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#1 2021-01-13 07:27:29

Sffred
Member
Registered: 2020-08-30
Posts: 42

[SOLVED] Udev rule not work enabling permissions for backlight control

I am trying to adjust backlight of my asus laptop after reading this wiki page https://wiki.archlinux.org/index.php/Backlight

$ls /sys/class/backlight
intel_backlight

I can change my backlight brightness using

# echo 5 > /sys/class/backlight/intel_backlight/brightness

However, I would like to set xbindkeys to adjust backlight using the Fn+ keys on my keyboard. So I tried to add this udev rule:

$ cat /etc/udev/rules.d/backlight.rules 
ACTION=="add", SUBSYSTEM=="backlight", KERNEL=="intel_backlight", GROUP="video", MODE="0664"

to allow my current user to change backlight, but it's no use.

$ echo 5 > /sys/class/backlight/intel_backlight/brightness 
bash: /sys/class/backlight/intel_backlight/brightness: Permission denied

How can I figure out what to do to solve the problem? Best wishes for any help. Thanks a lot.

Last edited by Sffred (2021-01-14 10:57:53)

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#2 2021-01-13 14:27:48

sashok_bg
Member
Registered: 2021-01-11
Posts: 6

Re: [SOLVED] Udev rule not work enabling permissions for backlight control

I had the same problem and ended up using xbacklight -inc / -dec which works very well and avoids me having to write shell scripts and manipulating files and so on.

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#3 2021-01-13 14:35:59

V1del
Forum Moderator
Registered: 2012-10-16
Posts: 11,800

Re: [SOLVED] Udev rule not work enabling permissions for backlight control

Is your user in the video group? And did you reboot/relog since adding the rule/your user to said group?

Don't use xbacklight the fact that it necessitates xf86-video-intel which has many reports of brokeneness with 5.10 pretty much rules that out. Use acpilight if anything.

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#4 2021-01-13 16:37:09

fistrosan
Member
Registered: 2020-04-01
Posts: 112

Re: [SOLVED] Udev rule not work enabling permissions for backlight control

Try the solution here. Not the first time the udev rules in the wiki fail when it comes to backlight.


https://bbs.archlinux.org/viewtopic.php?id=260428

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#5 2021-01-14 07:16:05

Sffred
Member
Registered: 2020-08-30
Posts: 42

Re: [SOLVED] Udev rule not work enabling permissions for backlight control

@sashok_bg xbacklight -inc/-dec does not work for me at first. But after I replaced xorg-xbacklight with acpilight, i can use it now.
@V1del yes. I am sure that my user is in the video group and I have rebooted several times since I changed the rule. acpilight is helpful. Thanks a lot. I have added this issue to Talk:Backlight.
@fistrosan Thanks a lot. Your problem is exactly the same with me, and the solution helps. I apologize for that I didn't find your post and posted a repeated topic.

Last edited by Sffred (2021-01-14 07:25:17)

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#6 2021-01-16 22:24:17

sashok_bg
Member
Registered: 2021-01-11
Posts: 6

Re: [SOLVED] Udev rule not work enabling permissions for backlight control

@Sffred yes I actually had a second problem afterwards related to graphics stability and ended up uninstalling xf86-video-intel after which my xbacklight stopped working. Then I installed acpilight and it worked again.

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