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Topic: Changing files in /sys/class/backlight does not affect brightness (Read 415 times) previous topic - next topic
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Changing files in /sys/class/backlight does not affect brightness

Hello dear Artix users,
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inxi -G
shows
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Graphics:
  Device-1: NVIDIA GP104BM [GeForce GTX 1070 Mobile] driver: nvidia
    v: 555.58.02
  Device-2: SunplusIT Chicony USB 2.0 Camera driver: uvcvideo type: USB
  Display: wayland server: X.org v: 1.21.1.13 with: Xwayland v: 24.1.1
    compositor: kwin_wayland driver: X: loaded: nvidia unloaded: modesetting
    failed: vesa gpu: nvidia resolution: 2048x1152
  API: EGL v: 1.5 drivers: nvidia,swrast,zink
    platforms: gbm,wayland,x11,surfaceless,device
  API: OpenGL v: 4.6.0 compat-v: 4.5 vendor: nvidia mesa v: 555.58.02
    renderer: NVIDIA GeForce GTX 1070/PCIe/SSE2
  API: Vulkan v: 1.3.285 drivers: nvidia surfaces: xcb,xlib,wayland
Even when I am root,
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echo 1 > /sys/class/backlight/nvidia0/brightness
doesn't reduce brightness at all (it was 100). As a side note, when I add
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acpi_osi=Linux acpi_backlight=video
to the GRUB_CMDLINE_LINUX variable, only nvidia0 folder becomes acpi_video0, but still the same issue. I tried this both on kde plasma (wayland) and tty. After hours of searching and researching, I am stuck.
Thank you

Re: Changing files in /sys/class/backlight does not affect brightness

Reply #2 –
I installed acpilight. The command
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xbacklight -set 1
Actually changes the file contents I talked about (I checked). This doesnt work because as I mentioned when I change the file contents, I cannot change the brightness (it didnt work btw).

Re: Changing files in /sys/class/backlight does not affect brightness

Reply #3 –
Quote from: polyester – on
I installed acpilight. The command
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xbacklight -set 1
Actually changes the file contents I talked about (I checked). This doesnt work because as I mentioned when I change the file contents, I cannot change the brightness (it didnt work btw).
Here are the notes I took, hoping that they may be of use to you:

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sudo pacman -S acpilight

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--> Permission denied: '/sys/class/backlight/intel_backlight/brightness'


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sudo chmod 766 /sys/class/backlight/intel_backlight/brightness


https://gitlab.com/wavexx/acpilight

Re: Changing files in /sys/class/backlight does not affect brightness

Reply #4 –
As I mentioned, I run the commands as root. If these commands worked, as the next step I was going to add my users to a group or something but I am stuck at the first of the first. I boldfaced the parts

Re: Changing files in /sys/class/backlight does not affect brightness

Reply #5 –
maybe a driver a driver issue, have you checked your device in arch wiki list or linux hardware.
I personally never used an NVIDIA product but for intel there was times I needed to set the ACPI parameter.
As the last resort you can manipulate the hardware directly, although I advice against that.
 

Re: Changing files in /sys/class/backlight does not affect brightness

Reply #6 –
As a workaround for now, I switched to x11, and installed a 3rd party app: brightness-controller which uses xrandr in the backend.