From mboxrd@z Thu Jan 1 00:00:00 1970 From: Douglas Gilbert Date: Fri, 06 Jan 2006 23:44:55 +0000 Subject: Re: [PATCH] /dev/disk/by-id incomplete and unhelpful for SATA drives Message-Id: <43BF00F7.9010104@torque.net> List-Id: 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> In-Reply-To: <20060106194652.GB6404@aracnet.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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 ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_idv37&alloc_id865&op=click _______________________________________________ Linux-hotplug-devel mailing list http://linux-hotplug.sourceforge.net Linux-hotplug-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel