@sugarfree Well, I wasn't quite sure what I did was right and I don't know the terminology too well, but I cloned the Raspberry Pi kernel, modified only the lines of code mentioned in the workaround (the file being vc4_v3d.c), then compiled and installed the kernel. It might have been just dumb luck that this worked, and my problem may have been something else entirely.

@mitu I tried now with config.txt

dtoverlay=vc4-kms-v3d,nohdmi

and emulationstation and mpv are working on display! (Only vlc makes troubles)

root@rpi5:/opt/videos# mpv --no-audio simpsons.mp4 (+) Video --vid=1 (*) (h264 640x480 25.000fps) Audio --aid=1 --alang=deu (*) (aac 1ch 48000Hz) [vo/gpu] VT_GETMODE failed: Inappropriate ioctl for device [vo/gpu/opengl] Failed to set up VT switcher. Terminal switching will be unavailable. VO: [gpu] 640x480 yuv420p V: 00:05:28 / 00:22:15 (25%) root@rpi5:/opt/videos# mpv --drm-connector=help Available connectors for card 0 (/dev/dri/card2): SPI-1 (connected) Available connectors for card 1 (/dev/dri/card1): Available connectors for card 2 (/dev/dri/card0): Cannot retrieve DRM resources: Operation not supported root@rpi5:/opt/videos# drmdevice --- Checking the number of DRM device available --- --- Devices reported 3 --- --- Retrieving devices information (PCI device revision is ignored) --- device[0] +-> available_nodes 0x01 +-> nodes | +-> nodes[0] /dev/dri/card2 +-> bustype 0002 | +-> platform | +-> fullname /axi/pcie@120000/rp1/spi@50000/panel@0 +-> deviceinfo +-> platform +-> compatible wavesku19650 panel-mipi-dbi-spi --- Opening device node /dev/dri/card2 --- --- Retrieving device info, for node /dev/dri/card2 --- device[0] +-> available_nodes 0x01 +-> nodes | +-> nodes[0] /dev/dri/card2 +-> bustype 0002 | +-> platform | +-> fullname /axi/pcie@120000/rp1/spi@50000/panel@0 +-> deviceinfo +-> platform +-> compatible wavesku19650 panel-mipi-dbi-spi device[1] +-> available_nodes 0x01 +-> nodes | +-> nodes[0] /dev/dri/card1 +-> bustype 0002 | +-> platform | +-> fullname /axi/gpu +-> deviceinfo +-> platform +-> compatible brcm,bcm2712-vc6 --- Opening device node /dev/dri/card1 --- --- Retrieving device info, for node /dev/dri/card1 --- device[1] +-> available_nodes 0x01 +-> nodes | +-> nodes[0] /dev/dri/card1 +-> bustype 0002 | +-> platform | +-> fullname /axi/gpu +-> deviceinfo +-> platform +-> compatible brcm,bcm2712-vc6 device[2] +-> available_nodes 0x05 +-> nodes | +-> nodes[0] /dev/dri/card0 | +-> nodes[2] /dev/dri/renderD128 +-> bustype 0002 | +-> platform | +-> fullname /axi/v3d@2000000 +-> deviceinfo +-> platform +-> compatible brcm,2712-v3d --- Opening device node /dev/dri/card0 --- --- Retrieving device info, for node /dev/dri/card0 --- device[2] +-> available_nodes 0x05 +-> nodes | +-> nodes[0] /dev/dri/card0 | +-> nodes[2] /dev/dri/renderD128 +-> bustype 0002 | +-> platform | +-> fullname /axi/v3d@2000000 +-> deviceinfo +-> platform +-> compatible brcm,2712-v3d --- Opening device node /dev/dri/renderD128 --- --- Retrieving device info, for node /dev/dri/renderD128 --- device[2] +-> available_nodes 0x05 +-> nodes | +-> nodes[0] /dev/dri/card0 | +-> nodes[2] /dev/dri/renderD128 +-> bustype 0002 | +-> platform | +-> fullname /axi/v3d@2000000 +-> deviceinfo +-> platform +-> compatible brcm,2712-v3d