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|
! Copyright (c) 1997 Helmut Wirth <hfwirth@ping.at>
! All rights reserved.
!
! Redistribution and use in source and binary forms, with or without
! modification, are permitted provided that the following conditions
! are met:
! 1. Redistributions of source code must retain the above copyright
! notice immediately at the beginning of the file, witout modification,
! this list of conditions, and the following disclaimer.
! 2. Redistributions in binary form must reproduce the above copyright
! notice, this list of conditions and the following disclaimer in the
! documentation and/or other materials provided with the distribution.
! 3. The name of the author may not be used to endorse or promote products
! derived from this software without specific prior written permission.
!
! THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
! IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
! OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
! IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
! INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
! NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
! DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
! THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
! (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
! THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
!
! $Id$
!
! This driver is needed for Expanded Memory emulation (EMS). A driver
! is needed here, because EMS drivers are installed as DOS devices
! with the name "EMMXXXX0" and programs look for such a device while
! checking the existence of EMS.
! The driver is installed by CONFIG.SYS, it has no options. It uses
! the emulator callback interrupt 0xff to initialize the EMS subsystem.
! If EMS is not configured or if there is an error inside the emulator
! the driver reports failure and does not install itself.
! If all works, the driver changes the interrupt vector for int 0x67 to
! point at itself. The resident part of the drivers simlpy routes calls
! to int 0x67 to the correct subfunction of the emulator callback interrupt.
use16
.text
.bss
.data
.align 0
.org 0
NumFunc = 15
! Emulator interrupt entry
EmulatorINT = 0xFF
! Emulator EMS callback function
EMU_EMS = 0x2
EMU_EMS_CTL = 0
EMU_EMS_CALL = 1
! DOS print message
DOSMesg = 0x9
cr = 0xd
lf = 0xa
eom = '$' ! DOS end of string
EMSintnum = 0x67
Intoffset = (EMSintnum * 4)
.globl _main
_main:
driverhead:
.long -1 ! link to next device driver
.word 0xC000 ! attribute word for driver
.word Strategy ! ptr to strategy routine
.word Interrupt ! ptr to interrupt service routine
.ascii "EMMXXXX0" ! logical device name
reqhead:
.long 0
vectordone:
.word 0 ! != 0 , if vector installed
FuncTable:
.word InitDrv ! initialize driver
.word Noop ! media Check
.word Noop ! build BPB
.word Noop ! Ioctl
.word Noop ! read
.word Noop ! non destructive read
.word Noop ! input status
.word Noop ! flush input
.word Noop ! write
.word Noop ! write with verify
.word Noop ! output status
.word Noop ! flush output
.word Noop ! ioctl output
.word Noop ! open device
.word Noop ! close device
.word Noop ! removeable media check
Strategy:
seg cs
mov [reqhead], bx
seg cs
mov [reqhead+2],es
retf
Interrupt:
push ax
push bx
push cx
push dx
push ds
push es
push di
push si
push bp
push cs
pop ds
les di,[reqhead] ! load pointer to request header
seg es
movb bl,[di+2]
xorb bh,bh
cmp bx, #NumFunc
jle dointr
call errorhandler
jmp intrend
dointr:
shl bx,#1
call [bx+FuncTable]
les di,[reqhead] ! load pointer to request header
intrend:
or ax,#0x100 ! done bit
seg es
mov [di+3],ax
pop bp
pop si
pop di
pop es
pop ds
pop dx
pop cx
pop bx
pop ax
retf
errorhandler:
mov ax,#0x8003 ! report error to caller
ret
! This is done for all functions except init. It supports the different
! methods for an EMS installation check described in the LIM EMS 4.0 spec
Noop:
call installvector
xor ax,ax
ret
! The interrupt vector installed for int 0x67 points to this routine
intr67:
push ax ! Save original AX
mov ah, #EMU_EMS ! Emuint function
mov al, #EMU_EMS_CALL ! Emuint subfunction
int EmulatorINT ! Call emulator for EMS
iret
installvector:
push cs
pop ds ! load DS to use local data
mov ax,[vectordone]
cmp ax,#0
jne isinstalled ! already installed
push di ! save request header pointer
push es
mov ax, #0 ! write the new interrupt vector
mov es, ax
mov di, #Intoffset
seg es
mov [di], #intr67
seg es
mov [di+2], cs
pop es
pop di
mov ax,#1
mov [vectordone],ax
isinstalled:
ret
InitDrv:
push cs
pop ds
push ax
mov ah, #EMU_EMS ! Emuint function
mov al, #EMU_EMS_CTL ! Emuint subfunction
int EmulatorINT
cmp ax,#0 ! check if successful
je Fail
call installvector
push cs
pop ds
mov ah, #DOSMesg
mov dx, #Success
int 0x21
seg es
mov [di+14], #InitDrv ! address break for driver
seg es
mov [di+16], cs
xor ax,ax
ret
Fail:
push cs
pop ds
mov ah, #DOSMesg
mov dx, #Failure
int 0x21
seg es
movb [di+13],#0
seg es
mov [di+20],cs
seg es
mov [di+14],#0 ! address break == 0, no driver
seg es
mov [di+16],cs
ret
Success:
.ascii "Doscmd EMS 4.0 driver installed"
.byte cr,lf,eom
Failure:
.byte cr,lf,lf
.ascii "EMS emulation is disabled"
.byte cr,lf
.ascii "Driver not installed"
.byte cr,lf,lf,eom
end
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