From owner-freebsd-scsi Tue Mar 26 05:08:52 1996 Return-Path: owner-freebsd-scsi Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id FAA03320 for freebsd-scsi-outgoing; Tue, 26 Mar 1996 05:08:52 -0800 (PST) Received: from hda.com ([199.232.245.71]) by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id FAA03314 for ; Tue, 26 Mar 1996 05:08:49 -0800 (PST) Received: (from dufault@localhost) by hda.com (8.6.11/8.6.9) id HAA03628; Tue, 26 Mar 1996 07:58:06 -0500 From: Peter Dufault Message-Id: <199603261258.HAA03628@hda.com> Subject: Re: HP 4020i CD-R wishes To: joerg_wunsch@uriah.heep.sax.de Date: Tue, 26 Mar 1996 07:58:06 -0500 (EST) Cc: freebsd-scsi@FreeBSD.org Reply-To: hdalog@zipnet.net In-Reply-To: <199603260741.IAA13432@uriah.heep.sax.de> from "J Wunsch" at Mar 26, 96 08:41:16 am X-Mailer: ELM [version 2.4 PL24] Content-Type: text Sender: owner-freebsd-scsi@FreeBSD.org X-Loop: FreeBSD.org Precedence: bulk > > 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