Comment 5 for bug 485218

CUPS backends spit out autodetection information
in the form which is described in "man 7 backend".

To find matching PPDs, the "device-make-and-model"
in the backend's output should match to
the "*ModelName" and "*NickName" entries in the PPD
and the optional "device-id" in the backend's output
should match to the optional "*1284DeviceID" entry
in the PPD.

As far as I know any other magic is not in compliance
to how CUPS works.

I.e. any other magic to find matching PPDs can only work
for those special printer setup tools which know about the
magic (e.g. only HPLIP's "hp-setup" may find the actually
right PPD while all other printer setup tools fail).

The hp backend could try to do PJL queries
or whatever it likes to find out the exact model
(and have a fallback if this does not work)
and spit out autodetection information accordingly
so that only the exact right PPDs which are provided
by HPLIP match exactly.

E.g. when PJL query works, it may spit out
"HP LaserJet 6P" or "HP LaserJet 6MP"
depending on the exact model and use
e.g. "HP LaserJet 6 series" as fallback
or something like this (I don't know about the
exact details and versions of those models).