# 看 HDMI 连接器状态（connected / disconnected）
radxa@rock-5b-plus:~$ cat /sys/class/drm/card0-HDMI-A-1/status
connected
# 看内核识别到的支持模式
radxa@rock-5b-plus:~$ cat /sys/class/drm/card0-HDMI-A-1/modes
1024x600
1920x1080
1920x1080
...
720x400
# EDID 原始数据
radxa@rock-5b-plus:~$ ls /sys/class/drm/*/edid
/sys/class/drm/card0-DP-1/edid /sys/class/drm/card0-HDMI-A-2/edid
/sys/class/drm/card0-HDMI-A-1/edid /sys/class/drm/card0-Writeback-1/edid