From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: sg driver and Fedora Core 2 Date: Sat, 29 May 2004 13:42:17 -0400 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <40B8CB79.9080303@pobox.com> References: <40B74725.90403@torque.net> <20040528172535.GD13961@devserv.devel.redhat.com> <1085846125.2101.29.camel@mulgrave> <20040529155744.GA32621@devserv.devel.redhat.com> <1085846840.2103.47.camel@mulgrave> <20040529162912.GA5922@devserv.devel.redhat.com> <1085849399.2004.101.camel@mulgrave> <40B8C81E.3050106@pobox.com> <20040529173530.GA24516@devserv.devel.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:25300 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id S264465AbUE2Rma (ORCPT ); Sat, 29 May 2004 13:42:30 -0400 In-Reply-To: <20040529173530.GA24516@devserv.devel.redhat.com> List-Id: linux-scsi@vger.kernel.org To: Alan Cox Cc: SCSI Mailing List , James Bottomley , Douglas Gilbert , Arjan van de Ven , Jens Axboe Alan Cox wrote: > On Sat, May 29, 2004 at 01:27:58PM -0400, Jeff Garzik wrote: > >>Really what needs to happen is a generic userland tap attaches to a >>chrdev, issues an ioctl(2) to attach to a request_queue, and then does >>read(2)/write(2)/mmap(2) to communicate with the request_queue. > > > Is there a reason that couldn't be part of the block layer sysfs in 2.7.x > > >>:) >>Call it /dev/bsg, or somesuch. > > > Except that I wonder if it should be in sysfs I agree entirely. I'll let others haggle over the device name and location sysfs or whereever is fine with me. I just care about the chrdev's behavior :) >> OTOH, the SG_IO ioctl does eliminate the userland app needing to >>worry about _any_ target/addressing information, since that is implicit >>in the dentry pointing to the blkdev's inode. > > > It makes it very hard to scan scsi busses, which is what the flash burner > app does, and what xsane does (although sane survives ok because there > are no kernel scanner device drivers) This is precisely the problem with the only-SG_IO approach as well: AFAICS, you lose the ability to scan the bus, just as you gain the ability to not have to care about scanning the bus. Getting back on topic, I agree with you that the Fedora change [if it is as you describe] is not a good one. And breakage in a stable kernel version is also quite annoying. Jeff