> Any SCSI device can return an ID (i.e. INQUIRY VPD page 0x80 or 0x83),
> so the logic need not be in sd. I don't know how removable media should
> be handled (not a SCSI device being added/removed from the system), for
> tape this is probably not an issue.
> ...
>
>>Here, the usb-storage driver does know about the real device (and already has
>>a huge exception table), so it has enough knowledge to probe for an identifier.
>
> usb-storage could emulate VPD page 0x83 to return the GID, and that could
> then be used by the mid-layer or a user level program to extract an ID.
Except that as I recall, that's not practical for all devices; they may not
have built in IDs. Hence there need to be topology-based IDs available.
Which is why I had pointed out usb_make_path() ... which returns a stable
controller ID for the "CBTU tuple". It isn't going to get re-assigned by
changing the bus probe sequence or driver load order. Even PCI has better
IDs available than those simple numbers (pci_device.slot_name).
If the driverfs names for all devices are supposed to be using stable IDs
(ones that don't change unless at least the hardware gets re-configured)
where possible, then those driverfs names will be better answers for the
"what is this device's topological ID" than those purely numeric CBTU tuples.
(And they won't address the volume/media/... ID level problems, which are
of course a separate issue.)
- Dave
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This archive was generated by hypermail 2b29 : Sun Jun 23 2002 - 22:00:13 EST