[cups] Problem with cups selecting manual tray on HP laserjet

[Kurt Pfeifle]

Am Fr., 16. Dez. 2022 um 00:41 Uhr schrieb Steinar Bang <sb at dod.no>:

> >>>>> Helge Blischke <helgeblischke-S0/GAf8tV78 at public.gmane.org>:
>
> [....]
>
> But at least I've learnt where the PPD file comes from (it comes from
> the printer).
>

The PPD is auto-generated by CUPS. (Yes, it comes from the printer, but
indirectly.)

The process is as follows:

1. CUPS uses the "driverless" backend to query the printer for its
capabilities
2. This query uses IPP parlance (the Internet Printing Protocol), and the
printer responds with IPP too.
3. "driverless" translates the printers responses into PPD-syntax to
describe the printer's capabilities to ensure that legacy applications
which need to see a "PPD" file for printing see one.
[4. "driverless" is provided by LinuxFoundation/Openprinting.org as an
add-on, and is not part of CUPS core.]