From mboxrd@z Thu Jan 1 00:00:00 1970 From: Douglas Gilbert Subject: Re: [Bug 7026] CD/DVD burning with USB writer doesn't work Date: Wed, 06 Dec 2006 11:57:05 -0500 Message-ID: <4576F661.2000802@torque.net> References: <1165355432.2785.20.camel@mulgrave.il.steeleye.com> <4575f6c6.RvoLkLFpmxoSf6pC%Joerg.Schilling@fokus.fraunhofer.de> <1165359506.2785.37.camel@mulgrave.il.steeleye.com> <4575fd53.ja06l7+Yx9/C/OYS%Joerg.Schilling@fokus.fraunhofer.de> <1165421548.2810.17.camel@mulgrave.il.steeleye.com> Reply-To: dougg@torque.net Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from pentafluge.infradead.org ([213.146.154.40]:53972 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936527AbWLFQ57 (ORCPT ); Wed, 6 Dec 2006 11:57:59 -0500 In-Reply-To: <1165421548.2810.17.camel@mulgrave.il.steeleye.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: Joerg Schilling , stern@rowland.harvard.edu, schilling@fokus.fraunhofer.de, linux-scsi@vger.kernel.org, dgilbert@interlog.com James Bottomley wrote: > On Wed, 2006-12-06 at 00:14 +0100, Joerg Schilling wrote: >> Well, accept the patch if it works. > > It's not about work/not work: it's about correctness. > >> And in case that you don't like it, make sure that the _parameter_ is >> moved to where it belongs: to the low level transport layer. > > It's not a low level property; it's a property of the generic queue, > namely the maximum request size. It exists for devices independent of > SCSI (i.e. you'll want it for IDE and weirder transport attachment CDs > as well). Too much smoke and mirrors. That maximum request size comes from the transport ** and in many cases is a kludge between maximum, optimal and defensive. The block paradigm is wrong for a pass through because it requests transports to guess a "maximum", trying to head off errors that the block layer isn't particularly well equipped to handle at run time. On the other hand a pass through gets layered error reporting. So if a host (and/or its LLD driver) doesn't like the size (or shape) of data to be sent/received with a command, then it can say so (and I don't mean EIO or ENOMEM). That leaves the ball in the court of the pass through user. Perhaps in this case sysfs could be useful. The problem may be transient. ** as always the OS could have run out of resources (e.g. ram) but again that is most likely transient. Doug Gilbert