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Monitor connected via eDP goes black for 1-2 seconds whenever I call xrandr

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On my hardware there is only one single monitor attached at eDP-1. And whenever I call xrandr --query the monitor turns black for 1-2 seconds, although the command completes without an error. Also, I did not see any relevant error messages elsewhere. (syslog, dmesg, ~/.xsession-errors).
The effect is not just a flicker, but a complete outage.

My theory is that either monitor firmware or something on the main board side crashes and takes the mentioned 1-2s for restarting. I do not think that there is a general problem with resolution/timings, as the monitor image is stable without calling xrandr.

If you wonder why I need to call xrandr more often: I wrote a service that may rotate and dim the display on external data. And to know if the image is in the right orientation and brightness, I regulary query its current state. I need all that for an application of mine.

I'm able to provoke the error when running this script. The screen turns black all the time until I stop the script.

while true
do
    echo -n "."
    xrandr --query >/dev/null
done

I already tried different combinations to get the location of the error

  • Same PC, different monitor on eDP-1 => Same problem
  • Same PC, different monitor on HDMI => No problem
  • Different PC, different monitor on HDMI, same SSD => No Problem
  • Trying next (but need to wait for hardware): different PC, same Monitor on eDP-1

I'm on Ubuntu MATE 20.04.03 and xrandr 1.5.9

Any ideas that could help to diagnose the error?
Where could I look for error messages?

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