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Table 2597

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)


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