From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH 1/5] add dma_max_segment_size option to scsi_host_template Date: Wed, 26 Sep 2007 06:11:45 -0400 Message-ID: <46FA3061.9060408@garzik.org> References: <20070925142144Z.tomof@acm.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:55906 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753920AbXIZKL5 (ORCPT ); Wed, 26 Sep 2007 06:11:57 -0400 In-Reply-To: <20070925142144Z.tomof@acm.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: FUJITA Tomonori Cc: James.Bottomley@SteelEye.com, jens.axboe@oracle.com, hch@infradead.org, gregkh@suse.de, hare@suse.de, linux-scsi@vger.kernel.org, fujita.tomonori@lab.ntt.co.jp FUJITA Tomonori wrote: > This patch moves blk_queue_max_segment_size to scsi_alloc_queue from > llds. It enables scsi_add_host to tells iommu lld's > dma_max_segment_size. If a low-level driver doesn't specify > dma_max_segment_size, scsi-ml uses 65536 (MAX_SEGMENT_SIZE). So there > are not any functional changes. > > Signed-off-by: FUJITA Tomonori > --- > drivers/scsi/hosts.c | 5 +++++ > drivers/scsi/scsi_lib.c | 1 + > include/scsi/scsi_host.h | 6 ++++++ > 3 files changed, 12 insertions(+), 0 deletions(-) hmmmmm... All the patches look technically correct, but IMO this really should behave more the the dma_mask interface: platform sets a sane dma_mask (usually 0xffffffff), and LLDD calls dma_set_mask() or pci_set_dma_mask(). Thus, IMO an LLDD should call dma_set_max_seg(), and then SCSI midlayer can obtain that value from struct device. Just like dma_mask, I think we can avoid a scsi_host_template addition. I echo Jens sentiment, though, in closing: thanks for doing this work, it's been needed for quite a while. Jeff