From owner-freebsd-scsi Thu Feb 21 15: 8:55 2002 Delivered-To: freebsd-scsi@freebsd.org Received: from rwcrmhc54.attbi.com (rwcrmhc54.attbi.com [216.148.227.87]) by hub.freebsd.org (Postfix) with ESMTP id 2285037B405 for ; Thu, 21 Feb 2002 15:08:51 -0800 (PST) Received: from gateway.posi.net ([12.236.90.177]) by rwcrmhc54.attbi.com (InterMail vM.4.01.03.27 201-229-121-127-20010626) with ESMTP id <20020221230850.DHUA1214.rwcrmhc54.attbi.com@gateway.posi.net>; Thu, 21 Feb 2002 23:08:50 +0000 Received: from localhost (kbyanc@localhost) by gateway.posi.net (8.11.6/8.11.6) with ESMTP id g1LN8nk89214; Thu, 21 Feb 2002 15:08:49 -0800 (PST) (envelope-from kbyanc@posi.net) X-Authentication-Warning: gateway.posi.net: kbyanc owned process doing -bs Date: Thu, 21 Feb 2002 15:08:49 -0800 (PST) From: Kelly Yancey To: Joerg Wunsch Cc: =?iso-8859-1?Q?G=E9rard_Roudier?= , Subject: Re: RBC support patch In-Reply-To: <20020221140554.N89039-100000@gateway.posi.net> Message-ID: <20020221150706.C89039-100000@gateway.posi.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=X-UNKNOWN Content-Transfer-Encoding: QUOTED-PRINTABLE Sender: owner-freebsd-scsi@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org Argh. Nevermind, it looks like Shimokawa-san is already on the problem. After his patch is committed, maybe then I'll look into 10->6 conversion fo= r READ if anyone still thinks it is necessary. Kelly kbyanc@{posi.net,FreeBSD.org} On Thu, 21 Feb 2002, Kelly Yancey wrote: > On Thu, 21 Feb 2002, Joerg Wunsch wrote: > > > As G=E9rard Roudier wrote: > > > > > My understanding is that WRITE(10) is just meaningless for read-only > > > devices, thus optionnal. But this is not worded this way in the > > > specs. > > > > Yep, i thought so, too, after reading the specs a bit more carefully. > > -- > > cheers, J"org .-.-. --... ...-- -.. . DL8DTL > > I stand corrected: READ(6) and READ(10) are both mandatory in SCSI2. I= just > eyeballed the WRITE commands (which are both optional) and assumed that > applied to READ also. But on second intespection, I see that you are cor= rect. > Nonetheless, per Justin's suggestion, I am preparing patches to convert 6= byte > commands to 10 byte once a device returns 'command not supported' for the= 6 > byte version. > Per recent discussion, I may try and implement 10 to 6 conversion that = may > be used if the command the DPO, FUA, and RelAdr bits are clear, the trans= fer > length is under 256 blocks, and the LBA fits in 21 bits. In which case, = if > a READ(10) fails, it can fall back to READ(6) (assuming a 6 byte read has= n't > already failed). In which case, we can determine which size we prefer to= try > first based on SCSI revision (>=3D2 try 10 byte commands first, <2 try 6 = byte > commands first) with fallback should that fail. But note that while > 6 to 10 appears fairly straightforward, currently I am only considering > converting 10 byte reads to 6 byte reads right now. I'm not too comforta= ble > about the number of restrictions involved to downgrade a later command se= t to > an earlier one (as demonstrated by the READ criteria I listed above). > This is all getting a bit more complicated than I had originally planne= d. > Still doable, it's just going to take me a little longer. Please hold of= f on > suggesting any more cases/features until I post patches. :) Thanks, > > Kelly > kbyanc@{posi.net,FreeBSD.org} > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-scsi" in the body of the message > -- Kelly Yancey - kbyanc@posi.net - Belmont, CA Lead Engineer, Backplane, Inc. http://www.backplane.com/ Maintainer, BSD Driver Database http://www.posi.net/freebsd/drivers/ Coordinator, Team FreeBSD http://www.posi.net/freebsd/Team-FreeBSD/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message