;
; read34.asm
;
; interface code for the "2 more players" parallel port hack.
;
	csect	text			; this here's the meat

	xdef	Name			; Name of our application, so that
Name	dc.b	'4play',0		; other applications will know
					; who's tying up the port. ;-)


	xdef	_read34			; function names for linker
	xdef	_getport
	xdef	_freeport

	xref	_portptr		; c pointer for port data
	xref	_fireptr		; c pointer for fire buttons

	xref	_SysBase		; exec system base (from c.o)


	INCLUDE	"resources/misc.i"


	xdef	MiscName
MiscName	MISCNAME		; macro from resources/misc.i

	xdef	_MiscResource
_MiscResource	dc.l	0		; place to store misc.resource base

;parallel port hardware addresses (from amiga.lib)

	xref	_ciaaprb			; the actual port address
	xref	_ciaaddrb		; data direction register

	xref	_ciabpra			; control lines are here
	xref	_ciabddra		; data direction register
;from amiga.lib
	xref	_LVOOpenResource
	xref	_LVOAllocMiscResource
	xref	_LVOFreeMiscResource

_getport
;This routine simply allocates the parallel port in a system friendly
;way, and sets up the lines we want to use as input lines.
;


;save registers on the stack

	movem.l	a2-a6/d2-d7,-(sp)	; push regs


;open the misc.resource

	lea	MiscName,a1		; put name of misc.resource in a1
	movea.l	_SysBase,a6		; put SysBase in a6
	jsr	_LVOOpenResource(a6)
	move.l	d0,_MiscResource	; store address of misc.resource
	bne.s	grabit

;Oops, couldn't open misc.resource.  Sounds like big trouble to me.

	moveq	#20,d0			; error code
	bra	done


;This is where we grab the hardware.  If some other task has allocated
;the parallel data port or the parallel control bits, this routine will
;return non-zero.

;This part grabs the port itself

grabit	lea	Name,a1			; The name of our app
	moveq	#MR_PARALLELPORT,d0	; what we want
	movea.l	_MiscResource,a6	; MiscResource Base is in A6
	jsr	_LVOAllocMiscResource(a6)
	move.l	d0,d1
	beq.s	grab2

;well, somebody else must've got the port first.

	moveq	#30,d0			; error code
	bra	done

;This part grabs the control bits (busy, pout, and sel.)
;We really don't need pout, but it comes free with PARALLELBITS,
;so we'll take it anyway.

grab2	lea	Name,a1			; The name of our app
	moveq	#MR_PARALLELBITS,d0	; what we want
	jsr	_LVOAllocMiscResource(a6)
	move.l	d0,d1
	beq.s	setread

;well, somebody else must've got the bits first.

	moveq	#40,d2
	bra	freepar


;set up parallel port for reading

setread	move.b	#0,_ciaaddrb		; all lines read

	andi.b	#$FF,_ciabddra		; busy, pout, and sel. to read

;Well, we made it this far, so we've got exclusive access to
;the parallel port, and all the lines we want to use are
;set up.   From here we can just put back the regs and return to
;the caller.

	bra	done


;If something happened AFTER we got exclusive access to the parallel port,
;we'll need to let go of the port before we return the error.

freepar	moveq	#MR_PARALLELPORT,d0
	movea.l	_MiscResource,a6
	jsr	_LVOFreeMiscResource(a6)

	move.l	d2,d0			; put error code into d0


;Restore registers and return
;(error code is in d0)

done	movem.l (sp)+,a2-a6/d2-d7	; pop regs
	rts


_freeport
;This routine just makes sure that we let go of the parallel port and
;control lines, so somebody else can use 'em, now that we're all done.
;
;PS - Don't call this one if you got an error from _getport, as some
;of the resources might not have been opened, etc.
;

;save registers on the stack

	movem.l	a2-a6/d2-d7,-(sp)	; push regs


;free control lines

	moveq	#MR_PARALLELBITS,d0
	movea.l	_MiscResource,a6
	jsr	_LVOFreeMiscResource(a6)


;free parallel port

	moveq	#MR_PARALLELPORT,d0
	movea.l	_MiscResource,a6
	jsr	_LVOFreeMiscResource(a6)


;Clean up, restore registers, and return

	movem.l (sp)+,a2-a6/d2-d7	; pop regs
	rts


_read34
;All this routine does is copy the data from the ports to other addresses.
;
;In this case the destinations happens to be whatever C variables are
;pointed at by _portptr and _fireptr.
;

	movea.l	_portptr,a1		; a1 now holds the destination
	move.b	_ciaaprb,(a1)		; move byte from port to dest

	movea.l	_fireptr,a1		; a1 now holds the destination
	move.b	_ciabpra,(a1)		; move byte from port to dest

	rts

	end