Re: scsi_id design choices, was: Looking for Patrick Mansfield of scsi_id fame

["Ken Brush" <kbrush@gmail.com>]

On Tue, Jun 10, 2008 at 2:07 PM, John Huttley <John@mib-infotech.co.nz> wrote:
> Hi folks, I've been pokeing in scsi_id trying to understand the serialnumber
> part.
>
> I don't understand the choices patrick made in doing this.
> My note to patrick follows:
>
>
> Hi patrick,
>
> I'm trying to undertstand your scsi_id program.
>
> I'm testing on an LTO drive and the code
> seems to call
>
> do_scsi_page83_inquiry() which returns the (not really) serial number.
>
> Why are you doing that? The page is.
>
> sg_inq -vpd --page=0x83 /dev/st2
> VPD INQUIRY: Device Identification page
>    inquiry cdb: 12 01 83 00 fc 00
>    inquiry: requested 252 bytes but got 42 bytes
>  Designation descriptor number 1, descriptor length: 38
>    id_type: T10 vendor identification,  code_set: ASCII
>    associated with the addressed logical unit
>      vendor id: HP
>      vendor specific: C7438A          HU107108XD
>
>
>
> Why not get the real serial number from page 0x80??
>
> sg_inq -vpd --page=0x80 /dev/st2
> VPD INQUIRY: Unit serial number page
>    inquiry cdb: 12 01 80 00 fc 00
>    inquiry: requested 252 bytes but got 14 bytes
>  Unit serial number: HU107108XD
> close error: No medium found

Did you read the scsi_id man page?

From the description part:
-- Start --
Description
scsi_id queries a SCSI device via the SCSI INQUIRY vital product data
(VPD) page 0x80 or 0x83 and uses the resulting data to generate a
value that is unique across all SCSI devices that properly support
page 0x80 or page 0x83.

If a result is generated it is sent to standard output, and the
program exits with a zero value. If no identifier is output, the
program exits with a non-zero value.

scsi_id is primarily for use by other utilities such as udev that
require a unique SCSI identifier.

By default all devices are assume black listed, the -g option must be
specified on the command line or in the config file for any useful
behaviour.

SCSI commands are sent directly to the device via the SG_IO ioctl interface.

In order to generate unique values for either page 0x80 or page 0x83,
the serial numbers or world wide names are prefixed as follows.

Identifiers based on page 0x80 are prefixed by the character 'S', the
SCSI vendor, the SCSI product (model) and then the the serial number
returned by page 0x80. For example:

# scsi_id -p 0x80 -s /block/sdg
SIBM     3542           1T05078453

Identifiers based on page 0x83 are prefixed by the identifier type
followed by the page 0x83 identifier. For example, a device with a NAA
(Name Address Authority) type of 3 (also in this case the page 0x83
identifier starts with the NAA value of 6):

# /sbin/scsi_id -p 0x83 -s /block/sdg
3600a0b80000b174b000000d63efc5c8c
-- End --