A simple tool for getting drm info and setting properties.
This tool came as an experiment when trying to use audio through HDMI in a ATI card. Audio started to work after starting Xorg.
This was tested on the following ATI cards:
- XFX R7 240
- XFX R7 850
Links of interest (none of this links solve the issue, but describe it):
- No audio using alsa on HDMI until Xorg is started - arch linux forum
- Radeon HDMI audio out defaults to disabled - arch linux forum
- No audio using alsa on HDMI until Xorg is started :: linuxquestions - reddit
Aparently Xorg enable the audio property when it starts. The function resposible to do this in the kernel is evergreen_hdmi_setmode (drivers/gpu/drm/radeon/evergreen_hdmi.c), this cards use the dce6 hdmi audio (drivers/gpu/drm/radeon/dce6_afmt.c). By default, when the cards are setted up audio is disabled.
In order to enable the audio the drmModeConnectorSetProperty(drm_fd, connector_id, prop_id, value); function of libdrm (/usr/include/xf86drmMode.h) must be called. The audio property id is usually 12 (in the tool the property is looked up by the name). Xorg sets this property with the value 2.
For more information on how to use the drm api check the followin links:
- docs - dvhrm :: github repository
- Linux DRM Mode-Setting API | Ponyhof
- Advanced DRM Mode-Setting API | Ponyhof
$ make
gcc -c -Wall -D_FILE_OFFSET_BITS=64 `pkg-config --cflags libdrm` -o "src/drm_tool.o" "src/drm_tool.c"
gcc `pkg-config --libs libdrm` src/drm_tool.o -o "./drm_tool"
$ ./drm_tool list
Card /dev/dri/card0
capability 'DUMP BUFFER' (1) : 1
capability 'VBLANK HIGH CRTC' (2) : 1
capability 'DUMB PREFERED DEPTH' (3) : 24
capability 'DUMB PREFER SHADOW' (4) : 1
capability 'PRIME' (5) : 3
capability 'TIMESTAMP MONOTONIC' (6) : 1
Connector: 27
unused connector 27
property (#1): EDID
property (#2): DPMS
property (#5): coherent
property (#9): underscan
property (#10): underscan hborder
property (#11): underscan vborder
property (#12): audio
property (#13): dither
Connector: 29
unused connector 29
property (#1): EDID
property (#2): DPMS
property (#5): coherent
property (#9): underscan
property (#10): underscan hborder
property (#11): underscan vborder
property (#12): audio
property (#13): dither
Connector: 31
mode 0: 1920x1080 60Hz 1920x1080
mode 1: 1920x1080 60Hz 1920x1080
mode 2: 1920x1080i 60Hz 1920x1080
mode 3: 1920x1080i 60Hz 1920x1080
mode 4: 1920x1080 50Hz 1920x1080
mode 5: 1920x1080i 50Hz 1920x1080
mode 6: 1600x1200 60Hz 1600x1200
mode 7: 1680x1050 60Hz 1680x1050
mode 8: 1280x1024 60Hz 1280x1024
mode 9: 1440x900 60Hz 1440x900
mode 10: 1280x960 60Hz 1280x960
mode 11: 1280x800 60Hz 1280x800
mode 12: 1280x720 60Hz 1280x720
mode 13: 1280x720 60Hz 1280x720
mode 14: 1280x720 50Hz 1280x720
mode 15: 1024x768 60Hz 1024x768
mode 16: 800x600 60Hz 800x600
mode 17: 800x600 56Hz 800x600
mode 18: 720x576 50Hz 720x576
mode 19: 720x480 60Hz 720x480
mode 20: 720x480 60Hz 720x480
mode 21: 640x480 60Hz 640x480
mode 22: 640x480 60Hz 640x480
property (#1): EDID
property (#2): DPMS
property (#5): coherent
property (#9): underscan
property (#10): underscan hborder
property (#11): underscan vborder
property (#12): audio
property (#13): dither
Connector: 33
unused connector 33
property (#1): EDID
property (#2): DPMS
property (#5): coherent
property (#9): underscan
property (#10): underscan hborder
property (#11): underscan vborder
property (#12): audio
property (#13): dither
Connector: 35
unused connector 35
property (#1): EDID
property (#2): DPMS
property (#5): coherent
property (#9): underscan
property (#10): underscan hborder
property (#11): underscan vborder
property (#12): audio
property (#13): dither
property (#6): load detection
$ ./drm_tool set /dev/dri/card0 31 audio 2
Setting 'audio' -> 2 - ret: 0 :: connector_id: 31 prop_id: 12