From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Christie Subject: Re: [PATCH] ieee1394: sbp2: lower block queue alignment requirement Date: Mon, 15 Jan 2007 13:50:28 -0600 Message-ID: <45ABDB04.1050307@cs.wisc.edu> References: <1168802387.2780.1.camel@mulgrave.il.steeleye.com> <59ad55d30701151139w6176e785g53404d7b3a42ce6e@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from sabe.cs.wisc.edu ([128.105.6.20]:49712 "EHLO sabe.cs.wisc.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751439AbXAOTu4 (ORCPT ); Mon, 15 Jan 2007 14:50:56 -0500 In-Reply-To: <59ad55d30701151139w6176e785g53404d7b3a42ce6e@mail.gmail.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: =?UTF-8?B?S3Jpc3RpYW4gSMO4Z3NiZXJn?= Cc: Stefan Richter , James Bottomley , linux1394-devel@lists.sourceforge.net, linux-scsi@vger.kernel.org Kristian H=C3=B8gsberg wrote: > On 1/14/07, Stefan Richter wrote: >> On 14 Jan, James Bottomley wrote: >> > The block layer currently provides sector (512) byte alignment >> > guarantees. However, there has been talk in SCSI of reducing that= to >> > word (4) since that's what most intelligent PCI controllers can co= pe >> > with. If you have any alignment constraints, they should be expre= ssed >> > in the slave configure. >> >> OK, thanks. I will keep the explicit setting of the mask then. >> I actually think that everything should work just fine with 4 bytes >> alignment, but the SBP-2 spec mentiones 8 bytes alignment for the S/= G >> tables. So maybe device firmwares will expect it that way even thou= gh >> IEEE 1394 doesn't impose such a restriction even on transfers with a >> payload of a multiple of 8 bytes. >=20 > Do you have a reference to this 8 byte alignment requirement? I > couldn't find it browsing through the standard. Also, since the SBP-= 2 > driver has to convert the scatterlist to an SBP-2 page table, it can > just allocate the page table on a 8-byte boundary if that is required= =2E > The entries in the scatter table have no alignment restrictions from > the SBP-2 side. >=20 > By the way, is there a way to ask the SCSI stack to limit the size of > the entries in the scatterlist to 64k? This would greatly simplify > the conversion to SBP-2 page tables, since this is the maximum size > these can hold. >=20 I think 64k is the limit already, but I think you can call blk_queue_max_segment_size in your scsi_host_template->slave_configure or slave_alloc to set the size to whatever you like. - To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html