Bug#822665: bumblebee: reports wrong error message from Xorg log

[ydirson at free.fr]

Package: bumblebee
Version: 3.2.1-10

When trying to use bumblebee those days, the reported failure is:

$ optirun xterm
[42519.843834] [ERROR]Cannot access secondary GPU - error: [XORG] (EE) /dev/dri/card0: failed to set DRM interface version 1.4: Permission denied

[42519.843864] [ERROR]Aborting because fallback start is disabled.
$ 

Looking in Xorg.8.log, we can see:

[ 42519.553] (II) xfree86: Adding drm device (/dev/dri/card1)
[ 42519.840] (II) xfree86: Adding drm device (/dev/dri/card0)
[ 42519.840] (EE) /dev/dri/card0: failed to set DRM interface version 1.4: Permission denied
[ 42519.841] (--) PCI:*(0:1:0:0) 10de:139b:1462:1139 rev 162, Mem @ 0xa2000000/16777216, 0xc0000000/268435456, 0xd0000000/33554432, I/O @ 0x00004000/128, BIOS @ 0x????????/524288
...
[ 42519.843] (II) [drm] nouveau interface version: 1.3.1
[ 42519.843] (EE) Unknown chipset: NV117
[ 42519.843] (EE) No devices detected.
[ 42519.843] (EE) 
Fatal server error:
[ 42519.843] (EE) no screens found(EE) 

The "permission denied" is quite strange, as the device does have the ACL allowing RW for the current user.
But anyway that card is already used by :0, could it be that the error code returned by the DRI device is
just wrong (EPERM instead of EBUSY) ?

Anyway, that error does not appear to be fatal to Xorg, which does list the second one as fatal,
and incidentally that error message looks like a much more understandable reason