From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [PATCH 2/3] scsi: add scsi_device->alt_capacity Date: Sat, 09 May 2009 16:23:43 +0000 Message-ID: <1241886223.3542.37.camel@mulgrave.int.hansenpartnership.com> References: <1241828002-12742-1-git-send-email-tj@kernel.org> <1241828002-12742-3-git-send-email-tj@kernel.org> <1241842999.6357.2.camel@mulgrave> <4A05AAA4.9010806@kernel.org> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from bedivere.hansenpartnership.com ([66.63.167.143]:47075 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751440AbZEIQXp (ORCPT ); Sat, 9 May 2009 12:23:45 -0400 In-Reply-To: <4A05AAA4.9010806@kernel.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo Cc: jeff@garzik.org, linux-ide@vger.kernel.org, jens.axboe@oracle.com, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, Mauelshagen@RedHat.com, dm-devel@RedHat.com, dan.j.williams@gmail.com On Sun, 2009-05-10 at 01:09 +0900, Tejun Heo wrote: > James Bottomley wrote: > > This is done at slightly the wrong level. Capacity is actually a > > property of struct scsi_disk not struct scsi_device ... shouldn't > > alt_capacity be at the same level? > > Hmmm... I think that was my first try and then I moved it to sdev for > some reason I can't rememer now. I'll look into it again and try to > move it into sdev. Really one of the things I was wondering is why even scsi_disk ... capacity is in there, but it's also in gendisk, so I've thought (admittedly never translated it to action) that we could just remove the duplication in scsi_disk. This alt_capacity looks to be a pure ATA thing ... I can't find it in the SCSI specs and there doesn't seem to be a SAT equivalent of the commands. Ideally, what should be happening is that the ata ULD would issue the capacity commands and just set the block alt_capacity without having to worry about transporting the value up and down the stack. Matthew Wilcox thought we could begin an implementation of the ATA uld using the ATA_16 command to transport it through SCSI ... this might provide the good reason to begin that. James