DSK_SETDEVICEPARAMS
- Category
- IOCTL_DISK (08h)
- Function
- DSK_SETDEVICEPARAMS (43h)
- Description
- Set Device Parameters
Description
This function sets the parameters for a specified device.
Command Information
The two low bits of the command byte are used to indicate one of three possible actions:
- 00: Revert to building the BIOS Parameter Block (BPB) off the medium for all subsequent Build BPB functions. This is used after a format operation to reset the device parameters to their original state.
- 01: Change the default BPB for the physical device. This changes the physical parameters for the drive as opposed to parameters for the media in the drive.
- 10: Change the BPB for the medium to the specified BPB, and return the new BPB for the medium for all subsequent Build BPB calls. This is used to prepare the device for a format media operation according to the device parameters specified.
- All other bits are reserved, and must be set to 0.
Parameter Packet Format
| Field | Length | C Datatype |
|---|---|---|
| Command Information | BYTE | UCHAR |
| Drive Unit | BYTE | UCHAR |
Extended BPB for Devices
The term Extended BPB refers to the BIOS Parameter Block. It is a table that describes the structure of the media and the physical layout of the drive (heads, tracks, sectors). The Extended BPB has the following format:
| Field | Length |
|---|---|
| Bytes per Sector | WORD |
| Sectors per Cluster | BYTE |
| Reserved Sectors | WORD |
| Number of FATs | BYTE |
| Root Directory Entries | WORD |
| Total Sectors | WORD |
| Media Descriptor | BYTE |
| Sectors per FAT | WORD |
| Sectors per Track | WORD |
| Number of Heads | WORD |
| Hidden Sectors | DWORD |
| Large Total Sectors | DWORD |
| Reserved | 6 BYTES |
Data Packet Format
| Field | Length | C Datatype |
|---|---|---|
| Extended BPB for Devices | 31 BYTES | BYTE[31] |
| Number of Cylinders | WORD | USHORT |
| Device Type | BYTE | BYTE |
| Device Attributes | WORD | USHORT |
Device Type
Describes the physical layout of the device specified, and has one of the following values:
- 0: 48 TPI low-density diskette drive
- 1: 96 TPI high-density diskette drive
- 2: Small (3.5-inch) 720KB drive
- 3: 8-inch single-density diskette drive
- 4: 8-inch double-density diskette drive
- 5: Fixed disk
- 6: Tape drive
- 7: Other (includes 1.44MB 3.5-inch diskette drive)
- 8: R/W optical disk
- 9: 3.5-inch 4.0MB diskette drive (2.88MB formatted)
Device Attributes
A bit field that returns flag information about the specified drive:
- Bit 0: Removable Media flag. This bit is set to 1 if the media cannot be removed. It is set to 0 if the media is removable.
- Bit 1: Changeline flag. This bit is set to 1 if the device support determines that the media was removed since the last I/O operation. To query whether the media has changed, call the device driver Strategy Command "1h - MEDIA CHECK". (See "Physical Device Driver Strategy Commands" in the Physical Device Driver Reference for more information.) If this bit is set to 0, then the physical device driver can return the value 0, Unsure if media has changed, from the Media Check function.
Returns
Possible values are shown in the following list:
| Code | Description |
|---|---|
| 0 | NO_ERROR |
| 1 | ERROR_INVALID_FUNCTION |
| 6 | ERROR_INVALID_HANDLE |
| 15 | ERROR_INVALID_DRIVE |
| 31 | ERROR_GEN_FAILURE |
| 87 | ERROR_INVALID_PARAMETER |
| 111 | ERROR_BUFFER_OVERFLOW |
| 115 | ERROR_PROTECTION_VIOLATION |
| 117 | ERROR_INVALID_CATEGORY |
| 119 | ERROR_BAD_DRIVER_LEVEL |
| 163 | ERROR_UNCERTAIN_MEDIA |
| 165 | ERROR_MONITORS_NOT_SUPPORTED |
Remarks
The Drive Unit field is used only when this IOCtl is issued without using a previously allocated file handle and when Command Information is set to 01. A file handle of -1 must be used. Note that media in the drive is not required. Drive Unit values are 0=A, 1=B, 2=C, and so forth. The BIOSPARAMETERBLOCK data structure can be used by C programmers. To include this data structure in your file, make sure INCL_DOSDEVIOCTL is defined before you include OS2.H.