Format of device driver request header:
Offset Size Description )
00h BYTE length of request header
01h BYTE subunit within device driver
02h BYTE command code (see #02595)
03h WORD status (filled in by device driver) (see #02596)
---DOS---
05h 4 BYTEs reserved (unused in DOS 2.x and 3.x)
09h DWORD (European MS-DOS 4.0 only) pointer to next request header in
device's request queue
(other versions) reserved (unused in DOS 2.x and 3.x)
---STARLITE architecture---
05h DWORD pointer to next request header
09h 4 BYTEs reserved
---command code 00h---
0Dh BYTE (ret) number of units
0Eh DWORD (call) pointer to DOS device helper function (see #02599)
(European MS-DOS 4.0 only)
(call) pointer past end of memory available to driver (DOS 5+)
(ret) address of first free byte following driver
12h DWORD (call) pointer to commandline arguments
(ret) pointer to BPB array (block drivers) or
0000h:0000h (character drivers)
16h BYTE (DOS 3.0+) drive number for first unit of block driver (0=A)
---European MS-DOS 4.0---
17h DWORD pointer to function to save registers on stack
---DOS 5+ ---
17h WORD (ret) error-message flag
0001h MS-DOS should display error msg on init failure
---command code 01h---
0Dh BYTE media descriptor
0Eh BYTE (ret) media status
00h don't know
01h media has not changed
FFh media has been changed
0Fh DWORD (ret, DOS 3.0+) pointer to previous volume ID if the
OPEN/CLOSE/RM bit in device header is set and disk changed
Note: some drives (or controllers???) forget the change line
status if another drive is accessed afterwards. The
DOS IO.SYS layer takes care of this by not relying
on the reported change line status when the change
line is not active and a different drive is accessed,
instead it reports "don't know" to the DOS kernel.
---command code 02h---
0Dh BYTE media descriptor
0Eh DWORD transfer address
-> scratch sector if NON-IBM FORMAT bit in device header set
-> first FAT sector otherwise
12h DWORD pointer to BPB (set by driver) (see #01663 at INT 21/AH=53h)
---command codes 03h,0Ch---
(see also INT 21/AX=4402h"DOS 2+",INT 21/AX=4403h"DOS")
0Dh BYTE media descriptor (block devices only)
0Eh DWORD transfer address
12h WORD (call) number of bytes to read/write
(ret) actual number of bytes read or written
---command codes 04h,08h,09h (except Compaq DOS 3.31, DR DOS 6)---
0Dh BYTE media descriptor (block devices only)
0Eh DWORD transfer address
12h WORD byte count (character devices) or sector count (block devices)
14h WORD starting sector number (block devices only)
16h DWORD (DOS 3.0+) pointer to volume ID if error 0Fh returned
1Ah DWORD (DOS 4.0+) 32-bit starting sector number (block devices with
device attribute word bit 1 set only) if starting sector
number above is FFFFh (see INT 21/AH=52h)
---command codes 04h,08h,09h (Compaq DOS 3.31, DR DOS 6)---
0Dh BYTE media descriptor (block devices only)
0Eh DWORD transfer address
12h WORD byte count (character devices) or sector count (block devices)
14h DWORD 32-bit starting sector number (block devices only)
Note: to reliably determine which variant of the request block for
functions 04h,08h,09h has been passed to the driver, check
the length field as well as the word at offset 14h. If the
length is 1Eh and 14h=FFFFh, use the DWORD at 1Ah as the
starting sector number; if the length is 18h, use the DWORD
at 14h; otherwise, use the WORD at 14h.
---command code 05h---
0Dh BYTE byte read from device if BUSY bit clear on return
---command codes 06h,07h,0Ah,0Bh,0Dh,0Eh,0Fh---
no further fields
---command code 10h---
0Dh BYTE unused
0Eh DWORD transfer address
12h WORD (call) number of bytes to write
(ret) actual number of bytes written
---command codes 11h,12h---
0Dh BYTE reserved
---command code 14h---
no further fields
Note: This is at least true for KKCFUNC.SYS' "device restore".
KKCFUNC.SYS checks that INT 2Fh in the IVT still points
to KKCFUNC's own INT 2Fh entry point. In this case it
restores the original INT 2Fh vector, as recorded at device
init, into the IVT.
SeeAlso: INT 2F/AH=4Dh
---command code 15h---
no further fields
---command codes 13h,19h---
0Dh BYTE category code
00h-7Fh reserved for Microsoft
00h unknown
01h COMn: (serial) (DOS 3.3+)
02h reserved for terminal control
03h CON (DOS 3.3+)
04h reserved for keyboard control
05h LPTn:
07h mouse (European MS-DOS 4.0)
08h disk
48h FAT32 disk control (MS-DOS 7.10+)
80h-FFh reserved for OEM/user-defined
9Eh (STARLITE) Media Access Control driver
EDh (DR PalmDOS) login security
SeeAlso: #01558
0Eh BYTE function code
00h (STARLITE) MAC Bind request
0Fh WORD copy of DS at time of IOCTL call (apparently unused in DOS 3.3)
SI contents (European MS-DOS 4.0)
11h WORD offset of device driver header (see #01646)
DI contents (European MS-DOS 4.0)
13h DWORD pointer to parameter block from INT 21/AX=440Ch or AX=440Dh
---command codes 80h,82h---
0Dh BYTE addressing mode
00h HSG (default)
01h Phillips/Sony Red Book
0Eh DWORD transfer address (ignored for command 82h)
12h WORD number of sectors to read
(if 0 for command 82h, request is an advisory seek)
14h DWORD starting sector number
logical sector number in HSG mode
frame/second/minute/unused in Red Book mode
(HSG sector = minute * 4500 + second * 75 + frame - 150)
18h BYTE data read mode
00h cooked (2048 bytes per frame)
01h raw (2352 bytes per frame, including EDC/ECC)
19h BYTE interleave size (number of sectors stored consecutively)
1Ah BYTE interleave skip factor
(number of sectors between consecutive portions)
---command code 83h---
0Dh BYTE addressing mode
00h HSG (default)
01h Phillips/Sony Red Book
0Eh DWORD transfer address (ignored)
12h WORD number of sectors to read (ignored)
14h DWORD starting sector number (see also above)
---command code 84h---
0Dh BYTE addressing mode
00h HSG (default)
01h Phillips/Sony Red Book
0Eh DWORD starting sector number (see also above)
12h DWORD number of sectors to play
---command codes 85h,88h---
no further fields
---command codes 86h,87h---
0Dh BYTE addressing mode
00h HSG (default)
01h Phillips/Sony Red Book
0Eh DWORD transfer address (ignored in write mode 0)
12h WORD number of sectors to write
14h DWORD starting sector number (also see above)
18h BYTE write mode
00h mode 0 (write all zeros)
01h mode 1 (default) (2048 bytes per sector)
02h mode 2 form 1 (2048 bytes per sector)
03h mode 2 form 2 (2336 bytes per sector)
19h BYTE interleave size (number of sectors stored consecutively)
1Ah BYTE interleave skip factor
(number of sectors between consecutive portions)