modesetting: workaround for stride/pitch mismatch

This helps for the cases where buffer stride is miscalculated, the most
notable example being 1366x768 resolution. From what I understand the code,
the stride calculation should distinguish between any pixmap and the one
used for FB, which is not the case and everything is calculated in

Fixes: xorg/xserver#889
Signed-off-by: Aleksander Miera <>
3 jobs for stride-mismatch-workaround in 5 minutes and 40 seconds (queued for 1 second)