From mboxrd@z Thu Jan 1 00:00:00 1970 From: Douglas Gilbert Subject: Re: [PATCH] /dev/disk/by-id incomplete and unhelpful for SATA drives Date: Sat, 07 Jan 2006 09:44:55 +1000 Message-ID: <43BF00F7.9010104@torque.net> References: <20051221185518.GA9100@vrfy.org> <43A9CFE0.2070103@edesix.com> <20051222043527.GA13175@vrfy.org> <43AA8D0B.10504@edesix.com> <20051222183525.GA17871@devserv.devel.redhat.com> <43AB40E2.1050009@edesix.com> <20060106013640.GA27841@aracnet.com> <43BDDCAE.7000506@torque.net> <43BE6506.7090901@torque.net> <20060106194652.GB6404@aracnet.com> Reply-To: dougg@torque.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from zorg.st.net.au ([203.16.233.9]:58589 "EHLO borg.st.net.au") by vger.kernel.org with ESMTP id S932279AbWAFXo3 (ORCPT ); Fri, 6 Jan 2006 18:44:29 -0500 In-Reply-To: <20060106194652.GB6404@aracnet.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Patrick Mansfield Cc: Chris Paulson-Ellis , Bill Nottingham , linux-hotplug-devel@lists.sourceforge.net, linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org, jgarzik@pobox.com Patrick Mansfield wrote: > On Fri, Jan 06, 2006 at 10:39:34PM +1000, Douglas Gilbert wrote: > > > I was trying to figure out if we are guranteed will have unique values > across all ATA devices with Doug's patch. I am not familiar with ATA and > IDENTIFY DEVICE. http://www.t13.org/docs2005/D1699r2a-ATA8-ACS.pdf is the most recent draft of the ATA-8 command set. > For page 0x83, Doug's change above gives us: > > ATA + 40 bytes of model/product (must have white space) + serial number > > Under "10.3.4.2.3 Logical unit name derived from the model number and > serial number" the spec says: > > NOTE 9 The logical unit name using the T10 vendor identification > format is not guaranteed to be worldwide unique, since ATA/ATAPI-7 > only requires the combination of the MODEL NUMBER field and SERIAL > NUMBER field to be unique for a given manufacturer but defines no > manufacturer identification field. > > I don't know why they have this given the above. So it is possible (though > unlikely?) that model numbers will overlap, and so scsi_id values too? Unlikely but two vendors could use the same model and serial numbers. > If we put had an actual vendor in the sdev->vendor, we could use page 0x83 > type 0 with no name collisions (if that vendor + model actually gives us > unique serial numbers). > > Why does the SAT translation spec have the vendor identification of ATA??? I guess because there is no requirement for a manufacturer of (s)ATA disks to have a registered t10 vendor id ... IEEE wants money for OUI registrations, t10 probably wants money for a t10 vendor id, t13 probably wants money etc ... BTW As I have mentioned in the past, linux probably should have a OUI registration (paid by whom??). > The "logical unit name derived from the world wide name" looks nicer, but I > assume not all vendors support that. Yes and not yet, until it becomes mandatory, if ever. ATA8-ACS shows a naa-5 (8 byte, 4 word) identifier starting at word 108 in the IDENTIFY DEVICE response. I like the ACS wording: "Words 111-108 shall contain the optional value of the world wide name"! The "shall" implies it is mandatory but obviously the "optional" doesn't. Perhaps it was written by a lawyer :-) We probably could and should add the naa-5 designator in VPD page 0x83, perhaps dependent on whether there is a 0x5 in word 108 bits 15-12 . For example, an old-ish Seagate ST380013AS sata disks has zero in those 8 bytes. Perhaps others could check their sata disks and report back if any have a real naa-5 wwn starting at word 108. ["sg_inq -AH" on a (s/p)ATA disk will dump the IDENTIFY DEVICE response in hex.] Doug Gilbert