help adding device serial numbers to /dev namespace?

[James R. Van Artsdalen]

Can anyone give me suggestions on how to implement putting disk driver
serial numbers in the /dev namespace, much as UFS ID's are put there now?

I want to propose adding the disk drive's hardware serial number, i.e.,
for this

# camcontrol identify ada0
pass0: <ST3750640AS 3.AAJ> ATA/ATAPI-7 SATA 1.x device
pass0: 150.000MB/s transfers

protocol              ATA/ATAPI-7 SATA 1.x
device model          ST3750640AS
firmware revision     3.AAJ
serial number         3QD0NWQT
...

I would add a name like /dev/serialnum/3QD0NWQT.  This differs from the
current name schemes I know of in that it describes the whole disk and
not any particular partition or region, and no on-disk storage is needed.

I think this needs to be done in GEOM, as a result of disk_create() and
using d_ident, but I'm getting lost and need some guidance to do an
example patch to "formally" propose the idea.

The immediate use today is for ZFS.