Date: Tue, 26 Mar 1996 07:58:06 -0500 (EST) From: Peter Dufault <dufault@hda.com> To: joerg_wunsch@uriah.heep.sax.de Cc: freebsd-scsi@FreeBSD.org Subject: Re: HP 4020i CD-R wishes Message-ID: <199603261258.HAA03628@hda.com> In-Reply-To: <199603260741.IAA13432@uriah.heep.sax.de> from "J Wunsch" at Mar 26, 96 08:41:16 am
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> > As JULIAN Elischer wrote: > > It is becoming clear that we need to be able to 'stack' SCSI drivers. > > I have three cases of this now... > > > > 1/WORM/CDROM > > 2/TAPE/CHANGER > > and the last.. more amazingly.. > > 3/WORM/CDROM/CHANGER > > > > how can one identify such a situation, and which 'done' routine get's called? > > I think we need some layering scenario like for ioctl commands on > ttys. They are being passed through the general ioctl code first, > then to the line discipline, then down to the physical driver. > (Something like this -- i didn't code-review it now.) We have some layering now, where you go through per-device ioctl code first and then hit the general code if it wasn't handled. It would probably benefit from one more layer: Specific device (specific WORM for example); Type device (WORM class) General device (set debugging, etc). In terms of stacking - how about "This is a WORM and a CDROM and a CHANGER", and you have to potentially open three devices to exercise all three "personalities". Then which done to call is clear. We have to pay attention to locking issues. -- Temporarily via "hdalog@zipnet.net"... Peter Dufault Real-Time Machine Control and Simulation HD Associates, Inc. Voice: 508 433 6936 dufault@hda.com Fax: 508 433 5267
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