Created attachment 127139 [details] [review]
[PATCH] glx: usability: *must* also log issue context (at "failed to  open drm device").

Hello,

[closely related complaint: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1539046 ]

On Debian with current libgl1-mesa-glx:i386 12.0.3-1,
when doing [issue reproduction...]
- install mpv
- make sure that user does not show "video" group in "groups" command
- mpv MOVIE.mpeg

I am getting

   libGL error: failed to open drm device: Permission denied
   libGL error: failed to load driver: r200

which has a problematic lack of useful context info
(most importantly, the device name is missing).


 LANG=C ls -l /dev/dri
total 0
crw-rw----+ 1 root video 226,   0 Sep  8 21:29 card0
crw-rw----  1 root video 226,  64 Sep  8 21:29 controlD64
crw-rw----+ 1 root video 226, 128 Sep  8 21:29 renderD128


IMHO the libGL error message has rather poor usability,
leading to the issues of
having a
not sufficiently easily correctable configuration problem
as observed by the other public report and mine.

thus I decided to create
the attached UNTESTED patch (well, git commit on trunk).


I am submitting this issue as
a bug report (with UNTESTED patch) rather than
a mailing list patch,
since completely unrelated outside developers
really can't be bothered
(there's the "usability" thingy again)
to have e.g. balance of a busy work/life endangered by
doing process/build/install/test of a
completely foreign multi-100-MB component
on a rather slow system to boot *),
for a nine-liner diffstat
(where the implementer would originally have needed
an additional measly 10s to have proper reporting provided),
as opposed to core developers
who are fully familiar and thus
always have that kind of environment fully active/testable.
So, probably simply consider this to be a more helpful
"issue report with suggestion of a patch and reproduction hints" rather than
"issue report".

Thanks, also for a very nice and important infrastructure component!

Andreas Mohr


*)
# LANG=C apt-get source libgl1-mesa-glx:i386
Reading package lists... Done
Picking 'mesa' as source package instead of 'libgl1-mesa-glx'
NOTICE: 'mesa' packaging is maintained in the 'Git' version control system at:
https://anonscm.debian.org/git/pkg-xorg/lib/mesa.git
Please use:
git clone https://anonscm.debian.org/git/pkg-xorg/lib/mesa.git
to retrieve the latest (possibly unreleased) updates to the package.
E: You don't have enough free space in ..