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I'll try to be as short and precise as I can but the problem is complicated.

I updated (clean install) from 16.04 to 20.04 today. I use i3wm with two displays, one being my laptop LCD and the other my HDMI monitor. I use the following command (generated by arandr) to enable the second monitor:

xrandr --output eDP-1 --primary --mode 1920x1080 --pos 0x0 --rotate normal --output VGA-1 --off --output DP-1-1 --off --output HDMI-1-1 --mode 1920x1080i --pos 1920x0 --rotate normal

The second monitor is not recognized and shows a "no signal" message until I run this command. I get no errors or warnings.

I use xbacklight to adjust the brightness on the main display. By default, it produces : "No outputs have backlight property". I need a custom xorg config to make sure it recognizes the intel backlight. For 16.04, the following sufficed:

Section "Device"
    Identifier  "Intel Graphics"
    Driver      "intel"
    Option      "Backlight"  "intel_backlight"
EndSection

In 20.04, it causes the second monitor to become blank but it also does not show a "no signal" message. Interestingly enough, the dashes in the device names disappear, e.g. "eDP-1" becomes "eDP1". Therefor the command complains about not finding "eDP-1" and "VGA-1". Correcting the device names still does nothing though.

I changed the xorg.conf file to also consider my nvidia GPU:

Section "Device"
    Identifier  "Device0"
    Driver      "intel"
    Option "Backlight" "intel_backlight"
EndSection
Section "Device"
    Identifier  "Device1"
    Driver      "nouveau"
EndSection

Now if I run the xrandr command it does enable the second monitor and I can change the brightness but it slows down the system to a halt for 10-15 seconds per brightness change. If I do multiple changes in a row or click something/type, I have to pretty much force restart my PC. I don't think xbacklight is the problem because the effect lingers a bit, even after xbacklight exits.

I'd appreciate any help or tip.

M47
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  • I have exactly the same issue! I have no solution for this yet. Hopefully someone can help us out with this issue. – user234562 Oct 26 '20 at 18:59
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    @TheMrkt this might help you but it didn't work for me. the problem seems to be the same, except they don't mention temporary slow downs. – M47 Oct 26 '20 at 22:47
  • Thanks! I also looked at that post. But dont want to install light for this to be honest. I think its just strange that adding the intel driver is slowing down the whole system. – user234562 Oct 27 '20 at 07:18

0 Answers0