From mboxrd@z Thu Jan 1 00:00:00 1970 From: Muli Ben-Yehuda Subject: Re: Proposals to change the way all drivers work with SCSI commands Date: Sat, 12 May 2007 09:35:44 +0300 Message-ID: <20070512063544.GO4523@rhun.ibm.com> References: <1178908422.3692.58.camel@mulgrave.il.steeleye.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mtagate4.uk.ibm.com ([195.212.29.137]:25060 "EHLO mtagate4.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754401AbXELGfs (ORCPT ); Sat, 12 May 2007 02:35:48 -0400 Received: from d06nrmr1407.portsmouth.uk.ibm.com (d06nrmr1407.portsmouth.uk.ibm.com [9.149.38.185]) by mtagate4.uk.ibm.com (8.13.8/8.13.8) with ESMTP id l4C6ZkcZ188722 for ; Sat, 12 May 2007 06:35:46 GMT Received: from d06av01.portsmouth.uk.ibm.com (d06av01.portsmouth.uk.ibm.com [9.149.37.212]) by d06nrmr1407.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v8.3) with ESMTP id l4C6ZkIe2519130 for ; Sat, 12 May 2007 07:35:46 +0100 Received: from d06av01.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av01.portsmouth.uk.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id l4C5YNPu031606 for ; Sat, 12 May 2007 06:34:24 +0100 Content-Disposition: inline In-Reply-To: <1178908422.3692.58.camel@mulgrave.il.steeleye.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: linux-scsi On Fri, May 11, 2007 at 01:33:41PM -0500, James Bottomley wrote: > Right at the moment, we're planning to clean up the way SCSI drivers > process commands. The proposals are essentially: > > 1. Get rid of the now unnecessary map_single path (every command is > either zero transfer or scatter/gather) > 2. use accessors to manipulate the SG lists (mainly so that we can > alter the implementation without affecting the drivers) > > It strikes me that in all of this, we could also consider doing the DMA > mapping inside the mid layer (instead of in every driver). This is > essentially what libata is already doing ... leading to confusion in > SCSI drivers that use libata for SATA. > > So what do people think about this? Yes please. It will be easier to modify the DMA API interface to better support hypervisors and other "DMA mapping heavy" users if it's localized to the mid-layer rather than spread out in drivers. Cheers, Muli