Patrick Mansfield wrote: > On Fri, Jan 06, 2006 at 10:39:34PM +1000, Douglas Gilbert wrote: > <snip> > > 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 - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
