From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH] minimal SAS transport class Date: Fri, 26 Aug 2005 14:48:10 -0400 Message-ID: <430F63EA.7020400@pobox.com> References: <9BB4DECD4CFE6D43AA8EA8D768ED51C21D7A40@xbl3.ma.emulex.com> <20050823154232.GA3464@us.ibm.com> <430BBBBE.4070408@adaptec.com> <430E1CB1.1050108@s5r6.in-berlin.de> <430E24AB.2060002@pobox.com> <430F46AA.2050305@adaptec.com> <1125076960.5079.61.camel@mulgrave> <430F5C8F.3030708@adaptec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail.dvmed.net ([216.237.124.58]:7083 "EHLO mail.dvmed.net") by vger.kernel.org with ESMTP id S1030184AbVHZSsV (ORCPT ); Fri, 26 Aug 2005 14:48:21 -0400 In-Reply-To: <430F5C8F.3030708@adaptec.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Luben Tuikov Cc: James Bottomley , SCSI Mailing List Luben Tuikov wrote: > On 08/26/05 13:22, James Bottomley wrote: > >>On Fri, 2005-08-26 at 12:43 -0400, Luben Tuikov wrote: >> >> >>>>A move away from forced HCIL addressing would be a good thing. >>>> >>>>However, its impossible to completely move away from addressing, as >>>>userspace and the SCSI core need ways to route CDBs to devices based on >>>>address. >>> >>>They can use _anyone_ label in the label list of the LU. >> >> >>I think what Jeff means is that the mid-layer needs to know which LLD to >>send the CDB to. > > > No, I thought he meant about user space apps, *NOT* SCSI Core. > > Since, the transport found the device on the domain (NOT LU!) > it then calls SCSI Core to register it. > > So you have: > > task->scsi_domain_device->lldd->lldd_execute_task(task). > > >>This is the routing information (and is really just >>the host number). > > > No host numbers, no routing information. This is all > transparent to SCSI Core, and NONE of its business. Routing is an essential part of the SCSI core's duties. The SCSI core is the resource manager responsible for routing messages [CDBs] to/from LLDs based on . This includes resolution of kernel-specific identifiers (device major/minor, etc.) into . This also includes direct use of userspace-provided identifiers as , such as via SG_IO ioctl. Moving away from HCIL requires a lot of thought, including thinking about userland app breakage -- a big deal in Linux. Ask yourself where all these HCIL-addressed CDBs come from... each one of those CDB submittors must be updated from HCIL addressing/routing to transport-specific. Jeff