From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [PATCH] [1/22] Add new sense_buffer_mask host template field Date: Mon, 25 Feb 2008 16:01:22 +0100 Message-ID: <20080225150122.GC16158@one.firstfloor.org> References: <200802251235.889863872@firstfloor.org> <20080224233513.F083B1B4183@basil.firstfloor.org> <1203950908.3254.18.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from one.firstfloor.org ([213.235.205.2]:46731 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754034AbYBYPAr (ORCPT ); Mon, 25 Feb 2008 10:00:47 -0500 Content-Disposition: inline In-Reply-To: <1203950908.3254.18.camel@localhost.localdomain> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: Andi Kleen , linux-scsi@vger.kernel.org On Mon, Feb 25, 2008 at 06:48:28AM -0800, James Bottomley wrote: > On Mon, 2008-02-25 at 00:35 +0100, Andi Kleen wrote: > > sense buffers are something that still needs to be explicitely > > bounced in the scsi layer. Instead of using the global unchecked_isa_dma > > flag define a special fine grained mask for this. > > > > I decided to use a full dma mask because that is most useful for some future > > infrastructure work I'm doing. > > Why do we need a separate mask? Why can't we just use the device > dma_mask? First a lot of drivers don't need it because they handle the sense buffers without DMA. So if we just used a device mask we would either do unnecessary work for those or require a special sense buffer mask in the device (which wouldn't belong into the device layer) Then there isn't really a device anywhere in these drivers and I didn't plan to rewrite them to add one. So just having a SCSI specific sense buffer mask seemed best. It is only set when a ISA driver actually does sense buffer DMA, which is only true in a handful of drivers. -Andi