Puzzle: Failed to set DRM interface

[alex lupu]

Hello,

SYSTEM
Linux BLFS, kernel 4.2.6, i686, 32-bit, Udev, NON-systemd
Motherboard: "ASUS P8H77-I" (with intel H77) and intel i7-3770
Xorg 7.7+, Server 1.18.0, evdev-2.10.1, intel-2.99.917,
libdrm-2.4.66

GENERAL
Typical system usage:  Boot to level3 ("console" mode).  Work.
Go to level5 ("graphical") over Xorg.  Work (browse, etc.).  Back to level3.
(repeat 3 -> 5 -> 3, as many times as necessary)

PROBLEM/PUZZLE/QUESTION
1.  On first Xorg/Server run:
Two EEs
[   154.428] (II) config/udev: Adding drm device (/dev/dri/card0)
[   154.428] (II) xfree86: Adding drm device (/dev/dri/card0)
[   154.428] (EE) /dev/dri/card0: failed to set DRM interface version 1.4:
 Permission denied

[   154.491] (II) config/udev: removing GPU device
 /sys/devices/pci0000:00/0000:00:02.0/drm/card0 /dev/dri/card0
[   154.491] (II) config/udev: Adding drm device (/dev/dri/card0)
[   154.491] (II) xfree86: Adding drm device (/dev/dri/card0)
[   154.491] (EE) /dev/dri/card0: failed to set DRM interface version 1.4:
 Permission denied

No /dev/dri/card0

2.  On the next (and following Xorg/server) run:
No EEs
[   724.630] (II) xfree86: Adding drm device (/dev/dri/card0)

crw-rw---- 1 root video 226, 0 2016-01-11 11:08 /dev/dri/card0

3.  I suppose the card0 node is created by server's
'hw/xfree86/os-support/linux/lnx_platform.c'
on first invocation.

4.  Questions:
4.1.  If possible, any advantages in forcing Udev to create card0 node
on system boot-up (i.e., before I start Xorg)?

4.2.  Aren't the first two "EEs" in the log somehow misleading, as long as
the server can (and apparently expects to) create the card0 node itself?

4.3.  Speaking of "Permission denied",
I invoke Xorg from an unprivileged account, group "video".

5.  If any other details are needed:  ready, willing & able to provide.

Thanks for any thoughts/help on this,
-- Alex
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