This code was largely lifted from the X server in
bb25b2ad29 but didn't take the copyright messages that
applied to that code.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Acked-by: Jonas Ådahl <jadahl@gmail.com>
Acked-by: Simon Thum <simon.thum@gmx.de>