Comment 3 for bug 485218

Regarding printers with an optional PostScript module:

Two different PPDs are needed,
one for the printer without the PostScript module
(usually a PPD for a PCL driver) and
one for the printer with the PostScript module.

I assume the problem is that usually both flavors of
such a printer show up at the USB or at the parallel port
as exactly the same model so that the usual generic
printer autodetection cannot distinguish them.

Stanislav Brabec, FYI:
What you described in your above comment #1
https://bugs.launchpad.net/hplip/+bug/485218/comments/1
is not done by generic printer autodetection.

When both flavors of such a printer are indistinguishable
by generic printer autodetection, the "recommended" PPD
must be the one which works without the PostScript module
to make sure that both flavors of such a printer work
out of the box.

To the HPLIP developers:

When both flavors of such a printer are indistinguishable
by generic CUPS printer autodetection, HPLIP's "hp" backend
may nevertheless try to do whatever additional more
sophisticated autodetection stuff (e.g. something like
what Stanislav Brabec described above) but it should
fall back to generic autodetection it the sophisticated
autodetection fails.

This way the "hp" backend could output different model names
for the two flavors of the printer.
Then each PPD which matches exactly to a particular flavour
must contain exactly the special name from the "hp" backend.
In the end a perfect automated setup via the "hp" backend
would be possible in a way which is still in full compliance
to CUPS (as far as I see currently).

Probably *ModelName and *NickName in both PPDs
should still contain the usual name but *1284DeviceID
contains the special name from the "hp" backend?
But currently I feel uncertain if this is really the best way
how to implement it.

But perhaps the root problem is that the PostScript PPDs
in HPLIP are not under the control of the HPLIP developers
because from HPLIP's point of view the PostScript PPDs
might be only a "third-party addon" (from somewhere at HP)
which is just bundled "as is"?

packaged "as is"