From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH 2.4] rewritable USB DVD-RAM vs. mode sense op choice Date: Mon, 23 Aug 2004 19:12:53 +0200 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <20040823171253.GD24089@suse.de> References: <1092673789.4297.7.camel@patlinux.iomegacorp.com> <20040823154850.GC2301@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from ns.virtualhost.dk ([195.184.98.160]:49058 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S266127AbUHWRM5 (ORCPT ); Mon, 23 Aug 2004 13:12:57 -0400 Content-Disposition: inline In-Reply-To: List-Id: linux-scsi@vger.kernel.org To: Pat LaVarre Cc: linux-scsi@vger.kernel.org On Mon, Aug 23 2004, Pat LaVarre wrote: > >the MODE_SENSE_10 a fall back when MODE_SENSE fails > > I believe the specs on the web instead tell us to try MODE_SENSE_10 > first and then fall back to MODE_SENSE. I hear you requesting the > reverse, I will deliver what I hear you request. That's what I would do as well, actually. But since this is 2.4 it's safe to keep old behaviour and only try something new if that fails. > >your device is failing ... ? > > Help, I have more than one device. Doesn't matter > My Iomega REV drive works here because that device accepts both ops, > implementing the SFF/ ANSI MMC specification for op x5A and the > incompatible ANSI SPC specification for op x1A. To achieve > compatibility, I believe every host should try both ops and every > device should accept both ops. > > I mean only to say that I see Linux 2.4 sr_mod mischaracterises the > many DVD/ CD devices that do reject op x1A while accepting only op x5A > MODE_SENSE_10. > > I hesitate to accept the Linux name MODE_SENSE for the op x1A, because > I do not find that claim well-founded in the web for PDT x05 = DVD/ CD > = MMC. I remember Mt Fuji in particular neglects to name op x1A. That's the classical naming, since the 6-byte variant was the original (and surely people would have found it stupid to name it MODE_SENSE_6 back then). So experience usually tell people that when you see READ and READ_10, the former is the old 6-byte variant. Mt Fuji doesn't name any of the 6-byte variants, since they are long deprecated for that class of devices. > >your device is failing ... ? > > In this thread I meant to share the example of 2.4 sr_mod > mischaracterising a USB DVD-RAM drive that rejects op x1A. > > I hear of PATAPI DVD/CD devices that reject op x1A also. I imagine > ide-cd works only by trying op x5A, and not just x1A. Want me to > check? I don't yet know how to trace in Linux the plain hex of the > CDB's that ide-cd sends. Only sr issues 6-byte commands, I don't think support for them was ever required for ATAPI devices. So if you add a fallback to issue MODE_SENSE_10 when _6 fails, you should be golden. -- Jens Axboe