Brightness key on keyboard not working

Question

So I have seen this a few times but haven't seen a solution. I also don't know if it is computer hardware related problem or not.

My brightness keys ( fn + F2 and F3) to set the brightness in Ubuntu 16.04 does nothing, I have a HP Pavillion Laptop computer. Can anyone help me fix this. I have seen a "sort of solution" downloading an application called "Brightness Controller" but that is not a real solution for me.

Please help me with this if you can.. Thanks W

When running acpi_listen command in the terminal I get the following output:

video/brightnessdown BRTDN 00000087 00000000 
video/brightnessdown BRTDN 00000087 00000000 
video/brightnessup BRTUP 00000086 00000000 
video/brightnessup BRTUP 00000086 00000000

nothing happening with {xbacklight -dec 20} .. the folder got "Intel Backlight" " acpi_video0" "acpi_video1" forlders inside — wblm, Jun 10 '16 at 14:09
I am finding it hard to change these settings.. please explain a bit more — wblm, Jun 10 '16 at 14:42
@Sneetsher I have found the following link and it seems to work. It is a manual approach. — wblm, Jun 10 '16 at 14:58
its a bit of a pain but thanks for you help..I'll stick with it for now. Thanks once again. This script work great , I modified it slightly to fit my system#!/bin/mksh printf " \n Entering file to change brightness in 3 seconds\n remember - no new line after number. "; sleep 3; sudo nano /sys/class/backlight/intel_backlight/brightness — wblm, Jun 10 '16 at 15:11

score 1 · Accepted Answer · edited Jun 18 '20 at 21:45

Run acpi_listen in the terminal, to test if the key event received by the system. Then press Fn+F2 & Fn+F3. Below an output example:

 # acpi_listen 
  PNP0C14:00 000000d0 00000000
 video/brightnessup BRTUP 00000086 00000000
  PNP0C14:00 000000d0 00000000
 video/brightnessdown BRTDN 00000087 00000000

See if you can control backlight using

 sudo apt-get install xbacklight
     xbacklight -inc 20
     xbacklight -dec 20

Another try at lower level

 # ls -l /sys/class/backlight/
 lrwxrwxrwx 1 root root 0 Jun 10 13:56 /sys/class/backlight/intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight
ls -l /sys/class/backlight/intel_backlight/
total 0
 -r--r--r-- 1 root root 4096 Jun 10 14:28 actual_brightness
 -rw-r--r-- 1 root root 4096 Jun 10 14:28 bl_power
 -rw-r--r-- 1 root root 4096 Jun 10 15:19 brightness
 lrwxrwxrwx 1 root root    0 Jun 10 14:28 device -> ../../card0-LVDS-1
 -r--r--r-- 1 root root 4096 Jun 10 14:28 max_brightness
 drwxr-xr-x 2 root root    0 Jun 10 14:28 power
 lrwxrwxrwx 1 root root    0 Jun 10 14:28 subsystem -> ../../../../../../../class/backlight
 -r--r--r-- 1 root root 4096 Jun 10 14:28 type
 -rw-r--r-- 1 root root 4096 Jun 10 14:28 uevent
echo 3600 > /sys/class/backlight/intel_backlight/brightness

Setup an ACPI script as explained in What code is executed when headphones are disconnected?

/etc/acpi/events/intel-backlight

 event=video/brightness*
 action=/etc/acpi/intel-backlight.sh

/etc/acpi/intel-backlight.sh

 #!/bin/bash
x=$(cat /sys/class/backlight/intel_backlight/actual_brightness)
if [ "$2" == "BRTUP" ]
   then
     x=$(echo $x+490 | bc)
     echo $x > /sys/class/backlight/intel_backlight/brightness
 fi
if [ "$2" == "BRTDN" ]
   then
     x=$(echo $x-490 | bc)
     echo $x > /sys/class/backlight/intel_backlight/brightness
 fi

Make the script executable with chmod +x /etc/acpi/intel-backlight.sh.

Brightness key on keyboard not working

1 Answers1

ls -l /sys/class/backlight/intel_backlight/

echo 3600 > /sys/class/backlight/intel_backlight/brightness

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