From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH] dc395x: Fix support for highmem Date: Sun, 20 Mar 2005 09:14:17 +0000 Message-ID: <20050320091417.GC12000@infradead.org> References: <200503160209.j2G29cAf010870@hera.kernel.org> <20050316075839.GC7842@suse.de> <1110986016.5771.3.camel@mulgrave> <20050316160447.GU7842@suse.de> <20050316164806.GO21986@parcelfarce.linux.theplanet.co.uk> <20050316165338.GX7842@suse.de> <20050316170259.GA25056@infradead.org> <20050316170417.GY7842@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Received: from pentafluge.infradead.org ([213.146.154.40]:14559 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S262038AbVCTJOV (ORCPT ); Sun, 20 Mar 2005 04:14:21 -0500 Content-Disposition: inline In-Reply-To: <20050316170417.GY7842@suse.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Jens Axboe Cc: Christoph Hellwig , Matthew Wilcox , James Bottomley , SCSI Mailing List , g.liakhovetski@gmx.de On Wed, Mar 16, 2005 at 06:04:17PM +0100, Jens Axboe wrote: > On Wed, Mar 16 2005, Christoph Hellwig wrote: > > On Wed, Mar 16, 2005 at 05:53:39PM +0100, Jens Axboe wrote: > > > The list doesn't really need dma mapping at that point, the problem here > > > is that the driver needs to punt to pio mode because of foo. So calling > > > pci/dma_map_* is pointless, since the CPU will have to do the transfer > > > anyways. What the driver is really looking for at this point, is a way > > > to map the pages in the sglist to a virtual address. > > > > Given that there's quite a few cases of this "problem" it would be nice > > to have common helpers for it. Especially as it's really difficult when > > we allow merging of sg list entries > > I thought about that when writing the above, but is there really more > than one case for SCSI drivers? If there is, sure lets add the helpers. > But I would consider it a quite rare occurence, I've never seen it > before. There's lots of pio only drivers, aswell as raid drivers that need to look into the non I/O-path command and things like iscsi.