Path: utzoo!attcan!uunet!lll-winken!ames!mailrus!purdue!decwrl!labrea!polya!kaufman
From: kaufman@polya.Stanford.EDU (Marc T. Kaufman)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Apple HD SC 80 does not support Asynch i/o.
Message-ID: <6010@polya.Stanford.EDU>
Date: 10 Jan 89 17:54:27 GMT
References: <11605@dartvax.Dartmouth.EDU> <271@berlin.acss.umn.edu> <27318@ucbvax.BERKELEY.EDU> <13271@cup.portal.com> <5958@polya.Stanford.EDU> <13369@cup.portal.com> <6006@polya.Stanford.EDU>
Reply-To: kaufman@polya.Stanford.EDU (Marc T. Kaufman)
Organization: Stanford University
Lines: 15

In article <6006@polya.Stanford.EDU> kaufman@polya.Stanford.EDU (Marc T. Kaufman) writes:

>I first thought that it would be sufficient to check for BUSY status before
>doing a SCSIget, but I see that an interrupt could occur between the check and
>the Get.  I haven't tried to trace SCSIget, but I think that an indivisible
>check-and-get (i.e. with interrupts off), that returned busy status if the
>bus was already in use, would work.  Is this worth a system patch? or does
>SCSIget already check for busy?

Silly me. I neglected to check the back of IM-V, where a new return from
SCSIget, 'scArbNBErr' is defined.  Given this, why can't we at least START
SCSI operations from interrupt routines (you wouldn't want to hold interrupts
off for the entire operation, though).

Marc Kaufman (kaufman@polya.stanford.edu)