From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: sg driver and Fedora Core 2 Date: Sun, 30 May 2004 12:20:42 +0200 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <20040530102041.GF18613@suse.de> 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> <1085852299.2004.206.camel@mulgrave> <40B8CF34.6080901@pobox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from ns.virtualhost.dk ([195.184.98.160]:26064 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S262029AbUE3KXH (ORCPT ); Sun, 30 May 2004 06:23:07 -0400 Content-Disposition: inline In-Reply-To: <40B8CF34.6080901@pobox.com> List-Id: linux-scsi@vger.kernel.org To: Jeff Garzik Cc: James Bottomley , SCSI Mailing List , Alan Cox , Douglas Gilbert , Arjan van de Ven On Sat, May 29 2004, Jeff Garzik wrote: > James Bottomley wrote: > >On Sat, 2004-05-29 at 12:27, 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. > >> > >>:) > >> > >>Call it /dev/bsg, or somesuch. > > > > > >Well, this touches on something else I'm thinking about: lazy > >attachment. In multi thousand disc environments, you don't want us > >wasting resources allocating a queue and reading a partition table for > >all of them; you really only want to do that for the devices you're > >actually going to use. Once we have this, I think dual attachment will > >be a dead issue. > > > Regardless of lazy attachment, request_queues need to support multiple > simultaneous producers of struct request's. That has always been the case, even if it was just driver private use before. As such there is no dual-attachment issue for sg. -- Jens Axboe