Path: utzoo!mnetor!uunet!husc6!hao!ames!ucbcad!ucbvax!CORY.BERKELEY.EDU!dillon
From: dillon@CORY.BERKELEY.EDU (Matt Dillon)
Newsgroups: comp.sys.amiga
Subject: Re: one last word on my simple device problem
Message-ID: <8712242040.AA01446@cory.Berkeley.EDU>
Date: 24 Dec 87 20:40:21 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 62

:In article <8712241144.AA26621@cory.Berkeley.EDU> dillon@CORY.BERKELEY.EDU (Matt Dillon) writes:
:>						The reply port is actually
:>	supplied by the device driver (I think.. at least it is NOT supplied
:>	by the DoIO() function, and NOT by the user, so that leaves the 
:>	device driver!)
:
:This give me a real uncomfortable feeling inside.  I'm not so sure that the
:use doesn't need to provide a ReplyPort for requests that are started using
:DoIO().  For all of the sample device drivers I've seen, as well as the
:diddly drivers that I've written, it sure seems that the user has to provide
:the port.
:
:In fact, the device can't provide its own internal reply port for DoIO() to
:use.  This is because the device doesn't know if he was called by DoIO(), or
:if the user decided to just do a BeginIO on his own with the QUICKIO flag
:set.
:

	You are right... it looks like DoIO() needs a reply port!  The DoIO()
ROM code itself makes an access through the replyport field without checking
to see if it is NULL first:

?			DoIO()

                   move.l  a1,-(a7)
                   move.b  #1,1e(a1)		set IOF_QUICK
                   move.l  a6,-(a7)
                   movea.l 14(a1),a6
                   jsr     -1e(a6)		call device driver
                   movea.l (a7)+,a6
                   movea.l (a7)+,a1
                   btst    #0,1e(a1)		check IOF_QUICK
                   bne.s   done2		if still set, DONE
                   move.l  a2,-(a7)
?u
                   movea.l a1,a2
                   movea.l e(a2),a0		A0=reply port
                   move.b  f(a0),d1		D1=sig bit
                   moveq   #0,d0
                   bset    d1,d0

		   Disable()

loop               cmpi.b  #7,8(a2)		nt_Type.. has request been
						returned?
                   beq.s   done
		   Wait()			Wait 
?u
                   bra.s   loop			Loop.
		   UnLink()			Unlink request
		   Enable()			Re-enable

done:              movea.l (a7)+,a2
done2:             move.b  1f(a1),d0		error field in request
                   ext.w   d0
                   ext.l   d0
                   rts

P.S. I simplified the disassembly... All the calls except Wait() are actually
in-line code.  

					-Matt