Arch Linux

Rainstripes

Member

Registered: 2025-06-17

Posts: 6

[SOLVED] Can't change brightness with nvidia_wmi_ec_backlight

I've tried sooo many tutorials, forum instructions, etc, but nothing works at all. What might be the problem is that I can only edit the brightness file in /sys/class/backlight/nvidia_wmi_ec_backlight, while scale is stuck on unknown, max_brightness is stuck on 255, and sudo permissions are denied editing privelages to them. Please help me.

Hyprland environment
nvidia proprietary drivers, (iirc)
nvidia 3060 GPU
intel i5 chip
standard linux kernel
systemd boot

Edit: solved with https://bbs.archlinux.org/viewtopic.php?id=296205
NO idea how I missed this one for so long. Thanks for everyone in the comments trying to help me out though!

Last edited by Rainstripes (2025-07-01 04:41:52)

V1del

Forum Moderator

Registered: 2012-10-16

Posts: 24,569

Re: [SOLVED] Can't change brightness with nvidia_wmi_ec_backlight

This is generally speaking only for laptops, if you want this to manipulate an external monitor, said monitor has to support the ddc protocol and you'll need ddcutil https://wiki.archlinux.org/title/Displa … (E-)DDC/CI

Rainstripes

Member

Registered: 2025-06-17

Posts: 6

Re: [SOLVED] Can't change brightness with nvidia_wmi_ec_backlight

This is generally speaking only for laptops, if you want this to manipulate an external monitor, said monitor has to support the ddc protocol and you'll need ddcutil https://wiki.archlinux.org/title/Displa … (E-)DDC/CI

I mean, yeah, I'm not using any external display. I have arch installed on my laptop and the brightness won't change.

V1del

Forum Moderator

Registered: 2012-10-16

Posts: 24,569

Re: [SOLVED] Can't change brightness with nvidia_wmi_ec_backlight

What laptop and how sure are you that the nvidia gpu is driving your display?

xrandr -q
ls -l /sys/class/backlight/
sudo journalctl -b | curl -F 'file=@-' 0x0.st

What exact command are you trying that "sudo permissions are denied editing privelages to them" what exact command are you issuing? Have you seen https://wiki.archlinux.org/title/Backli … _utilities and checked e.g. brightnessctl or so.

Rainstripes

Member

Registered: 2025-06-17

Posts: 6

Re: [SOLVED] Can't change brightness with nvidia_wmi_ec_backlight

What laptop and how sure are you that the nvidia gpu is driving your display?

xrandr -q
ls -l /sys/class/backlight/
sudo journalctl -b | curl -F 'file=@-' 0x0.st

What exact command are you trying that "sudo permissions are denied editing privelages to them" what exact command are you issuing? Have you seen https://wiki.archlinux.org/title/Backli … _utilities and checked e.g. brightnessctl or so.

1. I have an Acer Nitro laptop
2. Well that's the GPU I have, and /sys/class/backlight's directory has nvidia_wmi_ec_backlight
3. I'm running this:

cd sys/class/backlight/nvidia_wmi_ec_backlight

-which works fine, but then I run:

sudo echo 5 > actual_brightness
and it returns:
bash: actual_brightness: Permission denied

Even when I use sudo nano, I can't write it. It gives me [Error writing actual_brightness: Permission denied

Last edited by Rainstripes (2025-06-18 17:40:11)

V1del

Forum Moderator

Registered: 2012-10-16

Posts: 24,569

Re: [SOLVED] Can't change brightness with nvidia_wmi_ec_backlight

please post the output of these three commands, I highly doubt that your display is driven by nvidia, and see the note below.

Also general primer,

sudo echo 5 > brightness

elevates the echo but not the > which does the actual write, to properly do that use either of

echo 5 | sudo tee brightness
sudo bash -c 'echo 5 > brightness'

Last edited by V1del (2025-06-18 18:04:31)

002445

Member

Registered: 2021-10-07

Posts: 28

Re: [SOLVED] Can't change brightness with nvidia_wmi_ec_backlight

sudo echo 5 > actual_brightness 

will never work.

You need to edit the 'brightness' file in that directory. Not actual_brightness or max_brightness.

I use 'brightnessctl' to manage the backlight on my laptop. This can be installed using pacman.

Last edited by 002445 (2025-06-18 18:03:54)

Rainstripes

Member

Registered: 2025-06-17

Posts: 6

Re: [SOLVED] Can't change brightness with nvidia_wmi_ec_backlight

sudo echo 5 > actual_brightness 

will never work.

You need to edit the 'brightness' file in that directory. Not actual_brightness or max_brightness.

I use 'brightnessctl' to manage the backlight on my laptop. This can be installed using pacman.

I've already tried brighnessctl; no dice. As I said earlier, I can update the brightness file just fine, but my actual display's brightness doesn't change when I do. I just thought it was worth mentioning that sudo permissions weren't working on any of the other files, even though they don't change my brightness

Last edited by Rainstripes (2025-06-18 21:14:58)

Rainstripes

Member

Registered: 2025-06-17

Posts: 6

Re: [SOLVED] Can't change brightness with nvidia_wmi_ec_backlight

please post the output of these three commands, I highly doubt that your display is driven by nvidia, and see the note below.

Also general primer,

sudo echo 5 > brightness

elevates the echo but not the > which does the actual write, to properly do that use either of

echo 5 | sudo tee brightness
sudo bash -c 'echo 5 > brightness'

Here's the output:

╰─ ❯❯ xrandr -q
ls -l /sys/class/backlight/
sudo journalctl -b | curl -F 'file=@-' 0x0.st
Screen 0: minimum 16 x 16, current 1920 x 1080, maximum 32767 x 32767
eDP-1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 340mm x 190mm
   1920x1080    143.88*+
   1440x1080    143.80  
   1400x1050    143.89  
   1280x1024    143.79  
   1280x960     143.86  
   1152x864     143.92  
   1024x768     143.87  
   800x600      143.83  
   640x480      143.85  
   320x240      142.05  
   1680x1050    143.88  
   1440x900     143.86  
   1280x800     143.84  
   1152x720     143.77  
   960x600      143.72  
   928x580      143.50  
   800x500      143.68  
   768x480      143.69  
   720x480      143.85  
   640x400      143.37  
   320x200      141.40  
   1600x900     143.93  
   1368x768     143.77  
   1280x720     143.85  
   1024x576     143.91  
   864x486      143.63  
   720x400      143.88  
   640x350      143.57  
lrwxrwxrwx - root 18 Jun 13:25  nvidia_wmi_ec_backlight -> ../../devices/pci0000:00/PNP0C14:01/wmi_bus/wmi_bus-PNP0C14:01/603E9613-EF25-4338-A3D0-C46177516DB7/backlight/nvidia_wmi_ec_backlight

002445

Member

Registered: 2021-10-07

Posts: 28

Re: [SOLVED] Can't change brightness with nvidia_wmi_ec_backlight

ls -l /sys/class/backlight/intel_backlight/
-r--r--r-- 1 root root  4096 Jun 19 08:19 actual_brightness
-rw-r--r-- 1 root root  4096 Jun 19 08:19 bl_power
-rw-rw-r-- 1 root video 4096 Jun 19 08:14 brightness
-r--r--r-- 1 root root  4096 Jun 19 08:14 max_brightness
-r--r--r-- 1 root root  4096 Jun 19 08:19 scale
-r--r--r-- 1 root root  4096 Jun 19 08:14 type
-rw-r--r-- 1 root root  4096 Jun 19 08:14 uevent

These are the permissions on my laptop. The reason you cannot change most files in that folder is that even root doesn't have write access. There is no issue with sudo or permissions from what you've told us.

You need to look into why the brightness doesn't change after changing the value in the 'brightness' file. I don't use an nvidia card so I am not familiar with that situation. Maybe there are some packages you need to install. I think there are open source and closed source drivers available for nvidia.

Last edited by 002445 (2025-06-19 06:25:28)

Rainstripes

Member

Registered: 2025-06-17

Posts: 6

Re: [SOLVED] Can't change brightness with nvidia_wmi_ec_backlight

I'm using the proprietary closed source ones. Are my drivers the problem then?