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About two years ago, I noticed an update had changed the behavior of my computer slightly. I ignored it because I thought it was unimportant (shame on me) and so I can't nail it down to the exact day / package update. Since this change, every time I change the brightness of the backlight, my external Nvidia GPU turns on for a few seconds. I can see that because my laptop has an indicator LED that turns from blue to orange when the eGPU runs. This also happens when my desktop environment decides to dim the display after a few minutes of inactivity to save energy. As long as the eGPU is active however, energy is being wasted.
While experimenting with my backlight due to a (unrelated) bug I posted in the bugtracker today, I found out that the eGPU does not get activated when I change the display brightness by issuing
echo 6 > /sys/class/backlight/acpi_video0/brightnessor similar commands on the command line. So now I'm wondering what different commands get executed when I either use the control panel of my desktop environment (in my case Cinnamon) or the Fn keys to change the brightness? I think it should be possible to avoid unnecessary activation of my Nvidia GPU. Who can point me to the software component to have a look at?
Just to avoid confusion: I issued the above echo command on a now outdated 4.15.15 kernel.
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