Debugging display blanking, atomic KMS mode-setting failures, or HDMI handshakes in the Linux Direct Rendering Manager (DRM) subsystem requires enabling kernel DRM debug logging bitmasks.

Enabling DRM Debug Bitmask via sysfs

Terminal Commandsbash
# Enable verbose DRM core, KMS, and driver debug logs (bitmask 0x1f = 31)
echo 0x1f | sudo tee /sys/module/drm/parameters/debug
 
# Inspect real-time DRM kernel logs via dmesg
sudo dmesg -w | grep -i "drm"