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#1 2023-01-05 17:01:56

flyback
Member
Registered: 2023-01-05
Posts: 1

Brightness control issues on Lenovo Legion 5

Hello,

I am experiencing weird issues with controlling the screen brightness on my laptop Lenovo Legion 5 15ARH05H.
I have dual GPUs but I am running only my dedicated GPU Nvidia RTX 2060m, because I couldn't both of them to work in hybrid mode.
I am using X11, systemd and i3 as my window manager.

Screen brightness behaviour seems weird and I haven't noticed it before.
It adjusts fine from 100% until 10%, but it seems that at 10% brightness, the screen brightness jumps up to 100%.
Like at 0 - 10% range it in reality adjusts from 0 - 100% (or at some different scale even), then when it's set to 11% it is actually 11% and goes up to 100% without a problem.

It looks like this is because of different values in files in: /sys/class/backlight/nvidia_0
This is the only folder I have available there.
max_brightness reads 100.
brightness goes from 0 - 100.
actual_brightness goes from 0 - 10. (I expected it to match the brightness value)

My system was installed around a year ago and I think it was working just fine, but I might be wrong.
I wasn't using my arch installation for a few months and then updated it to 6.1.1 from 5.18.1

I've just installed polybar and added a brightness indicator and this made me notice this issue.
When I boot up my PC, the brightness indicator shows 10%, even though the screen is at full brightness.
I've set the use-actual-brightness in polybar config to false and it adjusts from 0 to 100, with some issues in 0-10 range as described above.
When I set it to true it does not go beyond 10% same as actual_brightness file.

I've bound brightnessctl commands in my i3 config to adjust the brightness by 10pts as follows:

bindsym XF86MonBrightnessUp exec brightnessctl s +10
bindsym XF86MonBrightnessDown exec brightnessctl s 10-

I've tried adjusting the brightness with brightnessctl and light packages and manually, all these methods work the same.
I don't think the way of adjusting brightness makes any difference in this behaviour.

Here are some examples from changing it manually with echoing the value to brightness file to try and explain what happens.

In the range that works fine:
When I echo 100 > /sys/class/backlight/nvidia_0/brightness, real screen brightness is definitely at 100%, brightness reads 100 and actual_brightness reads 10.
When I echo 75 > /sys/class/backlight/nvidia_0/brightness, real screen brightness seems to be at 75%, brightness reads 75% and actual brightness reads 3.
When I echo 50 > /sys/class/backlight/nvidia_0/brightness, real screen brightness seems to be at 50%, brightness reads 50 and actual_brightness reads 1.
When I echo 25 > /sys/class/backlight/nvidia_0/brightness, real screen brightness seems to be at 25%, brightness reads 25 and actual_brightness reads 0.
When I echo 11 > /sys/class/backlight/nvidia_0/brightness, real screen brightness seems to be at 11% and definitely lower than before, brightness reads 11 and actual_brightness still reads 0, even though there's a clear difference in brightness.

In the 0-10 range:
When I echo 10 > /sys/class/backlight/nvidia_0/brightness, real screen brightness is definitely at 100%, brightness reads 10 and actual_brightness reads 10.
When I echo 7 > /sys/class/backlight/nvidia_0/brightness, real screen brightness seems to be at 70% or a bit higher, brightness reads 7 and actual_brightness reads 7. It is brighter than when I echo 70.
When I echo 5 > /sys/class/backlight/nvidia_0/brightness, real screen brightness seems to be at 50% or a bit higher, brightness reads 5 and actual_brightness reads 5. It is brighter than when I echo 50.
When I echo 1 > /sys/class/backlight/nvidia_0/brightness, real screen brightness seems to be at 10% or a bit higher, brightness reads 1 and actual_brightness reads 1.
When I echo 0 > /sys/class/backlight/nvidia_0/brightness, real screen brightness seems to be at 0%, brightness reads 0 and actual_brightness reads 0.

Sorry if the post seems convoluted, I'm trying to understand this issue for a few days already and I've tried numerous different possible solutions with no success. I am not certain when this issue started and what could've caused this.
Is this behaviour expected? Am I missing something?

I would like to be able to adjust my brightness from 0 - 100 in finer increments as I was able to do before.

Please let me know if I can help with more information.

Thank you!

Last edited by flyback (2023-01-05 22:51:52)

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#2 2023-01-08 09:23:24

13905069
Member
From: China
Registered: 2022-04-21
Posts: 15

Re: Brightness control issues on Lenovo Legion 5

too,but my laptop is Lenovo Legion Y7000 2019 PG0

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#3 2023-01-08 09:27:35

13905069
Member
From: China
Registered: 2022-04-21
Posts: 15

Re: Brightness control issues on Lenovo Legion 5

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