DRM Framebuffer for 1366x768 resolution has incorrect pitch (exactly 4*1366) on EVDI-backed display
When using DisplayLink device that uses evdi module to add screens together with X Server 1.20.4 1366x768 shows completely corrupted image on the dock-connected screen. The bug is related to this particular resolution only. It has been reproduced on Ubuntu 19.04 with 5.0.0-27-generic kernel. Same situation does not happen on while using Wayland. Investigation on our side has led to conclusion that for this particular resolution the pitch of EVDI-associated /dev/dri/cardX is exactly 4*1366, while for Wayland/earlier, properly functioning Xorg versions it is slightly larger. Hardcoding it in evdi confirms it.
Steps to reproduce (even w/o physical docking station): Build and install evdi: https://github.com/displaylink/evdi Install monitorsim https://github.com/mlukaszek/evdipp/ Load evdi, e.g. using modprobe run monitorsim with the edid provided in this report. (optionally) use xrandr/arandr/similar tool to activate the new screen if it doesn't happen automatically.
AFAIR similar could have been observed in Wayland and was fix with the following commit: https://gitlab.gnome.org/GNOME/mutter/commit/a3d826c54b770f9ea54e0a0f3356b0c0193bc5f3?merge_request_iid=225