a byte-granular address. Otherwise, pVDM is a page-granular address.
VDHInstallFaultHook - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: Any fault hooks for the terminating DOS session must be released by using VDHRemoveFaultHook.
Notes: In order for the fault handler to terminate the DOS session, it must call VDHKillVDM and return. Page fault hooks are stored on a per-DOS session basis.
VDHInstallFaultHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHInstallIntHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function sets a handler for a V86 interrupt . The virtual device driver ' s interrupt handler gets control after any subsequently hooked DOS interrupt handlers . * / include mvdm . inc EXTERN VDHInstallIntHook : NEAR Reserved DD ? ; Reserved ; must be set to 0 Vector DD ? ; Number of the interrupt vector to hook HookFcn DD ? ; Address of the hook routine OptionFlag DD ? ; Interface options flag PUSH Reserved ; Push Reserved PUSH Vector ; Push Vector PUSH HookFcn ; Push HookFcn PUSH OptionFlag ; Push OptionFlag CALL VDHInstallIntHook ; Call the function
VDHInstallIntHook - Format
/* This function sets a handler for a V86 interrupt . The virtual device driver ' s interrupt handler gets control after any subsequently hooked DOS interrupt handlers . * / include mvdm . inc EXTERN VDHInstallIntHook : NEAR Reserved DD ? ; Reserved ; must be set to 0 Vector DD ? ; Number of the interrupt vector to hook HookFcn DD ? ; Address of the hook routine OptionFlag DD ? ; Interface options flag PUSH Reserved ; Push Reserved PUSH Vector ; Push Vector PUSH HookFcn ; Push HookFcn PUSH OptionFlag ; Push OptionFlag CALL VDHInstallIntHook ; Call the function
VDHInstallIntHook Parameter - Reserved
Reserved(DD) Reserved. Must be set to 0.
VDHInstallIntHook Parameter - Vector
Vector(DD) Number of the interrupt vector to hook (0-255).
VDHInstallIntHook Parameter - HookFcn
HookFcn(DD) Address of the hook routine.
VDHInstallIntHook Parameter - OptionFlag
OptionFlag(DD) Interface options flag.
Possible values:
VDH_ASM_HOOK Use assembler language hook interface (for the assembler language interface refer to the function VDHInstallIOHook). Otherwise, use the calling convention in the function prototype VDHENTRY found in the MVDM .INC include file, which is included with the Toolkit.
VDH_PRE_HOOK If set, install handler as a pre-reflection hook; that is, call the hook routine before reflecting the interrupt to V86 mode.
C Language Interface for the interrupt hook routine:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY EBX - pcrf - Client register frame pointer ; EXIT If carry flag set, chain to next virtual device driver ; If carry flag clear, don't chain to the next virtual ; device driver ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS Session-task
VDHInstallIntHook Return Value - rc
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If HookFcnis invalid or if Vectoris out of range, a system halt occurs.
VDHInstallIntHook - Parameters
Reserved(DD) Reserved. Must be set to 0.
Vector(DD) Number of the interrupt vector to hook (0-255).
HookFcn(DD) Address of the hook routine.
OptionFlag(DD) Interface options flag.
Possible values:
VDH_ASM_HOOK Use assembler language hook interface (for the assembler language interface refer to the function VDHInstallIOHook). Otherwise, use the calling convention in the function prototype VDHENTRY found in the MVDM .INC include file, which is included with the Toolkit.
VDH_PRE_HOOK If set, install handler as a pre-reflection hook; that is, call the hook routine before reflecting the interrupt to V86 mode.
C Language Interface for the interrupt hook routine:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY EBX - pcrf - Client register frame pointer ; EXIT If carry flag set, chain to next virtual device driver ; If carry flag clear, don't chain to the next virtual ; device driver ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS Session-task
VDHInstallIntHook - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function. Interrupt hooks are automatically removed during DOS session termination.
Notes: The effect of this service is per-DOS session; the software interrupt handler must be installed as each DOS session is created. The return value from the interrupt hook controls whether the next virtual device driver is chained to or not. An explicit VDHPopIntis needed to remove the software interrupt (so that the ROM code is not executed).
VDHInstallIntHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHInstallIOHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is used to install I / O port hooks . * / include mvdm . inc EXTERN VDHInstallIOHook : NEAR Reserved DD ? ; Reserved ; must be set to 0 StartingPort DD ? ; Starting port number NumPorts DD ? ; The number of ports from the starting point IOPortHookEntry DD ? ; Pointer to I / O port hook entry Flags DD ? ; Indicates interface and trapping options PUSH Reserved ; Push Reserved PUSH StartingPort ; Push StartingPort PUSH NumPorts ; Push NumPorts PUSH IOPortHookEntry ; Push IOPortHookEntry PUSH Flags ; Push Flags CALL VDHInstallIOHook ; Call the function
VDHInstallIOHook - Format
/* This function is used to install I / O port hooks . * / include mvdm . inc EXTERN VDHInstallIOHook : NEAR Reserved DD ? ; Reserved ; must be set to 0 StartingPort DD ? ; Starting port number NumPorts DD ? ; The number of ports from the starting point IOPortHookEntry DD ? ; Pointer to I / O port hook entry Flags DD ? ; Indicates interface and trapping options PUSH Reserved ; Push Reserved PUSH StartingPort ; Push StartingPort PUSH NumPorts ; Push NumPorts PUSH IOPortHookEntry ; Push IOPortHookEntry PUSH Flags ; Push Flags CALL VDHInstallIOHook ; Call the function
VDHInstallIOHook Parameter - Reserved
Reserved(DD) Reserved. Must be set to 0 (zero).
VDHInstallIOHook Parameter - StartingPort
StartingPort(DD) Number of the starting port.
VDHInstallIOHook Parameter - NumPorts
NumPorts(DD) The number of ports from the starting port.
VDHInstallIOHook Parameter - IOPortHookEntry
IOPortHookEntry(DD) Pointer to I/O port hook entry.
VDHInstallIOHook Parameter - Flags
Flags(DD) Indicates interface and trapping options.
Possible values:
VDHIIH_ASM_HOOK Use assembler language hook interface (register-based). Otherwise, use a C hook interface (stack-based).
VDHIIH_ALWAYS_TRAP Always trap this range of addresses. The virtual device driver cannot call VDHSetIOHookState on any ports in the range.
VDHIIH_NO_SIMULATE Does not change WORD or other I/O handlers to simulation routines; allows WORD handlers for 1-port ranges.
VDHIIH_IGNORE Sets a system handler that does the following:
On WRITES: The OUT succeeds, but no actual I/O is performed.
On READS: The IN succeeds, and always returns -1 (all bits set to 1).
This is also the default behavior of unhooked ports. This behavior is compatible with the behavior of a machine when there is no hardware on a particular I/O address.
VDHInstallIOHook Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If IOPortHookEntryis invalid, or if StartingPortor NumPortsare out of range, a system halt occurs.
VDHInstallIOHook - Parameters
Reserved(DD) Reserved. Must be set to 0 (zero).
StartingPort(DD) Number of the starting port.
NumPorts(DD) The number of ports from the starting port.
IOPortHookEntry(DD) Pointer to I/O port hook entry.
Flags(DD) Indicates interface and trapping options.
Possible values:
VDHIIH_ASM_HOOK Use assembler language hook interface (register-based). Otherwise, use a C hook interface (stack-based).
VDHIIH_ALWAYS_TRAP Always trap this range of addresses. The virtual device driver cannot call VDHSetIOHookState on any ports in the range.
VDHIIH_NO_SIMULATE Does not change WORD or other I/O handlers to simulation routines; allows WORD handlers for 1-port ranges.
VDHIIH_IGNORE Sets a system handler that does the following:
On WRITES: The OUT succeeds, but no actual I/O is performed.
On READS: The IN succeeds, and always returns -1 (all bits set to 1).
This is also the default behavior of unhooked ports. This behavior is compatible with the behavior of a machine when there is no hardware on a particular I/O address.
VDHInstallIOHook - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function. I/O hooks are automatically removed during DOS session termination.
Notes: This function installs I/O port trap handlers for a contiguous range of I/O addresses. Trapping is initially enabled for the specified ports. The I/O hook entry contains the handlers for each kind of I/O operation. If an entry in the table is NULL, that I/O type is simulated by using a lower I/O type (for example, WORD-I/O is simulated by performing two-byte I/O operations). I/O port hooks are kept on a per-DOS session basis; a virtual device driver generally installs I/O hooks at DOS session creation time.
VDHSetIOHookState can be used to enable or disable I/O trapping on a per- port, per-DOS session basis except when the VDHIIH_ALWAYS_TRAP option is specified. In this case, VDHSetIOHookState cannot be called on any port in the range for the current DOS session.
I/O hooks can take their parameters either from registers or the stack. High-performance hooks take register parameters (the I/O hook router is optimized for this case). Hooks with lower performance requirements take stack parameters, and therefore can be written in the C language.
WordInput, WordOutput and Other hooks can be NULL. In this case, the DOS Session Manager simulates these routines by using the ByteInput and ByteOutput routines. If the ByteInput or ByteOutput handlers are NULL, the DOS Session Manager uses default internal routines that do input and output to the hardware ports. This is most useful when a virtual device driver shadows the hardware state (by trapping OUT instructions) but does not care what is returned by IN instructions.
The client register frame (CRF) is updated as the instructions are simulated. For example, when the string I/O instructions are simulated, the client's EDI/ESI and ECX is incremented or decremented.
In a particular DOS session, a particular I/O port address can be hooked only by a single virtual device driver. If this function fails, no I/O hooks are installed.
The routing of I/O instructions to the supplied port hooks covers the specified range exactly. If an I/O instruction overlaps port address ranges hooked on separate VDHInstallIOHook calls, the instruction is simulated with smaller I/O operations to ensure that the hooks in each range are called correctly. For example, a virtual device driver that hooks 100H-103H , and installs a byte, WORD, and DWORD (other) handler would work as follows:
VDHInstallIOHook (reserved,0x100,4,&iohA,NULL);
The I/O instructions to each address with the length indicated cause the following hooks to be called:
/--------------------------------------------------------------\ |Address |Length |Hooks Called | |---------------+---------------+------------------------------| | 100 | 4 |iohA.Other(100,DWORD) | |---------------+---------------+------------------------------| | 101 | 4 |iohA.Word(101) iohA.Byte(103) | |---------------+---------------+------------------------------| | 102 | 4 |iohA.Word(102) | |---------------+---------------+------------------------------| | 103 | 4 |iohA.Byte(103) | \--------------------------------------------------------------/
VDHRemoveIOHook must be called with identical StartingPort and NumPorts in order to remove these I/O hooks. Port hooks cannot be removed for a subset of the range of ports hooked on the call to VDHInstallIOHook. If the IOPortHookEntry is in instance data, the address passed to VDHInstallIOHook must be the same address passed to VDHRemoveIOHook or VDHSetIOHookState.
Virtual device drivers hook ports in all cases, even if the desired behavior is to act as though direct port access were allowed. This keeps the I/O Permissions Map small. Only a port that requires high performance ( for example, a graphics card) is allowed to go straight through. The existence of such ports increases the size of the I/O Permissions Map in the Task State segment even if SetIOHookState is never called for them.
Interfaces for IOPortHookEntry are as follows:
ioh STRUC
ioh_pbihByteInput DD ?
ioh_pbohByteOutput DD ?
ioh_pwihWordInput DD ?
ioh_pwohWordOutput DD ?
ioh_pothOther DD ?
ioh ENDS
ByteInput PROC NEAR ; PARAMETERS ; ENTRY - port - Port number ; - pcrf - Client register frame pointer ; EXIT Data read returned in AL ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS session-task
ByteOutput PROC NEAR ; PARAMETERS ; ENTRY - bOutputData - Data to write ; - port - Port number ; - pcrf - Client register frame pointer ; EXIT None ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS session-task
WordInput PROC NEAR ; PARAMETERS ; ENTRY - port - Port number ; - pcrf - Client register frame pointer ; EXIT Data read returned in AX ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS session-task
WordOutput PROC NEAR ; PARAMETERS ; ENTRY - usOutputData - Data to write ; - port - Port number ; - pcrf - Client register frame pointer ; EXIT None ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS session-task
OtherHook PROC NEAR ; PARAMETERS ; ENTRY EAX - ulOutputData - Data for DWORD writes ; [ESP + 16] - pulInputData - Pointer to put input data ; (See NOTE, below) ; EDX - port - Port number ; ECX - flType - I/O type ; IO_TYPE_SHIFT - Shift for type ; IO_TYPE_MASK - Mask for type ; IO_TYPE_INPUT - If set input else output ; IO_TYPE_BYTE - If set byte else WORD/DWORD ; IO_TYPE_DWORD ; IO_TYPE_STRING ; IO_TYPE_REVERSE ; IO_TYPE_ADDR32 ; IO_TYPE_REP ; IO_SEG_SHIFT - Shift for SEG field ; IO_SEG_MASK - Mask for SEG field ; IO_SEG_CS ; IO_SEG_SS ; IO_SEG_ES ; IO_SEG_FS ; IO_SEG_GS ; EBX - pcrf - Client register frame pointer ; EXIT If assembly language hook, ; EAX - Data from DWORD reads ; If carry flag set, simulate the I/O operation ; If carry flag clear, I/O is done ; If C hook ; *pulInputData - Data from DWORD reads ; If returns 0 in EAX, simulate the I/O operation ; If returns a non-zero value in EAX, I/O is done ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS session-task ; NOTES The ASM OtherHook hook does not need the pulInputData parameter ; because it returns DWORD input values in EAX, with the ; carry flag used to indicate done/simulate. ; The C hook has to use EAX to return status, and so needs the ; additional parameter.
VDHInstallIOHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHInstallUserHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is used to set a handler for a specific DOS session event . * / include mvdm . inc EXTERN VDHInstallUserHook : NEAR Event DD ? ; A DOS session event for which a handler is installed UserHook DD ? ; User ' s handler for this event PUSH Event ; Push Event PUSH UserHook ; Push UserHook CALL VDHInstallUserHook ; Call the function
VDHInstallUserHook - Format
/* This function is used to set a handler for a specific DOS session event . * / include mvdm . inc EXTERN VDHInstallUserHook : NEAR Event DD ? ; A DOS session event for which a handler is installed UserHook DD ? ; User ' s handler for this event PUSH Event ; Push Event PUSH UserHook ; Push UserHook CALL VDHInstallUserHook ; Call the function
VDHInstallUserHook Parameter - Event
Event(DD) A DOS session event (such as DOS session termination).
Possible values are:
VDD_EXIT DOS session support is shutting down
VDM_CREATE DOS session creation
VDM_TERMINATE DOS session termination
VDM_FOREGROUND DOS session to the foreground
VDM_BACKGROUND DOS session to the background
VDM_CREATE_DONE DOS session creation completed successfully
VDM_VDD_CREATE_DONE DOS session virtual device driver creation completed
VDM_PDB_DESTROY DOS Program Data Block (PDB) destroyed in DOS session
VDM_PDB_CHANGE PDB changed in DOS session
VDM_CODEPAGE_CHANGE Code page change event
VDM_TITLE_CHANGE DOS session title change event
VDM_MEMORY_MAPPED_IN Pages mapped into a DOS session (0 to 1MB+64KB)
VDM_MEMORY_UN_MAPPED Pages unmapped from a DOS session (0 to 1MB+64KB).
VDM_BEGIN_VPM_TASK Protected-mode task has started
VDM_END_VPM_TASK Protected-mode task has ended
The interfaces for the UserHookhandlers (depending on the event that is handled) are:
pfnCreate PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - hvdm - Handle to DOS session ; EXIT SUCCESS Return a non-zero value ; FAILURE Return 0 ; DOS session creation fails; the DOS Session Manager calls ; all the VDM_TERMINATE hooks for all virtual ; device drivers that returned SUCCESS on this ; DOS session creation. ; ; ; CONTEXT DOS session-task
pfnTerminate PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - hvdm - DOS session being terminated ; EXIT None ; ; CONTEXT DOS session-task
pfnForeground PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - hvdm - DOS session coming to the foreground ; EXIT None ; ; CONTEXT Task
pfnBackground PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - hvdm - DOS session going to the background ; EXIT None ; ; CONTEXT Task
pfnExit PROC NEAR ; PARAMETERS ; ENTRY None ; EXIT None ; ; CONTEXT Initialization and Task
pfnCreateDone PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - hvdm - Handle to DOS session ; EXIT None ; ; CONTEXT DOS session creation
pfnVDDCreateDone PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - hvdm - Handle to DOS session ; EXIT None ; ; CONTEXT DOS session Creation
pfnPDBDestroyed PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - hvdm - Handle to DOS session ; [ESP + 4] - segPDB - V86 segment of terminating PDB ; EXIT None ; ; CONTEXT DOS session-task
pfnPDBSwitched PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - hvdm - Handle to DOS session ; [ESP + 4] - segPDB - V86 segment of new PDB ; EXIT None ; ; CONTEXT DOS session-task
pfnCodePageChanged PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - ulCodePage - New code page ; EXIT SUCCESS Return a non-zero value in EAX ; FAILURE Return 0 in EAX ; An error is returned on the set code-page operation, but ; the rest of the device-code-page handlers are called. ; ; CONTEXT DOS session-task
pfnVDMTitleChange PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - pszTitle - new DOS session Title ; EXIT SUCCESS Return a non-zero value in EAX ; FAILURE Return 0 in EAX ; ; CONTEXT DOS session-task ; NOTES 1. This event is called for both full screen and windowed DOS session. ; 2. If pszTitle is NULL, the virtual device driver should treat it ; as the DOS session's default and original title. ; 3. Ideally there should be only one virtual device driver for this ; hook, but this is not a restriction. One of the virtual device ; drivers registered is responsible for putting the title. Only ; this virtual device driver returns a non-zero value, all others ; return 0.
pfnMemoryMappedIn PROC NEAR ; PARAMETERS ; ENTRY [ESP + 16] - hvdm - Handle to DOS session ; [ESP + 12] - page - Page address ; [ESP + 8] - cpages - Number of pages mapped in from ; the starting page address ; [ESP + 4] - fl - Type of mapping, (see VDHMapPages) ; EXIT SUCCESS Return a non-zero value in EAX ; FAILURE Return 0 in EAX ; ; CONTEXT DOS session-task
pfnMemoryUnMapped PROC NEAR ; PARAMETERS ; ENTRY [ESP + 16] - hvdm - Handle to DOS session ; [ESP + 12] - page - Page address ; [ESP + 8] - cpages - Number of pages unmapped from ; the starting page address ; [ESP + 4] - fl - Type of mapping, (see VDHMapPages) ; EXIT SUCCESS Return a non-zero value in EAX ; FAILURE Return 0 in EAX ; ; CONTEXT DOS session-task
VDHInstallUserHook Parameter - UserHook
UserHook(DD) A user-defined handler for the event.
VDHInstallUserHook Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, an invalid input parameter or a kernel heap overflow (that is, if the system runs out of memory) causes a system halt.
VDHInstallUserHook - Parameters
Event(DD) A DOS session event (such as DOS session termination).
Possible values are:
VDD_EXIT DOS session support is shutting down
VDM_CREATE DOS session creation
VDM_TERMINATE DOS session termination
VDM_FOREGROUND DOS session to the foreground
VDM_BACKGROUND DOS session to the background
VDM_CREATE_DONE DOS session creation completed successfully
VDM_VDD_CREATE_DONE DOS session virtual device driver creation completed
VDM_PDB_DESTROY DOS Program Data Block (PDB) destroyed in DOS session
VDM_PDB_CHANGE PDB changed in DOS session
VDM_CODEPAGE_CHANGE Code page change event
VDM_TITLE_CHANGE DOS session title change event
VDM_MEMORY_MAPPED_IN Pages mapped into a DOS session (0 to 1MB+64KB)
VDM_MEMORY_UN_MAPPED Pages unmapped from a DOS session (0 to 1MB+64KB).
VDM_BEGIN_VPM_TASK Protected-mode task has started
VDM_END_VPM_TASK Protected-mode task has ended
The interfaces for the UserHookhandlers (depending on the event that is handled) are:
pfnCreate PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - hvdm - Handle to DOS session ; EXIT SUCCESS Return a non-zero value ; FAILURE Return 0 ; DOS session creation fails; the DOS Session Manager calls ; all the VDM_TERMINATE hooks for all virtual ; device drivers that returned SUCCESS on this ; DOS session creation. ; ; ; CONTEXT DOS session-task
pfnTerminate PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - hvdm - DOS session being terminated ; EXIT None ; ; CONTEXT DOS session-task
pfnForeground PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - hvdm - DOS session coming to the foreground ; EXIT None ; ; CONTEXT Task
pfnBackground PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - hvdm - DOS session going to the background ; EXIT None ; ; CONTEXT Task
pfnExit PROC NEAR ; PARAMETERS ; ENTRY None ; EXIT None ; ; CONTEXT Initialization and Task
pfnCreateDone PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - hvdm - Handle to DOS session ; EXIT None ; ; CONTEXT DOS session creation
pfnVDDCreateDone PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - hvdm - Handle to DOS session ; EXIT None ; ; CONTEXT DOS session Creation
pfnPDBDestroyed PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - hvdm - Handle to DOS session ; [ESP + 4] - segPDB - V86 segment of terminating PDB ; EXIT None ; ; CONTEXT DOS session-task
pfnPDBSwitched PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - hvdm - Handle to DOS session ; [ESP + 4] - segPDB - V86 segment of new PDB ; EXIT None ; ; CONTEXT DOS session-task
pfnCodePageChanged PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - ulCodePage - New code page ; EXIT SUCCESS Return a non-zero value in EAX ; FAILURE Return 0 in EAX ; An error is returned on the set code-page operation, but ; the rest of the device-code-page handlers are called. ; ; CONTEXT DOS session-task
pfnVDMTitleChange PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - pszTitle - new DOS session Title ; EXIT SUCCESS Return a non-zero value in EAX ; FAILURE Return 0 in EAX ; ; CONTEXT DOS session-task ; NOTES 1. This event is called for both full screen and windowed DOS session. ; 2. If pszTitle is NULL, the virtual device driver should treat it ; as the DOS session's default and original title. ; 3. Ideally there should be only one virtual device driver for this ; hook, but this is not a restriction. One of the virtual device ; drivers registered is responsible for putting the title. Only ; this virtual device driver returns a non-zero value, all others ; return 0.
pfnMemoryMappedIn PROC NEAR ; PARAMETERS ; ENTRY [ESP + 16] - hvdm - Handle to DOS session ; [ESP + 12] - page - Page address ; [ESP + 8] - cpages - Number of pages mapped in from ; the starting page address ; [ESP + 4] - fl - Type of mapping, (see VDHMapPages) ; EXIT SUCCESS Return a non-zero value in EAX ; FAILURE Return 0 in EAX ; ; CONTEXT DOS session-task
pfnMemoryUnMapped PROC NEAR ; PARAMETERS ; ENTRY [ESP + 16] - hvdm - Handle to DOS session ; [ESP + 12] - page - Page address ; [ESP + 8] - cpages - Number of pages unmapped from ; the starting page address ; [ESP + 4] - fl - Type of mapping, (see VDHMapPages) ; EXIT SUCCESS Return a non-zero value in EAX ; FAILURE Return 0 in EAX ; ; CONTEXT DOS session-task
UserHook(DD) A user-defined handler for the event.
VDHInstallUserHook - Purpose
Context Issues: This function can be called only in the initialization context.
DOS Sessions Terminations: The VDM_TERMINATE hook is called at DOS session termination. In the case of a partially created DOS session, the VDM_ TERMINATE handler is called only if all the registered VDM_CREATE handlers are called successfully. Partially created DOS sessions might occur when, for example, the Create_Handlerfor Virtual Device Driver A returned successfully, but the Create_Handlerfor Virtual Device Driver B failed. In this case, the Terminate_Handlerfor Virtual Device Driver A will not be called. This should be taken into consideration when deciding what to do in a Create_Handlerand a Create_Done_Handler.
VDHInstallUserHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHIsVDMFrozen
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function returns the freeze state of a DOS session . * / include mvdm . inc EXTERN VDHIsVDMFrozen : NEAR VDMHandle DD ? ; Handle to the DOS session PUSH VDMHandle ; Push VDMHandle CALL VDHIsVDMFrozen ; Call the function
VDHIsVDMFrozen - Format
/* This function returns the freeze state of a DOS session . * / include mvdm . inc EXTERN VDHIsVDMFrozen : NEAR VDMHandle DD ? ; Handle to the DOS session PUSH VDMHandle ; Push VDMHandle CALL VDHIsVDMFrozen ; Call the function
VDHIsVDMFrozen Parameter - VDMHandle
VDMHandle(DD) Handle to the DOS session in question.
VDHIsVDMFrozen Return Value - rc
Success If the DOS session is not frozen, the function returns 0 (zero). Otherwise, the function returns a nonzero value indicating the DOS session' s freeze count.
Failure If VDMHandleis an invalid DOS session handle, a system halt occurs .
VDHIsVDMFrozen - Parameters
VDMHandle(DD) Handle to the DOS session in question.
VDHIsVDMFrozen - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: See VDHFreezeVDMfor a full discussion of freeze counting.
VDHIsVDMFrozen - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHKillVDM
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function terminates the DOS session at the earliest opportunity . V86 code is no longer executed in the context of the terminated DOS session . * / include mvdm . inc EXTERN VDHKillVDM : NEAR VDMHandle DD ? ; Handle to the DOS session to terminate PUSH VDMHandle ; Push VDMHandle CALL VDHKillVDM ; Call the function
VDHKillVDM - Format
/* This function terminates the DOS session at the earliest opportunity . V86 code is no longer executed in the context of the terminated DOS session . * / include mvdm . inc EXTERN VDHKillVDM : NEAR VDMHandle DD ? ; Handle to the DOS session to terminate PUSH VDMHandle ; Push VDMHandle CALL VDHKillVDM ; Call the function
VDHKillVDM Parameter - VDMHandle
VDMHandle(DD) Handle to the DOS session to terminate. A value of 0 (zero) indicates the current DOS session.
VDHKillVDM Return Value - rc
Success If the function is successful, it returns nothing.
Failure If VDMHandleis not a valid DOS session handle, a system halt occurs.
VDHKillVDM - Parameters
VDMHandle(DD) Handle to the DOS session to terminate. A value of 0 (zero) indicates the current DOS session.
VDHKillVDM - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: When a DOS session is terminating, all virtual device drivers that registered a VDM_TERMINATE hook by using VDHInstallUserHookare called.
Notes: This function sets a flag and returns. If the calling virtual device driver is in the context of the DOS session to be terminated, it must return to its caller in order for the termination to occur.
VDHKillVDM - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHLockMem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function verifies that a specified region is accessible in the requested manner , and locks the memory in the requested manner . * / include mvdm . inc EXTERN VDHLockMem : NEAR StartingLinAddr DD ? ; Starting address of region in user process NumBytes DD ? ; The size of the region to lock , in bytes . OptionFlag DD ? ; Access option flags PagelistArrayPtr DD ? ; Pointer to array of VDHPageList _ s structures ArrayCountPtr DD ? ; Points to count of VDHPageList _ selements PUSH StartingLinAddr ; Push StartingLinAddr PUSH NumBytes ; Push NumBytes PUSH OptionFlag ; Push OptionFlag PUSH PagelistArrayPtr ; Push PagelistArrayPtr PUSH ArrayCountPtr ; Push ArrayCountPtr CALL VDHLockMem ; Call the function
VDHLockMem - Format
/* This function verifies that a specified region is accessible in the requested manner , and locks the memory in the requested manner . * / include mvdm . inc EXTERN VDHLockMem : NEAR StartingLinAddr DD ? ; Starting address of region in user process NumBytes DD ? ; The size of the region to lock , in bytes . OptionFlag DD ? ; Access option flags PagelistArrayPtr DD ? ; Pointer to array of VDHPageList _ s structures ArrayCountPtr DD ? ; Points to count of VDHPageList _ selements PUSH StartingLinAddr ; Push StartingLinAddr PUSH NumBytes ; Push NumBytes PUSH OptionFlag ; Push OptionFlag PUSH PagelistArrayPtr ; Push PagelistArrayPtr PUSH ArrayCountPtr ; Push ArrayCountPtr CALL VDHLockMem ; Call the function
VDHLockMem Parameter - StartingLinAddr
StartingLinAddr(DD) Starting linear address of the region in the user process that is to be locked.
VDHLockMem Parameter - NumBytes
NumBytes(DD) Size in bytes of the region to lock.
VDHLockMem Parameter - OptionFlag
OptionFlag(DD) Used to set access options for the locked region. The VDHLM _READ and VDHLM_WRITE flags are for verification purposes and are not mixed with the VDHLM_RESIDENT flag. Either the VDHLM_READ, VDHLM_WRITE, or VDHLM_ RESIDENT flag must be used. Note that VDHLM_RESIDENT cannot be combined with other flags.
Possible values are:
VDHLM_RESIDENT Lock physical pages.
VDHLM_READ Verify read access. VDHLM_READ is a verify lock, and is not mixed with other flags. Nonverify locks always make the region resident.
VDHLM_WRITE Verify write access. VDHLM_WRITE is a verify lock, and is not mixed with other flags. Nonverify locks always make the region resident.
VDHLM_CONTIGUOUS Force physical pages contiguous; can be used only for 64KB or less.
VDHLM_NOBLOCK Lock must not give up the CPU.
VDHLM_16M Must reside below the 16MB physical memory address.
VDHLockMem Parameter - PagelistArrayPtr
PagelistArrayPtr(DD) Pointer to array of VDHPageList_s structures.
VDHLockMemfills this array. Each VDHPageList_sstructure describes a single physically contiguous sub-area of the physical memory that was locked. If PagelistArrayPtris set to VDHLM_NO_ADDR, no array is returned. The area that PagelistArrayPtrpoints to must contain enough VDHPageList_sstructures to handle a worst case of one structure per page plus one more structure, that is, the region does not begin on a page boundary.
VDHLockMem Parameter - ArrayCountPtr
ArrayCountPtr(DD) Pointer to a variable where a count of the number of elements returned in the PagelistArrayPtrarray is placed by VDHLockMem. If PagelistArrayPtris set to VDHLM_NO_ADDR, ArrayCountPtris ignored.
VDHLockMem Return Value - rc
Success If the function is successful, it returns a lock handle. This is a global handle that can be used in any task context.
Failure If the function fails, it returns 0. If the function fails, call VDHGetErrorto determine the nature of the problem. If NumBytesequals 0, a system halt occurs.
VDHLockMem - Parameters
StartingLinAddr(DD) Starting linear address of the region in the user process that is to be locked.
NumBytes(DD) Size in bytes of the region to lock.
OptionFlag(DD) Used to set access options for the locked region. The VDHLM _READ and VDHLM_WRITE flags are for verification purposes and are not mixed with the VDHLM_RESIDENT flag. Either the VDHLM_READ, VDHLM_WRITE, or VDHLM_ RESIDENT flag must be used. Note that VDHLM_RESIDENT cannot be combined with other flags.
Possible values are:
VDHLM_RESIDENT Lock physical pages.
VDHLM_READ Verify read access. VDHLM_READ is a verify lock, and is not mixed with other flags. Nonverify locks always make the region resident.
VDHLM_WRITE Verify write access. VDHLM_WRITE is a verify lock, and is not mixed with other flags. Nonverify locks always make the region resident.
VDHLM_CONTIGUOUS Force physical pages contiguous; can be used only for 64KB or less.
VDHLM_NOBLOCK Lock must not give up the CPU.
VDHLM_16M Must reside below the 16MB physical memory address.
PagelistArrayPtr(DD) Pointer to array of VDHPageList_s structures.
VDHLockMemfills this array. Each VDHPageList_sstructure describes a single physically contiguous sub-area of the physical memory that was locked. If PagelistArrayPtris set to VDHLM_NO_ADDR, no array is returned. The area that PagelistArrayPtrpoints to must contain enough VDHPageList_sstructures to handle a worst case of one structure per page plus one more structure, that is, the region does not begin on a page boundary.
ArrayCountPtr(DD) Pointer to a variable where a count of the number of elements returned in the PagelistArrayPtrarray is placed by VDHLockMem. If PagelistArrayPtris set to VDHLM_NO_ADDR, ArrayCountPtris ignored.
VDHLockMem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function. There cannot be any memory locked on behalf of a particular DOS session.
Notes: The caller must call VDHUnlockMemto remove this lock. All locks are long-term. This function must be used prior to using any pointers passed to a virtual device driver from an OS/2 process (through DOSRequestVDD). This might also be useful to the callers of VDHCopyMemand VDHExchangeMem.
VDHMapPages, VDHReallocPages, and VDHFreePageswill block if applied to pages that are locked. They unblock when the lock is released.
VDHLockMem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHMapPages
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function maps a linear address region in the V86 address space . * / include mvdm . inc EXTERN VDHMapPages : NEAR pvdhmsSourceRegion DD ? ; Pointer to source region definition pvdhmtTargetRegion DD ? ; Target region definition flMappingFlag DD ? ; Mapping options flag PUSH pvdhmsSourceRegion ; Push pvdhmsSourceRegion PUSH pvdhmtTargetRegion ; Push pvdhmtTargetRegion PUSH flMappingFlag ; Push flMappingFlag CALL VDHMapPages ; Call the function
VDHMapPages - Format
/* This function maps a linear address region in the V86 address space . * / include mvdm . inc EXTERN VDHMapPages : NEAR pvdhmsSourceRegion DD ? ; Pointer to source region definition pvdhmtTargetRegion DD ? ; Target region definition flMappingFlag DD ? ; Mapping options flag PUSH pvdhmsSourceRegion ; Push pvdhmsSourceRegion PUSH pvdhmtTargetRegion ; Push pvdhmtTargetRegion PUSH flMappingFlag ; Push flMappingFlag CALL VDHMapPages ; Call the function
VDHMapPages Parameter - pvdhmsSourceRegion
pvdhmsSourceRegion(DD) Pointer to VDHMAPSOURCE structure.
VDHMAPSOURCE is the source region definition for VDHMapPageswith a data structure as follows:
VDHMapSource_s STRUC
vdhms_laddr DD ? ; Source linear address of source memory object.
; Source address to be mapped. Defines the
; start of the source region for the mapping.
; The region is the same length as the target
; region.
vdhms_hobj DD ? ; Memory object handle set by the service to
; hold a source handle for VDHMT_LINEAR
; mappings. See the VDHMT_LINEAR description
; under MappingFlag.
VDHMapSource_s ENDS
VDHMapPages Parameter - pvdhmtTargetRegion
pvdhmtTargetRegion(DD) Target region definition. Pointer to VDHMAPTARGET structure.
VDHMAPTARGET is the target region definition for VDHMapPageswith a data structure as follows:
VDHMapTarget_s STRUC
vdhmt_laddr DD ? ; Address in V86-space to be mapped
; (0 <= vdhmt_laddr < 1MB+64KB)
vdhmt_cpg DD ? ; Count of pages to map
vdhmt_hmap DD ? ; Mapping handle. Must be zero on the first call to
; VDHMapPages for region. Set by the service to
; hold a handle used for remapping the region. The
; handle is reset each time it is used. vdhmt_hmap
; must be the value returned from the previous
; VDHMapPages call for the region unless the pages
; are either already invalid or else are being made
; invalid. If either the old or new mapping is
; invalid pages, vdhmt_hmap can be 0. Making a
; region invalid restores pages in the region to
; their reserved state, and sets vdhmt_hmap to 0.
VDHMapTarget_s ENDS
VDHMapPages Parameter - flMappingFlag
flMappingFlag(DD) Mapping options flag.
Possible values are:
VDHMT_INVALID Make target region pages invalid. vdhmt_hmapcan be 0 (zero). This service is faster when the handle is provided, but virtual device drivers that do not store handles can map to invalid before remapping a region. Note that pvdhmsSourceRegionis ignored.
VDHMT_LINEAR Map linear source region into target region. vdhms_laddrcontains the linear address to map at the start of the target region. This can only be a page-granular address in a memory allocation that was obtained by using VDHAllocPagesor VDHReallocPages. After a successful mapping, the target region aliases the corresponding region of the source.
vdhms_hobjmust be 0 (zero) the first time a newly allocated or reallocated source object is mapped. On a successful mapping, vdhms_hobjis filled in. Using this handle on the next mapping that uses the same source object speeds up that mapping call. Any linear address (laddr) at the start of the target region can be mapped using the handle. The returned result must be stored after each mapping call. Virtual device drivers can avoid storing this handle and always use 0 (zero), however, the call will be slower.
VDHMT_PHYSICAL Map physical source region into target region. vdhms_laddrcontains the physical address to map at the start of the target region. vdhms_hobjis ignored.
VDHMT_BLACK_HOLE Map target region to black hole pages. pvdhmsSourceRegionis ignored.
VDHMapPages Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHMapPages - Parameters
pvdhmsSourceRegion(DD) Pointer to VDHMAPSOURCE structure.
VDHMAPSOURCE is the source region definition for VDHMapPageswith a data structure as follows:
VDHMapSource_s STRUC
vdhms_laddr DD ? ; Source linear address of source memory object.
; Source address to be mapped. Defines the
; start of the source region for the mapping.
; The region is the same length as the target
; region.
vdhms_hobj DD ? ; Memory object handle set by the service to
; hold a source handle for VDHMT_LINEAR
; mappings. See the VDHMT_LINEAR description
; under MappingFlag.
VDHMapSource_s ENDS
pvdhmtTargetRegion(DD) Target region definition. Pointer to VDHMAPTARGET structure.
VDHMAPTARGET is the target region definition for VDHMapPageswith a data structure as follows:
VDHMapTarget_s STRUC
vdhmt_laddr DD ? ; Address in V86-space to be mapped
; (0 <= vdhmt_laddr < 1MB+64KB)
vdhmt_cpg DD ? ; Count of pages to map
vdhmt_hmap DD ? ; Mapping handle. Must be zero on the first call to
; VDHMapPages for region. Set by the service to
; hold a handle used for remapping the region. The
; handle is reset each time it is used. vdhmt_hmap
; must be the value returned from the previous
; VDHMapPages call for the region unless the pages
; are either already invalid or else are being made
; invalid. If either the old or new mapping is
; invalid pages, vdhmt_hmap can be 0. Making a
; region invalid restores pages in the region to
; their reserved state, and sets vdhmt_hmap to 0.
VDHMapTarget_s ENDS
flMappingFlag(DD) Mapping options flag.
Possible values are:
VDHMT_INVALID Make target region pages invalid. vdhmt_hmapcan be 0 (zero). This service is faster when the handle is provided, but virtual device drivers that do not store handles can map to invalid before remapping a region. Note that pvdhmsSourceRegionis ignored.
VDHMT_LINEAR Map linear source region into target region. vdhms_laddrcontains the linear address to map at the start of the target region. This can only be a page-granular address in a memory allocation that was obtained by using VDHAllocPagesor VDHReallocPages. After a successful mapping, the target region aliases the corresponding region of the source.
vdhms_hobjmust be 0 (zero) the first time a newly allocated or reallocated source object is mapped. On a successful mapping, vdhms_hobjis filled in. Using this handle on the next mapping that uses the same source object speeds up that mapping call. Any linear address (laddr) at the start of the target region can be mapped using the handle. The returned result must be stored after each mapping call. Virtual device drivers can avoid storing this handle and always use 0 (zero), however, the call will be slower.
VDHMT_PHYSICAL Map physical source region into target region. vdhms_laddrcontains the physical address to map at the start of the target region. vdhms_hobjis ignored.
VDHMT_BLACK_HOLE Map target region to black hole pages. pvdhmsSourceRegionis ignored.
VDHMapPages - Purpose
This function maps a linear address region in the V86 address space to:
- Part of a virtual memory object
*Specific physical addresses (for physical devices)
*Undefined memory (black holes)
*Invalid pages (the unmapped state, which is the default state for reserved pages)
VDHMapPagesalso changes the virtual address contents of regions in the V86 address space (below 11000H (1MB+64KB)). Pages in this range can be made to address:
- Part of a memory object previously allocated using VDHAllocPagesor VDHReallocPages
*Physical addresses for a device
*Black hole (undefined memory) addresses that are read or written but do not retain their values
*Invalid pages, which cause faults when accessed (see VDHInstallFaultHook)
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Mapping succeeds only if it completely replaces a previous mapping, or if the region contains only invalid pages. To change the size of a region, it must first be made invalid. The entire target region must lie below 11000H (1MB+64KB) and must be contained in pages previously reserved by VDHReservePages. VDHMapPagesand VDHAllocPagescan be used on the same target region but care must be taken. Before switching from one service to the other, the pages affected must first be made invalid. If pages are left invalid, a pagefault handler must be registered (through VDHInstallFaultHook) to handle page faults, in case the pages are accessed.
Both target and source addresses must be on page boundaries. If they are not, the page offset part of the address is ignored.
VDHMapPages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHOpen
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function opens a file or device and returns a handle . The handle can be used with VDHRead , VDHWrite , VDHSeek , VDHClose , and VDHDevIOCtl . The parameters and error return codes are the same as those found in the DosOpen API . Refer to the OS / 2 Control Program Programming Reference for a complete descriptions of each DosOpen API parameter . * / include mvdm . inc EXTERN VDHOpen : NEAR FileName DD ? ; Pointer to the name of the file or device to open FileHandle DD ? ; Where the system returns the file handle ActionTaken DD ? ; Where a description of the action taken is returned FileSize DD ? ; The new file ' s logical size ( EOD ) in bytes FileAttribute DD ? ; File attribute bits used on file creation OpenFLag DD ? ; Specifies action taken , based on whether file exists OpenMode DD ? ; Describes the mode of the Open function EABuf DD ? ; Address of a VDH _ EAOP structure or NULL PUSH FileName ; Push FileName PUSH FileHandle ; Push FileHandle PUSH ActionTaken ; Push ActionTaken PUSH FileSize ; Push FileSize PUSH FileAttribute ; Push FileAttribute PUSH OpenFLag ; Push OpenFLag PUSH OpenMode ; Push OpenMode PUSH EABuf ; Push EABuf CALL VDHOpen ; Call the function
VDHOpen - Format
/* This function opens a file or device and returns a handle . The handle can be used with VDHRead , VDHWrite , VDHSeek , VDHClose , and VDHDevIOCtl . The parameters and error return codes are the same as those found in the DosOpen API . Refer to the OS / 2 Control Program Programming Reference for a complete descriptions of each DosOpen API parameter . * / include mvdm . inc EXTERN VDHOpen : NEAR FileName DD ? ; Pointer to the name of the file or device to open FileHandle DD ? ; Where the system returns the file handle ActionTaken DD ? ; Where a description of the action taken is returned FileSize DD ? ; The new file ' s logical size ( EOD ) in bytes FileAttribute DD ? ; File attribute bits used on file creation OpenFLag DD ? ; Specifies action taken , based on whether file exists OpenMode DD ? ; Describes the mode of the Open function EABuf DD ? ; Address of a VDH _ EAOP structure or NULL PUSH FileName ; Push FileName PUSH FileHandle ; Push FileHandle PUSH ActionTaken ; Push ActionTaken PUSH FileSize ; Push FileSize PUSH FileAttribute ; Push FileAttribute PUSH OpenFLag ; Push OpenFLag PUSH OpenMode ; Push OpenMode PUSH EABuf ; Push EABuf CALL VDHOpen ; Call the function
VDHOpen Parameter - FileName
FileName(DD) Pointer to the ASCIIZ string containing the name of the device or file to open.
VDHOpen Parameter - FileHandle
FileHandle(DD) Where the system returns the file handle.
VDHOpen Parameter - ActionTaken
ActionTaken(DD) Where the system returns a description of the action taken as a result of this function call.
VDHOpen Parameter - FileSize
FileSize(DD) The new file's logical size (EOD) in bytes.
VDHOpen Parameter - FileAttribute
FileAttribute(DD) File attribute bits used on file creation.
VDHOpen Parameter - OpenFLag
OpenFLag(DD) Specifies the action taken depending on whether the file exists.
Possible actions are:
VDHOPEN_FILE_EXISTED File existed
VDHOPEN_FILE_CREATED File created
VDHOPEN_FILE_TRUNCATED File replaced
VDHOpen Parameter - OpenMode
OpenMode(DD) Describes the mode of the Openfunction.
VDHOpen Parameter - EABuf
EABuf(DD) Address of a VDH_EAOP structure, or NULL.
VDHOpen Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). If the function fails, VDHGetErrorshould be called to determine the nature of the problem. VDHGetErrorcan return the following errors:
ERROR_DISK_FULL
ERROR_OPEN_FAILED
ERROR_FILE_NOT_FOUND
ERROR_INVALID_PARAMETER
ERROR_PATH_NOT_FOUND
ERROR_ACCESS_DENIED
ERROR_DRIVE_LOCKED
ERROR_NOT_DOS_DISK
ERROR_SHARING_BUFFER_EXCEEDED
ERROR_SHARING_VIOLATION
ERROR_INVALID_ACCESS
ERROR_CANNOT_MAKE
ERROR_TOO_MANY_OPEN_FILES
ERROR_NOT_ENOUGH_MEMORY
If the function is called at other than DOS session-task time, or if the pszFileNamepointer is invalid, a system halt occurs.
VDHOpen - Parameters
FileName(DD) Pointer to the ASCIIZ string containing the name of the device or file to open.
FileHandle(DD) Where the system returns the file handle.
ActionTaken(DD) Where the system returns a description of the action taken as a result of this function call.
FileSize(DD) The new file's logical size (EOD) in bytes.
FileAttribute(DD) File attribute bits used on file creation.
OpenFLag(DD) Specifies the action taken depending on whether the file exists.
Possible actions are:
VDHOPEN_FILE_EXISTED File existed
VDHOPEN_FILE_CREATED File created
VDHOPEN_FILE_TRUNCATED File replaced
OpenMode(DD) Describes the mode of the Openfunction.
EABuf(DD) Address of a VDH_EAOP structure, or NULL.
VDHOpen - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: Any handles the virtual device driver opened for the terminating DOS session must be closed with VDHClose.
Notes: Using VDHOpendoes not interfere with the handle space available to the DOS session with INT 21H, except that it does count against the system- wide limit on the number of open file handles. These VDHOpenhandles and the handles returned from INT 21H $Open cannot be used interchangeably.
VDHOpen - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHOpenPDD
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function gets the address of the routine in a physical device driver that the virtual device driver uses to communicate with the physical device driver . The physical device driver ' s device must have previously registered its name and entry point using the DevHlp service RegisterPDD . * / include mvdm . inc EXTERN VDHOpenPDD : NEAR DeviceName DD ? ; Pointer to device name of physical device driver to open VDDEntryPoint DQ ? ; VDD entry point for VDD / PDD communication PUSH DeviceName ; Push DeviceName PUSH VDDEntryPoint ; Push VDDEntryPoint CALL VDHOpenPDD ; Call the function
VDHOpenPDD - Format
/* This function gets the address of the routine in a physical device driver that the virtual device driver uses to communicate with the physical device driver . The physical device driver ' s device must have previously registered its name and entry point using the DevHlp service RegisterPDD . * / include mvdm . inc EXTERN VDHOpenPDD : NEAR DeviceName DD ? ; Pointer to device name of physical device driver to open VDDEntryPoint DQ ? ; VDD entry point for VDD / PDD communication PUSH DeviceName ; Push DeviceName PUSH VDDEntryPoint ; Push VDDEntryPoint CALL VDHOpenPDD ; Call the function
VDHOpenPDD Parameter - DeviceName
DeviceName(DD) Pointer to the device name of the physical device driver to open.
VDHOpenPDD Parameter - VDDEntryPoint
VDDEntryPoint(DQ) Virtual device driver entry point for use by the physical device driver. Since physical device drivers are 16:16 modules, this is a 16:32 entry point.
The interface for the VDDEntryPoint:
EntryPoint PROC NEAR ; PARAMETERS ; ENTRY [ESP + 12] - ulFunc (DD) - Function code ; All function codes are private to a PDD/VDD pair. ; [ESP + 8] - ul1 (DD) - Function-specific ; If a pointer, it is 16:16, and will generally ; be an input packet. ; [ESP + 4] - ul2 (DD) - Function-specific ; If a pointer, it is 16:16, and will generally ; be an output packet. ; EXIT SUCCESS Returns a non-zero value in EAX ; FAILURE Returns 0 in EAX
VDHOpenPDD Return Value - rc
Success If the function is successful, it returns a pointer to the physical device driver Inter-Device-Driver Communication (IDC) function. See " RegisterPDD" in the OS/2 Physical Device Driver Referencefor a description of the physical device driver's IDC function.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHOpenPDD - Parameters
DeviceName(DD) Pointer to the device name of the physical device driver to open.
VDDEntryPoint(DQ) Virtual device driver entry point for use by the physical device driver. Since physical device drivers are 16:16 modules, this is a 16:32 entry point.
The interface for the VDDEntryPoint:
EntryPoint PROC NEAR ; PARAMETERS ; ENTRY [ESP + 12] - ulFunc (DD) - Function code ; All function codes are private to a PDD/VDD pair. ; [ESP + 8] - ul1 (DD) - Function-specific ; If a pointer, it is 16:16, and will generally ; be an input packet. ; [ESP + 4] - ul2 (DD) - Function-specific ; If a pointer, it is 16:16, and will generally ; be an output packet. ; EXIT SUCCESS Returns a non-zero value in EAX ; FAILURE Returns 0 in EAX
VDHOpenPDD - Purpose
Context Issues: This function can be called only in the initialization context.
DOS Session Terminations: The virtual device driver must communicate with the physical device driver to ensure that any resources the physical device driver has for the terminating DOS session are freed.
VDHOpenPDD - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHOpenVDD
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function returns a handle to a virtual device driver that can be used with VDHRequestVDD to enable a virtual device driver to communicate with another virtual device driver . The name must be one that was previously registered by using VDHRegisterVDD . * / include mvdm . inc EXTERN VDHOpenVDD : NEAR VDDName DD ? ; Pointer to the name of the virtual device driver to open PUSH VDDName ; Push VDDName CALL VDHOpenVDD ; Call the function
VDHOpenVDD - Format
/* This function returns a handle to a virtual device driver that can be used with VDHRequestVDD to enable a virtual device driver to communicate with another virtual device driver . The name must be one that was previously registered by using VDHRegisterVDD . * / include mvdm . inc EXTERN VDHOpenVDD : NEAR VDDName DD ? ; Pointer to the name of the virtual device driver to open PUSH VDDName ; Push VDDName CALL VDHOpenVDD ; Call the function
VDHOpenVDD Parameter - VDDName
VDDName(DD) Pointer to a string containing the name of the virtual device driver to open.
VDHOpenVDD Return Value - rc
Success If the function is successful, it returns a handle to the virtual device driver.
Failure If the function fails, it returns 0 (zero). This can occur if:
- The virtual device driver referenced by VDDNameis not found.
*The virtual device driver was found, but has not registered a worker function (the routine that gets control when this interface is called) for virtual device driver/virtual device driver communication.
If this function is called with invalid parameters or in the incorrect context, a system halt occurs.
VDHOpenVDD - Parameters
VDDName(DD) Pointer to a string containing the name of the virtual device driver to open.
VDHOpenVDD - Purpose
Context Issues: This function can be called only in the DOS session-task context, typically during DOS session creation.
DOS Session Terminations: The virtual device driver must communicate with the opened virtual device driver to ensure that any resources for the terminating DOS session are freed. In addition, the virtual device driver must communicate with any virtual device driver or OS/2 clients to ensure that any resources created due to the connection are freed. Notes: The recommended way for two virtual device drivers to rendezvous with this function is for each to attempt to open the other at the first creation of a DOS session. This allows the two virtual device drivers to work together regardless of the order in which they are initialized.
VDHOpenVDD - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHOpenVIRQ
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function returns an IRQ handle for use with the other Virtual Programmable Interrupt Controller ( VPIC ) services and , optionally , sets handlers called when an End Of Interrupt ( EOI ) or Interrupt Return ( IRET ) is executed during a simulated interrupt . * / include mvdm . inc EXTERN VDHOpenVIRQ : NEAR IRQNumber DD ? ; Number of the IRQ to open EOIHandler DD ? ; Address of End - Of - Interrupt ( EOI ) handler IRETHandler DD ? ; Address of Interrupt Return ( IRET ) handler Timeout DD ? ; IRET timeout value in milliseconds OptionFlag DD ? ; Indicates whether the IRQ can be shared PUSH IRQNumber ; Push IRQNumber PUSH EOIHandler ; Push EOIHandler PUSH IRETHandler ; Push IRETHandler PUSH Timeout ; Push Timeout PUSH OptionFlag ; Push OptionFlag CALL VDHOpenVIRQ ; Call the function
VDHOpenVIRQ - Format
/* This function returns an IRQ handle for use with the other Virtual Programmable Interrupt Controller ( VPIC ) services and , optionally , sets handlers called when an End Of Interrupt ( EOI ) or Interrupt Return ( IRET ) is executed during a simulated interrupt . * / include mvdm . inc EXTERN VDHOpenVIRQ : NEAR IRQNumber DD ? ; Number of the IRQ to open EOIHandler DD ? ; Address of End - Of - Interrupt ( EOI ) handler IRETHandler DD ? ; Address of Interrupt Return ( IRET ) handler Timeout DD ? ; IRET timeout value in milliseconds OptionFlag DD ? ; Indicates whether the IRQ can be shared PUSH IRQNumber ; Push IRQNumber PUSH EOIHandler ; Push EOIHandler PUSH IRETHandler ; Push IRETHandler PUSH Timeout ; Push Timeout PUSH OptionFlag ; Push OptionFlag CALL VDHOpenVIRQ ; Call the function
VDHOpenVIRQ Parameter - IRQNumber
IRQNumber(DD) Number of the IRQ to open.
VDHOpenVIRQ Parameter - EOIHandler
EOIHandler(DD) Address of End-Of-Interrupt (EOI) handler.
Linear address of the handler to be called when EOI is received by VPIC from a DOS session for the IRQ. If this is not desired, put a 0 (zero) in this parameter. Note that the IRQ is no longer "in service" (the ISR bit has been cleared) when the virtual device driver's EOI handler is called. The interface to the EOI handler is:
EOIHdlr PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - pcrf - Pointer to client register frame ; EXIT None ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS session-task
VDHOpenVIRQ Parameter - IRETHandler
IRETHandler(DD) Address of Interrupt Return (IRET) handler.
Linear address of the handler to be called when the IRET in the DOS session 's interrupt code is executed for this IRQ. If this is not desired, set the parameter to 0 (zero). The interface for the IRET routine is:
IRETHdlr PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - pcrf - Pointer to client register frame ; EXIT None ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS session-task
VDHOpenVIRQ Parameter - Timeout
Timeout(DD) IRET timeout value in milliseconds. When the timeout expires, the virtual device driver's IRET handler is called as if the IRET had occurred. A value of -1 indicates that no timeout occurs.
VDHOpenVIRQ Parameter - OptionFlag
OptionFlag(DD) Option flag. Indicates whether the IRQ can be shared.
Possible value:
VPIC_SHARE_IRQ Indicates that the virtual device driver is willing to share the IRQ with another virtual device driver. All virtual device drivers that virtualize the same IRQ must pass this flag. Whether a particular IRQ is shared or unshared is determined by the setting of OptionFlagby the first virtual device driver to open the IRQ.
VDHOpenVIRQ Return Value - rc
Success If the function is successful, it returns an IRQ handle.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If IRQNumber, EOIHandler, IRETHandler, or OptionFlagare invalid, a system halt occurs.
VDHOpenVIRQ - Parameters
IRQNumber(DD) Number of the IRQ to open.
EOIHandler(DD) Address of End-Of-Interrupt (EOI) handler.
Linear address of the handler to be called when EOI is received by VPIC from a DOS session for the IRQ. If this is not desired, put a 0 (zero) in this parameter. Note that the IRQ is no longer "in service" (the ISR bit has been cleared) when the virtual device driver's EOI handler is called. The interface to the EOI handler is:
EOIHdlr PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - pcrf - Pointer to client register frame ; EXIT None ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS session-task
IRETHandler(DD) Address of Interrupt Return (IRET) handler.
Linear address of the handler to be called when the IRET in the DOS session 's interrupt code is executed for this IRQ. If this is not desired, set the parameter to 0 (zero). The interface for the IRET routine is:
IRETHdlr PROC NEAR ; PARAMETERS ; ENTRY [ESP + 4] - pcrf - Pointer to client register frame ; EXIT None ; ; USES EAX, ECX, EDX, FS, GS, Flags ; CONTEXT DOS session-task
Timeout(DD) IRET timeout value in milliseconds. When the timeout expires, the virtual device driver's IRET handler is called as if the IRET had occurred. A value of -1 indicates that no timeout occurs.
OptionFlag(DD) Option flag. Indicates whether the IRQ can be shared.
Possible value:
VPIC_SHARE_IRQ Indicates that the virtual device driver is willing to share the IRQ with another virtual device driver. All virtual device drivers that virtualize the same IRQ must pass this flag. Whether a particular IRQ is shared or unshared is determined by the setting of OptionFlagby the first virtual device driver to open the IRQ.
VDHOpenVIRQ - Purpose
Context Issues: This function can be called only in the initialization context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: A maximum of 32 virtual device drivers can share an IRQ.
VDHOpenVIRQ - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPhysicalDisk
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function returns information about partitionable disks . * / include mvdm . inc EXTERN VDHPhysicalDisk : NEAR Function DD ? ; Type of partitionable disks ' information DataPtr DD ? ; Pointer to the return buffer DataLen DD ? ; Length of the return buffer ParmPtr DD ? ; Pointer to the user - supplied information ParmLen DD ? ; Length of the user - supplied information PUSH Function ; Push Function PUSH DataPtr ; Push DataPtr PUSH DataLen ; Push DataLen PUSH ParmPtr ; Push ParmPtr PUSH ParmLen ; Push ParmLen CALL VDHPhysicalDisk ; Call the function
VDHPhysicalDisk - Format
/* This function returns information about partitionable disks . * / include mvdm . inc EXTERN VDHPhysicalDisk : NEAR Function DD ? ; Type of partitionable disks ' information DataPtr DD ? ; Pointer to the return buffer DataLen DD ? ; Length of the return buffer ParmPtr DD ? ; Pointer to the user - supplied information ParmLen DD ? ; Length of the user - supplied information PUSH Function ; Push Function PUSH DataPtr ; Push DataPtr PUSH DataLen ; Push DataLen PUSH ParmPtr ; Push ParmPtr PUSH ParmLen ; Push ParmLen CALL VDHPhysicalDisk ; Call the function
VDHPhysicalDisk Parameter - Function
Function(DD) Type of partitionable disks' information to obtain.
Possible values are:
VDHPHYD_GET_DISKS Obtain the total number of partitionable disks
VDHPHYD_GET_HANDLE Obtain a handle to use with the Category 9 IOCtls
VDHPHYD_RELEASE_HANDLE Release a handle for a partitionable disk
VDHPhysicalDisk Parameter - DataPtr
DataPtr(DD) Pointer to the return buffer.
VDHPhysicalDisk Parameter - DataLen
DataLen(DD) Length of the return buffer.
The returned data for each function is described as follows (all lengths are in bytes):
VDHPHYD_GET_DISKS Data Length=2. Total number of partitionable disks in the system. 1-based.
VDHPHYD_GET_HANDLE Data Length=2. Handle for the specified partitionable disk for Category 9 IOCtls.
VDHPHYD_RELEASE_HANDLE Data Length=0. None; pointer must be 0 (zero).
VDHPhysicalDisk Parameter - ParmPtr
ParmPtr(DD) Pointer to the user-supplied information.
VDHPhysicalDisk Parameter - ParmLen
ParmLen(DD) Length of the user-supplied information (all lengths are in bytes):
VDHPHYD_GET_DISKS Parm Length=0. None; must be set to 0 (zero). 1-based.
VDHPHYD_GET_HANDLE Parm Length=string length. ASCIIZ string that specifies the partitionable disk.
VDHPHYD_RELEASE_HANDLE Parm Length=2. Handle obtained from VDHPHYD_GET_ HANDLE.
VDHPhysicalDisk Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. VDHGetErrorcan return the following error codes:
ERROR_ACCESS_DENIED
ERROR_INVALID_FUNCTION
ERROR_INVALID_HANDLE
ERROR_INVALID_PARAMETER
ERROR_LOCK_VIOLATION
If VDHPhysicalDiskis called in any context except DOS session task time, a system halt occurs.
VDHPhysicalDisk - Parameters
Function(DD) Type of partitionable disks' information to obtain.
Possible values are:
VDHPHYD_GET_DISKS Obtain the total number of partitionable disks
VDHPHYD_GET_HANDLE Obtain a handle to use with the Category 9 IOCtls
VDHPHYD_RELEASE_HANDLE Release a handle for a partitionable disk
DataPtr(DD) Pointer to the return buffer.
DataLen(DD) Length of the return buffer.
The returned data for each function is described as follows (all lengths are in bytes):
VDHPHYD_GET_DISKS Data Length=2. Total number of partitionable disks in the system. 1-based.
VDHPHYD_GET_HANDLE Data Length=2. Handle for the specified partitionable disk for Category 9 IOCtls.
VDHPHYD_RELEASE_HANDLE Data Length=0. None; pointer must be 0 (zero).
ParmPtr(DD) Pointer to the user-supplied information.
ParmLen(DD) Length of the user-supplied information (all lengths are in bytes):
VDHPHYD_GET_DISKS Parm Length=0. None; must be set to 0 (zero). 1-based.
VDHPHYD_GET_HANDLE Parm Length=string length. ASCIIZ string that specifies the partitionable disk.
VDHPHYD_RELEASE_HANDLE Parm Length=2. Handle obtained from VDHPHYD_GET_ HANDLE.
VDHPhysicalDisk - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: The handle obtained with Function Value=2 is released with Function Value=3. The ASCIIZ string used to specify the partitionable disk must be of the following format:
number:<null byte>
Where:
number Specifies the partitionable disk (1-based) number in ASCII
: Must be present
<null byte> Specifies the byte of 0 for the ASCIIZ string
Notes: If the pointers passed by this function are allocated from the stack , then the SSToDSmacro must be used to make the DS pointer relative. Addresses (pointers) inside device-specific data and parameter packets are not translated.
VDHPhysicalDisk - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPopInt
Select an item:
Format Parameters Return Codes Purpose Glossary
/*
This function reverses the effects of VDHPushInt .
It removes the Interrupt Return
( IRET ) frame from the client ' s stack and restores
the client ' s CS : IP
to what was in the IRET frame .
* /
include mvdm . inc
EXTERN VDHPopInt : NEAR
DD ?
PUSH ; Push
CALL VDHP ; Call the function
VDHPopInt - Format
/*
This function reverses the effects of VDHPushInt .
It removes the Interrupt Return
( IRET ) frame from the client ' s stack and restores
the client ' s CS : IP
to what was in the IRET frame .
* /
include mvdm . inc
EXTERN VDHPopInt : NEAR
DD ?
PUSH ; Push
CALL VDHP ; Call the function
VDHPopInt Parameter -
(DD) None.
VDHPopInt Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack overflow would occur. A stack exception will be simulated to the client.
VDHPopInt - Parameters
(DD) None.
VDHPopInt - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This function always returns Successful when the DOS session is in client mode because no data accesses below 1MB can cause a fault.
VDHPopInt - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPopRegs
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function reverses the VDHPushRegs by popping the specified client registers into the Client Register Frame ( CRF ) from the client ' s stack . * / include mvdm . inc EXTERN VDHPopRegs : NEAR RegFlag DD ? ; Indicates which client registers to pop PUSH RegFlag ; Push RegFlag CALL VDHPopRegs ; Call the function
VDHPopRegs - Format
/* This function reverses the VDHPushRegs by popping the specified client registers into the Client Register Frame ( CRF ) from the client ' s stack . * / include mvdm . inc EXTERN VDHPopRegs : NEAR RegFlag DD ? ; Indicates which client registers to pop PUSH RegFlag ; Push RegFlag CALL VDHPopRegs ; Call the function
VDHPopRegs Parameter - RegFlag
RegFlag(DD) Flag indicating which client registers to pop.
These flags can be "ORed" together to indicate more than one register. Possible values are:
VDHREG_AX Pop the AX register
VDHREG_BX Pop the BX register
VDHREG_CX Pop the CX register
VDHREG_DX Pop the DX register
VDHREG_SI Pop the SI register
VDHREG_DI Pop the DI register
VDHREG_BP Pop the BP register
VDHREG_SP Pop the SP register
VDHREG_DS Pop the DS register
VDHREG_ES Pop the ES register
VDHREG_SS Pop the SS register
VDHREG_FLAG Pop the Flags register
VDHREG_ALL Pop all the registers
VDHREG_GENERAL Pop all the registers except SS and SP
VDHPopRegs Return Value - rc
Success If the function was successful, it returns a nonzero value.
Failure If this function fails, it returns 0 (zero) if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception is simulated to the client. If RegFlagis invalid, a system halt occurs.
VDHPopRegs - Parameters
RegFlag(DD) Flag indicating which client registers to pop.
These flags can be "ORed" together to indicate more than one register. Possible values are:
VDHREG_AX Pop the AX register
VDHREG_BX Pop the BX register
VDHREG_CX Pop the CX register
VDHREG_DX Pop the DX register
VDHREG_SI Pop the SI register
VDHREG_DI Pop the DI register
VDHREG_BP Pop the BP register
VDHREG_SP Pop the SP register
VDHREG_DS Pop the DS register
VDHREG_ES Pop the ES register
VDHREG_SS Pop the SS register
VDHREG_FLAG Pop the Flags register
VDHREG_ALL Pop all the registers
VDHREG_GENERAL Pop all the registers except SS and SP
VDHPopRegs - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: The caller should be careful to pass the same RegFlagvalue to VDHPopRegsthat was used for the corresponding VDHPushRegscall. If the caller does not do this, the client stack can become damaged. This function always returns Successful when RegFlagis valid and the DOS session is in V86 mode because no data accesses below 1MB can cause a fault.
VDHPopRegs - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPopStack
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function pops the data off the client ' s stack . * / include mvdm . inc EXTERN VDHPopStack : NEAR NumBytes DD ? ; Number of bytes to pop off the client ' s stack DataPtr DD ? ; Pointer to data to pop off client ' s stack PUSH NumBytes ; Push NumBytes PUSH DataPtr ; Push DataPtr CALL VDHPopStack ; Call the function
VDHPopStack - Format
/* This function pops the data off the client ' s stack . * / include mvdm . inc EXTERN VDHPopStack : NEAR NumBytes DD ? ; Number of bytes to pop off the client ' s stack DataPtr DD ? ; Pointer to data to pop off client ' s stack PUSH NumBytes ; Push NumBytes PUSH DataPtr ; Push DataPtr CALL VDHPopStack ; Call the function
VDHPopStack Parameter - NumBytes
NumBytes(DD) Number of bytes to pop off the client's stack. Must be an even number.
VDHPopStack Parameter - DataPtr
DataPtr(DD) Pointer to the data to pop off the client's stack.
VDHPopStack Return Value - rc
Success If the function was successful, it returns a nonzero value.
Failure If this function fails, it returns 0 (zero) if a fault would occur when accessing the user stack. If NumBytesis odd, a system halt occurs.
VDHPopStack - Parameters
NumBytes(DD) Number of bytes to pop off the client's stack. Must be an even number.
DataPtr(DD) Pointer to the data to pop off the client's stack.
VDHPopStack - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This is a very low-level service. Appropriate care should be exercised in its use to ensure that the client's stack is not damaged. This service handles stack wraparound, and always returns successful when the DOS session is in V86-mode because no data accesses below 1MB can cause a fault.
VDHPopStack - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPopup
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function displays a message according to the Message ID , and gets a response from the user . * / include mvdm . inc EXTERN VDHPopup : NEAR ParmTable DD ? ; Pointer to a table of substitution strings StrCount DD ? ; Number of substitution strings MsgNumber DD ? ; Message number RespPtr DD ? ; Pointer to a DD to receive the response RespAllowed DD ? ; Bit field describing the allowed responses Reserved DD ? ; Reserved ; must be set to NULL PUSH ParmTable ; Push ParmTable PUSH StrCount ; Push StrCount PUSH MsgNumber ; Push MsgNumber PUSH RespPtr ; Push RespPtr PUSH RespAllowed ; Push RespAllowed PUSH Reserved ; Push Reserved CALL VDHPopup ; Call the function
VDHPopup - Format
/* This function displays a message according to the Message ID , and gets a response from the user . * / include mvdm . inc EXTERN VDHPopup : NEAR ParmTable DD ? ; Pointer to a table of substitution strings StrCount DD ? ; Number of substitution strings MsgNumber DD ? ; Message number RespPtr DD ? ; Pointer to a DD to receive the response RespAllowed DD ? ; Bit field describing the allowed responses Reserved DD ? ; Reserved ; must be set to NULL PUSH ParmTable ; Push ParmTable PUSH StrCount ; Push StrCount PUSH MsgNumber ; Push MsgNumber PUSH RespPtr ; Push RespPtr PUSH RespAllowed ; Push RespAllowed PUSH Reserved ; Push Reserved CALL VDHPopup ; Call the function
VDHPopup Parameter - ParmTable
ParmTable(DD) Pointer to a table of substitution strings.
VDHPopup Parameter - StrCount
StrCount(DD) Number of substitution strings.
VDHPopup Parameter - MsgNumber
MsgNumber(DD) Message number.
VDHPopup Parameter - RespPtr
RespPtr(DD) Pointer to a DD to receive the returned response, filled on exit.
VDHPopup Parameter - RespAllowed
RespAllowed(DD) Bit field describing the allowed responses.
The allowed values are (any combination of these flags can be specified):
VDHP_FAIL (0001H)
VDHP_RETRY (0004H)
VDHP_IGNORE (0008H)
VDHP_TERMINATE_SESSION (0002H)
VDHPopup Parameter - Reserved
Reserved(DD) Reserved. Must be set to NULL.
VDHPopup Return Value - rc
Success If the function is successful, it returns a nonzero value and the variable pointed to by RespPtris filled in with actual response selected by the user.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHPopup - Parameters
ParmTable(DD) Pointer to a table of substitution strings.
StrCount(DD) Number of substitution strings.
MsgNumber(DD) Message number.
RespPtr(DD) Pointer to a DD to receive the returned response, filled on exit.
RespAllowed(DD) Bit field describing the allowed responses.
The allowed values are (any combination of these flags can be specified):
VDHP_FAIL (0001H)
VDHP_RETRY (0004H)
VDHP_IGNORE (0008H)
VDHP_TERMINATE_SESSION (0002H)
Reserved(DD) Reserved. Must be set to NULL.
VDHPopup - Purpose
Context Issues: This function can be called in the initialization context or the DOS session-task context. If it is called at initialization time, the message is displayed as a string on the console as if a DosWriteto standard output (stdout) had been made. No prompt is displayed, and no user response is returned. ResponsePtris filled in with 0 (zero).
DOS Session Terminations: A DOS session cannot be terminated if it is waiting in this call for a user response.
Notes: This service is intended for virtual device drivers, which must inform the user of some extraordinary circumstance. For example, the virtual COM device driver (VCOM) issues this call to inform the user that a COM port is busy and gives the user a choice of how to handle the situation .
The input value of ResponsePtris not used. "Retry" is the default action chosen for hard errors. If Retry is not allowed, "End the Program" is chosen as the default.
VDHPopup - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPostEventSem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function posts an event semaphore . All the threads blocked on this semaphore will wake up . * / include mvdm . inc EXTERN VDHPostEventSem : NEAR EventSemHandle DD ? ; Handle of an event semaphore PUSH EventSemHandle ; Push EventSemHandle CALL VDHPostEventSem ; Call the function
VDHPostEventSem - Format
/* This function posts an event semaphore . All the threads blocked on this semaphore will wake up . * / include mvdm . inc EXTERN VDHPostEventSem : NEAR EventSemHandle DD ? ; Handle of an event semaphore PUSH EventSemHandle ; Push EventSemHandle CALL VDHPostEventSem ; Call the function
VDHPostEventSem Parameter - EventSemHandle
EventSemHandle(DD) Handle of the event semaphore to post.
VDHPostEventSem Return Value - rc
Success If the function is successful, it will return nothing.
Failure Posting a semaphore that is invalid or is already posted causes a system halt to occur.
VDHPostEventSem - Parameters
EventSemHandle(DD) Handle of the event semaphore to post.
VDHPostEventSem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHPostEventSem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPrintClose
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is called by other virtual device drivers to flush and close a DOS session ' s open printers that have been opened for INT 17H printing . A DOS session can have more than one printer open . This service flushes and closes all of them . * / include mvdm . inc EXTERN VDHPrintClose : NEAR VDMHandle DD ? ; DOS session handle PUSH VDMHandle ; Push VDMHandle CALL VDHPrintClose ; Call the function
VDHPrintClose - Format
/* This function is called by other virtual device drivers to flush and close a DOS session ' s open printers that have been opened for INT 17H printing . A DOS session can have more than one printer open . This service flushes and closes all of them . * / include mvdm . inc EXTERN VDHPrintClose : NEAR VDMHandle DD ? ; DOS session handle PUSH VDMHandle ; Push VDMHandle CALL VDHPrintClose ; Call the function
VDHPrintClose Parameter - VDMHandle
VDMHandle(DD) DOS session handle.
VDHPrintClose Return Value - rc
None.
VDHPrintClose - Parameters
VDMHandle(DD) DOS session handle.
VDHPrintClose - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: The system will flush and close any open printers when the DOS session is terminated.
Notes: If a printer has been left open because of direct access to the parallel ports, it will also be closed.
VDHPrintClose - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPushFarCall
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function simulates a Far Call to V86 code as if a DOS program had executed a Far Call instruction . * / include mvdm . inc EXTERN VDHPushFarCall : NEAR SegOffAddr DQ ? ; Address of V86 mode or protected mode code to call PUSH SegOffAddr ; Push SegOffAddr CALL VDHPushFarCall ; Call the function
VDHPushFarCall - Format
/* This function simulates a Far Call to V86 code as if a DOS program had executed a Far Call instruction . * / include mvdm . inc EXTERN VDHPushFarCall : NEAR SegOffAddr DQ ? ; Address of V86 mode or protected mode code to call PUSH SegOffAddr ; Push SegOffAddr CALL VDHPushFarCall ; Call the function
VDHPushFarCall Parameter - SegOffAddr
SegOffAddr(DQ) The V86-mode segment:offset address of the V86-mode code to call, or selector:offset of protected-mode code to call.
VDHPushFarCall Return Value - rc
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception is simulated to the client.
VDHPushFarCall - Parameters
SegOffAddr(DQ) The V86-mode segment:offset address of the V86-mode code to call, or selector:offset of protected-mode code to call.
VDHPushFarCall - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This function does not take effect until the operating system returns to the DOS session. In most cases, VDHArmReturnHookis called after this service. This allows the virtual device driver to regain control when the called V86 code executes its Far Return (RETF).
This function always returns successful when the DOS session is in V86 mode because no data accesses below 1MB can cause a fault.
VDHPushFarCall - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPushInt
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is used to change the DOS session ' s control flow to the interrupt handler when an interrupt is simulated . This function also simulates an interrupt to a specified V86 - interrupt vector as if a DOS program has executed an INT n instruction . Any virtual device driver hooked on this interrupt with VDHInstallIntHook will get control as expected . The VDHArmReturnHook service can be used after this function is called to regain control when the V86 code executes the Interrupt Return ( IRET ) . If the DOS session is in V86 - mode , the V86 - mode handler from the IVT is called . If the DOS session is in protected mode , the protected - mode interrupt handler is called . * / include mvdm . inc EXTERN VDHPushInt : NEAR Vector DD ? ; Number of the interrupt vector to push PUSH Vector ; Push Vector CALL VDHPushIn ; Call the function
VDHPushInt - Format
/* This function is used to change the DOS session ' s control flow to the interrupt handler when an interrupt is simulated . This function also simulates an interrupt to a specified V86 - interrupt vector as if a DOS program has executed an INT n instruction . Any virtual device driver hooked on this interrupt with VDHInstallIntHook will get control as expected . The VDHArmReturnHook service can be used after this function is called to regain control when the V86 code executes the Interrupt Return ( IRET ) . If the DOS session is in V86 - mode , the V86 - mode handler from the IVT is called . If the DOS session is in protected mode , the protected - mode interrupt handler is called . * / include mvdm . inc EXTERN VDHPushInt : NEAR Vector DD ? ; Number of the interrupt vector to push PUSH Vector ; Push Vector CALL VDHPushIn ; Call the function
VDHPushInt Parameter - Vector
Vector(DD) Number of the interrupt vector to push (0-255).
VDHPushInt Return Value - rc
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception will be simulated to the client. If Vectoris invalid, a system halt occurs.
VDHPushInt - Parameters
Vector(DD) Number of the interrupt vector to push (0-255).
VDHPushInt - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This function does not take effect until the operating system returns to V86 mode. This function always returns successful when the DOS session is in V86 mode because no data accesses below 1MB can cause a fault .
VDHPushInt - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPushRegs
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function pushes the specified client register from the Client Register Frame ( CRF ) to the client ' s stack . This service is usually used in conjunction with VDHPushFarCall to preserve user registers . * / include mvdm . inc EXTERN VDHPushRegs : NEAR RegFlag DD ? ; Flag indicating which client registers to push PUSH RegFlag ; Push RegFlag CALL VDHPushRegs ; Call the function
VDHPushRegs - Format
/* This function pushes the specified client register from the Client Register Frame ( CRF ) to the client ' s stack . This service is usually used in conjunction with VDHPushFarCall to preserve user registers . * / include mvdm . inc EXTERN VDHPushRegs : NEAR RegFlag DD ? ; Flag indicating which client registers to push PUSH RegFlag ; Push RegFlag CALL VDHPushRegs ; Call the function
VDHPushRegs Parameter - RegFlag
RegFlag(DD) Flag indicating which client registers to push. These flags can be ORed together to indicate more than one register.
Possible values are:
VDHREG_AX Push the AX register
VDHREG_BX Push the BX register
VDHREG_CX Push the CX register
VDHREG_DX Push the DX register
VDHREG_SI Push the SI register
VDHREG_DI Push the DI register
VDHREG_BP Push the BP register
VDHREG_SP Push the SP register
VDHREG_DS Push the DS register
VDHREG_ES Push the ES register
VDHREG_SS Push the SS register
VDHREG_FLAG Push the Flags register
VDHREG_ALL Push all the registers
VDHREG_GENERAL Push all the registers except SS and SP
VDHPushRegs Return Value - rc
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception will be simulated to the client. If RegFlagis invalid, a system halt occurs.
VDHPushRegs - Parameters
RegFlag(DD) Flag indicating which client registers to push. These flags can be ORed together to indicate more than one register.
Possible values are:
VDHREG_AX Push the AX register
VDHREG_BX Push the BX register
VDHREG_CX Push the CX register
VDHREG_DX Push the DX register
VDHREG_SI Push the SI register
VDHREG_DI Push the DI register
VDHREG_BP Push the BP register
VDHREG_SP Push the SP register
VDHREG_DS Push the DS register
VDHREG_ES Push the ES register
VDHREG_SS Push the SS register
VDHREG_FLAG Push the Flags register
VDHREG_ALL Push all the registers
VDHREG_GENERAL Push all the registers except SS and SP
VDHPushRegs - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Because the registers are saved on the DOS session stack (as opposed to a virtual device driver data structure), the virtual device driver is in no danger of losing track of data if the DOS session does not return to the virtual device driver. This service is used sparingly as it consumes DOS session stack space, and most DOS applications cannot tolerate excessive stack usage beyond their own needs.
This function always returns successful when RegFlagis valid and the DOS session is in V86 mode because no data accessed below 1MB can cause a fault .
VDHPushRegs - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPushStack
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function pushes data onto the client ' s stack . * / include mvdm . inc EXTERN VDHPushStack : NEAR NumBytes DD ? ; Number of bytes to push on the client ' s stack DataPtr DD ? ; Pointer to the data to push on the stack PUSH NumBytes ; Push NumBytes PUSH DataPtr ; Push DataPtr CALL VDHPushStack ; Call the function
VDHPushStack - Format
/* This function pushes data onto the client ' s stack . * / include mvdm . inc EXTERN VDHPushStack : NEAR NumBytes DD ? ; Number of bytes to push on the client ' s stack DataPtr DD ? ; Pointer to the data to push on the stack PUSH NumBytes ; Push NumBytes PUSH DataPtr ; Push DataPtr CALL VDHPushStack ; Call the function
VDHPushStack Parameter - NumBytes
NumBytes(DD) Number of bytes to push onto the client's stack. Must be an even number.
VDHPushStack Parameter - DataPtr
DataPtr(DD) A pointer to the data to be pushed.
VDHPushStack Return Value - rc
Success If the function was successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if the client is in protected mode and the stack is invalid or a stack underflow would occur. A stack exception will be simulated to the client. If NumBytes is odd, a system halt occurs.
VDHPushStack - Parameters
NumBytes(DD) Number of bytes to push onto the client's stack. Must be an even number.
DataPtr(DD) A pointer to the data to be pushed.
VDHPushStack - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This is a very low-level service. Appropriate care should be exercised in its use to ensure that the client's stack is not corrupted. This service handles stack wraparound, and always returns successful when the DOS session is in V86-mode because no data accesses below 1MB can cause a fault.
VDHPushStack - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHPutSysValue
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function sets a system value . * / include mvdm . inc EXTERN VDHPutSysValue : NEAR Index DD ? ; Index of the system variable to set Value DD ? ; New value for the system variable PUSH Index ; Push Index PUSH Value ; Push Value CALL VDHPutSysVal ; Call the function
VDHPutSysValue - Format
/* This function sets a system value . * / include mvdm . inc EXTERN VDHPutSysValue : NEAR Index DD ? ; Index of the system variable to set Value DD ? ; New value for the system variable PUSH Index ; Push Index PUSH Value ; Push Value CALL VDHPutSysVal ; Call the function
VDHPutSysValue Parameter - Index
Index(DD) Index of the system value to set. System value indexes are defined in VDMM.INC and listed in VDHQuerySysValue.
VDHPutSysValue Parameter - Value
Value(DD) New value for the system variable.
VDHPutSysValue Return Value - rc
Success If the function was successful, it returns nothing.
Failure If Index is invalid, a system halt occurs.
VDHPutSysValue - Parameters
Index(DD) Index of the system value to set. System value indexes are defined in VDMM.INC and listed in VDHQuerySysValue.
Value(DD) New value for the system variable.
VDHPutSysValue - Purpose
Context Issues: This function can be called in the initialization or DOS session-task (DOS session creation) context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This service is intended for system virtual device drivers to export system constants, such as ROM memory size. The behavior of the system is undefined if this service is used for any other purpose.
VDHPutSysValue - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQueryFreePages
Select an item:
Format Parameters Return Codes Purpose Glossary
/*
This function returns the total amount of free virtual memory in bytes .
This is the amount of memory that could be allocated successfully .
* /
include mvdm . inc
EXTERN VDHQueryFreePages : NEAR
DD ?
PUSH ; Push
CALL VDHQueryFree ; Call the function
VDHQueryFreePages - Format
/*
This function returns the total amount of free virtual memory in bytes .
This is the amount of memory that could be allocated successfully .
* /
include mvdm . inc
EXTERN VDHQueryFreePages : NEAR
DD ?
PUSH ; Push
CALL VDHQueryFree ; Call the function
VDHQueryFreePages Parameter -
(DD) None.
VDHQueryFreePages Return Value - rc
Success If the function is successful, it returns the number of bytes of free virtual memory.
Failure If the function fails, it returns nothing.
VDHQueryFreePages - Parameters
(DD) None.
VDHQueryFreePages - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This is a system-wide value that is not specific to the virtual address space of the DOS session.
VDHQueryFreePages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQueryHookData
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function returns a pointer to the reference data created during the call to VDHAllocHook . * / include mvdm . inc EXTERN VDHQueryHookData : NEAR HookHandle DD ? ; Hook handle from VDHAllocHook PUSH HookHandle ; Push HookHandle CALL VDHQueryHookData ; Call the function
VDHQueryHookData - Format
/* This function returns a pointer to the reference data created during the call to VDHAllocHook . * / include mvdm . inc EXTERN VDHQueryHookData : NEAR HookHandle DD ? ; Hook handle from VDHAllocHook PUSH HookHandle ; Push HookHandle CALL VDHQueryHookData ; Call the function
VDHQueryHookData Parameter - HookHandle
HookHandle(DD) Hook handle (from VDHAllocHook) for the hook to query.
VDHQueryHookData Return Value - rc
Success If the function is successful, it returns a pointer to the reference data block.
Failure If HookHandle is invalid or if there is no reference data (that is, the RefDataSize parameter for VDHAllocHook is 0), a system halt occurs.
VDHQueryHookData - Parameters
HookHandle(DD) Hook handle (from VDHAllocHook) for the hook to query.
VDHQueryHookData - Purpose
Context Issues: This function can be called in the initialization, task, or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHQueryHookData - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQueryLin
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function converts a 16 : 16 ( Far16 ) address to a 0 : 32 address . The 16 : 16 address can be a LDT - based or GDT - based address . The function is also callable on stack - based addresses . * / include mvdm . inc EXTERN VDHQueryLin : NEAR Far16Addr DD ? ; 16 : 16 addressto be converted PUSH Far16Addr ; Push Far16Addr CALL VDHQueryLin ; Call the function
VDHQueryLin - Format
/* This function converts a 16 : 16 ( Far16 ) address to a 0 : 32 address . The 16 : 16 address can be a LDT - based or GDT - based address . The function is also callable on stack - based addresses . * / include mvdm . inc EXTERN VDHQueryLin : NEAR Far16Addr DD ? ; 16 : 16 addressto be converted PUSH Far16Addr ; Push Far16Addr CALL VDHQueryLin ; Call the function
VDHQueryLin Parameter - Far16Addr
Far16Addr(DD) The 16:16 address to be converted to a 0:32 address.
VDHQueryLin Return Value - rc
Success If the function is successful, it returns the 0:32 address that corresponds to Far16Addr.
Failure If Far16Addr is an invalid selector, a system halt occurs.
VDHQueryLin - Parameters
Far16Addr(DD) The 16:16 address to be converted to a 0:32 address.
VDHQueryLin - Purpose
Context Issues: This function can be called in the initialization, task, or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This service does minimal checking on Far16Addr. The caller should make sure that Far16Addr is not invalid. If an invalid address is passed, this service can return an invalid address.
VDHQueryLin - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQueryKeyShift
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is called by the virtual mouse device driver to query the keyboard shift state of a DOS session . * / include mvdm . inc EXTERN VDHQueryKeyShift : NEAR VDMHandle DD ? ; DOS session handle PUSH VDMHandle ; Push VDMHandle CALL VDHQueryKeyShift ; Call the function
VDHQueryKeyShift - Format
/* This function is called by the virtual mouse device driver to query the keyboard shift state of a DOS session . * / include mvdm . inc EXTERN VDHQueryKeyShift : NEAR VDMHandle DD ? ; DOS session handle PUSH VDMHandle ; Push VDMHandle CALL VDHQueryKeyShift ; Call the function
VDHQueryKeyShift Parameter - VDMHandle
VDMHandle(DD) DOS session handle.
VDHQueryKeyShift Return Value - rc
Returns a USHORT which is a bitmask that indicates the current key state:
Right Shift 1
Left Shift 2
Ctrl 4
ALT 8
Left Ctrl 100
Left ALT 200
Right Ctrl 400
Right ALT 800
VDHQueryKeyShift - Parameters
VDMHandle(DD) DOS session handle.
VDHQueryKeyShift - Purpose
Context Issues: This function can be called only in the interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHQueryKeyShift - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQueryProperty
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function returns the current value of the specified DOS Setting . * / include mvdm . inc EXTERN VDHQueryProperty : NEAR PropertyName DD ? ; Pointer to a property name PUSH PropertyName ; Push PropertyName CALL VDHQueryProperty ; Call the function
VDHQueryProperty - Format
/* This function returns the current value of the specified DOS Setting . * / include mvdm . inc EXTERN VDHQueryProperty : NEAR PropertyName DD ? ; Pointer to a property name PUSH PropertyName ; Push PropertyName CALL VDHQueryProperty ; Call the function
VDHQueryProperty Parameter - PropertyName
PropertyName(DD) Pointer to an ASCIIZ string containing the property name for which information is being sought. Maximum length is 40 characters, including the terminating NULL.
VDHQueryProperty Return Value - rc
Success The format of the return value for successful depends on the type of the property being queried:
VDMP_BOOL The return value is a BOOL (Boolean). A 0value represents FALSE and a nonzero value represents TRUE.
VDMP_INT The return value is a DD. It is guaranteed to be valid with respect to the bounding information specified in VDHRegisterVDD. Only the low half (DW) of the DD is significant. The high half is always 0.
VDMP_ENUM The return value is a pointer to a NULL-terminated string. The string is guaranteed to be one of those specified in VDHRegisterVDD.
VDMP_STRING The return value is a pointer to a NULL-terminated string. The string is guaranteed to be, at most, as long as the limit specified in VDHRegisterVDD.
VDMP_MLSTR The return value is a pointer to a NULL-terminated string. The string is guaranteed to be, at most, as long as the limit specified in VDHRegisterVDD.
Note:For property types VDMP_ENUM, VDMP_STRING, and VDMP_MLSTR, a pointer to the current value is returned to the virtual device driver, thereby avoiding a condition where an OS/2 process might be trying to change the same value. The virtual device driver calls VDHFreeMem to free the string after the virtual device driver is finished with it.
Failure If the function fails, it returns NULL for property types VDMP_ENUM , VDMP_STRING, and VDMP_MLSTR, if there is insufficient memory to create a copy of the string value. In this case, the virtual device driver uses the default property value. NULL is also returned if pszName is invalid or is not a registered virtual device driver name.
VDHQueryProperty - Parameters
PropertyName(DD) Pointer to an ASCIIZ string containing the property name for which information is being sought. Maximum length is 40 characters, including the terminating NULL.
VDHQueryProperty - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: All memory allocated by a virtual device driver for use by the terminating DOS session is freed by using VDHFreeMem.
Notes: A virtual device driver can assume that the property value is valid. The system validates all types, except VDMP_STRING and VDMP_MLSTR, by using the validation values passed on the call to VDHRegisterProperty. The string types are validated by calling the virtual device driver function registered through VDHRegisterProperty.
VDHQueryProperty - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQuerySel
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function returns the selector part of a 16 : 16 far pointer from a flat 0 : 32 address . The selector is in the Global Descriptor Table ( GDT ) . * / include mvdm . inc EXTERN VDHQuerySel : NEAR VirtAddress DD ? ; 0 : 32 virtual address PUSH VirtAddress ; Push VirtAddress CALL VDHQuerySel ; Call the function
VDHQuerySel - Format
/* This function returns the selector part of a 16 : 16 far pointer from a flat 0 : 32 address . The selector is in the Global Descriptor Table ( GDT ) . * / include mvdm . inc EXTERN VDHQuerySel : NEAR VirtAddress DD ? ; 0 : 32 virtual address PUSH VirtAddress ; Push VirtAddress CALL VDHQuerySel ; Call the function
VDHQuerySel Parameter - VirtAddress
VirtAddress(DD) A 0:32 virtual address.
VDHQuerySel Return Value - rc
Success If the function is successful, it returns a nonzero selector.
Failure If the specified linear address is not in a virtual device driver data object, a system halt occurs.
VDHQuerySel - Parameters
VirtAddress(DD) A 0:32 virtual address.
VDHQuerySel - Purpose
Context Issues: This function can be called in the initialization and task context:
- During initialization time; query is allowed only on initialization and global data.
*Global, instance, and stack data are allowed during task time (typically DOS session creation time), but initialization data is not.
DOS Session Terminations: Selectors for virtual device driver instance data are destroyed when the DOS session terminates. The virtual device driver must ensure that any physical device driver that was given this kind of selector is finished with it.
Notes: This function works only on 0:32 addresses in virtual device driver data objects and stacks. Each virtual device driver data object is limited to a maximum of 64KB in size so that the following formula can be used. A virtual device driver that needs more than 64KB of a particular class (INIT , global, or instance) must use multiple objects.
Notice that the selectors for virtual device driver data are created to map starting at a 64KB linear address boundary. As a result, VDHQuerySelneeds to be called only once. The returned selector is valid for any memory in the particular object that contains the passed address, because the DOS Session Manager does not allow a virtual device driver data object to span a 64KB linear address boundary.
For virtual device driver instance data, this function returns a different GDT selector for each DOS session, and it can be called only in the context of a DOS session.
VDHQuerySel - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQuerySem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function queries the state of an event or mutex semaphore . * / include mvdm . inc EXTERN VDHQuerySem : NEAR SemHandle DD ? ; Handle to an event or mutex semaphore SemStatePtr DD ? ; Pointer to a VDHSEMSTATE data area PUSH SemHandle ; Push SemHandle PUSH SemStatePtr ; Push SemStatePtr CALL VDHQuerySem ; Call the function
VDHQuerySem - Format
/* This function queries the state of an event or mutex semaphore . * / include mvdm . inc EXTERN VDHQuerySem : NEAR SemHandle DD ? ; Handle to an event or mutex semaphore SemStatePtr DD ? ; Pointer to a VDHSEMSTATE data area PUSH SemHandle ; Push SemHandle PUSH SemStatePtr ; Push SemStatePtr CALL VDHQuerySem ; Call the function
VDHQuerySem Parameter - SemHandle
SemHandle(DD) Semaphore handle.
VDHQuerySem Parameter - SemStatePtr
SemStatePtr(DD) A pointer to the data area to be filled with the state of the semaphore.
SemStatePtr points to a variable defined in VDMM.INC and structured as follows:
VDHSemState_s STRUC
vss_SemType DB ? ; VDH_EVENTSEM/VDH_MUTEXSEM
vss_fOwned DB ? ; 0 = Not Owned; 1 = Owned
vss_fWaiter DW ? ; 0 = No one waiting; 1 = Waiting
vss_cRequest DW ? ; Request count in mutex case
vss_tid DW ? ; TID of the owner, if owned
VDHSemState_s ENDS
VDHQuerySem Return Value -
None.
VDHQuerySem - Parameters
SemHandle(DD) Semaphore handle.
SemStatePtr(DD) A pointer to the data area to be filled with the state of the semaphore.
SemStatePtr points to a variable defined in VDMM.INC and structured as follows:
VDHSemState_s STRUC
vss_SemType DB ? ; VDH_EVENTSEM/VDH_MUTEXSEM
vss_fOwned DB ? ; 0 = Not Owned; 1 = Owned
vss_fWaiter DW ? ; 0 = No one waiting; 1 = Waiting
vss_cRequest DW ? ; Request count in mutex case
vss_tid DW ? ; TID of the owner, if owned
VDHSemState_s ENDS
VDHQuerySem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for state checking services.
Notes: The validity of SemStatePtr is not checked. The calling program must pass the address of a valid data area.
VDHQuerySem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQuerySysValue
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function queries a system value . * / include mvdm . inc EXTERN VDHQuerySysValue : NEAR VDMHandle DD ? ; Index of the system variable handle of the DOS session Index DD ? ; Index values PUSH VDMHandle ; Push VDMHandle PUSH Index ; Push Index CALL VDHQuerySysValue ; Call the function
VDHQuerySysValue - Format
/* This function queries a system value . * / include mvdm . inc EXTERN VDHQuerySysValue : NEAR VDMHandle DD ? ; Index of the system variable handle of the DOS session Index DD ? ; Index values PUSH VDMHandle ; Push VDMHandle PUSH Index ; Push Index CALL VDHQuerySysValue ; Call the function
VDHQuerySysValue Parameter - VDMHandle
VDMHandle(DD) Index of the system variable handle of the DOS session to query. A value of 0 (zero) indicates the current DOS session.
VDHQuerySysValue Parameter - Index
Index(DD) VDHQuerySysValueindex values (as defined in VDMM.INC) and descriptions:
Global Values Ordinal Type Units Range _____________ _______ ____ _____ _____ VDHGSV_DAY 0 DD days 1 < = x < = 31 VDHGSV_MONTH 1 DD months 1 < = x < = 12 VDHGSV_YEAR 2 DD years 1980 < = x < = MAXULONG VDHGSV_DAYOFWEEK 3 DD days 0 < = x < = 6 VDHGSV_HOUR 4 DD hours 0 < = x < = 24 VDHGSV_MINUTE 5 DD minutes 0 < = x < = 60 VDHGSV_SECOND 6 DD seconds 0 < = x < = 60 VDHGSV_HUNDREDTH 7 DD 1/100S 0 < = x < = 100 VDHGSV_SECONDS1970 8 DD seconds 0 < = x < = MAXULONG VDHGSV_TIMEZONE 9 DD minutes 0 < = x < = MAXULONG VDHGSV_MSECSBOOT 10 DD milliseconds 0 < = x < = MAXULONG VDHGSV_TIMERINTERVAL 11 DD milliseconds 0 < = x < = 1000 VDHGSV_DYNVARIATION 12 DD TRUE(nonzero)/FALSE(0) VDHGSV_MAXWAIT 13 DD seconds 0 < = x < = MAXULONG VDHGSV_MINTIMESLICE 14 DD milliseconds 0 < = x < = MAXULONG VDHGSV_MAXTIMESLICE 15 DD milliseconds 0 < = x < = MAXULONG
Global Values Ordinal Type Units Range
_____________ _______ ____ _____ _____
VDHGSV_YIELD 16 DD TRUE(nonzero)/FALSE(0)
VDHGSV_TCYIELD 17 DD TRUE(nonzero)/FALSE(0)
VDHGSV_VERMAJOR 18 DD 0 < = x < = MAXULONG
VDHGSV_VERMINOR 19 DD 0 < = x < = MAXULONG
VDHGSV_VERREVISION 20 DD 0 < = x < = 255
VDHGSV_MACHINETYPE 21 DD MACHINE_TYPE_
VDHGSV_BLACKHOLEADDR 22 DD bytes 0 < = x < = MAXULONG
VDHGSV_BLACKHOLESIZE 23 DD bytes 0 < = x < = MAXULONG
VDHGSV_FGNDSESSIONID 24 DD 0 < = x < = MAXSESSIONS
VDHGSV_ARPLADDR 29 DD
VDHGSV_MACHINEINFO 30 DD Pointer to System
Configuration table
VDHGSV_PPOSREGS 31 DD Pointer to POS Regs
structure
VDHGSV_PICMASK 32 DD Original PIC mask values
Local Values Ordinal Type Units Range
____________ _______ ____ _____ _____
VDHLSV_HVDM 4096 DD
VDHLSV_PID 4097 DD
VDHLSV_PCRF 4098 DD
VDHLSV_SESSIONID 4099 DD N < = x < MAXSESSIONS
VDHLSV_FOREGROUND 4100 DD TRUE(nonzero)/FALSE(0)
VDHLSV_RMSIZE 4101 DD KB 0 < x < = 640
VDHLSV_CODEPAGEID 4102 DD See DosGetCP
VDHLSV_PRIORITYCLASS 4103 DD See VDHSetPriority
VDHLSV_PRIORITYLEVEL 4104 DD See VDHSetPriority
VDHLSV_VPICBASE 4105 DD
VDHQuerySysValue Return Value - rc
Success If the function is successful, it returns the value of the system variable. If the value is 0 and VDHGetErrorreturns 0, then 0 is the correct value.
Failure If VDMHandleor Indexis invalid, a system halt occurs.
VDHQuerySysValue - Parameters
VDMHandle(DD) Index of the system variable handle of the DOS session to query. A value of 0 (zero) indicates the current DOS session.
Index(DD) VDHQuerySysValueindex values (as defined in VDMM.INC) and descriptions:
Global Values Ordinal Type Units Range _____________ _______ ____ _____ _____ VDHGSV_DAY 0 DD days 1 < = x < = 31 VDHGSV_MONTH 1 DD months 1 < = x < = 12 VDHGSV_YEAR 2 DD years 1980 < = x < = MAXULONG VDHGSV_DAYOFWEEK 3 DD days 0 < = x < = 6 VDHGSV_HOUR 4 DD hours 0 < = x < = 24 VDHGSV_MINUTE 5 DD minutes 0 < = x < = 60 VDHGSV_SECOND 6 DD seconds 0 < = x < = 60 VDHGSV_HUNDREDTH 7 DD 1/100S 0 < = x < = 100 VDHGSV_SECONDS1970 8 DD seconds 0 < = x < = MAXULONG VDHGSV_TIMEZONE 9 DD minutes 0 < = x < = MAXULONG VDHGSV_MSECSBOOT 10 DD milliseconds 0 < = x < = MAXULONG VDHGSV_TIMERINTERVAL 11 DD milliseconds 0 < = x < = 1000 VDHGSV_DYNVARIATION 12 DD TRUE(nonzero)/FALSE(0) VDHGSV_MAXWAIT 13 DD seconds 0 < = x < = MAXULONG VDHGSV_MINTIMESLICE 14 DD milliseconds 0 < = x < = MAXULONG VDHGSV_MAXTIMESLICE 15 DD milliseconds 0 < = x < = MAXULONG
Global Values Ordinal Type Units Range
_____________ _______ ____ _____ _____
VDHGSV_YIELD 16 DD TRUE(nonzero)/FALSE(0)
VDHGSV_TCYIELD 17 DD TRUE(nonzero)/FALSE(0)
VDHGSV_VERMAJOR 18 DD 0 < = x < = MAXULONG
VDHGSV_VERMINOR 19 DD 0 < = x < = MAXULONG
VDHGSV_VERREVISION 20 DD 0 < = x < = 255
VDHGSV_MACHINETYPE 21 DD MACHINE_TYPE_
VDHGSV_BLACKHOLEADDR 22 DD bytes 0 < = x < = MAXULONG
VDHGSV_BLACKHOLESIZE 23 DD bytes 0 < = x < = MAXULONG
VDHGSV_FGNDSESSIONID 24 DD 0 < = x < = MAXSESSIONS
VDHGSV_ARPLADDR 29 DD
VDHGSV_MACHINEINFO 30 DD Pointer to System
Configuration table
VDHGSV_PPOSREGS 31 DD Pointer to POS Regs
structure
VDHGSV_PICMASK 32 DD Original PIC mask values
Local Values Ordinal Type Units Range
____________ _______ ____ _____ _____
VDHLSV_HVDM 4096 DD
VDHLSV_PID 4097 DD
VDHLSV_PCRF 4098 DD
VDHLSV_SESSIONID 4099 DD N < = x < MAXSESSIONS
VDHLSV_FOREGROUND 4100 DD TRUE(nonzero)/FALSE(0)
VDHLSV_RMSIZE 4101 DD KB 0 < x < = 640
VDHLSV_CODEPAGEID 4102 DD See DosGetCP
VDHLSV_PRIORITYCLASS 4103 DD See VDHSetPriority
VDHLSV_PRIORITYLEVEL 4104 DD See VDHSetPriority
VDHLSV_VPICBASE 4105 DD
VDHQuerySysValue - Purpose
Context Issues: This function can be called in any context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Systems values are of two classes, global and per-DOS session. These classes are distinguished by the prefix of the index name. Variables with prefixes of VDHGSV_are global. Variables with a VDHLSV_prefix are per-DOS session.
VDHQuerySysValue - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHQueryVIRQ
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function returns information about the virtual mask , interrupt request flag , interrupt in - service flag , and pending virtual device driver Interrupt Return ( IRET ) handlers for the specified IRQ , device , or DOS session . * / include mvdm . inc EXTERN VDHQueryVIRQ : NEAR VDMHandle DD ? ; IRQ handle from DOS session handle IRQHandle DD ? ; IRQ handle from VDHOpenVIRQ PUSH VDMHandle ; Push VDMHandle PUSH IRQHandle ; Push IRQHandle CALL VDHQueryVIRQ ; Call the function
VDHQueryVIRQ - Format
/* This function returns information about the virtual mask , interrupt request flag , interrupt in - service flag , and pending virtual device driver Interrupt Return ( IRET ) handlers for the specified IRQ , device , or DOS session . * / include mvdm . inc EXTERN VDHQueryVIRQ : NEAR VDMHandle DD ? ; IRQ handle from DOS session handle IRQHandle DD ? ; IRQ handle from VDHOpenVIRQ PUSH VDMHandle ; Push VDMHandle PUSH IRQHandle ; Push IRQHandle CALL VDHQueryVIRQ ; Call the function
VDHQueryVIRQ Parameter - VDMHandle
VDMHandle(DD) IRQ handle from VDHOpenVIRQDOS session handle. A value of 0 (zero) indicates the current DOS session.
VDHQueryVIRQ Parameter - IRQHandle
IRQHandle(DD) IRQ handle from VDHOpenVIRQ.
VDHQueryVIRQ Return Value - rc
Success If the function is successful, it returns the IRQ status as a DD of flag bits:
VPICQ_REQUEST_PENDING Request is pending for the queried IRQ
VPICQ_IN_SERVICE Queried IRQ is in service
VPICQ_VIRT_MASK Mask is turned ON for the queried IRQ
VPICQ_STAT_IRET_PENDING IRET is pending for the queried IRQ.
Failure If VDMHandleor IRQHandleis invalid, a system halt occurs.
VDHQueryVIRQ - Parameters
VDMHandle(DD) IRQ handle from VDHOpenVIRQDOS session handle. A value of 0 (zero) indicates the current DOS session.
IRQHandle(DD) IRQ handle from VDHOpenVIRQ.
VDHQueryVIRQ - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHQueryVIRQ - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRaiseException
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is used to raise an exception , which is reflected to a DOS session as if the exception were caused by the hardware . * / include mvdm . inc EXTERN VDHRaiseException : NEAR Exception DD ? ; An exception number ErrorCode DD ? ; Error code for the exception ExtraCode DD ? ; Extra error code PUSH Exception ; Push Exception PUSH ErrorCode ; Push ErrorCode PUSH ExtraCode ; Push ExtraCode CALL VDHRaiseException ; Call the function
VDHRaiseException - Format
/* This function is used to raise an exception , which is reflected to a DOS session as if the exception were caused by the hardware . * / include mvdm . inc EXTERN VDHRaiseException : NEAR Exception DD ? ; An exception number ErrorCode DD ? ; Error code for the exception ExtraCode DD ? ; Extra error code PUSH Exception ; Push Exception PUSH ErrorCode ; Push ErrorCode PUSH ExtraCode ; Push ExtraCode CALL VDHRaiseException ; Call the function
VDHRaiseException Parameter - Exception
Exception(DD) An exception number that might be caused by the 80386 microprocessor.
VDHRaiseException Parameter - ErrorCode
ErrorCode(DD) Error code for the exception defined for the 80386 microprocessor.
VDHRaiseException Parameter - ExtraCode
ExtraCode(DD) Extra error code for DPMI 1.0 page faults.
VDHRaiseException Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero).
VDHRaiseException - Parameters
Exception(DD) An exception number that might be caused by the 80386 microprocessor.
ErrorCode(DD) Error code for the exception defined for the 80386 microprocessor.
ExtraCode(DD) Extra error code for DPMI 1.0 page faults.
VDHRaiseException - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHRaiseException - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRead
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function reads bytes from a file or device previously opened by VDHOpen . * / include mvdm . inc EXTERN VDHRead : NEAR FileHandle DW ? ; Handle to the file or device to read ReadBufferPtr DD ? ; Address of the buffer to store the bytes read NumBytes DD ? ; Number of bytes to read PUSH FileHandle ; Push FileHandle PUSH ReadBufferPtr ; Push ReadBufferPtr PUSH NumBytes ; Push NumBytes CALL VDHRead ; Call the function
VDHRead - Format
/* This function reads bytes from a file or device previously opened by VDHOpen . * / include mvdm . inc EXTERN VDHRead : NEAR FileHandle DW ? ; Handle to the file or device to read ReadBufferPtr DD ? ; Address of the buffer to store the bytes read NumBytes DD ? ; Number of bytes to read PUSH FileHandle ; Push FileHandle PUSH ReadBufferPtr ; Push ReadBufferPtr PUSH NumBytes ; Push NumBytes CALL VDHRead ; Call the function
VDHRead Parameter - FileHandle
FileHandle(DW) Handle to the file or device to read.
VDHRead Parameter - ReadBufferPtr
ReadBufferPtr(DD) Address of the buffer to store the bytes read.
VDHRead Parameter - NumBytes
NumBytes(DD) Number of bytes to read.
VDHRead Return Value - rc
Success If the function is successful, it returns a count of the number of bytes read; this can be equal to 0 (zero).
Failure If the function fails, it returns 0FFFFFFFFH. VDHGetErrorshould be called to determine the nature of the problem. If FileHandleis invalid or this function is called in any context except DOS session-task, a system halt occurs.
VDHRead - Parameters
FileHandle(DW) Handle to the file or device to read.
ReadBufferPtr(DD) Address of the buffer to store the bytes read.
NumBytes(DD) Number of bytes to read.
VDHRead - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHRead - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHReadUBuf
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is used to read from protected - mode address space as if the read were done at Ring 3 . This means any other faults are trapped . All faults are passed on to the DOS session application handler through VDHRaiseException . * / include mvdm . inc EXTERN VDHReadUBuf : NEAR DestBuffer DD ? ; Destination buffer for copy . ByteCount DD ? ; Count of bytes Selector DW ? ; Application selector OffsetPointer DD ? ; Address of the variable containing the offset Flag DD ? ; Checking controls flag PUSH DestBuffer ; Push DestBuffer PUSH ByteCount ; Push ByteCount PUSH Selector ; Push Selector PUSH OffsetPointer ; Push OffsetPointer PUSH Flag ; Push Flag CALL VDHReadUBuf ; Call the function
VDHReadUBuf - Format
/* This function is used to read from protected - mode address space as if the read were done at Ring 3 . This means any other faults are trapped . All faults are passed on to the DOS session application handler through VDHRaiseException . * / include mvdm . inc EXTERN VDHReadUBuf : NEAR DestBuffer DD ? ; Destination buffer for copy . ByteCount DD ? ; Count of bytes Selector DW ? ; Application selector OffsetPointer DD ? ; Address of the variable containing the offset Flag DD ? ; Checking controls flag PUSH DestBuffer ; Push DestBuffer PUSH ByteCount ; Push ByteCount PUSH Selector ; Push Selector PUSH OffsetPointer ; Push OffsetPointer PUSH Flag ; Push Flag CALL VDHReadUBuf ; Call the function
VDHReadUBuf Parameter - DestBuffer
DestBuffer(DD) Destination buffer for copy.
VDHReadUBuf Parameter - ByteCount
ByteCount(DD) Count of bytes.
VDHReadUBuf Parameter - Selector
Selector(DW) Application selector.
VDHReadUBuf Parameter - OffsetPointer
OffsetPointer(DD) Address of the variable containing the offset for the start of the read.
VDHReadUBuf Parameter - Flag
Flag(DD) Flag containing checking controls.
Possible values are:
VPM_PROT_READ Check for read.
VPM_PROT_WRITE Check for write.
VPM_FAULT_IF_SU_SET Fault, if supervisor pages.
VPM_FAULT_IF_RO Fault, if writing to read-only descriptor.
VPM_SEL_PRESENT Caller knows descriptor is present.
VPM_SEL_WRITEABLE Caller knows descriptor is writable.
VPM_SEL_IS_SS Selector is client's stack.
VPM_XCPTRET_ALT After exception, return to alternate mode. For example, if the client was in protected mode when the service was called, return in V86 mode after the exception is handled.
VDHReadUBuf Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 if a bad address reference is causing the fault. In this case, OffsetPointeris updated with the address of the fault. For selector faults, OffsetPointeris unchanged.
VDHReadUBuf - Parameters
DestBuffer(DD) Destination buffer for copy.
ByteCount(DD) Count of bytes.
Selector(DW) Application selector.
OffsetPointer(DD) Address of the variable containing the offset for the start of the read.
Flag(DD) Flag containing checking controls.
Possible values are:
VPM_PROT_READ Check for read.
VPM_PROT_WRITE Check for write.
VPM_FAULT_IF_SU_SET Fault, if supervisor pages.
VPM_FAULT_IF_RO Fault, if writing to read-only descriptor.
VPM_SEL_PRESENT Caller knows descriptor is present.
VPM_SEL_WRITEABLE Caller knows descriptor is writable.
VPM_SEL_IS_SS Selector is client's stack.
VPM_XCPTRET_ALT After exception, return to alternate mode. For example, if the client was in protected mode when the service was called, return in V86 mode after the exception is handled.
VDHReadUBuf - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: If the routine fails, the caller must clean up and exit so that the exception can be simulated to the user. Supervisor pages can be read without faults to avoid the overhead of checking.
VDHReadUBuf - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHReallocPages
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function expands or shrinks a memory object . * / include mvdm . inc EXTERN VDHReallocPages : NEAR ObjectAddress DD ? ; Address of the memory object to resize NumPages DD ? ; New size of the memory object ( in 4KB pages ) Reserved DD ? ; Must be zero PUSH ObjectAddress ; Push ObjectAddress PUSH NumPages ; Push NumPages PUSH Reserved ; Push Reserved CALL VDHReallocPages ; Call the function
VDHReallocPages - Format
/* This function expands or shrinks a memory object . * / include mvdm . inc EXTERN VDHReallocPages : NEAR ObjectAddress DD ? ; Address of the memory object to resize NumPages DD ? ; New size of the memory object ( in 4KB pages ) Reserved DD ? ; Must be zero PUSH ObjectAddress ; Push ObjectAddress PUSH NumPages ; Push NumPages PUSH Reserved ; Push Reserved CALL VDHReallocPages ; Call the function
VDHReallocPages Parameter - ObjectAddress
ObjectAddress(DD) Address of the memory object to reallocate or resize.
VDHReallocPages Parameter - NumPages
NumPages(DD) The new size of the memory object (in 4KB pages).
VDHReallocPages Parameter - Reserved
Reserved(DD) Must be set to zero.
VDHReallocPages Return Value - rc
Success If the function is successful, it returns that address of the reallocated memory block.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If the memory object at ObjectAddresswas not allocated by VDHAllocPagesor VDHReallocPages, or if the NumPagesor Reservedparameters are invalid, a system halt occurs.
VDHReallocPages - Parameters
ObjectAddress(DD) Address of the memory object to reallocate or resize.
NumPages(DD) The new size of the memory object (in 4KB pages).
Reserved(DD) Must be set to zero.
VDHReallocPages - Purpose
Context Issues: This function can be called in the initialization or task context.
DOS Session Terminations: Any allocations that are not in the terminating DOS session's private area must be released by using VDHFreePages.
Notes: When an allocation made with VDHAllocPagesis shrunk by VDHReallocPages, the linear range between the end of the allocation and the original end of the allocation remains available for object growth without movement. If the linear range encompassed by the new size was reserved ( with VDHReservePages), reallocation occurs without movement. Reallocation also succeeds without movement if the object was larger than the desired size since it last moved. Regardless of VDHReallocPagesactivity, all pages in the allocation retain the same properties, that is, fixed, system, and physical.
VDHReallocPages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRegisterAPI
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is used to register a virtual device driver ' s API handler that can be called by a DOS or DPMI application in the DOS session . A V86 - mode or protected - mode ( or both ) API handler is set for a particular virtual device driver . Each virtual device driver must register with a unique virtual device driver name . This service provides a mechanism for DOS applications to communicate directly with the virtual device driver . * / include mvdm . inc EXTERN VDHRegisterAPI : NEAR VDDName DD ? ; Pointer to the name of the virtual device driver pfnV86Hook DD ? ; V86 - mode hook routine address pfnVPMHook DD ? ; VPM - mode hook routine address PUSH VDDName ; Push VDDName PUSH pfnV86Hook ; Push pfnV86Hook PUSH pfnVPMHook ; Push pfnVPMHook CALL VDHRegisterAPI ; Call the function
VDHRegisterAPI - Format
/* This function is used to register a virtual device driver ' s API handler that can be called by a DOS or DPMI application in the DOS session . A V86 - mode or protected - mode ( or both ) API handler is set for a particular virtual device driver . Each virtual device driver must register with a unique virtual device driver name . This service provides a mechanism for DOS applications to communicate directly with the virtual device driver . * / include mvdm . inc EXTERN VDHRegisterAPI : NEAR VDDName DD ? ; Pointer to the name of the virtual device driver pfnV86Hook DD ? ; V86 - mode hook routine address pfnVPMHook DD ? ; VPM - mode hook routine address PUSH VDDName ; Push VDDName PUSH pfnV86Hook ; Push pfnV86Hook PUSH pfnVPMHook ; Push pfnVPMHook CALL VDHRegisterAPI ; Call the function
VDHRegisterAPI Parameter - VDDName
VDDName(DD) Pointer to the name of the virtual device driver. Maximum length is MAXLENXDD.
VDHRegisterAPI Parameter - pfnV86Hook
pfnV86Hook(DD) V86-mode hook routine address (NULL if no V86-mode handler is needed).
VDHRegisterAPI Parameter - pfnVPMHook
pfnVPMHook(DD) VPM-mode hook routine address (NULL if no VPM-mode handler is needed).
VDHRegisterAPI Return Value - rc
Success Returns TRUE
Failure Returns FALSE
VDHRegisterAPI - Parameters
VDDName(DD) Pointer to the name of the virtual device driver. Maximum length is MAXLENXDD.
pfnV86Hook(DD) V86-mode hook routine address (NULL if no V86-mode handler is needed).
pfnVPMHook(DD) VPM-mode hook routine address (NULL if no VPM-mode handler is needed).
VDHRegisterAPI - Purpose
Context Issues: This function can only be called in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function. The hook(s) are freed when the DOS session is terminated .
Notes:
Hook routine:
HookRoutine PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - p - reserved ; [ESP + 4] - pcrf - pointer ; to client register frame ; EXIT None ; CONTEXT DOS session-task
DOS or DPMI applications issue the following INT 2F calls to determine if they are running under OS/2, and then get the virtual device driver API entry point.
Get OS/2 version (DOS or DPMI applications can use this INT 2F call to get the OS/2 version):
ENTRY AX = 0x4010
EXIT If OS/2 is running:
AX = 0
BX = OS/2 version (example:BX = 1400 for 2.0)
If OS/2 is not present, AX is unchanged
Get virtual device driver API entry points. DOS or DPMI applications can use this INT 2F call to get the address to call the virtual device driver entry points. If the INT 2F is issued in V86 mode, an address that calls the V86 virtual device driver API handler is returned. If the INT 2F call is issued in protected-mode, an address that corresponds to the protected- mode API handler is returned.
ENTRY AX = 0x4011
DS:(E)SI = pointer to ASCIIZ name registered
with VDHRegisterAPI
EXIT If VDD API handler exists:
ES:DI = address to call to invoke handler
If handler is not registered:
ES:DI = NULL
The DOS or DPMI application can then issue a far call to the address returned to invoke the virtual device driver API handler.
VDHRegisterAPI - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRegisterDMAChannel
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is used by virtual device drivers to register with the virtual DMA device driver ( VDMA ) to get the ownership of a DMA channel . * / include mvdm . inc EXTERN VDHRegisterDMAChannel : NEAR DMAChannel DD ? ; DMA channel DMAHandlerFunc DD ? ; The virtual device driver ' s DMA - handling routine PUSH DMAChannel ; Push DMAChannel PUSH DMAHandlerFunc ; Push DMAHandlerFunc CALL VDHRegisterDMAChannel ; Call the function
VDHRegisterDMAChannel - Format
/* This function is used by virtual device drivers to register with the virtual DMA device driver ( VDMA ) to get the ownership of a DMA channel . * / include mvdm . inc EXTERN VDHRegisterDMAChannel : NEAR DMAChannel DD ? ; DMA channel DMAHandlerFunc DD ? ; The virtual device driver ' s DMA - handling routine PUSH DMAChannel ; Push DMAChannel PUSH DMAHandlerFunc ; Push DMAHandlerFunc CALL VDHRegisterDMAChannel ; Call the function
VDHRegisterDMAChannel Parameter - DMAChannel
DMAChannel(DD) DMA channel.
VDHRegisterDMAChannel Parameter - DMAHandlerFunc
DMAHandlerFunc(DD) The virtual device driver's DMA-handler function.
The interface for the DMA-handler routine is as follows:
DMAHandler PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - hvdm - DOS session requesting DMA ; [ESP + 4] - iEvent - VDD_DMA_MASKOFF (Start DMA, Event) ; VDD_DMA_MASK (Stop DMA, Event) ; EXIT SUCCESS - Returns nonzero in EAX ; If VDD_DMA_MASKOFF, ; the virtual DMA device driver will program the DMA ; If VDD_DMA_MASK, don't care ; FAILURE - Returns 0 (zero) in EAX
VDHRegisterDMAChannel Return Value - rc
Success If the function is successful, it returns 1.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem.
VDHRegisterDMAChannel - Parameters
DMAChannel(DD) DMA channel.
DMAHandlerFunc(DD) The virtual device driver's DMA-handler function.
The interface for the DMA-handler routine is as follows:
DMAHandler PROC NEAR ; PARAMETERS ; ENTRY [ESP + 8] - hvdm - DOS session requesting DMA ; [ESP + 4] - iEvent - VDD_DMA_MASKOFF (Start DMA, Event) ; VDD_DMA_MASK (Stop DMA, Event) ; EXIT SUCCESS - Returns nonzero in EAX ; If VDD_DMA_MASKOFF, ; the virtual DMA device driver will program the DMA ; If VDD_DMA_MASK, don't care ; FAILURE - Returns 0 (zero) in EAX
VDHRegisterDMAChannel - Purpose
Context Issues: This function can be called only in the initialization context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: In the case of VDD_DMA_MASKOFF, the virtual device driver gets the hardware ownership and unhooks all the ports. If hardware ownership is not available immediately, it blocks the DOS session. On VDD_DMA_MASK, the virtual device driver returns the ownership and hooks back the ports.
If the DOS application programs the hardware handled by a virtual device driver first, and then programs the DMA, this virtual device driver receives ownership of hardware, unhooks all ports on first port access, and arms a timer for a safe period. This is a preventive measure to protect the system from errant I/O to DMA ports. If the timer fires, the virtual device driver releases the hardware. In this case, the virtual device driver does nothing when the virtual DMA device driver later calls with VDD_DMA_MASKOFF .
It is the virtual device driver's responsibility (in DMAHandlerFunc) to handle the unavailability of hardware ownership. This means the virtual device driver must put up the pop-up and suspend (or terminate) the DOS session. The virtual device driver passes the interrupt notification to the virtual DMA device driver before simulating that interrupt to the DOS session, if it owns the hardware.
In between VDD_DMA_MASKOFF and VDD_DMA_MASK events, the virtual DMA device driver always returns the physical DMA state, if the application polls its status or transfer count. This is appropriate because the virtual device driver owns the device during this period. VDD_DMA_MASK event notification takes place before actually masking the register in DMA. VDD_DMA_MASKOFF takes place after masking off the DMA.
DMA Channel 4 is not supported.
VDHRegisterDMAChannel - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRegisterProperty
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function registers a virtual device driver property with the DOS Session Manager . * / include mvdm . inc EXTERN VDHRegisterProperty : NEAR PropertyName DD ? ; Property name pointer Reserved DD ? ; Must be set to 0 Reserved DD ? ; Must be set to 0 PropertyType DW ? ; Property type PropertyOrdinal DW ? ; Property ordinal PropertyFlag DD ? ; Property flag DefaultValue DD ? ; Default value of the property ValidationData DD ? ; Validation data ValidationFunc DD ? ; Pointer to a virtual device driver property function PUSH PropertyName ; Push PropertyName PUSH Reserved ; Push Reserved PUSH Reserved ; Push Reserved PUSH PropertyType ; Push PropertyType PUSH PropertyOrdinal ; Push PropertyOrdinal PUSH PropertyFlag ; Push PropertyFlag PUSH DefaultValue ; Push DefaultValue PUSH ValidationData ; Push ValidationData PUSH ValidationFunc ; Push ValidationFunc CALL VDHRegisterProperty ; Call the function
VDHRegisterProperty - Format
/* This function registers a virtual device driver property with the DOS Session Manager . * / include mvdm . inc EXTERN VDHRegisterProperty : NEAR PropertyName DD ? ; Property name pointer Reserved DD ? ; Must be set to 0 Reserved DD ? ; Must be set to 0 PropertyType DW ? ; Property type PropertyOrdinal DW ? ; Property ordinal PropertyFlag DD ? ; Property flag DefaultValue DD ? ; Default value of the property ValidationData DD ? ; Validation data ValidationFunc DD ? ; Pointer to a virtual device driver property function PUSH PropertyName ; Push PropertyName PUSH Reserved ; Push Reserved PUSH Reserved ; Push Reserved PUSH PropertyType ; Push PropertyType PUSH PropertyOrdinal ; Push PropertyOrdinal PUSH PropertyFlag ; Push PropertyFlag PUSH DefaultValue ; Push DefaultValue PUSH ValidationData ; Push ValidationData PUSH ValidationFunc ; Push ValidationFunc CALL VDHRegisterProperty ; Call the function
VDHRegisterProperty Parameter - PropertyName
PropertyName(DD) Pointer to an ASCIIZ string containing the property name. Maximum length is 40 characters.
VDHRegisterProperty Parameter - Reserved
Reserved(DD) Must be set to 0 (zero).
VDHRegisterProperty Parameter - Reserved
Reserved(DD) Must be set to 0 (zero).
VDHRegisterProperty Parameter - PropertyType
PropertyType(DW) Property type.
Values are:
VDMP_BOOL 0-Boolean
VDMP_INT 1-Integer. DD size, but only DW is valid
VDMP_ENUM 2-Enumeration
VDMP_STRING 3-ASCIIZ string
VDMP_MLSTR 4-Multi-line string, separated by linefeed (0AH)
VDHRegisterProperty Parameter - PropertyOrdinal
PropertyOrdinal(DW) Property ordinal.
Values are:
VDMP_ORD_OTHER 0-Custom virtual device driver property
VDMP_ORD_KERNEL 1-ASCIIZ path of DOS kernel
VDMP_ORD_SHELL 2-ASCIIZ path of DOS_SHELL
VDMP_ORD_RMSIZE 3-Integer size of DOS box (128KB-640KB)
VDMP_ORD_FCB 4-Integer total FCBs
VDMP_ORD_FCB2 5-Integer FCBs immune to close LRUing
VDMP_ORD_BREAK 6-Boolean Break flag
VDMP_ORD_DOSDD 7-Multi-line string DOS_DEVICE
VDMP_ORD_VMBOOT 8-ASCIIZ string virtual machine boot drives
VDMP_ORD_VERSION 10-Multi-line string fake version entries
VDMP_ORD_DOS_UMB 11-Boolean flag. DOS_UMB
VDMP_ORD_DOS_HIGH 12-Boolean flag. DOS_HIGH
VDMP_ORD_LASTDRIVE 13-ASCIIZ DOS_LASTDRIVE
VDMP_ORD_FILES 14-Integer total FILES
VDHRegisterProperty Parameter - PropertyFlag
PropertyFlag(DD) Property flag.
Possible value:
VDMP_CREATE Property can be specified only at DOS session creation. Any change to the property after DOS session creation is ignored.
VDHRegisterProperty Parameter - DefaultValue
DefaultValue(DD) Default value of the property.
The format of this field depends on the value of PropertyType:
VDMP_BOOL DefaultValue is interpreted as a BOOL (Boolean) value.
VDMP_INT DefaultValue is interpreted as a DD value. Only the low half is used (the high half is ignored) so this is more similar to a DW than a DD.
VDMP_ENUM DefaultValue is interpreted as a pointer to an ASCIIZ string.
VDMP_STRING DefaultValue is interpreted as a pointer to an ASCIIZ string.
VDMP_MLSTR DefaultValue is interpreted as a pointer to an ASCIIZ string.
VDHRegisterProperty Parameter - ValidationData
ValidationData(DD) Validation data.
The value of this field depends on the value of PropertyType.
VDMP_BOOL ValidationData is NULL. The user is expected to validate Booleans .
VDMP_INT ValidationData is a pointer to a VPBOUND structure:
VPBOUND Limits for VDMP_INT properties. Note that maximum >minimum must hold, the range of maximum to minimum must be a multiple of step, and step= 1 implies that all values between minimum and maximum are valid:
VPBOUND_s STRUC
min DW ? ; minimum allowed value
max DW ? ; maximum allowed value
step DW ? ; increment between values
VPBOUND_s ENDS
VDMP_ENUM ValidationData is a pointer to a set of ASCIIZ strings terminated by a zero byte, which is the allowed set of responses. The Shell uses this to construct a list or combination box for the user to pick from. Empty ("\ 0") strings are not allowed.
VDMP_STRING ValidationData is a DD that is the maximum allowed string length (including the NULL terminator).
VDMP_MLSTR ValidationData is a DD that is the maximum allowed string length (including the NULL terminator).
VDHRegisterProperty Parameter - ValidationFunc
ValidationFunc(DD) Function that validates and accepts changes to this property for a running DOS session. Ignored if VDMP_CREATE is specified in conjunction with VDMP_BOOL, VDMP_INT, or VDMP_ENUM.
The interface for the ValidationFunc is defined as follows:
VDHPROP_VALIDATE EQU 0x00000000L VDHPROP_SET EQU 0x00000001L ValidationFunc PROC NEAR ; PARAMETERS ; ENTRY [ESP + 16] - op (DD) ; [ESP + 12] - hvdm (DD) ; [ESP + 8] - cb (DD) ; [ESP + 4] - pch (DD)
PFNVDHRP is a pointer to a property function of the virtual device driver that performs property setting and validation. This routine is required for any property that does not specify VDMP_CREATE. Set operations can be requested any time after a DOS session is created. The validation operation can be requested at any time, even before a DOS session is created. Validation is requested only for VDMP_STRING and VDMP_MLSTR types because all other types can be validated using the information supplied by VDHRegisterProperty.
Parameter Data Type Description
_________ _________ ___________
op DD Operation to perform. See the following
parameter.
hvdm DD Handle of DOS session. Undefined if op =
VDHPROP_VALIDATE.
cb DD Count of bytes pointed by pch. See the
following parameter.
pch DD Pointer to the value set or validate. See the
following parameter.
op Operation to perform (enumeration):
VDHPROP_VALIDATE Validate property for any process. Only called for VDMP_ STRING and VDMP_MLSTR properties.
VDHPROP_SET Set an already validated property for specified hvdm. The return code is ignored.
cb Count of bytes pointed to by pch. Value depends upon PropertyType:
VDMPROP_BOOL Undefined
VDMPROP_INT Undefined
VDMPROP_ENUM Length of ASCIIZ string including NULL terminator
VDMPROP_STRING Length of ASCIIZ string including NULL terminator
VDMPROP_MLSTR Length of ASCIIZ string including NULL terminator
pch Value to set/validate. The format depends on the property type:
VDMPROP_BOOL pch is interpreted as a BOOL (Boolean). Value 0 is FALSE; a nonzero value is TRUE.
VDMPROP_INT pch is interpreted as a DD, and is guaranteed to meet the registered bounds.
VDMPROP_ENUM pch points to an ASCIIZ string, and is guaranteed to be one of the registered enumeration strings.
VDMPROP_STRING pch points to an ASCIIZ string, and is guaranteed to be equal to or less than the registered maximum string length.
VDMPROP_MLSTR pch points to an ASCIIZ string. Multiple lines are separated by a line feed (0x0A). It is guaranteed to be less than or equal to the registered maximum string length.
VDHRegisterProperty Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0. VDHGetErrorshould be called to determine the nature of the problem. A system halt occurs if:
- Any of the pointers (PropertyName, HelpFile, ValidationData, or ValidationFunc) are invalid
*PropertyFlag or PropertyType are invalid
*A VPBOUND structure has invalid contents
*The maximum string length for a VDMP_STRING is less than the length of the default string value
VDHRegisterProperty - Parameters
PropertyName(DD) Pointer to an ASCIIZ string containing the property name. Maximum length is 40 characters.
Reserved(DD) Must be set to 0 (zero).
Reserved(DD) Must be set to 0 (zero).
PropertyType(DW) Property type.
Values are:
VDMP_BOOL 0-Boolean
VDMP_INT 1-Integer. DD size, but only DW is valid
VDMP_ENUM 2-Enumeration
VDMP_STRING 3-ASCIIZ string
VDMP_MLSTR 4-Multi-line string, separated by linefeed (0AH)
PropertyOrdinal(DW) Property ordinal.
Values are:
VDMP_ORD_OTHER 0-Custom virtual device driver property
VDMP_ORD_KERNEL 1-ASCIIZ path of DOS kernel
VDMP_ORD_SHELL 2-ASCIIZ path of DOS_SHELL
VDMP_ORD_RMSIZE 3-Integer size of DOS box (128KB-640KB)
VDMP_ORD_FCB 4-Integer total FCBs
VDMP_ORD_FCB2 5-Integer FCBs immune to close LRUing
VDMP_ORD_BREAK 6-Boolean Break flag
VDMP_ORD_DOSDD 7-Multi-line string DOS_DEVICE
VDMP_ORD_VMBOOT 8-ASCIIZ string virtual machine boot drives
VDMP_ORD_VERSION 10-Multi-line string fake version entries
VDMP_ORD_DOS_UMB 11-Boolean flag. DOS_UMB
VDMP_ORD_DOS_HIGH 12-Boolean flag. DOS_HIGH
VDMP_ORD_LASTDRIVE 13-ASCIIZ DOS_LASTDRIVE
VDMP_ORD_FILES 14-Integer total FILES
PropertyFlag(DD) Property flag.
Possible value:
VDMP_CREATE Property can be specified only at DOS session creation. Any change to the property after DOS session creation is ignored.
DefaultValue(DD) Default value of the property.
The format of this field depends on the value of PropertyType:
VDMP_BOOL DefaultValue is interpreted as a BOOL (Boolean) value.
VDMP_INT DefaultValue is interpreted as a DD value. Only the low half is used (the high half is ignored) so this is more similar to a DW than a DD.
VDMP_ENUM DefaultValue is interpreted as a pointer to an ASCIIZ string.
VDMP_STRING DefaultValue is interpreted as a pointer to an ASCIIZ string.
VDMP_MLSTR DefaultValue is interpreted as a pointer to an ASCIIZ string.
ValidationData(DD) Validation data.
The value of this field depends on the value of PropertyType.
VDMP_BOOL ValidationData is NULL. The user is expected to validate Booleans .
VDMP_INT ValidationData is a pointer to a VPBOUND structure:
VPBOUND Limits for VDMP_INT properties. Note that maximum >minimum must hold, the range of maximum to minimum must be a multiple of step, and step= 1 implies that all values between minimum and maximum are valid:
VPBOUND_s STRUC
min DW ? ; minimum allowed value
max DW ? ; maximum allowed value
step DW ? ; increment between values
VPBOUND_s ENDS
VDMP_ENUM ValidationData is a pointer to a set of ASCIIZ strings terminated by a zero byte, which is the allowed set of responses. The Shell uses this to construct a list or combination box for the user to pick from. Empty ("\ 0") strings are not allowed.
VDMP_STRING ValidationData is a DD that is the maximum allowed string length (including the NULL terminator).
VDMP_MLSTR ValidationData is a DD that is the maximum allowed string length (including the NULL terminator).
ValidationFunc(DD) Function that validates and accepts changes to this property for a running DOS session. Ignored if VDMP_CREATE is specified in conjunction with VDMP_BOOL, VDMP_INT, or VDMP_ENUM.
The interface for the ValidationFunc is defined as follows:
VDHPROP_VALIDATE EQU 0x00000000L VDHPROP_SET EQU 0x00000001L ValidationFunc PROC NEAR ; PARAMETERS ; ENTRY [ESP + 16] - op (DD) ; [ESP + 12] - hvdm (DD) ; [ESP + 8] - cb (DD) ; [ESP + 4] - pch (DD)
PFNVDHRP is a pointer to a property function of the virtual device driver that performs property setting and validation. This routine is required for any property that does not specify VDMP_CREATE. Set operations can be requested any time after a DOS session is created. The validation operation can be requested at any time, even before a DOS session is created. Validation is requested only for VDMP_STRING and VDMP_ MLSTR types because all other types can be validated using the information supplied by VDHRegisterProperty.
Parameter Data Type Description
_________ _________ ___________
op DD Operation to perform. See the following
parameter.
hvdm DD Handle of DOS session. Undefined if op =
VDHPROP_VALIDATE.
cb DD Count of bytes pointed by pch. See the
following parameter.
pch DD Pointer to the value set or validate. See the
following parameter.
op Operation to perform (enumeration):
VDHPROP_VALIDATE Validate property for any process. Only called for VDMP_ STRING and VDMP_MLSTR properties.
VDHPROP_SET Set an already validated property for specified hvdm. The return code is ignored.
cb Count of bytes pointed to by pch. Value depends upon PropertyType:
VDMPROP_BOOL Undefined
VDMPROP_INT Undefined
VDMPROP_ENUM Length of ASCIIZ string including NULL terminator
VDMPROP_STRING Length of ASCIIZ string including NULL terminator
VDMPROP_MLSTR Length of ASCIIZ string including NULL terminator
pch Value to set/validate. The format depends on the property type:
VDMPROP_BOOL pch is interpreted as a BOOL (Boolean). Value 0 is FALSE; a nonzero value is TRUE.
VDMPROP_INT pch is interpreted as a DD, and is guaranteed to meet the registered bounds.
VDMPROP_ENUM pch points to an ASCIIZ string, and is guaranteed to be one of the registered enumeration strings.
VDMPROP_STRING pch points to an ASCIIZ string, and is guaranteed to be equal to or less than the registered maximum string length.
VDMPROP_MLSTR pch points to an ASCIIZ string. Multiple lines are separated by a line feed (0x0A). It is guaranteed to be less than or equal to the registered maximum string length.
VDHRegisterProperty - Purpose
Context Issues: This function can be called only in the initialization context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: VDHQueryProperty is used to obtain the value of a virtual device driver property for a particular DOS session.
VDHRegisterProperty - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRegisterVDD
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function registers virtual device driver entry points for use by other virtual device drivers ( through VDHOpenVDD and VDHRequestVDD ) , and by OS / 2 applications ( through DosOpenVDD and DosRequestVDD ) . * / include mvdm . inc EXTERN VDHRegisterVDD : NEAR VDDName DD ? ; Pointer to the name of the virtual device driver DosReqFcn DD ? ; Function for use by DosRequestVDD VDDReqFcn DD ? ; Function for use by VDHRequestVDD PUSH VDDName ; Push VDDName PUSH DosReqFcn ; Push DosReqFcn PUSH VDDReqFcn ; Push VDDReqFcn CALL VDHRegisterVDD ; Call the function
VDHRegisterVDD - Format
/* This function registers virtual device driver entry points for use by other virtual device drivers ( through VDHOpenVDD and VDHRequestVDD ) , and by OS / 2 applications ( through DosOpenVDD and DosRequestVDD ) . * / include mvdm . inc EXTERN VDHRegisterVDD : NEAR VDDName DD ? ; Pointer to the name of the virtual device driver DosReqFcn DD ? ; Function for use by DosRequestVDD VDDReqFcn DD ? ; Function for use by VDHRequestVDD PUSH VDDName ; Push VDDName PUSH DosReqFcn ; Push DosReqFcn PUSH VDDReqFcn ; Push VDDReqFcn CALL VDHRegisterVDD ; Call the function
VDHRegisterVDD Parameter - VDDName
VDDName(DD) Pointer to the name of the virtual device driver. Maximum length is MAXLENXDD.
VDHRegisterVDD Parameter - DosReqFcn
DosReqFcn(DD) Function used by DosRequestVDD. NULL, if none.
The interface for the DosReqFcnis:
DosReqFcn PROC NEAR ; PARAMETERS ; ENTRY [ESP + 24] - SGid (DW) - Screen Group ID ; [ESP + 20] - ulCmd (DD) - Command ; [ESP + 16] - cbIn (DD) - Input buffer size ; [ESP + 12] - pReqIn (DD) - Input packet ; [ESP + 8] - cbOut (DD) - Output buffer size ; [ESP + 4] - pReqOut (DD) - Output packet ; EXIT VDDREQ_PASS - DOS session manager calls the next routine ; registered under same name. ; Non-zero - Return failure (For APIs, 0 is success) ; 0 - Return the caller success
VDHRegisterVDD Parameter - VDDReqFcn
VDDReqFcn(DD) Function used by VDHRequestVDD. NULL, if none.
The interface for the VDDReqFcnis:
VDDReqFcn PROC NEAR ; PARAMETERS ; ENTRY [ESP + 16] - hvdm (DD) - DOS session handle ; [ESP + 12] - ulCmd (DD) - Command ; [ESP + 8] - pReqIn (DD) - Input packet ; [ESP + 4] - pReqOut (DD) - Output packe ; EXIT VDDREQ_PASS - DOS session manager calls the next routine ; registered under same name. ; Non-zero - Return success (For Virtual DevHlp services, 1 is success) ; 0 - Return the caller failure
VDHRegisterVDD Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0. If this function is called with invalid parameters or in an incorrect context, a system halt occurs.
VDHRegisterVDD - Parameters
VDDName(DD) Pointer to the name of the virtual device driver. Maximum length is MAXLENXDD.
DosReqFcn(DD) Function used by DosRequestVDD. NULL, if none.
The interface for the DosReqFcnis:
DosReqFcn PROC NEAR ; PARAMETERS ; ENTRY [ESP + 24] - SGid (DW) - Screen Group ID ; [ESP + 20] - ulCmd (DD) - Command ; [ESP + 16] - cbIn (DD) - Input buffer size ; [ESP + 12] - pReqIn (DD) - Input packet ; [ESP + 8] - cbOut (DD) - Output buffer size ; [ESP + 4] - pReqOut (DD) - Output packet ; EXIT VDDREQ_PASS - DOS session manager calls the next routine ; registered under same name. ; Non-zero - Return failure (For APIs, 0 is success) ; 0 - Return the caller success
VDDReqFcn(DD) Function used by VDHRequestVDD. NULL, if none.
The interface for the VDDReqFcnis:
VDDReqFcn PROC NEAR ; PARAMETERS ; ENTRY [ESP + 16] - hvdm (DD) - DOS session handle ; [ESP + 12] - ulCmd (DD) - Command ; [ESP + 8] - pReqIn (DD) - Input packet ; [ESP + 4] - pReqOut (DD) - Output packe ; EXIT VDDREQ_PASS - DOS session manager calls the next routine ; registered under same name. ; Non-zero - Return success (For Virtual DevHlp services, 1 is success) ; 0 - Return the caller failure
VDHRegisterVDD - Purpose
Context Issues: This function can be called only in the initialization context.
DOS Session Terminations: The virtual device driver must communicate with any virtual device driver or OS/2 clients, to ensure that the resources for the terminating DOS session are freed.
Notes: If a virtual device driver fails in its INIT routine after registering (through VDHRegisterVDD), the deregistration is done automatically at the time the virtual device driver is unloaded. Because two or more virtual device drivers can register the same name (VDDName), the DOS Session Manager calls each virtual device driver's routine in turn, until one of them returns a nonzero value.
Note that the order of the calling sequence is not consistent.
VDHRegisterVDD - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHReleaseCodePageFont
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function releases a code page font loaded with VDHGetCodePageFont . If system memory was allocated to hold the specified font , this call will free that memory . * / include mvdm . inc EXTERN VDHReleaseCodePageFont : NEAR FontPtr DD ? ; Pointer returned by VDHGetCodePageFont PUSH FontPtr ; Push FontPtr CALL VDHReleaseCodePageFont ; Call the function
VDHReleaseCodePageFont - Format
/* This function releases a code page font loaded with VDHGetCodePageFont . If system memory was allocated to hold the specified font , this call will free that memory . * / include mvdm . inc EXTERN VDHReleaseCodePageFont : NEAR FontPtr DD ? ; Pointer returned by VDHGetCodePageFont PUSH FontPtr ; Push FontPtr CALL VDHReleaseCodePageFont ; Call the function
VDHReleaseCodePageFont Parameter - FontPtr
FontPtr(DD) Pointer returned in FontAddressby VDHGetCodePageFont.
VDHReleaseCodePageFont Return Value - rc
Success If the function is successful, it returns nothing.
Failure If FontPtris not valid, a system halt occurs.
VDHReleaseCodePageFont - Parameters
FontPtr(DD) Pointer returned in FontAddressby VDHGetCodePageFont.
VDHReleaseCodePageFont - Purpose
Context Issues: This function can be called only in the DOS session task context.
DOS Session Terminations: The virtual device driver must call this function for any code page fonts loaded for this DOS session.
VDHReleaseCodePageFont - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHReleaseMutexSem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function releases the ownership of a mutex semaphore . If the request count becomes 0 ( zero ) , the highest priority semaphore is awakened . * / include mvdm . inc EXTERN VDHReleaseMutexSem : NEAR MutexSemHandle DD ? ; Handle of the semaphore to be released PUSH MutexSemHandle ; Push MutexSemHandle CALL VDHReleaseMutexSem ; Call the function
VDHReleaseMutexSem - Format
/* This function releases the ownership of a mutex semaphore . If the request count becomes 0 ( zero ) , the highest priority semaphore is awakened . * / include mvdm . inc EXTERN VDHReleaseMutexSem : NEAR MutexSemHandle DD ? ; Handle of the semaphore to be released PUSH MutexSemHandle ; Push MutexSemHandle CALL VDHReleaseMutexSem ; Call the function
VDHReleaseMutexSem Parameter - MutexSemHandle
MutexSemHandle(DD) Handle of the semaphore to be released.
VDHReleaseMutexSem Return Value - rc
Success If the function is successful, it returns nothing and the semaphore in MutexSemHandleis released.
Failure If the virtual device driver that called VDHReleaseMutexSemis not the owner of the semaphore to be released, or if MutexSemHandleinvalid, a system halt occurs.
VDHReleaseMutexSem - Parameters
MutexSemHandle(DD) Handle of the semaphore to be released.
VDHReleaseMutexSem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHReleaseMutexSem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRemoveFaultHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function removes the page fault handler hook for the specified DOS session page range . * / include mvdm . inc EXTERN VDHRemoveFaultHook : NEAR VDMHandle DD ? ; DOS session handle . 0 = current DOS session StartingAddress DD ? ; Starting linear address Pages DD ? ; Number of pages PageFaultHandlerFcnPtr DD ? ; Function supplied to VDHInstallFaultHook PUSH VDMHandle ; Push VDMHandle PUSH StartingAddress ; Push StartingAddress PUSH Pages ; Push Pages PUSH PageFaultHandlerFcnPtr ; Push PageFaultHandlerFcnPtr CALL VDHRemoveFaultHook ; Call the function
VDHRemoveFaultHook - Format
/* This function removes the page fault handler hook for the specified DOS session page range . * / include mvdm . inc EXTERN VDHRemoveFaultHook : NEAR VDMHandle DD ? ; DOS session handle . 0 = current DOS session StartingAddress DD ? ; Starting linear address Pages DD ? ; Number of pages PageFaultHandlerFcnPtr DD ? ; Function supplied to VDHInstallFaultHook PUSH VDMHandle ; Push VDMHandle PUSH StartingAddress ; Push StartingAddress PUSH Pages ; Push Pages PUSH PageFaultHandlerFcnPtr ; Push PageFaultHandlerFcnPtr CALL VDHRemoveFaultHook ; Call the function
VDHRemoveFaultHook Parameter - VDMHandle
VDMHandle(DD) DOS session handle. A value of 0 (zero) indicates the current DOS session.
VDHRemoveFaultHook Parameter - StartingAddress
StartingAddress(DD) Starting linear address.
VDHRemoveFaultHook Parameter - Pages
Pages(DD) Number of pages.
VDHRemoveFaultHook Parameter - PageFaultHandlerFcnPtr
PageFaultHandlerFcnPtr(DD) Function supplied to VDHInstallFaultHook. This is used to verify that the calling virtual device driver is the one that installed the fault hook.
VDHRemoveFaultHook Return Value - rc
Success If the function is successful, it returns nothing.
Failure If any of the input parameters are invalid, a system halt occurs.
VDHRemoveFaultHook - Parameters
VDMHandle(DD) DOS session handle. A value of 0 (zero) indicates the current DOS session.
StartingAddress(DD) Starting linear address.
Pages(DD) Number of pages.
PageFaultHandlerFcnPtr(DD) Function supplied to VDHInstallFaultHook. This is used to verify that the calling virtual device driver is the one that installed the fault hook.
VDHRemoveFaultHook - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: Any fault hooks for the terminating DOS session must be released.
VDHRemoveFaultHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRemoveIOHook
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function must be called with StartingPort and NumPorts to remove the I / O hooks for the specified I / O ports . Port hooks cannot be removed for a subset of the range of ports hooked by VDHInstallIOHook . * / include mvdm . inc EXTERN VDHRemoveIOHook : NEAR Reserved DD ? ; Reserved . Must be set to 0 ( zero ) . StartingPort DD ? ; Starting port number NumPorts DD ? ; Number of ports in the range IOPortHook DD ? ; Pointer to installed I / O hook entry PUSH Reserved ; Push Reserved PUSH StartingPort ; Push StartingPort PUSH NumPorts ; Push NumPorts PUSH IOPortHook ; Push IOPortHook CALL VDHRemoveIOHook ; Call the function
VDHRemoveIOHook - Format
/* This function must be called with StartingPort and NumPorts to remove the I / O hooks for the specified I / O ports . Port hooks cannot be removed for a subset of the range of ports hooked by VDHInstallIOHook . * / include mvdm . inc EXTERN VDHRemoveIOHook : NEAR Reserved DD ? ; Reserved . Must be set to 0 ( zero ) . StartingPort DD ? ; Starting port number NumPorts DD ? ; Number of ports in the range IOPortHook DD ? ; Pointer to installed I / O hook entry PUSH Reserved ; Push Reserved PUSH StartingPort ; Push StartingPort PUSH NumPorts ; Push NumPorts PUSH IOPortHook ; Push IOPortHook CALL VDHRemoveIOHook ; Call the function
VDHRemoveIOHook Parameter - Reserved
Reserved(DD) Reserved. Must be set to 0.
VDHRemoveIOHook Parameter - StartingPort
StartingPort(DD) Starting port number.
VDHRemoveIOHook Parameter - NumPorts
NumPorts(DD) Number of ports in the range.
VDHRemoveIOHook Parameter - IOPortHook
IOPortHook(DD) Pointer to installed I/O hook entry. This parameter is used to verify that the calling virtual device driver is the one that installed the I/O hook.
VDHRemoveIOHook Return Value - rc
Success If the function was successful, it returns nothing.
Failure If IOPortHookEntryis invalid or if StartingPortor NumPortsare out of range, a system halt occurs.
VDHRemoveIOHook - Parameters
Reserved(DD) Reserved. Must be set to 0.
StartingPort(DD) Starting port number.
NumPorts(DD) Number of ports in the range.
IOPortHook(DD) Pointer to installed I/O hook entry. This parameter is used to verify that the calling virtual device driver is the one that installed the I/O hook.
VDHRemoveIOHook - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function. I/O hooks are automatically removed during DOS session termination.
Notes: If the IOPortHookis in instance data, the address passed VDHInstallIOHookmust be the same address passed to VDHRemoveIOHookor VDHSetIOHookState.
VDHRemoveIOHook - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHReportPeek
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function reports DOS session polling activity . A counter of idle polling activity is incremented . If the count exceeds a threshold , the current DOS session is put to sleep for a period . * / include mvdm . inc EXTERN VDHReportPeek : NEAR PeekWeight DD ? ; Value to add to the idle counter PUSH PeekWeight ; Push PeekWeight CALL VDHReportPeek ; Call the function
VDHReportPeek - Format
/* This function reports DOS session polling activity . A counter of idle polling activity is incremented . If the count exceeds a threshold , the current DOS session is put to sleep for a period . * / include mvdm . inc EXTERN VDHReportPeek : NEAR PeekWeight DD ? ; Value to add to the idle counter PUSH PeekWeight ; Push PeekWeight CALL VDHReportPeek ; Call the function
VDHReportPeek Parameter - PeekWeight
PeekWeight(DD) Value to add to the idle counter.
VDHReportPeek Return Value - rc
Success If the function is successful, it returns nothing.
Failure If the current process is not a DOS session, a system halt occurs.
VDHReportPeek - Parameters
PeekWeight(DD) Value to add to the idle counter.
VDHReportPeek - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Any virtual device driver that can detect idle polling activity can call this service to report it. If the sum of peek weights exceeds 64KB in a single VDHGSV_MSECSBOOT clock tick (see VDHQuerySysValue), the DOS session is considered idle. It is the responsibility of the virtual device driver to calibrate its peek weight. This depends on machine speed and the Ring 0 trap overhead time, and therefore cannot be calibrated from measuring peek rate under DOS.
Note that testing the time before the count ensures that new tests begin at the first peek in a time slice. This allows use of a very short test period .
VDHReportPeek - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRequestMutexSem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function requests the ownership of a mutex semaphore . If the semaphore is owned and the caller is not the owner , the thread will block . If the caller is the owner , a request count is incremented . Request calls can be nested . A maximum of 65 , 535 ( 64KB ) requests are allowed for each semaphore at any one time . Exceeding this limit results in a system halt . * / include mvdm . inc EXTERN VDHRequestMutexSem : NEAR MutexSemHandle DD ? ; Mutex semaphore handle Timeout DD ? ; Timeout ( in milliseconds ) PUSH MutexSemHandle ; Push MutexSemHandle PUSH Timeout ; Push Timeout CALL VDHRequestMutexSem ; Call the function
VDHRequestMutexSem - Format
/* This function requests the ownership of a mutex semaphore . If the semaphore is owned and the caller is not the owner , the thread will block . If the caller is the owner , a request count is incremented . Request calls can be nested . A maximum of 65 , 535 ( 64KB ) requests are allowed for each semaphore at any one time . Exceeding this limit results in a system halt . * / include mvdm . inc EXTERN VDHRequestMutexSem : NEAR MutexSemHandle DD ? ; Mutex semaphore handle Timeout DD ? ; Timeout ( in milliseconds ) PUSH MutexSemHandle ; Push MutexSemHandle PUSH Timeout ; Push Timeout CALL VDHRequestMutexSem ; Call the function
VDHRequestMutexSem Parameter - MutexSemHandle
MutexSemHandle(DD) Mutex semaphore handle.
VDHRequestMutexSem Parameter - Timeout
Timeout(DD) Number of milliseconds to wait before timing out the semaphore .
VDHRequestMutexSem Return Value - rc
Success If the function is successful, it returns 1.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. An invalid semaphore will result in a system halt. A system halt also occurs if the request count crosses the 64KB limit.
VDHRequestMutexSem - Parameters
MutexSemHandle(DD) Mutex semaphore handle.
Timeout(DD) Number of milliseconds to wait before timing out the semaphore .
VDHRequestMutexSem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHRequestMutexSem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHRequestVDD
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function requests an operation of a virtual device driver . This service is also used for communication between two or more virtual device drivers where dynamic linkage between them is not appropriate . * / include mvdm . inc EXTERN VDHRequestVDD : NEAR VDDHandle DD ? ; Virtual device driver handle VDMHandle DD ? ; DOS session handle Command DD ? ; Command requested InputRequestPacket DD ? ; Pointer to the input packet OutputRequestPacket DD ? ; Pointer to the output packet PUSH VDDHandle ; Push VDDHandle PUSH VDMHandle ; Push VDMHandle PUSH Command ; Push Command PUSH InputRequestPacket ; Push InputRequestPacket PUSH OutputRequestPacket ; Push OutputRequestPacket CALL VDHRequestVDD ; Call the function
VDHRequestVDD - Format
/* This function requests an operation of a virtual device driver . This service is also used for communication between two or more virtual device drivers where dynamic linkage between them is not appropriate . * / include mvdm . inc EXTERN VDHRequestVDD : NEAR VDDHandle DD ? ; Virtual device driver handle VDMHandle DD ? ; DOS session handle Command DD ? ; Command requested InputRequestPacket DD ? ; Pointer to the input packet OutputRequestPacket DD ? ; Pointer to the output packet PUSH VDDHandle ; Push VDDHandle PUSH VDMHandle ; Push VDMHandle PUSH Command ; Push Command PUSH InputRequestPacket ; Push InputRequestPacket PUSH OutputRequestPacket ; Push OutputRequestPacket CALL VDHRequestVDD ; Call the function
VDHRequestVDD Parameter - VDDHandle
VDDHandle(DD) Handle to a virtual device driver.
VDHRequestVDD Parameter - VDMHandle
VDMHandle(DD) Handle to a DOS session.
VDHRequestVDD Parameter - Command
Command(DD) Command requested.
VDHRequestVDD Parameter - InputRequestPacket
InputRequestPacket(DD) Pointer to the input packet.
VDHRequestVDD Parameter - OutputRequestPacket
OutputRequestPacket(DD) Pointer to the output packet.
VDHRequestVDD Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If VDDHandleor VDMHandleis invalid, a system halt occurs.
VDHRequestVDD - Parameters
VDDHandle(DD) Handle to a virtual device driver.
VDMHandle(DD) Handle to a DOS session.
Command(DD) Command requested.
InputRequestPacket(DD) Pointer to the input packet.
OutputRequestPacket(DD) Pointer to the output packet.
VDHRequestVDD - Purpose
Context Issues: This function can be called in the task or the interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Every VDHRequestVDDprocedure registered under the virtual device driver name associated with the given handle is called until one returns a nonzero value. No assumption should be made about the order of the calling sequence.
The virtual device driver worker routine sets the error with VDHSetErrorwhen it returns 0 (zero). If the calling virtual device driver is registered under the same name as the virtual device driver handle, then its entry point is also called. Furthermore, the DOS Session Manager does not prevent any of the called virtual device drivers from issuing another VDHRequestVDD.
VDHRequestVDD - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHReservePages
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function reserves a range of linear addresses for later use with VDHMapPages or VDHAllocPages . A reserved area cannot contain a mixture of pages set by VDHMapPages and VDHAllocPages , but it can be used successively with either one . * / include mvdm . inc EXTERN VDHReservePages : NEAR StartingAddress DD ? ; Starting address of the linear memory to reserve NumPages DD ? ; Number of pages to reserve PUSH StartingAddress ; Push StartingAddress PUSH NumPages ; Push NumPages CALL VDHReservePages ; Call the function
VDHReservePages - Format
/* This function reserves a range of linear addresses for later use with VDHMapPages or VDHAllocPages . A reserved area cannot contain a mixture of pages set by VDHMapPages and VDHAllocPages , but it can be used successively with either one . * / include mvdm . inc EXTERN VDHReservePages : NEAR StartingAddress DD ? ; Starting address of the linear memory to reserve NumPages DD ? ; Number of pages to reserve PUSH StartingAddress ; Push StartingAddress PUSH NumPages ; Push NumPages CALL VDHReservePages ; Call the function
VDHReservePages Parameter - StartingAddress
StartingAddress(DD) Starting address of the linear memory to reserve. Must be page aligned and must be less than 110000H (1MB + 64KB).
VDHReservePages Parameter - NumPages
NumPages(DD) Number of pages to reserve.
VDHReservePages Return Value - rc
Success If the function is successful, it returns a nonzero value and the pages are reserved for later access.
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If StartingAddressor NumPagesis invalid, a system halt occurs.
VDHReservePages - Parameters
StartingAddress(DD) Starting address of the linear memory to reserve. Must be page aligned and must be less than 110000H (1MB + 64KB).
NumPages(DD) Number of pages to reserve.
VDHReservePages - Purpose
Context Issues: This function can be called in the initialization and DOS session-task contexts. In the initialization context, the reservation affects only the global linear memory map. In the DOS session-task context, reservations affect only the local linear memory map.
DOS Session Terminations: There are no DOS session termination implications for this function. The DOS Session Manager will clean up these reservations when the DOS session terminates.
VDHReservePages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHResetEventSem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function resets an event semaphore . * / include mvdm . inc EXTERN VDHResetEventSem : NEAR EventSemHandle DD ? ; Handle to the event semaphore to be reset PUSH EventSemHandle ; Push EventSemHandle CALL VDHResetEventSem ; Call the function
VDHResetEventSem - Format
/* This function resets an event semaphore . * / include mvdm . inc EXTERN VDHResetEventSem : NEAR EventSemHandle DD ? ; Handle to the event semaphore to be reset PUSH EventSemHandle ; Push EventSemHandle CALL VDHResetEventSem ; Call the function
VDHResetEventSem Parameter - EventSemHandle
EventSemHandle(DD) Handle to the event semaphore to be reset.
VDHResetEventSem Return Value - rc
Success If the function is successful, it returns nothing and the semaphore is reset.
Failure Resetting a semaphore that is invalid or is already reset causes a system halt to occur.
VDHResetEventSem - Parameters
EventSemHandle(DD) Handle to the event semaphore to be reset.
VDHResetEventSem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHResetEventSem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSeek
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function seeks to a specified position within a file previously opened by VDHOpen . * / include mvdm . inc EXTERN VDHSeek : NEAR FileHandle DW ? ; Handle to the file NewOffset DD ? ; Offset of the new file - pointer position MoveTypeFlag DD ? ; Type of move ( absolute , relative ) PUSH FileHandle ; Push FileHandle PUSH NewOffset ; Push NewOffset PUSH MoveTypeFlag ; Push MoveTypeFlag CALL VDHSeek ; Call the function
VDHSeek - Format
/* This function seeks to a specified position within a file previously opened by VDHOpen . * / include mvdm . inc EXTERN VDHSeek : NEAR FileHandle DW ? ; Handle to the file NewOffset DD ? ; Offset of the new file - pointer position MoveTypeFlag DD ? ; Type of move ( absolute , relative ) PUSH FileHandle ; Push FileHandle PUSH NewOffset ; Push NewOffset PUSH MoveTypeFlag ; Push MoveTypeFlag CALL VDHSeek ; Call the function
VDHSeek Parameter - FileHandle
FileHandle(DW) Handle to the file.
VDHSeek Parameter - NewOffset
NewOffset(DD) Offset to the new file-pointer position. Depending on the value of MoveTypeFlag, this can be the offset from the beginning of the file, the ending of the file, or the current position of the file-pointer.
VDHSeek Parameter - MoveTypeFlag
MoveTypeFlag(DD) Indicates what type of move is being done.
Possible values are:
VDHSK_ABSOLUTE Move file-pointer to a location relative to the beginning of the file
VDHSK_CURRENT_POSITION Move file-pointer relative to its current position
VDHSK_END_OF_FILE Move file-pointer to a location relative to the end of the file
VDHSeek Return Value - rc
Success If the function is successful, it returns the new current absolute position of the file-pointer within the file.
Failure If the function fails, it returns 0FFFFFFFFH. VDHGetErrorshould be called to determine the nature of the problem. If FileHandleis invalid, or if this function is not called in the DOS session-task context, a system halt occurs.
VDHSeek - Parameters
FileHandle(DW) Handle to the file.
NewOffset(DD) Offset to the new file-pointer position. Depending on the value of MoveTypeFlag, this can be the offset from the beginning of the file, the ending of the file, or the current position of the file-pointer.
MoveTypeFlag(DD) Indicates what type of move is being done.
Possible values are:
VDHSK_ABSOLUTE Move file-pointer to a location relative to the beginning of the file
VDHSK_CURRENT_POSITION Move file-pointer relative to its current position
VDHSK_END_OF_FILE Move file-pointer to a location relative to the end of the file
VDHSeek - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHSeek - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSendVEOI
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function sends a virtual End - Of - Interrupt ( EOI ) signal to the Virtual Programmable Interrupt Controller ( VPIC ) , and clears the in - service state of the IRQ for the calling device . The EOI handler for the IRQ is called , if one exists . * / include mvdm . inc EXTERN VDHSendVEOI : NEAR IRQHandle DD ? ; IRQ handle PUSH IRQHandle ; Push IRQHandle CALL VDHSendVEOI ; Call the function
VDHSendVEOI - Format
/* This function sends a virtual End - Of - Interrupt ( EOI ) signal to the Virtual Programmable Interrupt Controller ( VPIC ) , and clears the in - service state of the IRQ for the calling device . The EOI handler for the IRQ is called , if one exists . * / include mvdm . inc EXTERN VDHSendVEOI : NEAR IRQHandle DD ? ; IRQ handle PUSH IRQHandle ; Push IRQHandle CALL VDHSendVEOI ; Call the function
VDHSendVEOI Parameter - IRQHandle
IRQHandle(DD) IRQ handle.
VDHSendVEOI Return Value - rc
Success If the function was successful, it returns nothing.
Failure If IRQHandleis invalid, a system halt occurs.
VDHSendVEOI - Parameters
IRQHandle(DD) IRQ handle.
VDHSendVEOI - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHSendVEOI - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetDosDevice
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function links a DOS device driver into the chain of DOS device drivers for a DOS session . * / include mvdm . inc EXTERN VDHSetDosDevice : NEAR vpDosDD DD ? ; V86 FAR address of the DOS device driver header PUSH vpDosDD ; Push vpDosDD CALL VDHSetDosDevice ; Call the function
VDHSetDosDevice - Format
/* This function links a DOS device driver into the chain of DOS device drivers for a DOS session . * / include mvdm . inc EXTERN VDHSetDosDevice : NEAR vpDosDD DD ? ; V86 FAR address of the DOS device driver header PUSH vpDosDD ; Push vpDosDD CALL VDHSetDosDevice ; Call the function
VDHSetDosDevice Parameter - vpDosDD
vpDosDD(DD) V86 FAR address of the DOS device driver header. This header ( and any headers chained to it) are entered into the DOS device driver list for this DOS session.
VDHSetDosDevice Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero).
VDHSetDosDevice - Parameters
vpDosDD(DD) V86 FAR address of the DOS device driver header. This header ( and any headers chained to it) are entered into the DOS device driver list for this DOS session.
VDHSetDosDevice - Purpose
Context Issues: This function can be called only in the DOS session-task context (DOS session creation only).
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHSetDosDevice - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetError
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function sets the error code for return by VDHGetError . * / include mvdm . inc EXTERN VDHSetError : NEAR ErrorCode DD ? ; Error code to set PUSH ErrorCode ; Push ErrorCode CALL VDHSetError ; Call the function
VDHSetError - Format
/* This function sets the error code for return by VDHGetError . * / include mvdm . inc EXTERN VDHSetError : NEAR ErrorCode DD ? ; Error code to set PUSH ErrorCode ; Push ErrorCode CALL VDHSetError ; Call the function
VDHSetError Parameter - ErrorCode
ErrorCode(DD) Error code to set for VDHGetError.
VDHSetError Return Value - rc
None.
VDHSetError - Parameters
ErrorCode(DD) Error code to set for VDHGetError.
VDHSetError - Purpose
Context Issues: This function can be called in any context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This function is intended for use by any virtual device driver that offers dynamic link services to other virtual device drivers. Most of the base errors are defined in BSEERR.INC. Where possible, these definitions are used when returning errors.
VDHSetError - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetFlags
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function sets the DOS session ' s Flags Register to specified values . * / include mvdm . inc EXTERN VDHSetFlags : NEAR FlagValue DD ? ; DOS session flag value PUSH FlagValue ; Push FlagValue CALL VDHSetFlags ; Call the function
VDHSetFlags - Format
/* This function sets the DOS session ' s Flags Register to specified values . * / include mvdm . inc EXTERN VDHSetFlags : NEAR FlagValue DD ? ; DOS session flag value PUSH FlagValue ; Push FlagValue CALL VDHSetFlags ; Call the function
VDHSetFlags Parameter - FlagValue
FlagValue(DD) DOS session flag value that sets the flag register of the DOS session.
VDHSetFlags Return Value -
None.
VDHSetFlags - Parameters
FlagValue(DD) DOS session flag value that sets the flag register of the DOS session.
VDHSetFlags - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Virtual device drivers must use this interface instead of the client register frame pointer to change the DOS session's flags. Changes to the interrupt flag and the I/O Privilege Level (IOPL) field must be under the control of 8086 emulation so that VDHArmSTIHookworks correctly.
Nested Task (NT) and Resume Flag (RF) flags are cleared, the virtual 8086 Mode (VM) flag is set, and the IOPL field is left unchanged. This function does not take effect until the operating system returns to V86 mode.
VDHSetFlags - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetIOHookState
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is used to enable and disable I / O port trapping for a range of ports . * / include mvdm . inc EXTERN VDHSetIOHookState : NEAR Reserved DD ? ; Reserved . Must be set to 0 StartingPort DD ? ; Starting port number NumPorts DD ? ; Number of ports in the range IOPortHook DD ? ; Pointer used to install I / O hooks EnableFlag DD ? ; FLag for setting I / O hooks PUSH Reserved ; Push Reserved PUSH StartingPort ; Push StartingPort PUSH NumPorts ; Push NumPorts PUSH IOPortHook ; Push IOPortHook PUSH EnableFlag ; Push EnableFlag CALL VDHSetIOHookState ; Call the function
VDHSetIOHookState - Format
/* This function is used to enable and disable I / O port trapping for a range of ports . * / include mvdm . inc EXTERN VDHSetIOHookState : NEAR Reserved DD ? ; Reserved . Must be set to 0 StartingPort DD ? ; Starting port number NumPorts DD ? ; Number of ports in the range IOPortHook DD ? ; Pointer used to install I / O hooks EnableFlag DD ? ; FLag for setting I / O hooks PUSH Reserved ; Push Reserved PUSH StartingPort ; Push StartingPort PUSH NumPorts ; Push NumPorts PUSH IOPortHook ; Push IOPortHook PUSH EnableFlag ; Push EnableFlag CALL VDHSetIOHookState ; Call the function
VDHSetIOHookState Parameter - Reserved
Reserved(DD) Reserved. Must be set to 0 (zero).
VDHSetIOHookState Parameter - StartingPort
StartingPort(DD) Starting port number.
VDHSetIOHookState Parameter - NumPorts
NumPorts(DD) Number of ports in the range.
VDHSetIOHookState Parameter - IOPortHook
IOPortHook(DD) Pointer used to install I/O hooks. This is used to verify that the calling virtual device driver is the one that installed the I/O hooks.
VDHSetIOHookState Parameter - EnableFlag
EnableFlag(DD) Flag for setting I/O hooks.
TRUE (Non-zero). Enable I/O hooks.
FALSE (0). Disable I/O hooks.
VDHSetIOHookState Return Value - rc
Success If the function was successful, it returns nothing.
Failure If IOPortHookis invalid, or if StartingPortor NumPortsare out of range, or if StartingPortand NumPortsoverlap a range of ports previously marked as VDHIIH_ALWAYS_TRAPby VDHInstallIOHook, a system halt occurs.
VDHSetIOHookState - Parameters
Reserved(DD) Reserved. Must be set to 0 (zero).
StartingPort(DD) Starting port number.
NumPorts(DD) Number of ports in the range.
IOPortHook(DD) Pointer used to install I/O hooks. This is used to verify that the calling virtual device driver is the one that installed the I/O hooks.
EnableFlag(DD) Flag for setting I/O hooks.
TRUE (Non-zero). Enable I/O hooks.
FALSE (0). Disable I/O hooks.
VDHSetIOHookState - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: If the IOPortHookis in instance data, the address passed to VDHInstallIOHookmust be the same address passed to VDHRemoveIOHookor VDHSetIOHookState. When trapping is enabled, the I/O port hooks for the specified range get control when a DOS session does I/O to that range. When trapping is disabled, DOS session I/O goes directly to the physical hardware ports. None of the ports in the range can be marked as VDHIIH_ ALWAYS_TRAP by VDHInstallIOHook.
VDHSetIOHookState - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetPriority
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function adjusts a DOS session ' s scheduler priority class and level . Priority levels within each priority class range from 0 - 31 . * / include mvdm . inc EXTERN VDHSetPriority : NEAR VDMHandle DD ? ; Handle to the DOS session with the priority to change ActionClassFlag DD ? ; Dual purpose flag , Action and Class NewPriority DD ? ; Change from the DOS session ' s previous priority level PUSH VDMHandle ; Push VDMHandle PUSH ActionClassFlag ; Push ActionClassFlag PUSH NewPriority ; Push NewPriority CALL VDHSetPriority ; Call the function
VDHSetPriority - Format
/* This function adjusts a DOS session ' s scheduler priority class and level . Priority levels within each priority class range from 0 - 31 . * / include mvdm . inc EXTERN VDHSetPriority : NEAR VDMHandle DD ? ; Handle to the DOS session with the priority to change ActionClassFlag DD ? ; Dual purpose flag , Action and Class NewPriority DD ? ; Change from the DOS session ' s previous priority level PUSH VDMHandle ; Push VDMHandle PUSH ActionClassFlag ; Push ActionClassFlag PUSH NewPriority ; Push NewPriority CALL VDHSetPriority ; Call the function
VDHSetPriority Parameter - VDMHandle
VDMHandle(DD) Handle to the DOS session with the priority to change.
VDHSetPriority Parameter - ActionClassFlag
ActionClassFlag(DD) A dual-purpose flag.
The Classcomponent of ActionClassFlagindicates the class to which the DOS session should be changed. The Actioncomponent of the ActionClassFlagallows the virtual device driver to manage when the priority is changed, and when to start, end, or continue use of the class. See "Notes" under Purpose.
The value of the Classcomponent can be one of the following:
VDHSP_TIME_CRITICAL Highest priority
VDHSP_SERVER Highest priority
VDHSP_REGULAR Highest priority
VDHSP_IDLE Lowest priority
VDHSP_NO_CHANGE Do not change the DOS session's class
The value of the Actioncomponent can be one of the following:
VDHSP_START_USE Start use of a class
VDHSP_CONTINUE_USE Continue use of a class
VDHSP_END_USE End use of a class
VDHSP_DEFAULT_ACTION If no action is specified, the default class is changed
VDHSetPriority Parameter - NewPriority
NewPriority(DD) Change from the DOS session's previous priority level.
VDHSetPriority Return Value - rc
Success If the function is successful, it returns nothing.
Failure If VDMHandleor ActionClassFlagare invalid, a system halt occurs.
VDHSetPriority - Parameters
VDMHandle(DD) Handle to the DOS session with the priority to change.
ActionClassFlag(DD) A dual-purpose flag.
The Classcomponent of ActionClassFlagindicates the class to which the DOS session should be changed. The Actioncomponent of the ActionClassFlagallows the virtual device driver to manage when the priority is changed, and when to start, end, or continue use of the class. See "Notes" under Purpose.
The value of the Classcomponent can be one of the following:
VDHSP_TIME_CRITICAL Highest priority
VDHSP_SERVER Highest priority
VDHSP_REGULAR Highest priority
VDHSP_IDLE Lowest priority
VDHSP_NO_CHANGE Do not change the DOS session's class
The value of the Actioncomponent can be one of the following:
VDHSP_START_USE Start use of a class
VDHSP_CONTINUE_USE Continue use of a class
VDHSP_END_USE End use of a class
VDHSP_DEFAULT_ACTION If no action is specified, the default class is changed
NewPriority(DD) Change from the DOS session's previous priority level.
VDHSetPriority - Purpose
Context Issues: This function can be called in the task or interrupt contexts.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: A count of the current users is maintained at each class. The actual priority class in effect at any time is always the highest priority class with current declared users. When there are no declared users, the default class is used. Changes to a class other than the effective class are made to saved values. These changes take effect when the class becomes the effective class.
The caller must signal when it begins use of the class, when it makes changes within the class, and when it finishes with the class. The typical user would make one or more changes to priority at a particular class, and finish the series of changes at the class. The virtual device driver uses the VDHSP_START_USE and VDHSP_END_USE flags at the first and last calls within the class, and the VDHSP_CONTINUE_USE flag for changes in between.
The default class is normally VDHSP_REGULAR unless the class or NewPriorityis changed without declaring a user (that is, without specifying a start, continue, or end action flag). This allows a user interface to adjust the default priority of a DOS session.
VDHSetPriority - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetVIRR
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function sets the Virtual Interrupt Request Register ( VIRR ) in the Virtual Programmable Interrupt Controller ( VPIC ) of the specified DOS session for the IRQ specified . This causes an interrupt to be simulated to the DOS session . * / include mvdm . inc EXTERN VDHSetVIRR : NEAR VDMHandle DD ? ; DOS session handle IRQHandle DD ? ; Handle from VDHOpenVIRQ PUSH VDMHandle ; Push VDMHandle PUSH IRQHandle ; Push IRQHandle CALL VDHSetVIRR ; Call the function
VDHSetVIRR - Format
/* This function sets the Virtual Interrupt Request Register ( VIRR ) in the Virtual Programmable Interrupt Controller ( VPIC ) of the specified DOS session for the IRQ specified . This causes an interrupt to be simulated to the DOS session . * / include mvdm . inc EXTERN VDHSetVIRR : NEAR VDMHandle DD ? ; DOS session handle IRQHandle DD ? ; Handle from VDHOpenVIRQ PUSH VDMHandle ; Push VDMHandle PUSH IRQHandle ; Push IRQHandle CALL VDHSetVIRR ; Call the function
VDHSetVIRR Parameter - VDMHandle
VDMHandle(DD) DOS session handle. A value of 0 (zero) indicates the current DOS session.
VDHSetVIRR Parameter - IRQHandle
IRQHandle(DD) IRQ handle from VDHOpenVIRQ.
VDHSetVIRR Return Value - rc
Success If the function was successful, it returns nothing.
Failure If either of the parameters is invalid, a system halt occurs.
VDHSetVIRR - Parameters
VDMHandle(DD) DOS session handle. A value of 0 (zero) indicates the current DOS session.
IRQHandle(DD) IRQ handle from VDHOpenVIRQ.
VDHSetVIRR - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: If the interrupt request has not been cleared when the DOS session issues an End-Of-Interrupt (EOI), another interrupt will be simulated to the DOS session.
VDHSetVIRR - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetVPMExcept
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function sets the current value in the protected - mode exception table . * / include mvdm . inc EXTERN VDHSetVPMExcept : NEAR Vector DD ? ; Interrupt vector number HandlerAddress DQ ? ; Far32 handler address Flag DB ? ; Flag indicating exception handler PUSH Vector ; Push Vector PUSH HandlerAddress ; Push HandlerAddress PUSH Flag ; Push Flag CALL VDHSetVPMExcept ; Call the function
VDHSetVPMExcept - Format
/* This function sets the current value in the protected - mode exception table . * / include mvdm . inc EXTERN VDHSetVPMExcept : NEAR Vector DD ? ; Interrupt vector number HandlerAddress DQ ? ; Far32 handler address Flag DB ? ; Flag indicating exception handler PUSH Vector ; Push Vector PUSH HandlerAddress ; Push HandlerAddress PUSH Flag ; Push Flag CALL VDHSetVPMExcept ; Call the function
VDHSetVPMExcept Parameter - Vector
Vector(DD) Interrupt vector number.
VDHSetVPMExcept Parameter - HandlerAddress
HandlerAddress(DQ) Far32 handler address.
VDHSetVPMExcept Parameter - Flag
Flag(DB) Flag indicating the kind of exception handler being registered.
Possible value:
VPMXCPT32 A 32-bit handler is being registered.
VDHSetVPMExcept Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero).
VDHSetVPMExcept - Parameters
Vector(DD) Interrupt vector number.
HandlerAddress(DQ) Far32 handler address.
Flag(DB) Flag indicating the kind of exception handler being registered.
Possible value:
VPMXCPT32 A 32-bit handler is being registered.
VDHSetVPMExcept - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: There must be a DPMI client running in the DOS session before calling this function.
VDHSetVPMExcept - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSetVPMIntVector
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function sets the application Ring 3 handler in the protected - mode interrupt chain . This is used only for DOS Protect Mode Interface ( DPMI ) support . * / include mvdm . inc EXTERN VDHSetVPMIntVector : NEAR Vector DD ? ; Interrupt vector number HandlerAddress DQ ? ; Far32 handler address Flag DB ? ; Flag . PUSH Vector ; Push Vector PUSH HandlerAddress ; Push HandlerAddress PUSH Flag ; Push Flag CALL VDHSetVPMIntVector ; Call the function
VDHSetVPMIntVector - Format
/* This function sets the application Ring 3 handler in the protected - mode interrupt chain . This is used only for DOS Protect Mode Interface ( DPMI ) support . * / include mvdm . inc EXTERN VDHSetVPMIntVector : NEAR Vector DD ? ; Interrupt vector number HandlerAddress DQ ? ; Far32 handler address Flag DB ? ; Flag . PUSH Vector ; Push Vector PUSH HandlerAddress ; Push HandlerAddress PUSH Flag ; Push Flag CALL VDHSetVPMIntVector ; Call the function
VDHSetVPMIntVector Parameter - Vector
Vector(DD) Interrupt vector number.
VDHSetVPMIntVector Parameter - HandlerAddress
HandlerAddress(DQ) Far32 handler address.
VDHSetVPMIntVector Parameter - Flag
Flag(DB) Flag.
VDHSetVPMIntVector Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero).
VDHSetVPMIntVector - Parameters
Vector(DD) Interrupt vector number.
HandlerAddress(DQ) Far32 handler address.
Flag(DB) Flag.
VDHSetVPMIntVector - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: There must be a DPMI client running in the DOS session before calling this function.
VDHSetVPMIntVector - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSwitchToVPM
Select an item:
Format Parameters Return Codes Purpose Glossary
/*
This function switches the current DOS session into protected mode .
This assumes that the appropriate initializations have already been
performed .
* /
include mvdm . inc
EXTERN VDHSwitchToVPM : NEAR
DD ?
PUSH ; Push
CALL VDHSwitchToVPM ; Call the function
VDHSwitchToVPM - Format
/*
This function switches the current DOS session into protected mode .
This assumes that the appropriate initializations have already been
performed .
* /
include mvdm . inc
EXTERN VDHSwitchToVPM : NEAR
DD ?
PUSH ; Push
CALL VDHSwitchToVPM ; Call the function
VDHSwitchToVPM Parameter -
(DD) None.
VDHSwitchToVPM Return Value -
None.
VDHSwitchToVPM - Parameters
(DD) None.
VDHSwitchToVPM - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHSwitchToVPM - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHSwitchToV86
Select an item:
Format Parameters Return Codes Purpose Glossary
/*
This function switches the current DOS session to V86 mode .
* /
include mvdm . inc
EXTERN VDHSwitchToV86 : NEAR
DD ?
PUSH ; Push
CALL VDHSwitchToV86 ; Call the function
VDHSwitchToV86 - Format
/*
This function switches the current DOS session to V86 mode .
* /
include mvdm . inc
EXTERN VDHSwitchToV86 : NEAR
DD ?
PUSH ; Push
CALL VDHSwitchToV86 ; Call the function
VDHSwitchToV86 Parameter -
(DD) None.
VDHSwitchToV86 Return Value -
None.
VDHSwitchToV86 - Parameters
(DD) None.
VDHSwitchToV86 - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHSwitchToV86 - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHThawVDM
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function reverses the effect of VDHFreezeVDM . The specified DOS session is allowed to run when the freeze count becomes 0 ( zero ) . * / include mvdm . inc EXTERN VDHThawVDM : NEAR VDMHandle DD ? ; Handle to the DOS session to thaw PUSH VDMHandle ; Push VDMHandle CALL VDHThawVDM ; Call the function
VDHThawVDM - Format
/* This function reverses the effect of VDHFreezeVDM . The specified DOS session is allowed to run when the freeze count becomes 0 ( zero ) . * / include mvdm . inc EXTERN VDHThawVDM : NEAR VDMHandle DD ? ; Handle to the DOS session to thaw PUSH VDMHandle ; Push VDMHandle CALL VDHThawVDM ; Call the function
VDHThawVDM Parameter - VDMHandle
VDMHandle(DD) Handle to the DOS session to allow to execute (thaw).
VDHThawVDM Return Value - rc
Success If the function is successful, it returns nothing. The freeze count for the DOS session is decremented.
Failure If VDMHandleis an invalid handle, a system halt occurs.
VDHThawVDM - Parameters
VDMHandle(DD) Handle to the DOS session to allow to execute (thaw).
VDHThawVDM - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: This function does nothing if called on behalf of a DOS session that is not frozen. See VDHFreezeVDMfor a full discussion of freeze counting.
VDHThawVDM - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHUnlockMem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function reverses the effect of VDHLockMem , unlocking a previously locked area of memory . * / include mvdm . inc EXTERN VDHUnlockMem : NEAR LockHandle DD ? ; Lock handle from VDHLockMem PUSH LockHandle ; Push LockHandle CALL VDHUnlockMem ; Call the function
VDHUnlockMem - Format
/* This function reverses the effect of VDHLockMem , unlocking a previously locked area of memory . * / include mvdm . inc EXTERN VDHUnlockMem : NEAR LockHandle DD ? ; Lock handle from VDHLockMem PUSH LockHandle ; Push LockHandle CALL VDHUnlockMem ; Call the function
VDHUnlockMem Parameter - LockHandle
LockHandle(DD) Lock handle of a locked memory area. Originally obtained from VDHLockMem.
VDHUnlockMem Return Value - rc
Success If the function is successful, it returns nothing.
Failure An invalid lock handle causes a system halt to occur.
VDHUnlockMem - Parameters
LockHandle(DD) Lock handle of a locked memory area. Originally obtained from VDHLockMem.
VDHUnlockMem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Because lock handles are global, this function can be made in any task context.
VDHUnlockMem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHUnreservePages
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function unreserves pages that were previously reserved with VDHReservePages . The starting address and size must be identical to the previous corresponding call to VDHReservePages . Note that any mapping made earlier on this region is unmapped before calling this function . * / include mvdm . inc EXTERN VDHUnreservePages : NEAR StartingAddress DD ? ; Starting address of the region to unreserve NumPages DD ? ; Size of the region to unreserve , in pages PUSH StartingAddress ; Push StartingAddress PUSH NumPages ; Push NumPages CALL VDHUnreservePages ; Call the function
VDHUnreservePages - Format
/* This function unreserves pages that were previously reserved with VDHReservePages . The starting address and size must be identical to the previous corresponding call to VDHReservePages . Note that any mapping made earlier on this region is unmapped before calling this function . * / include mvdm . inc EXTERN VDHUnreservePages : NEAR StartingAddress DD ? ; Starting address of the region to unreserve NumPages DD ? ; Size of the region to unreserve , in pages PUSH StartingAddress ; Push StartingAddress PUSH NumPages ; Push NumPages CALL VDHUnreservePages ; Call the function
VDHUnreservePages Parameter - StartingAddress
StartingAddress(DD) Starting address of the region to unreserve. Must be less than 110000H (1MB+64KB) and must be page-aligned. In addition, StartingAddressmust match a previous VDHReservePagescall.
VDHUnreservePages Parameter - NumPages
NumPages(DD) Size, in pages, of the region to unreserve. Must match the corresponding parameter to a previous call to VDHReservePages.
VDHUnreservePages Return Value - rc
Success If the function is successful, it returns nothing.
Failure If StartingAddressor NumPagesis invalid, or if they were not used together in an earlier call to VDHReservePages, a system halt occurs.
VDHUnreservePages - Parameters
StartingAddress(DD) Starting address of the region to unreserve. Must be less than 110000H (1MB+64KB) and must be page-aligned. In addition, StartingAddressmust match a previous VDHReservePagescall.
NumPages(DD) Size, in pages, of the region to unreserve. Must match the corresponding parameter to a previous call to VDHReservePages.
VDHUnreservePages - Purpose
Context Issues: This function can be called in the initialization or DOS session-task context (DOS session creation). In the initialization context, memory can be unreserved only from the global linear memory map. In the DOS session-task context, memory can be unreserved only from the local linear memory map.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: StartingAddressmust be less than 110000H(1MB+64KB) and must be page -aligned. Additionally, StartingAddressmust match a previous call to VDHReservePages. NumPagesmust match the corresponding parameter to a previous call to VDHReservePages.
VDHUnreservePages - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHWaitEventSem
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function is used to wait on an event semaphore . If the semaphore is posted , it will return immediately . * / include mvdm . inc EXTERN VDHWaitEventSem : NEAR EventSemHandle DD ? ; Event semaphore handle Timeout DD ? ; Timeout ( in milliseconds ) PUSH EventSemHandle ; Push EventSemHandle PUSH Timeout ; Push Timeout CALL VDHWaitEventSem ; Call the function
VDHWaitEventSem - Format
/* This function is used to wait on an event semaphore . If the semaphore is posted , it will return immediately . * / include mvdm . inc EXTERN VDHWaitEventSem : NEAR EventSemHandle DD ? ; Event semaphore handle Timeout DD ? ; Timeout ( in milliseconds ) PUSH EventSemHandle ; Push EventSemHandle PUSH Timeout ; Push Timeout CALL VDHWaitEventSem ; Call the function
VDHWaitEventSem Parameter - EventSemHandle
EventSemHandle(DD) Event semaphore handle.
VDHWaitEventSem Parameter - Timeout
Timeout(DD) Number of milliseconds to wait before timing out.
VDHWaitEventSem Return Value - rc
Success If the function is successful, it returns 1 (one).
Failure If the function fails, it returns 0 (zero). VDHGetErrorshould be called to determine the nature of the problem. If EventSemHandleis invalid , a system halt occurs.
VDHWaitEventSem - Parameters
EventSemHandle(DD) Event semaphore handle.
Timeout(DD) Number of milliseconds to wait before timing out.
VDHWaitEventSem - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function. If Timeoutis 0 (zero), the caller will not block; however, ERROR_TIMEOUT is returned. If Timeoutis -1, the caller is blocked until the semaphore is posted. Otherwise, the caller blocks for the time specified (in milliseconds) in Timeout.
VDHWaitEventSem - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHWaitVIRRs
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function waits until any virtual interrupt is simulated to the current DOS session . * / include mvdm . inc EXTERN VDHWaitVIRRs : NEAR PostInFcnHook DD ? ; Hook handle PUSH PostInFcnHook ; Push PostInFcnHook CALL VDHWaitVIRRs ; Call the function
VDHWaitVIRRs - Format
/* This function waits until any virtual interrupt is simulated to the current DOS session . * / include mvdm . inc EXTERN VDHWaitVIRRs : NEAR PostInFcnHook DD ? ; Hook handle PUSH PostInFcnHook ; Push PostInFcnHook CALL VDHWaitVIRRs ; Call the function
VDHWaitVIRRs Parameter - PostInFcnHook
PostInFcnHook(DD) Hook handle of a routine that is to be called after interrupts are simulated.
VDHWaitVIRRs Return Value - rc
Success The function returns a nonzero value, if it woke up because of a simulated interrupt. If it woke up because of a VDHWakeVIRRscall, the function returns 0 (zero).
Failure If the function fails, it returns nothing.
VDHWaitVIRRs - Parameters
PostInFcnHook(DD) Hook handle of a routine that is to be called after interrupts are simulated.
VDHWaitVIRRs - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: The hook handle must be allocated as a VDH_WAITVIRRS_HOOK type. This function is intended for virtual device drivers that need to simulate a spin loop without stopping virtual interrupt simulation. This allows the virtual device driver to be compatible with DOS but avoid wasting CPU time in a spin loop.
The DOS session's interrupts must be enabled, using VDHSetFlags, before this service is used.
Generally, the virtual device driver will be in a loop when calling this function. When it returns a nonzero value, the virtual device driver returns to V86 mode so that the interrupt can be simulated. The hook function passed to this service is executed after all interrupts are simulated. When this function returns 0 (zero), it is because some other portion of the virtual device driver (likely in response to a physical hardware interrupt) has determined that the DOS session no longer needs to spin. The virtual device driver exits the loop at this point.
The virtual keyboard device driver behaves in this manner in order to emulate the ROM BIOS Read Keyboard function (INT 16H, AH=00) without using excessive CPU time, by allowing the ROM BIOS to spin out in V86 mode, or stopping simulated interrupts by performing a VDHWaitEventSem.
VDHWaitVIRRs - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHWakeIdle
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function notes that the DOS session is busy ( doing useful work ) . If the DOS session is currently sleeping or running at a lower priority because of the polling activities , the DOS session is awakened , its priority is restored , and it is no longer considered idle . * / include mvdm . inc EXTERN VDHWakeIdle : NEAR VDMHandle DD ? ; Handle to the DOS session to wake up PUSH VDMHandle ; Push VDMHandle CALL VDHWakeIdle ; Call the function
VDHWakeIdle - Format
/* This function notes that the DOS session is busy ( doing useful work ) . If the DOS session is currently sleeping or running at a lower priority because of the polling activities , the DOS session is awakened , its priority is restored , and it is no longer considered idle . * / include mvdm . inc EXTERN VDHWakeIdle : NEAR VDMHandle DD ? ; Handle to the DOS session to wake up PUSH VDMHandle ; Push VDMHandle CALL VDHWakeIdle ; Call the function
VDHWakeIdle Parameter - VDMHandle
VDMHandle(DD) Handle to the DOS session to be awakened.
VDHWakeIdle Return Value -
None.
VDHWakeIdle - Parameters
VDMHandle(DD) Handle to the DOS session to be awakened.
VDHWakeIdle - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHWakeIdle - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHWakeVIRRs
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function wakes up a DOS session that is waiting with the VDHWaitVIRRs service . See VDHWaitVIRRs for a full description of the use of this function . * / include mvdm . inc EXTERN VDHWakeVIRRs : NEAR VDMHandle DD ? ; Handle of the DOS session to wake up PUSH VDMHandle ; Push VDMHandle CALL VDHWakeVIRRs ; Call the function
VDHWakeVIRRs - Format
/* This function wakes up a DOS session that is waiting with the VDHWaitVIRRs service . See VDHWaitVIRRs for a full description of the use of this function . * / include mvdm . inc EXTERN VDHWakeVIRRs : NEAR VDMHandle DD ? ; Handle of the DOS session to wake up PUSH VDMHandle ; Push VDMHandle CALL VDHWakeVIRRs ; Call the function
VDHWakeVIRRs Parameter - VDMHandle
VDMHandle(DD) Handle of the DOS session to be awakened.
VDHWakeVIRRs Return Value - rc
Success If the function was successful, it returns nothing.
Failure If VDMHandleis invalid, a system halt occurs.
VDHWakeVIRRs - Parameters
VDMHandle(DD) Handle of the DOS session to be awakened.
VDHWakeVIRRs - Purpose
Context Issues: This function can be called in the task or interrupt context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: Use with caution because it wakes up every virtual device driver that is waiting on a VDHWaitVIRRs.
VDHWakeVIRRs - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHWrite
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function writes bytes to a file or device previously opened by VDHOpen . * / include mvdm . inc EXTERN VDHWrite : NEAR FileHandle DW ? ; Handle to the file or device to write to WriteBufferPtr DD ? ; Pointer to the buffer to write NumBytes DD ? ; Number of bytes to write PUSH FileHandle ; Push FileHandle PUSH WriteBufferPtr ; Push WriteBufferPtr PUSH NumBytes ; Push NumBytes CALL VDHWrite ; Call the function
VDHWrite - Format
/* This function writes bytes to a file or device previously opened by VDHOpen . * / include mvdm . inc EXTERN VDHWrite : NEAR FileHandle DW ? ; Handle to the file or device to write to WriteBufferPtr DD ? ; Pointer to the buffer to write NumBytes DD ? ; Number of bytes to write PUSH FileHandle ; Push FileHandle PUSH WriteBufferPtr ; Push WriteBufferPtr PUSH NumBytes ; Push NumBytes CALL VDHWrite ; Call the function
VDHWrite Parameter - FileHandle
FileHandle(DW) Handle to the file or device to write to.
VDHWrite Parameter - WriteBufferPtr
WriteBufferPtr(DD) Pointer to the buffer to write.
VDHWrite Parameter - NumBytes
NumBytes(DD) Number of bytes to write.
VDHWrite Return Value - rc
Success If the function is successful, it returns a count of the bytes written. This can be equal to 0 (zero).
Failure If the function fails, it returns 0FFFFFFFFH. VDHGetErrorshould be called to determine the nature of the problem. If FileHandleis invalid, or this function is called in any context except DOS session-task, a system halt occurs.
VDHWrite - Parameters
FileHandle(DW) Handle to the file or device to write to.
WriteBufferPtr(DD) Pointer to the buffer to write.
NumBytes(DD) Number of bytes to write.
VDHWrite - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
VDHWrite - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHWriteUBuf
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function writes to protected - mode address space as if access were done at Ring 3 . This means checking for supervisor and read - only faults , and trapping any other faults . All faults are passed on to the DOS session application handler through VDHRaiseException . * / include mvdm . inc EXTERN VDHWriteUBuf : NEAR SourceBuffer DD ? ; Source buffer from which to copy ByteCount DD ? ; Count of bytes Selector DW ? ; Application selector OffsetPointer DD ? ; Address of the variable containing the offset Flag DD ? ; Flag for checking controls PUSH SourceBuffer ; Push SourceBuffer PUSH ByteCount ; Push ByteCount PUSH Selector ; Push Selector PUSH OffsetPointer ; Push OffsetPointer PUSH Flag ; Push Flag CALL VDHWriteUBuf ; Call the function
VDHWriteUBuf - Format
/* This function writes to protected - mode address space as if access were done at Ring 3 . This means checking for supervisor and read - only faults , and trapping any other faults . All faults are passed on to the DOS session application handler through VDHRaiseException . * / include mvdm . inc EXTERN VDHWriteUBuf : NEAR SourceBuffer DD ? ; Source buffer from which to copy ByteCount DD ? ; Count of bytes Selector DW ? ; Application selector OffsetPointer DD ? ; Address of the variable containing the offset Flag DD ? ; Flag for checking controls PUSH SourceBuffer ; Push SourceBuffer PUSH ByteCount ; Push ByteCount PUSH Selector ; Push Selector PUSH OffsetPointer ; Push OffsetPointer PUSH Flag ; Push Flag CALL VDHWriteUBuf ; Call the function
VDHWriteUBuf Parameter - SourceBuffer
SourceBuffer(DD) Source buffer from which to copy.
VDHWriteUBuf Parameter - ByteCount
ByteCount(DD) Count of bytes.
VDHWriteUBuf Parameter - Selector
Selector(DW) Application selector.
VDHWriteUBuf Parameter - OffsetPointer
OffsetPointer(DD) Address of the variable containing the offset for the start of the write.
VDHWriteUBuf Parameter - Flag
Flag(DD) Checking control.
Possible values are:
VPM_PROT_READ Check for read.
VPM_PROT_WRITE Check for write.
VPM_FAULT_IF_SU_SET Fault, if supervisor pages.
VPM_FAULT_IF_RO Fault, if writing to read-only descriptor.
VPM_SEL_PRESENT Caller knows descriptor is present.
VPM_SEL_WRITEABLE Caller knows descriptor is writable.
VPM_SEL_IS_SS Selector is client's stack.
VPM_XCPTRET_ALT After exception, return to alternate mode. For example, if the client was in protected mode when the service was called, return in V86 mode after the exception is handled.
VDHWriteUBuf Return Value - rc
Success If the function is successful, it returns a nonzero value.
Failure If the function fails, it returns 0 (zero) if there is a bad address reference, which causes a fault. In such a case, OffsetPointeris updated with the address of the fault. For Selector Faults, OffsetPointerremains unchanged.
VDHWriteUBuf - Parameters
SourceBuffer(DD) Source buffer from which to copy.
ByteCount(DD) Count of bytes.
Selector(DW) Application selector.
OffsetPointer(DD) Address of the variable containing the offset for the start of the write.
Flag(DD) Checking control.
Possible values are:
VPM_PROT_READ Check for read.
VPM_PROT_WRITE Check for write.
VPM_FAULT_IF_SU_SET Fault, if supervisor pages.
VPM_FAULT_IF_RO Fault, if writing to read-only descriptor.
VPM_SEL_PRESENT Caller knows descriptor is present.
VPM_SEL_WRITEABLE Caller knows descriptor is writable.
VPM_SEL_IS_SS Selector is client's stack.
VPM_XCPTRET_ALT After exception, return to alternate mode. For example, if the client was in protected mode when the service was called, return in V86 mode after the exception is handled.
VDHWriteUBuf - Purpose
Context Issues: This function can be called only in the DOS session-task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: When the routine fails, the caller must clean up and exit so that the exception can be simulated to the user.
VDHWriteUBuf - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
VDHYield
Select an item:
Format Parameters Return Codes Purpose Glossary
/* This function yields the processor to any other thread of equal or higher priority . * / include mvdm . inc EXTERN VDHYield : NEAR OptionFlag DD ? ; Yield options PUSH OptionFlag ; Push OptionFlag CALL VDHYield ; Call the function
VDHYield - Format
/* This function yields the processor to any other thread of equal or higher priority . * / include mvdm . inc EXTERN VDHYield : NEAR OptionFlag DD ? ; Yield options PUSH OptionFlag ; Push OptionFlag CALL VDHYield ; Call the function
VDHYield Parameter - OptionFlag
OptionFlag(DD) Yield options.
Possible value:
VDH_YIELD_TIME_CRITICAL Yield only to time-critical threads.
VDHYield Return Value -
None.
VDHYield - Parameters
OptionFlag(DD) Yield options.
Possible value:
VDH_YIELD_TIME_CRITICAL Yield only to time-critical threads.
VDHYield - Purpose
Context Issues: This function can be called only in the task context.
DOS Session Terminations: There are no DOS session termination implications for this function.
Notes: If OptionFlagis VDH_YIELD_TIME_CRITICAL, and no time-critical thread is able to run, the caller keeps the CPU.
VDHYield - Topics
Select an item:
Format Parameters Return Codes Purpose Glossary
Notices
OS/2 Developer Connection Device Driver Kit, Version 4 Edition (June 1996)
The following paragraph does not apply to the United Kingdom or any country where such provisions are inconsistent with local law:INTERNATIONAL BUSINESS MACHINES CORPORATION PROVIDES THIS PUBLICATION "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Some states do not allow disclaimer of express or implied warranties in certain transactions, therefore, this statement may not apply to you.
This publication could include technical inaccuracies or typographical errors. Changes are periodically made to the information herein; these changes will be incorporated in new editions of the publication. IBM may make improvements and/or changes in the product(s) and/or the program(s) described in this publication at any time.
It is possible that this publication may contain reference to, or information about, IBM products (machines and programs), programming, or services that are not announced in your country. Such references or information must not be construed to mean that IBM intends to announce such IBM products, programming, or services in your country.
Requests for technical information about IBM products should be made to your IBM reseller or IBM marketing representative.
Copyright Notices
COPYRIGHT LICENSE: This publication contains printed sample application programs in source language, which illustrate OS/2 programming techniques. You may copy, modify, and distribute these sample programs in any form without payment to IBM, for the purposes of developing, using, marketing or distributing application programs conforming to the OS/2 application programming interface.
Each copy of any portion of these sample programs or any derivative work, which is distributed to others, must include a copyright notice as follows: "(C) (your company name) (year). All rights reserved."
(C) Copyright International Business Machines Corporation 1996. All rights reserved.
Note to U.S. Government Users - Documentation related to restricted rights - Use, duplication or disclosure is subject to restrictions set forth in GSA ADP Schedule Contract with IBM Corp.
Disclaimers
References in this publication to IBM products, programs, or services do not imply that IBM intends to make these available in all countries in which IBM operates. Any reference to an IBM product, program, or service is not intended to state or imply that only that IBM product, program, or service may be used. Subject to IBM's valid intellectual property or other legally protectable rights, any functionally equivalent product, program, or service may be used instead of the IBM product, program, or service. The evaluation and verification of operation in conjunction with other products , except those expressly designated by IBM, are the responsibility of the user.
IBM may have patents or pending patent applications covering subject matter in this document. The furnishing of this document does not give you any license to these patents. You can send license inquiries, in writing, to:
IBM Director of Licensing
IBM Corporation
500 Columbus Avenue
Thornwood, NY 10594
U.S.A.
Trademarks
The following terms are trademarks of the IBM Corporation in the United States or other countries or both:
IBM Multimedia Presentation Manager/2 OS/2 Ultimotion
The following terms are trademarks of other companies:
Helvetica Linotype Company
MASM Microsoft Corporation
Mitsumi Mitsumi Denki Kabushki Kaisha
Panasonic Matsushita Electric Industrial Co., Ltd.
OPTi OPTi, Inc.
Pioneer Pioneer Electric Corporation
ProAudio Spectrum Media Vision, Inc.
ProAudio Spectrum 16 Media Vision, Inc.
QuickVia Jovian Logic Corp.
ReelMagic Sigma Designs, Inc.
Sound Blaster Creative Technology Ltd.
SuperVia Jovian Logic Corp.
Super VideoWindows New Media Graphics Corporation
Video Blaster Creative Technology, Inc.
Yamaha Yamaha Corporation
Windows is a trademark of Microsoft Corporation.
UNIX is a registered trademark in the United States and other countries licensed exclusively through X/Open Company Limited.
Other company, product, and service names, which may be denoted by a double asterisk (**), may be trademarks or service marks of others. *.im (ddkglos scrpol)
Glossary
This glossary contains terms and definitions that are, for the most part, used for OS/2 products. This is not a complete dictionary of computer terms .
Introduction
This glossary defines many of the terms used in this book. It includes terms and definitions from the IBM Dictionary of Computing, as well as terms specific to the Presentation Manager, but it is not a complete glossary for OS/2.
Other primary sources for these definitions are:
- The American National Standard Dictionary for Information Systems, ANSI X3 .172-1990, copyrighted 1990 by the American National Standards Institute, 11 West 42nd Street, New York, New York 10036. These definitions are identified by the symbol (A) after the definition.
- The Information Technology Vocabulary, developed by Subcommittee 1, Joint Technical Committee 1, of the International Organization for Standardization and the International Electrotechnical Commission (ISO/IEC JTC1/SC1). Definitions of published parts of this vocabulary are identified by the symbol (I) after the definition; definitions taken from draft international standards, committee drafts, and working papers being developed by ISO/IEC JTC1/SC1 are identified by the symbol (T) after the definition, indicating that final agreement has not yet been reached among the participating National Bodies of SC1.
Glossary Listing
Select a starting letter of glossary terms:
Glossary - A
A
ABIOS -Advanced BIOS. See BIOS.
accumulator -(1) A register in which one operand of an operation can be stored and subsequently replaced by the result of that operation. (T) (2) In the IBM 3800 Printing Subsystem Models 3 and 8, a feature that supplies a separate storage that can hold data in raster form. It can be used either for composing a sheet of data that combines a large amount of variable and constant data, or for storing an electronic overlay in raster form that will be merged with variable data as the sheet is printed.
access permission -All access rights a user has regarding an object. (I)
adapter -A piece of hardware that modifies the system unit to allow it to operate in a particular way, often by connecting the system unit to an external device such as a video monitor.
adapter device driver -A device driver that provides hardware-dependent services for an OEMadapter.
address space -(1) The range of addresses available to a program. (A) ( 2) The area of virtual storage available for a particular job.
all points addressable (APA) -In computer graphics, pertaining to the ability to address and display or not display each picture element (pel) on a display surface.
anchor block -An area of the internal resources of OS/2 Presentation Manager which is allocated to a process or thread that calls WinInitialize.
anchor point -The position or choice from which selection or deselection is extended.
APA -All points addressable.
API -Application programming interface.
application programming interface (API) -A functional interface supplied by the operating system, or by a separately-orderable licensed program, that allows an application program written in a high-level language to use specific data or functions of the operating system or the licensed program.
archive flag -In the OS/2 operating system, a flag of files and directories that the operating system uses to determine which files are new or modified. Files with this flag are included when a backup copy is made or when all the files are restored on a hard disk. See flag.
area -In computer graphics, a filled shape such as a solid rectangle.
ASCIIZ -A string of ASCII characters that is terminated with a byte containing the value 0.
aspect ratio -(1) The ratio of the height of a rectangle to its width. A rectangle of width 10 inches and height 5 inches has an aspect ratio of 10/ 5 or 2. (2) On a display screen, the ratio of the maximum length of a display line to the maximum length of a display column.
asynchronous (ASYNC) -(1) Pertaining to two or more processes that do not depend upon the occurrence of specific events such as common timing signals . (T) (2) Without regular time relationship; unexpected or unpredictable with respect to the execution of program instructions.
atom -A constant that represents a string. Once a string has been defined as an atom, the atom can be used in place of the string to save space. Strings are associated with their respective atoms in an atom table. See integer atom.
atom table -A table used to associate atoms with the strings that they represent. This table contains the mechanism by which the presence of a string can be verified.
AVIO -Advanced Video Input/Output
Glossary - B
B
background color -The color assigned to a background image.
background mix -An attribute that determines how the background of a graphic primitive is combined with the existing color of the graphics presentation space.
base device driver -An OS/2 device driver that performs I/O during the OS/ 2 kernel boot sequence to provide IPL support. Base device drivers are loaded by way of the CONFIG.SYS BASEDEV keyword, rather than the DEVICE keyword. See BASEDEV keyword, adapter device driver, and device manager.
BASEDEV keyword -New CONFIG.SYS keyword; loads a base device driver into the operating system.
Basic Input/Output System (BIOS) -Code that controls basic hardware operations, such as interactions with diskette drives, hard disk drives, and the keyboard.
Bezier curve -A mathematical technique of specifying a smooth, continuous line or surface, requiring a starting point and an ending point, with several intermediate points that influence or control the path of the linking curve.
BIOS -Basic Input/Output System.
bit-block transfer (bitblt) -Transfer of a rectangular array of bit-map data.
bitblt -Bit-block transfer.
bit map -A representation of an image by an array of bits.
block -(1) In programming languages, a compound statement that coincides with the scope of at least one of the declarations contained within it. A block may also specify storage allocation or segment programs for other purposes. (I) (2) A string of data elements recorded or transmitted as a unit. The elements may be characters, words or physical records. (T) (3) A collection of contiguous records recorded as a unit. Blocks are separated by interblock gaps and each block may contain one or more records. (A)
Bit block transfer (bitblt) -The process of transferring one or more blocks of data.
border -A visual indicator of a window's boundaries.
BPB -BIOS Parameter Block.
breakpoint -(1) A point in a computer program where execution may be halted. A breakpoint is usually at the beginning of an instruction where halts, caused by external intervention, are convenient for resuming execution. (T) (2) An instruction in a program for halting execution. Breakpoints are usually established at positions in a program where halts, caused by external intervention, are convenient for restarting. (T) (3) A place in a program, specified by a command or a condition, where the system halts execution and gives control to the workstation user or to a specified program.
Bus Master adapter -An adapter capable of performing Reads and Writes to physical storage by communicating directly with the storage subsystem ( memory) rather than depending on a host DMA channel or host CPU. Synonymous with first-party DMA adapter.
Glossary - C
C
cached micro presentation space -A presentation space from a Presentation Manager owned store of micro presentation spaces. It can be used for drawing to a window only, and must be returned to the store when the task is complete.
CDB -Command Descriptor Block.
cell -See character cell.
character box -(1) An imaginary parallelogram on a display surface that contains all parts of one graphic character. Synonymous with bounding box. (T) (2) The maximum area in which a symbol and all associated elements, such as a cursor, an underline, or space surrounding the symbol to separate it from other symbols, can be printed or displayed. Synonymous with character cell. (3) The imaginary parallelogram whose boundaries govern the size, orientation, and spacing of individual characters to be displayed on a graphics display device.
character cell -(1) An addressable location on a display surface or printing medium. (2) The physical width and height in pels of a font. See also bounding box. (3) The imaginary box whose boundaries govern the size , orientation, and spacing of individual characters to be displayed on a workstation.
character mode -A mode that, in conjunction with the font type, determines the extent to which graphics characters are affected by the character box, shear, and angle attributes.
clipping -In computer graphics, removing those parts of display elements that lie outside of given boundary.
clip limits -The area of the paper that can be reached by a printer or plotter.
clipping path -A clipping boundary in world-coordinate space.
code page -An assignment of graphic characters and control function meanings to all code points; for example, assignment of characters and meanings to 256 code points for an 8-bit code, assignment of characters and meanings to 128 code points for a 7-bit code.
code point -A 1-byte code representing one of 256 potential characters.
code segment -An executable section of programming code within a load module.
color conversion -Changing one color format to another. Required, for example, when the source color format is different from the destination color format. When going from the monochrome color format to the color format, 1 (one) bits are converted to the image foreground color, and 0 ( zero) bits are converted to the image background color.
When going from color to monochrome, all pels that match the passed background color are converted to the image background color of the destination.
All other pels are converted to the image foreground color of the destination. The color conversion takes place prior to any mix mode.
color dithering -See dithering.
command code -In this specification, refers to a group of related commands that an adapter device driver can receive.
All command codes have a prefix of "IOCC_". For example, common I/O requests (such as Read, Write, etc.) are grouped under the command code IOCC_EXECUTE_IO.
command data block -A data structure defined by the Small Computer System Interface standard to send commands to devices that conform to SCSI standards.
command descriptor block (CDB) -The structure used to communicate commands from a source to a destination.
command modifier -In this specification, a specific operation that an adapter device driver is to perform.
All command modifiers have a prefix of "IOCM_". For example, an adapter device driver might receive an IOCC_EXECUTE_IO command with a command modifier of IOCM_READ.
compatibility kernel -The portion of the OS/2 kernel that exists to support DOS INT 20, 21, 25, 26, and 27 functions. It acts as an interface to common kernel functionality such as the file system.
CON -Character-device name reserved for the console keyboard and screen.
conditional compilation -Processing by the preprocessor of certain specified code in the file, depending on the evaluation of a specified condition.
context hook -Similar to a "force flag" in earlier versions of OS/2. These are events, signaled by a virtual device driver, that are processed at task time. Forcing an IRET, and simulating an NMI, can fall into this category.
control program -A computer program designed to schedule and to supervise the execution of programs of a computer system.
controller sector buffer -One or more buffers, managed by a hardware adapter, to improve I/O transfer rates by helping to match a device and software timing requirements.
Glossary - D
D
DASD -Direct-access storage device.
data bus -A bus used to communicate data internally and externally to and from a processing unit, storage, and peripheral devices. (A) See bus.
data structure -The syntactic structure of symbolic expressions and their storage allocation characteristics. (T)
DBCS -Double-byte character set.
DC -Device context.
DDB -Device-dependent bit map.
deinstantiation -See instantiation.
DevHlp -Device helper.
device context (DC) -A logical description of a data destination such as memory, metafile, display, printer, or plotter. See also direct device context, information device context, memory device context, metafile device context, and screen device context.
device driver -A file that contains the code needed to attach and use a device such as a display, printer, or plotter.
device driver initialization (init) time -See initialization (init) time, device driver.
device driver profile -A file with a "DDP" extension, containing a script that is interpreted by the OS/2 DDINSTAL utility. Among other things, it defines which files to copy from installation diskettes to target directories and specifies how the CONFIG.SYS file will be updated.
device helper (DevHlp) -(1) A kernel service (memory, hardware interrupt, software interrupt, queuing, semaphore, and so forth) provided to physical device drivers. (2) A callable C-language or assembler-language routine that provides an operating system service for an OS/2 device driver.
device object -A device that provides a means of communication between a computer and the outside world. A printer is an example of a device object.
device table -A data structure containing a summary of the adapters an adapter device driver supports and a list of the I/O devices attached to each adapter. This data structure is built by the adapter device driver in response to an IOCC_CONFIGURATION IOCM_GET_DEVICE_TABLE request.
direct access storage device (DASD) -A device in which access time is effectively independent of the location of the data.
direct memory access (DMA) -(1) A technique for moving data directly between main storage and peripheral equipment without requiring processing of the data by the processing unit. (2) The transfer of data between memory and input/output units without processor intervention.
display frame -(1) In computer graphics, an area in storage in which a display image can be recorded. (2) In computer micrographics, an area on a microform in which a display image can be recorded.
dispatch table -(1) A block of memory, allocated by the graphics engine, for the containment of entry points for use by a display driver. (2) An array of pointers to function-handling routines.
dithering -A technique for interleaving dark and light pels so that the resulting image looks smoothly shaded from a distance.
DLL -Dynamic link library.
DMA -Direct memory access.
double-byte character set (DBCS) -A set of characters in which each character is represented by two bytes. Languages such as Japanese, Chinese, and Korean, which contain more characters than can be represented by 256 code points, require double-byte character sets. Because each character requires 2 bytes, the typing, display, and printing of DBCS characters requires hardware and programs that support DBCS. Contrast with single-byte character set.
driver -(1) A program (and possibly data files) that contain information needed to run a particular unit, such as a plotter, printer, port, or mouse. See also device driver and printer driver. (2) A system or device that enables a functional unit to operate.
dynamic link library (DLL) -A file containing executable code and data bound to a program at load time or run time, rather than during linking. The code and data in a dynamic link library can be shared by several applications simultaneously.
Glossary - E
E
entry point -(1) In a database, the record that is first accessed upon entry into a database, caused by a user's command. (T) (2) The address or label of the first instruction executed on entering a computer program, routine, or subroutine. A computer program, routine, or subroutine may have a number of different entry points, each perhaps corresponding to a different function or purpose. (I) (A) Synonymous with entrance, entry. (3) In a routine, any place to which control can be passed. (A) (4) In the C, FORTRAN, and Pascal languages, the address or label of the first instruction processed or entered in a program, routine, or subroutine. A program, routine, or subroutine can have a number of different entry points , each corresponding to a different function or purpose.
EOI -End Of Interrupt
Glossary - F
F
Far call -Code that calls from one segment into another segment.
fillet -An arc that is tangential to the end points of two adjacent lines. See also polyfillet.
filter adapter device driver -A special class of adapter device drivers that do not manage the hardware directly, but monitor the stream of commands between a device manager and an adapter device driver. See Device Managerand adapter device driver.
first-party DMA adapter -See bus master adapter.
flag -A characteristic of a file or directory that enables it to be used in certain ways. See also archive flag, hidden flag, and read-only flag.
flat address -See linear address.
frame styles -Standard window layouts provided by the Presentation Manager .
freeze and thaw services -Functions that prevent a DOS session from executing (VDHFreezeVDM) until the matching thaw function (VDHThawVDM) is called. The freeze occurs when the specified DOS session leaves kernel mode .
Glossary - G
G
GDT -Global descriptor table.
Global Descriptor Table (GDT) -A table that defines code and data segments available to all tasks in an application.
glyph -A graphic symbol whose appearance conveys information; for example, the vertical and horizontal arrows on cursor keys that indicate the directions in which they control cursor movement, the sunburst symbol on the screen illumination control of a display device.
GPI -Graphics programming interface
graphic primitive -In computer graphics, a basic element, such as an arc or a line, that is not made up of smaller parts and that is used to create diagrams and pictures.
graphics attributes -The attributes that apply to graphics primitives. Examples are color selection, line type, and shading pattern definition. Contrast with segment attributes.
Graphics programming interface (GPI) -The formally-defined programming language that lies between an IBM graphics program and the user of the program.
graphics segment -A sequence of related graphic primitives and graphics attributes. See also graphic primitive.
GRE -Graphics engine.
Glossary - H
H
handle -(1) An identifier that represents an object, such as a device or a window, to the Presentation Interface. (2) In the Advanced DOS and OS/2 operating systems, a binary value created by the system that identifies a drive, directory, and file so that the file can be found and opened.
handshaking -A method by which two pieces of hardware, such as a personal computer and a plotter, can communicate. Depending upon the devices communicating, handshaking occurs either as a hardware function or through software, such as a device driver.
hard error -An error condition on a network that requires that the network be reconfigured or that the source of the error be removed before the network can resume reliable operation.
hardware palette -The array of RGBs that the physical device is displaying .
heap -An area of free storage available for dynamic allocation by an application. Its size varies depending on the storage requirements of the application.
hex -See hexadecimal
hexadecimal -Pertaining to a system of numbers to the base 16; hexadecimal digits range from 0 through 9 and A through F, where A represents 10 and F represents 15.
hook -A point in a system-defined function where an application can supply additional code that the system processes as though it were part of the function.
hook chain -A sequence of hook procedures that are "chained" together so that each event is passed in turn to each procedure in the chain.
Glossary - I
I
IDC -Inter-device-driver communication.
in-memory buffer -A block of memory in the address space of the host machine, used for data transfer.
init time -See initialization time, device driver.
initialization time, device driver -After the OS/2 loads a device driver, it sends it an OS/2 request packet to initialize. During this initialization, certain DevHlp functions are not permitted. Also called init time.
Input/Output Control (IOCtl) -A system service that provides a way for an application to send device-specific control commands to a device driver.
Input/Output Privilege Level (IOPL) -Allows part of a Ring 3 application or device driver to execute at Ring 0.
input router -OS/2 internal process that removes messages from the system queue.
inter-device-driver communication (IDC) -A mechanism that enables a physical device driver to communicate with another physical device driver.
interprocess communication -In the OS/2 operating system, the exchange of information between processes or threads through semaphores, queues, and shared memory.
interrupt -An instruction that directs the microprocessor to suspend what it is doing and run a specified routine. When the routine is complete, the microprocessor resumes its original work. See also routine.
interrupt request (IR) -Broadly, an "interrupt request level", referring to pending or in-service interrupt requests, or to a specific level (for example, IR 4).
interrupt request flag -A bit in the 8259 PIC controller that indicates an interrupt is pending on particular level. The VPIC also maintains a virtual interrupt request flag for each interrupt level for each DOS session.
interrupt service flag -A bit in the 8259 PIC controller that indicates an interrupt request is being serviced. It is cleared when the PIC is sent EOI . The VPIC maintains a virtual interrupt service flag indicating that a simulated interrupt is in-progress in a DOS session.
interrupt time -When a device driver is run because of an interrupt rather than because of an application request. OS/2 device drivers receive interrupts either from the hardware they manage or from the system real- time clock.
During interrupt time, certain DevHlp functions are not permitted. Also, addresses received directly from OS/2 applications might not be valid unless they are converted system addresses.
IOCtl -Input/Output Control.
IOPL -Input/Output Privilege Level.
IORB -Input/Output Request Block.
Input/Output Request Block (IORB) -A data structure defined by this specification that is passed as a parameter on all calls to an adapter device driver. It contains a fixed section, followed by a command-dependent section.
IORBH -Input/Output Request Block Header
IRET -Interrupt return.
IRQ -Interrupt Request.
Glossary - J
J
journal -A special-purpose file or data set that can be used to provide an audit trail of operator and system actions, or as a means of recovering superseded data.
Glossary - K
K
kanji -A graphic character set consisting of symbols used in Japanese ideographic alphabets. Each character is represented by 2 bytes.
kernel -(1) The part of an operating system that performs basic functions such as allocating hardware resources. (2) A program that can run under different operating system environments.
kerning -The design of graphic characters so that their character boxes overlap. The toned picture elements (pels) of the character appear outside the character cell.
Note:Kerning allows character boxes to overlap and characters to run together, so that characters can be designed for cursive languages, ligatures, or any other kind of character that requires more than one character box. It also allows for design of proportional-spaced fonts. By overlapping character boxes, characters can be placed closer together, or they can be placed farther apart by using overlapped blank character boxes.
Glossary - L
L
LCT -logical color table.
LDT -Local descriptor table.
LIFO stack -A data structure from which data is retrieved in "Last-In, First-Out" order.
linked list -A list in which the data elements may be dispersed, but in which each data element contains information for locating the next. Synonym for chained list.
linear address -A unique value that identifies the memory object.
Local Descriptor Table (LDT) -A table that defines code and data segments specific to a single task.
logical palette -An array of RGB and mapping index pairs, created by the device driver when defining a palette (as a result of a GpqCreatePalette call).
LVB -Logical Video Buffer.
Glossary - M
M
memory device context -A logical description of a data destination that is a memory bit map. See also device context.
metafile -A file containing a series of attributes that set color, shape, and size, usually of a picture or a drawing. Using a program that can interpret these attributes, a user can view the assembled image.
metafile device context -A logical description of a data destination that is a metafile which is used for graphics interchange. See also device context.
mickey -A unit of measurement for physical mouse motion whose value depends on the mouse device driver that is currently loaded.
mixed character string -A string containing a mixture of one-byte and kanji or Hangeul (two-byte) characters.
mutex semaphore -(Mutual exclusion semaphore). A semaphore that enables threads to serialize their access to resources. Only the thread that currently owns the mutex semaphore can gain access to the resource, thus preventing one thread from interrupting operations being performed by another.
Glossary - N
N
named pipe -A named buffer that provides client-to-server, server-to- client or duplex communication between unrelated processes. Contrast with unnamed pipe.
notification callout -The feature that provides for a routine to be called on completion of an input/output request. See also notification routine.
notification routine -The routine indicated in an input/output request block to be called on completion of that request. See also notification callout.
null-terminated string -A string of (n+1) characters where the (n+1)th character is the "null" character (X'00') and is used to represent an n- character string with implicit length. Also called a "zero-terminated" string or an "ASCIIZ". string.
Glossary - O
O
Glossary - P
P
palette -A list of colors assigned to various areas on a panel. A user can change the color of these areas.
PDD -Physical Device Driver.
PDE -PageDirectoryEntry.
pel -Picture element.
permissible action -In a conceptual schema language, an action conforming to specified rules or constraints that changes a presumably consistent collection of sentences into a consistent one or makes known a consistent one present in the information base or conceptual schema.
phase alignment -Aligning source bits with destination bits. Often required in a Bitblt function move operation where byte blocks are moved on bit boundaries.
physical address -A 32-bit byte address giving the actual address in physical storage for a data item.
physical device driver (PDD) -A system interface that handles hardware interrupts and supports a set of input and output functions.
pipe -See named pipe, unnamed pipe.
picture element (pel, pixel) -(1) In computer graphics, the smallest element of a display surface that can be independently assigned color and intensity. (T) . (2) The area of the finest detail that can be reproduced effectively on the recording medium. (3) An element of a raster pattern about which a toned area on a photoconductor can appear.
PIO -Programmed I/O.
pixel -Picture element.
polyfillet -A curve based on a sequence of lines. The curve is tangential to the end points of the first and last lines, and tangential also to the midpoints of all other lines.
polyline -In computer graphics, a sequence of adjoining lines.
pop -To remove an item from the top of a pushdown list. Contrast with push .
prefetch -To locate and load a quantity of data in anticipation of a request.
presence-check function -A Ring 3 (non-privileged) .EXE program that determines whether a given hardware interface is present on a workstation.
PRESENCECHECK -A keyword, interpreted by the DDINSTAL utility, to determine whether to process the device driver profile file, based on the return code from PRESENCECHECK.
printer driver -A file that describes the physical characteristics of a printer, plotter, or other peripheral device, and is used to convert graphics and text into device-specific data at the time of printing or plotting.
Print Manager -In the Presentation Manager, the part of the spooler that manages the spooling process. It also allows the user to view print queues and to manipulate print jobs.
privilege level -A method of protection that allows only certain program instructions to be used by certain programs.
program group -Several programs that can be acted upon as a single entity.
protect mode -A method of program operation that limits or prevents access to certain instructions or areas of storage. Contrast with real mode.
push -To add an item to the top of a pushdown list. Contrast with pop.
Glossary - Q
Q
queued device context -A logical description of a data destination (for example, a printer or plotter) where the output is to go through the spooler. See also device context.
Glossary - R
R
read-only memory basic input/output system (ROM-BIOS) -Microcode in read- only memory that controls basic input/output operations such as interactions with cassettes, diskette drives, hard disk drives, and the keyboard. See also BIOS, NetBIOS.
Note:ROM BIOS allows the user to write programs and add or remove devices without concern for characteristics such as device addresses.
real mode -In the OS/2 operating system, a method of program operation that does not limit or prevent access to any instructions or areas of storage. The operating system loads the entire program into storage and gives the program access to all system resources.
reentrant -The attribute of a program or routine that allows the same copy of the program or routine to be used concurrently by two or more tasks.
removable-media indicator -A flag (bit) indicating that a device permits media removal.
resource -The means of providing extra information used in the definition of a window. A resource can contain definitions of fonts, templates, accelerators and mnemonics; the definitions are held in a resource file.
resurrection -The Presentation Manager event that occurs when switched back from a full-screen DOS or WIN-OS/2 session.
RETF -Return far.
reverse video -A form of highlighting a character, field, or cursor by reversing the color of the character, field, or cursor with its background; for example, changing a red character on a black background to a black character on a red background.
ROM BIOS -Read-Only Memory Basic Input/Output System.
ROP -Raster operation.
RTC -Real-Time Clock.
Glossary - S
S
SBCS -Single-byte character set
SCB -See subsystem control block architecture.
screen device context -A logical description of a data destination that is a particular window on the screen. See also device context.
SCSI -Small Computer System Interface.
seamless windows -An architecture contained within OS/2 which permits one or more applications to share windowed desktop graphical space and other resources, while executing concurrently. Application session windows managed by seamless windows can share border information, and pointing device transitions from session to session are handled smoothly and transparently.
second-party DMA adapter -See DMA slave.
semaphore -(1) A variable that is used to enforce mutual exclusion. (T) (2) An indicator used to control access to a file; for example, in a multiuser application, a flag that prevents simultaneous access to a file. (3) An entity used to control access to system resources. Processes can be locked to a resource with semaphores if the processes follow certain programming conventions.
sense data -Data which describes an I/O error as defined by the ANSI SCSI specifications.
single-byte character set (SBCS) -A character set in which each character is represented by a one-byte code. Contrast with double-byte character set.
Small Computer System Interface (SCSI) -An input and output bus that provides a standard interface between the OS/2 multimedia system and peripheral devices.
spline curve -In computer graphics, a shape created when a user specifies a series of points and the computer software draws a curve that smoothly approaches those points.
spooler -A program that intercepts data going to a device driver and writes it to a disk. The data is later printed or plotted when the required device is available. A spooler prevents output from different sources from being intermixed.
synchronous -Pertaining to two or more processes that depend upon the occurrence of specific events such as common timing signals.
Glossary - T
T
text window -See VIO window.
thread -The smallest unit of operation to be performed within a process.
thunk -term used to describe the process of address conversion, stack, and structure realignment that is necessary when passing control between 16-bit and 32-bit modules.
thunk layer -An interface that converts 32-bit parameters to 16-bit parameters, and maps linear addresses to segmented addresses.
time slice -(1) The period of processing time allocated for running a program. (2) An interval of time on the processing unit allocated for use in performing a task. After the interval has expired, processing unit time is allocated to another task, so a task cannot monopolize processing unit time beyond a fixed limit.
tuple -In a relational database, a part of a relation that uniquely describes an entity and its attribute.
Glossary - U
U
unnamed pipe -A circular buffer created in memory; used by related processes to communicate with one another. Contrast with named pipe.
Glossary - V
V
VBIOS -Virtual BIOS device driver
VCMOS -Virtual CMOS device driver
VDD -Virtual device driver
VDH -Virtual video Device Handler
VDM -Virtual DOS Machine; use DOS session.
VDMA -Virtual Direct Memory Access device driver
VDSK -Virtual hard DiSK device driver
video graphics adapter (VGA) -A computer adapter that provides high- resolution graphics and a total of 256 colors.
VIO -Virtual Input/Output
VIRR -Virtual Interrupt Request Register
Virtual Device Driver (VDD) -In the OS/2 operating system, a type of device driver used by DOS programs running in a DOS session to access devices, such as the screen or mouse, which must be shared with other processes in the system. The virtual device driver maps DOS device commands to the normal (physical) device driver under OS/2 2.0 and later versions of the operating system.
virtual DevHlp (VDH) -Kernel (linear memory, paging, hardware interrupt, event control, port control) services provided to virtual device drivers.
virtual I/O (VIO) -A facility that pages data into and out of external page storage.
virtual memory -Synonym for virtual storage.
Virtual Programmable Interrupt Controller -Virtualizes the 8259 Programmable Interrupt Controller (PIC). A special virtual device driver, in that it provides services to other virtual device drivers.
virtual storage -Addressable space that is apparent to the user as the processor storage space, from which the instructions and the data are mapped into the processor storage locations. Synonymous with virtual memory .
visible region -A window's presentation space clipped to the boundary of the window and the boundaries of any overlying window.
VPIC -Virtual Programmable Interrupt Controller device driver.
VRAM -Video Random-Access Memory.
VTIMER -Virtual TIMER device driver.
V86 mode -Virtual 8086 mode of the 80386 CPU.
Glossary - W
W
window coordinates -A set of coordinates by which a window position or size is defined; measured in device units, or pels.
Glossary - X
X
Glossary - Y
Y
There are no glossary terms for this initial letter.
Glossary - Z
Z