[Bug 68231] New: /dev/fb0 ioctl operation switches X11 display to old console display

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=68231

          Priority: medium
            Bug ID: 68231
          Assignee: chris at chris-wilson.co.uk
           Summary: /dev/fb0 ioctl operation switches X11 display to old
                    console display
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
          Severity: normal
    Classification: Unclassified
                OS: Linux (All)
          Reporter: horsley1953 at gmail.com
          Hardware: x86-64 (AMD64)
            Status: NEW
           Version: unspecified
         Component: Driver/intel
           Product: xorg

All the info is attached to this redhat bugzilla:

https://bugzilla.redhat.com/show_bug.cgi?id=958326

Turns out that running mplayer (at least on one particular video file) with no
$DISPLAY tries (I think) to fallback on the low level frame buffer device. When
it does a couple of ioctl calls on /dev/fb0, the X11 display gets hidden and
replaced with the old contents of the VT1 console buffer (but I'm not actually
switched to that console, typing has no effect).

Doing Ctrl-Alt-F2 then Ctrl-Alt-F1 gets the X11 display back to normal and
nothing except my eyeballs seems to be aware that anything unusual happened. No
log entries are made of any kind.

This is on a fedora 19 system with this version of the intel drivers from the
fedora repos. I have no idea how to correlate this with the driver versions
here at freedesktop :-).

xorg-x11-drv-intel-2.21.12-2.fc19.x86_64

I also have a long description of finding this bug at:

http://home.comcast.net/~tomhorsley/game/heisenbug.html

This seems like a real bug to me. I wouldn't think this should happen
(especially with all the mode setting code now residing in kernel drivers), but
maybe you will disagree.

It is simple to work around once found, just add the "-vo null" argument to the
mplayer command like so it doesen't try to talk to any video device.

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