From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269690AbUJMMsP (ORCPT ); Wed, 13 Oct 2004 08:48:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269692AbUJMMsP (ORCPT ); Wed, 13 Oct 2004 08:48:15 -0400 Received: from a26.t1.student.liu.se ([130.236.221.26]:9954 "EHLO mail.drzeus.cx") by vger.kernel.org with ESMTP id S269690AbUJMMsK (ORCPT ); Wed, 13 Oct 2004 08:48:10 -0400 Message-ID: <416D2406.1040002@drzeus.cx> Date: Wed, 13 Oct 2004 14:48:06 +0200 From: Pierre Ossman User-Agent: Mozilla Thunderbird 0.8 (X11/20040919) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Russell King CC: LKML Subject: Re: Choosing scatter/gather limits References: <416A6623.9000105@drzeus.cx> <20041013122234.A23105@flint.arm.linux.org.uk> In-Reply-To: <20041013122234.A23105@flint.arm.linux.org.uk> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Russell King wrote: >On Mon, Oct 11, 2004 at 12:53:23PM +0200, Pierre Ossman wrote: > > >>I've been adding scatter/gather support for the MMC host driver I'm >>writing. I cannot find any documentation on how to chose the limits though. >> >> > >It seems that you have to read the block layer code to find out what's >going on with these limits. There's some documentation on it in >Documentation/block/bio.txt. If it's lacking, then please send >comments to the block layer people to add the necessary information. > > > I just wanted to make sure I don't pick values that causes problems somewhere else. I'll make an attempt to dig through the bio code though. >Please also note that I'm intending to make the MMC host drivers >know nothing about block IO stuff, so all you'll be passed is the >MMC commands and a scatter gather list - so making sure that your >driver always uses blk_rq_map_sg() and works from the SG list will >ensure that your driver remains easy to update. > > > Shouldn't be a problem. The SGIO support in the driver is done. Just need to get rid of all bugs. Rgds Pierre