Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932075AbVIKNlc (ORCPT ); Sun, 11 Sep 2005 09:41:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751034AbVIKNlc (ORCPT ); Sun, 11 Sep 2005 09:41:32 -0400 Received: from stat9.steeleye.com ([209.192.50.41]:3003 "EHLO hancock.sc.steeleye.com") by vger.kernel.org with ESMTP id S1750817AbVIKNlb (ORCPT ); Sun, 11 Sep 2005 09:41:31 -0400 Subject: Re: [PATCH 2.6.13 14/14] sas-class: SCSI Host glue From: James Bottomley To: ak@muc.de Cc: Rik van Riel , Luben Tuikov , Linux Kernel Mailing List , SCSI Mailing List In-Reply-To: <20050911035621.87661.qmail@mail.muc.de> References: <20050910041218.29183.qmail@web51612.mail.yahoo.com> <20050911035621.87661.qmail@mail.muc.de> Content-Type: text/plain Date: Sun, 11 Sep 2005 08:41:10 -0500 Message-Id: <1126446071.4831.5.camel@mulgrave> Mime-Version: 1.0 X-Mailer: Evolution 2.0.4 (2.0.4-6) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1540 Lines: 34 On Sun, 2005-09-11 at 05:56 +0200, ak@muc.de wrote: > >> Naturally, aic94xx has _no limitations_. :-) But hey, our hardware just > >> kicks a*s! > > > > That's very nice for you - but lets face it, a SAS layer > > that'll be unable to also deal with the El-Cheapo brand > > controllers isn't going to be very useful. > > Nobody knows what these bu^wlimitations will be though. So you cannot > really plan for them in advance. When someone writes drivers for such > limited hardware they can add code to handle the limitations. But it > seems reasonable to start with a clean hardware model, and only > add the hacks later when they are really needed and the requirements > are understood. But my point was that we already have a mechanism for coping with this: The scsi template parameterises some of these things (max sector size, sg table elements, clustering, etc). For less standard things it doesn't cover the driver uses the blk_ adjustors directly from slave_alloc/slave_configure (This is currently how USB and firewire communicate their alignment requirements). By wrappering both the template and the slave_alloc/slave_configure methods in the SAS class and not providing the driver access, it can't use existing methods to make any adjustments that may be necessary. James - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/