name driver
page 55,132
title 'DRIVER --- installable driver template'
;
; This is a "template" for a MS-DOS installable device driver.
; The actual driver subroutines are stubs only and have
; no effect but to return a non-error "done" status.
;
; Ray Duncan
; Laboratory Microsystems Inc.
; April 1985
code segment public 'CODE'
driver proc far
assume cs:code,ds:code,es:code
org 0
Max_Cmd equ 15 ; MS-DOS command code maximum
; this is 15 for MS-DOS 3.x
; and 12 for MS-DOS 2.x
cr equ 0dh ; ASCII carriage return
lf equ 0ah ; ASCII line feed
eom equ '$' ; end of message signal
page
;
; Device Driver Header
;
Header dd -1 ;link to next device,-1= end of list
dw 8000h ;attribute word
;bit 15=1 for character devices
dw Strat ;device "Strategy" entry point
dw Intr ;device "Interrupt" entry point
db 'DRIVER ' ;char device name, 8 char, or
;if block device, no. of units
;in first byte followed by
;7 don't care bytes
; IntERPretation of Attribute word:
;
; Bit Significance
;
; 15 =1 for character drivers
; 14 =1 if driver can handle IOCTL
; 13 =1 if block device & non-IBM format
; 12 0
; 11 open/close/RM supported (DOS 3.x)
; 10 0
; 9 0
; 8 0
; 7 0
; 6 0
; 5 0
; 4 0
; 3 =1 if CLOCK device
; 2 =1 if NUL device
; 1 =1 if Standard Output
; 0 =1 if Standard Input
page
;
; local variables for use by driver
;
RH_Ptr dd ? ; pointer to request header
; passed to Strat by BDOS
Ident db cr,lf,lf
db 'LMI Example Device Driver 1.0'
db cr,lf
db 'Copyright (c) 1985 '
db 'Laboratory Microsystems Inc.'
db cr,lf,lf,eom
;
; MS-DOS Command Codes dispatch table.
; The "Interrupt" routine uses this table and the
; Command Code supplied in the Request Header to
; transfer to the appropriate driver subroutine.
Dispatch:
dw Init ; 0 = init driver into system
dw Media_Chk ; 1 = media check on blk dev
dw Build_BPB ; 2 = build BIOS param block
dw Ioctl_Inp ; 3 = I/O ctrl read from dev
dw Input ; 4 = normal destructive read
dw Nd_Input ; 5 = non-destructive read,no wait
dw Inp_Stat ; 6 = return current input status
dw Inp_Flush ; 7 = flush device input buffers
dw Output ; 8 = normal output to device
dw Outp_Vfy ; 9 = output with verify
dw Outp_Stat ; 10 = return current output status
dw Outp_Flush ; 11 = flush output buffers
dw Ioctl_Outp ; 12 = I/O control output
dw Dev_Open ; 13 = device open (MS-DOS 3.x)
dw Dev_Close ; 14 = device close (MS-DOS 3.x)
dw Rem_Media ; 15 = removeable media (MS-DOS 3.x)
page
;
; MS-DOS Request Header structure definition
;
; The first 13 bytes of all Request Headers are the same
; and are referred to as the "Static" part of the Header.
; The number and meaning of the following bytes varies.
; In this "Struc" definition we show the Request Header
; contents for Read and Write calls.
;
Request struc ; request header template structure
; beginning of "Static" portion
Rlength db ? ; length of request header
Unit db ? ; unit number for this request
Command db ? ; request header's command code
Status dw ? ; driver's return status word
Reserve db 8 dup (?) ; reserved area
; end of "Static" portion
Media db ? ; media descriptor byte
Address dd ? ; memory address for transfer
Count dw ? ; byte/sector count value
Sector dw ? ; starting sector value
Request ends ; end of request header template
;
; Status word is interpreted as follows:
;
; Bit(s) Significance
; 15 Error
; 10-14 Reserved
; 9 Busy
; 8 Done
; 0-7 Error code if bit 15=1
; Predefined BDOS error codes are:
;
; 0 Write protect violation
; 1 Unknown unit
; 2 Drive not ready
; 3 Unknown command
; 4 CRC error
; 5 Bad drive request structure length
; 6 Seek error
; 7 Unknown media
; 8 Sector not found
; 9 Printer out of paper
; 10 Write fault
; 11 Read fault
; 12 General failure
; 13-14 Reserved
; 15 Invalid disk change (MS-DOS 3.x)
page
; Device Driver "Strategy Routine"
; Each time a request is made for this device, the BDOS
; first calls "Strategy routine", then immediately calls
; the "Interrupt routine".
; The Strategy routine is passed the address of the
; Request Header in ES:BX, which it saves in a local
; variable and then returns to the BDOS.
Strat proc far
; save address of Request Header
mov word ptr cs:[RH_Ptr],bx
mov word ptr cs:[RH_Ptr+2],es
ret ; back to BDOS
Strat endp
page
; Device Driver "Interrupt Routine"
; This entry point is called by the BDOS immediately after
; the call to the "Strategy Routine", which saved the long
; address of the Request Header in the local variable "RH_Ptr".
; The "Interrupt Routine" uses the Command Code passed in
; the Request Header to transfer to the appropriate device
; handling routine. Each command code routine is responsible
; for any necessary return information into the Request Header,
; then transfers to Error or Exit to set the Return Status code.
Intr proc far
push ax ; save general re
