DRM KMS troubleshooting grid

Some typical issues related to the DRM/KMS framework are listed below. Solutions or debugging methods are proposed for these issues.

If your issue is not listed, try also looking in the articles in the DRM/KMS or troubleshooting grids categories.


Symptom Resolution
Board $> ./myQtApplication
Could not queue DRM page flip! (Permission denied)
Could not queue DRM page flip! (Permission denied)

The psplash-drm userland splash screen is running and is then the DRM master, avoiding other DRM applications to access to DRM/KMS. Please stop this psplash-drm application with the command below before running your use case:

Board $> psplash-drm-quit

Note: You may need to enter "export QT_QPA_EGLFS_ALWAYS_SET_MODE=1" before running your Qt application, please refer to the Qt documentation.

Board $> echo 32 > /sys/class/backlight/5a000000.dsi.0/brightness
sh: write error: No such device or address

On this board, the panel backlight is related to a MIPI® DSI panel. This backlight can be modified only if the panel is already powered on. That is probably not the case here.
Before modifying its backlight, the panel must be restarted, For that, start any display-related application. For further information, refer to DRM KMS overview and Wayland Weston overview articles.