xdma.lst

DOS下的dma读写驱动

   487 0000021E 1F                      	pop	ds
   488 0000021F C3                      VDExit	ret			;Exit.
   489                                  ;
   490                                  ; Subroutine to execute read and write commands.
   491                                  ;
   492 00000220 66C7473000000000        BufDMA	mov	dword [bx+IOAdr-@],0 ;Buffered -- set XMS buffer addr.
   493                                  @XBufAd	equ	$-4		;(XMS 32-bit buffer address, Init set).
   494 00000228 8B5708                  DoDMA	mov	dx,[bx+DMAAd-@]	;Ensure any previous DMA is stopped!
   495 0000022B EC                      	in	al,dx		;(On some older chipsets, if DMA is
   496 0000022C 24FE                    	and	al,0FEh		;  running, reading an IDE register
   497 0000022E EE                      	out	dx,al		;  causes the chipset to "HANG"!!).
   498 0000022F 8A4720                  	mov	al,[bx+DSCmd-@]	;Select our desired disk.
   499 00000232 24F0                    	and	al,0F0h
   500 00000234 8A5707                  	mov	dl,[bx+IDEAd-@]
   501 00000237 B601                    	mov	dh,001h
   502 00000239 EE                      	out	dx,al
   503 0000023A 89D7                    	mov	di,dx		;Save IDE drive-select address.
   504 0000023C B94008                  	mov	cx,(RDYTO*256)+(FLT*2)  ;Get timeout & "fault" mask.
   505 0000023F E85600                  	call	Await		;Await controller- and disk-ready.
   506 00000242 72DB                    	jc	VDExit		;If any errors, exit above!
   507 00000244 56                      	push	si		;Save BIOS timer pointer.
   508 00000245 BE[1400]                	mov	si,PRDAd	;Point to parameters we will output.
   509 00000248 F6440D12                	test	byte [si+IOCmd-PRDAd],012h  ;Is this a write request?
   510 0000024C 7502                    	jnz	SetDMA		;Yes, reset DMA command register.
   511 0000024E B008                    	mov	al,008h		;Get "DMA read" command bit.
   512 00000250 8B5708                  SetDMA	mov	dx,[bx+DMAAd-@]	;Reset DMA commands and set DMA mode.
   513 00000253 EE                      	out	dx,al
   514 00000254 42                      	inc	dx		;Point to DMA status register.
   515 00000255 42                      	inc	dx
   516 00000256 EC                      	in	al,dx		;Reset DMA status register.
   517 00000257 0C06                    	or	al,006h		;(Done this way so we do NOT alter
   518 00000259 EE                      	out	dx,al		;  the "DMA capable" status flags!).
   519 0000025A 42                      	inc	dx		;Set PRD pointer to our DMA address.
   520 0000025B 42                      	inc	dx
   521 0000025C 666F                    	outsd
   522 0000025E B8F701                  	mov	ax,001F7h	;Set IDE parameter-output flags.
   523 00000261 8D55FB                  NxtPar	lea	dx,[di+CSECCT-CDSEL-1]  ;Point to IDE sector count -1.
   524 00000264 42                      IDEPar	inc	dx		;Output all ten LBA48 parameter bytes.
   525 00000265 6E                      	outsb			;(1st 4 overlayed by 2nd 4 if LBA28!).
   526 00000266 D1E8                    	shr	ax,1		;More parameters to go in this group?
   527 00000268 72FA                    	jc	IDEPar		;Yes, loop back and output next one.
   528 0000026A 75F5                    	jnz	NxtPar		;If first 4 done, go output last 6.
   529 0000026C 5E                      	pop	si		;Reload BIOS timer pointer.
   530 0000026D B603                    	mov	dh,003h		;Get IDE alternate-status address.
   531 0000026F 4A                      	dec	dx		;(Primary-status address | 300h - 1).
   532 00000270 263A2C                  ChkDRQ	cmp	ch,[es:si]	;Too long without 1st data-request?
   533 00000273 7476                    	je	DMAEnd		;Yes?  Return carry and DMA timeout!
   534 00000275 EC                      	in	al,dx		;Read IDE alternate status.
   535 00000276 2408                    	and	al,DRQ		;Has 1st data-request arrived?
   536 00000278 74F6                    	jz	ChkDRQ		;No, loop back and check again.
   537 0000027A 8B5708                  	mov	dx,[bx+DMAAd-@]	;Point to DMA command register.
   538 0000027D EC                      	in	al,dx		;Set DMA Start/Stop bit (starts DMA).
   539 0000027E 40                      	inc	ax
   540 0000027F EE                      	out	dx,al
   541 00000280 F6472100                	test	byte [bx+IOCmd-@],0	;Overlap output request?
   542                                  @Ovlp2	equ	$-1			;(012h if overlap enabled).
   543 00000284 741E                    	jz	ChkDMA			;No, go await input end.
   544 00000286 8A4713                  	mov	al,[bx+ReqBF-@]		;Post channel "overlap" flag,
   545 00000289 2460                    	and	al,060h			;  so other IDE drivers WAIT!
   546 0000028B C0E802                  	shr	al,2
   547 0000028E 084712                  	or	[bx+Flags-@],al
   548 00000291 C6470608                	mov	byte [bx+Timer-@],RDYTO	;Set 400-msec timeout count.
   549 00000295 31C0                    	xor	ax,ax			;Return success & zero carry.
   550 00000297 C3                      	ret				;Exit back to "BufOut" logic.
   551                                  ;
   552                                  ; Subroutine to await end of I-O.
   553                                  ;
   554 00000298 8EC3                    Await	mov	es,bx		;Point to low-memory BIOS timer.
   555 0000029A BE6C04                  	mov	si,BIOSTMR
   556 0000029D 26022C                  	add	ch,[es:si]	;Set timeout limit in CH-reg.
   557 000002A0 D0E9                    	shr	cl,1		;Are we only checking drive "ready"?
   558 000002A2 7320                    	jnc	ChkRdy		;Yes, use logic below.
   559 000002A4 42                      ChkDMA	inc	dx		;Point to DMA status register.
   560 000002A5 42                      	inc	dx
   561 000002A6 EC                      	in	al,dx		;Read DMA controller status.
   562 000002A7 4A                      	dec	dx		;Point back to DMA command register.
   563 000002A8 4A                      	dec	dx
   564 000002A9 2406                    	and	al,DMI+DME	;DMA interrupt or DMA error?
   565 000002AB 7505                    	jnz	HltDMA		;Yes, halt DMA and check results.
   566 000002AD 263A2C                  	cmp	ch,[es:si]	;Has our DMA transfer timed out?
   567 000002B0 75F2                    	jne	ChkDMA		;No, loop back and check again.
   568 000002B2 50                      HltDMA	push	ax		;Save ending DMA status.
   569 000002B3 EC                      	in	al,dx		;Reset DMA Start/Stop bit.
   570 000002B4 24FE                    	and	al,0FEh
   571 000002B6 EE                      	out	dx,al
   572 000002B7 58                      	pop	ax		;Reload ending DMA status.
   573 000002B8 3C04                    	cmp	al,DMI		;Did DMA end with only an interrupt?
   574 000002BA 752D                    	jne	ErrDMA		;No?  Go see what went wrong.
   575 000002BC 42                      	inc	dx		;Reread DMA controller status.
   576 000002BD 42                      	inc	dx
   577 000002BE EC                      	in	al,dx
   578 000002BF A802                    	test	al,DME		;Any "late" DMA error after DMA end?
   579 000002C1 7528                    	jnz	DMAEnd		;Yes?  Return carry and DMA error!
   580 000002C3 41                      	inc	cx		;Check "fault" and hard-error at end.
   581 000002C4 8D5501                  ChkRdy	lea	dx,[di+CSTAT-CDSEL]  ;Read IDE primary status.
   582 000002C7 EC                      	in	al,dx
   583 000002C8 A8C0                    	test	al,BSY+RDY	;Controller or disk still busy?
   584 000002CA 7F0C                    	jg	ChkErr		;No, go check for "fault" or error.
   585 000002CC 263A2C                  	cmp	ch,[es:si]	;Too long without becoming ready?
   586 000002CF 75F3                    	jne	ChkRdy		;No, loop back and check again.
   587 000002D1 A880                    	test	al,BSY		;BAAAD News!  Did controller go ready?
   588 000002D3 B88A00                  	mov	ax,(256*CTLRERR)+DISKERR ;(Get not-ready error codes).
   589 000002D6 EB09                    	jmp	short WhichE	;Go see which error code to return.
   590 000002D8 20C8                    ChkErr	and	al,cl		;Disk "fault" or hard-error?
   591 000002DA 740C                    	jz	ChkExit		;No, all is well -- go exit below.
   592 000002DC A820                    	test	al,FLT		;BAAAD News!  Is the disk "faulted"?
   593 000002DE B8BFAC                  	mov	ax,(256*FAULTED)+HARDERR ;(Get hardware error codes).
   594 000002E1 7402                    WhichE	jz	EndErr		;If "zero", use AL-reg. return code.
   595 000002E3 88E0                    	mov	al,ah		;Use AH-reg. return code of this pair.
   596 000002E5 00C8                    EndErr	add	al,cl		;Add 1 if error occurred at I-O end.
   597 000002E7 F9                      Kaput	stc			;Set carry flag to denote "error"!
   598 000002E8 C3                      ChkExit	ret			;Exit.
   599 000002E9 A802                    ErrDMA	test	al,DME		;BAAAD News!  Did DMA end with error?
   600 000002EB B8E8EF                  DMAEnd	mov	ax,(256*DMAERR)+DMATIMO	 ;(Get DMA error codes).
   601 000002EE EBF1                    	jmp	short WhichE	;Go see which error code to return.
   602                                  BaseLmt	equ	$		;End of resident "basic" logic.
   603                                  BaseEnd	equ	$+BSTACK	;End of resident "basic" driver.
   604                                  ;
   605                                  ; Subroutine to display an error-message number.   At entry, the BL-
   606                                  ;   register has the digits count, and the AX-register has the data.
   607                                  ;
   608 000002F0 43                      Dsply4	inc	bx		;Set 4-digit display count.
   609 000002F1 43                      	inc	bx
   610 000002F2 43                      Dsply2	inc	bx		;Set 2-digit display count.
   611 000002F3 43                      Dsply1	inc	bx		;Set 1-digit display count.
   612 000002F4 C1C004                  DsplyN	rol	ax,4		;Get next hex digit in low-order.
   613 000002F7 50                      	push	ax		;Save remaining digits.
   614 000002F8 240F                    	and	al,00Fh		;Mask off next hex digit.
   615 000002FA 3C09                    	cmp	al,009h		;Is digit 0-9?
   616 000002FC 7602                    	jbe	DspNmA		;Yes, convert to ASCII.
   617 000002FE 0407                    	add	al,007h		;Add A-F offset.
   618 00000300 0430                    DspNmA	add	al,030h		;Convert digit to ASCII.
   619 00000302 E87800                  	call	DsplyB		;Display digit using the BIOS.
   620 00000305 58                      	pop	ax		;Reload remaining digits.
   621 00000306 4B                      	dec	bx		;More digits to go?
   622 00000307 75EB                    	jnz	DsplyN		;Yes, loop back.
   623 00000309 C3                      	ret			;Exit.
   624                                  ;
   625                                  ; Subroutine to display an error-message "text" element.
   626                                  ;   At entry, the "text" pointer is in the SI-register.
   627                                  ;
   628 0000030A E87000                  DspNxt	call	DsplyB		;Display byte using the BIOS.
   629 0000030D FC                      DsplyM 	cld			;Ensure FORWARD "string" commands!
   630 0000030E AC                      	lodsb			;Get next output byte.
   631 0000030F 08C0                    	or	al,al		;Are we at the terminating "null"?
   632 00000311 75F7                    	jnz	DspNxt		;No, loop back & display next byte.
   633 00000313 C3                      	ret			;Exit.
   634                                  ;
   635                                  ; Subroutine to await overlap end and display any output-error message.
   636                                  ; NOTE:  Starting in V3.1 XDMA, "OCheck" is FIXED to address 00314h, so
   637                                  ;	 XCDROM or other IDE drivers can call "OCheck" and have it wait
   638                                  ;	 for overlap-end, before doing their own I-O on an IDE channel.
   639                                  ;
   640 00000314 60                      OCheck	pusha			;Save all CPU registers.
   641 00000315 1E                      	push	ds
   642 00000316 06                      	push	es
   643 00000317 0E                      	push	cs		;Set our DS-register.
   644 00000318 1F                      	pop	ds
   645 00000319 31DB                    	xor	bx,bx		;Zero BX-reg. for relative commands.
   646 0000031B 804F1280                	or	byte [bx+Flags-@],080h  ;Set driver I-O "busy" flag.
   647 0000031F FB                      	sti			;Re-enable CPU interrupts.
   648 00000320 B94101                  	mov	cx,257+(FLT*2)	;Set 1 extra count & "fault" mask.