Date: Wed, 21 Aug 2002 12:27:00 -0500 (CDT) From: Chris Dillon <cdillon@wolves.k12.mo.us> To: Terry Lambert <tlambert2@mindspring.com> Cc: "Kenneth D. Merry" <ken@kdm.org>, Thomas Quinot <thomas@cuivre.fr.eu.org>, Nate Lawson <nate@root.org>, <scsi@FreeBSD.ORG>, <current@FreeBSD.ORG> Subject: Re: Proliferating quirk table entries Message-ID: <20020821121019.P93963-100000@duey.wolves.k12.mo.us> In-Reply-To: <3D632D84.1CDEAD3@mindspring.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Tue, 20 Aug 2002, Terry Lambert wrote: > I think everyone in this thread needs to read the last instance of > this same thread, the first time it came up. > > I believe the general consensus was to send the 6, and if it failed, > retry with the 10, and set a flag so that subsequent requests were > 10 (this instead of a static quirk table that could find itself out > of date). As someone mentioned, some devices choke on the first 6-byte command and then just don't work anymore even if you start sending the 10-byte commands from then on. I have a USB multi-flash (CF/MD, MMC, SD, etc) card reader that does exactly that. I have to enable "kern.cam.da.no_6_byte=1" before try to use the device and everything works fine. I also don't have any problems with any of my other SCSI devices (various SCSI CD-ROMs, a SCSI CD-RW, a SCSI ZIP drive, and SCSI DDS2 and DDS3 tape drives) when using only 10-byte commands. What problems would occur if you try 10 first and then 6 if that fails? Will the devices that only take 6-byte commands choke permanently on the first 10-byte command as some of the non-SCSI stuff does on the 6-byte commands, or would they truncate 4 bytes and treat it as the wrong command? I believe someone already proposed this, but since only some very old SCSI devices won't handle 10-byte commands correctly (correct me if I'm wrong there) and should affect very few people, how about just enabling 10-byte commands by default and offering a sysctl to turn on the 6-byte-then-10-byte method when it is needed? The benefit of that should greatly outweigh the drawbacks with the state of the hardware as it is today. -- Chris Dillon - cdillon(at)wolves.k12.mo.us FreeBSD: The fastest and most stable server OS on the planet - Available for IA32 (Intel x86) and Alpha architectures - IA64, PowerPC, UltraSPARC, ARM, and S/390 under development - http://www.freebsd.org No trees were harmed in the composition of this message, although some electrons were mildly inconvenienced. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20020821121019.P93963-100000>