[Printing-architecture] 'driverless' doesn't find CUPS shared print queues - expected or a bug?
till.kamppeter at gmail.com
Tue Jun 8 08:58:40 UTC 2021
What you have observed is correct.
The "driverless" utility filters out remote CUPS queues, as its
intention is to retro-fit driverless printer support into classic
printer setup tools which do not support driverless printing by themselves.
"driverless" here emulates the presence of a driver. When correctly
installed it is linked into both the /usr/lib/cups/backend and
/usr/lib/cups/driver directory. In the former it provides discovery of
the supported driverless IPP printers with correct IPP URIs ("lpinfo -v"
or equivalent API/IPP calls). This way the printer setup tool discovers
the printers in question and shows them as network printers.
The link into /usr/lib/cups/driver makes the utility being run (with
"list" argument) when CUPS is searching for PPD files/drivers ("lpinfo
-m" or equivalent API/IPP calls). Here the tool runs ippfind again and
shows for each printer a PPD URI. This makes the printer setup tool
listing a "driver" for the discovered IPP printer, named "driverless".
Selection of this "driver" ("lpadmin ... -m PPD URI" or equivalent
API/IPP calls) makes the tool being called with "cat PPD URI" command
line argument and this way it does an get-printer-attributes IPP request
on the printer and generates a PPD file based on the result.
As remote CUPS queues are auto-setup by cups-browsed you usually do not
set them up with a printer setup tool. therefore I suppressed these
queues in the result of "driverless", to avoid clutter in printer setup
Note that https://github.com/OpenPrinting/cups-filters/issues/375 is
actually a bug. ippfind actually exits with 1 if there is no suitable
printer found, whereas a CUPS backend in discovery mode should exit with
0 if no suitable printer got found.
On 07/06/2021 08:29, Zdenek Dohnal wrote:
> Hi Till,
> I have an bug which I can reproduce in my LAN
> (https://bugzilla.redhat.com/show_bug.cgi?id=1954469) and in that bug
> Solomon reported a problem which he has with driverless in his setup.
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