[libdc] Possible bug: cameras not detected by normal user (not root) if no gnome session is running

[Joan P. B. <joa...@so...>]

Working over ssh on a remote machine with two cameras connected, I found
the following issue:

If no desktop session is running on the remote machine,
the cameras are not detected by libdc1394 as non-privileged user.

In more detail, while the remote machine is stopped at the display manager
GDM after a restart,
all these commands fail:
    - Coriander shows the failure window "Warning: could not find a Digital
Camera on the bus".
    - dc1394_reset_bus fails with "libdc1394 error: No cameras found".
    - Gstreamer pipe 'gst-launch -v dc1394src ! ffmpegcolorspace !
autovideosink' fails with:
      "ERROR: from element /GstPipeline:pipeline0/GstDc1394:dc13940: There
were no cameras"

After initiating a desktop session in the remote machine by login in the
GDM screen
(after all it is not that remote, it is in the same room), and coming back
to the ssh session,
all those commands work as expected when run as a normal user (coriander
shows
the two cameras connected, the bus is reset using a camera, the pipe plays
properly).

Also, the commands work when run as root (via sudo) even when the desktop
session
has not been initiated. Under /dev, the files /dev/fw{0..4} are always
present, too.

Any clue on what is going on?

Thank you very much.

These are the details of the system:

System:
    Ubuntu 14.04 x86-64

uname -a:
    Linux SCBD023 3.13.0-52-generic #85-Ubuntu SMP Wed Apr 29 16:44:17 UTC
2015 x86_64 x86_64 x86_64 GNU/Linux

aptitude show libdc1394-22:
    Package: libdc1394-22
    Version: 2.2.1-2ubuntu2


--
Joan Pau Beltran