DosPortAccess: Difference between revisions
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This call requests or releases access to ports for I/O privilege. | This call requests or releases access to ports for I/O privilege. | ||
==Syntax== | ==Syntax== | ||
DosPortAccess (Reserved, TypeOfAccess, FirstPort, LastPort) | |||
DosPortAccess | |||
==Parameters== | ==Parameters== | ||
; | ;Reserved (USHORT) - input : Must be set to zero. | ||
;TypeOfAccess (USHORT) - input : A request for or release of access to a port. | |||
; TypeOfAccess (USHORT) - input : A request for or release of access to a port. | ::0 - Request access | ||
::1 - Release access. | |||
; FirstPort (USHORT) - input : Starting (low) number in a contiguous range or a single port. | |||
; FirstPort (USHORT) - input : Starting (low) number in a contiguous range or a single port. | |||
; LastPort (USHORT) - input : Ending (high) number in a contiguous range or a single port. If only one port is being used, FirstPort and LastPort should both be set to this port. | ; LastPort (USHORT) - input : Ending (high) number in a contiguous range or a single port. If only one port is being used, FirstPort and LastPort should both be set to this port. | ||
==Return Code== | ==Return Code== | ||
;rc (USHORT) - return:Return code descriptions are: | |||
*0 NO_ERROR | |||
Return code descriptions are: | *5 ERROR_ACCESS_DENIED | ||
* 0 | |||
* 5 | |||
==Remarks== | ==Remarks== | ||
Note that CLI/STI privilege is also granted automatically. There is no need to make an additional call to DosCLIAccess. | Note that CLI/STI privilege is also granted automatically. There is no need to make an additional call to [[DosCLIAccess]]. | ||
Applications that perform I/O to port(s) in IOPL segments must request port access from the operating system. | Applications that perform I/O to port(s) in IOPL segments must request port access from the operating system. | ||
An application with no IOPL segments that accesses a device through a device driver or by an interface package such as VIO, does not need to issue this call. The device driver or interface package is responsible for obtaining the necessary I/O access. | An application with no IOPL segments that accesses a device through a device driver or by an interface package such as VIO, does not need to issue this call. The device driver or interface package is responsible for obtaining the necessary I/O access. | ||
== | ==Bindings== | ||
===C | ===C=== | ||
<PRE> | <PRE> | ||
#define INCL_DOSDEVICES | #define INCL_DOSDEVICES | ||
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USHORT rc = DosPortAccess(Reserved, TypeOfAccess, FirstPort, LastPort); | USHORT rc = DosPortAccess(Reserved, TypeOfAccess, FirstPort, LastPort); | ||
USHORT | USHORT 0; /* 0 */ | ||
USHORT | USHORT TypeOfAccess; /* Request or release */ | ||
USHORT | USHORT FirstPort; /* First port number */ | ||
USHORT | USHORT LastPort; /* Last port number */ | ||
USHORT | USHORT rc; /* return code */ | ||
</PRE> | </PRE> | ||
===MASM | ===MASM=== | ||
<PRE> | <PRE> | ||
EXTRN DosPortAccess:FAR | EXTRN DosPortAccess:FAR | ||
| Line 67: | Line 52: | ||
Returns WORD | Returns WORD | ||
</PRE> | </PRE> | ||
[[Category: | [[Category:Dos16]] | ||
Latest revision as of 05:20, 26 January 2020
This call requests or releases access to ports for I/O privilege.
Syntax
DosPortAccess (Reserved, TypeOfAccess, FirstPort, LastPort)
Parameters
- Reserved (USHORT) - input
- Must be set to zero.
- TypeOfAccess (USHORT) - input
- A request for or release of access to a port.
- 0 - Request access
- 1 - Release access.
- FirstPort (USHORT) - input
- Starting (low) number in a contiguous range or a single port.
- LastPort (USHORT) - input
- Ending (high) number in a contiguous range or a single port. If only one port is being used, FirstPort and LastPort should both be set to this port.
Return Code
- rc (USHORT) - return
- Return code descriptions are:
- 0 NO_ERROR
- 5 ERROR_ACCESS_DENIED
Remarks
Note that CLI/STI privilege is also granted automatically. There is no need to make an additional call to DosCLIAccess.
Applications that perform I/O to port(s) in IOPL segments must request port access from the operating system.
An application with no IOPL segments that accesses a device through a device driver or by an interface package such as VIO, does not need to issue this call. The device driver or interface package is responsible for obtaining the necessary I/O access.
Bindings
C
#define INCL_DOSDEVICES USHORT rc = DosPortAccess(Reserved, TypeOfAccess, FirstPort, LastPort); USHORT 0; /* 0 */ USHORT TypeOfAccess; /* Request or release */ USHORT FirstPort; /* First port number */ USHORT LastPort; /* Last port number */ USHORT rc; /* return code */
MASM
EXTRN DosPortAccess:FAR INCL_DOSDEVICES EQU 1 PUSH WORD 0 ;Reserved (must be zero) PUSH WORD TypeOfAccess ;Request or release PUSH WORD FirstPort ;First port number PUSH WORD LastPort ;Last port number CALL DosPortAccess Returns WORD