Ubuntu – GUI changes brightness in wrong /sys/class/backlight/*/brightness

Don't know if this answers are sufficient - here are links :

A workaround in arch Linux - but backlight is here only explained at edge.

https://wiki.archlinux.org/index.php/Intel_Graphics

And here is more detailed explanation concerning intel 945GM :

http://linux.die.net/man/4/intel

There beyond "Output Configuration" are the options of backlight.

As you can read there - brightness and backlight are two different things which can be adjusted.

xrandr --prop

delivers the current set datas.

Perhaps it is of matter if you install saucy-kernel 3.10 ( download it at ubuntu ) - only in case if you still use kernel 3.2.0-49 ? ( if this does not work, then you still have kernel 3.2.0-49 in your system to go back there ) :

http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.10-saucy

So - don't know if Kernel 3.10 is necessary for below additions - you can test without danger after downloaded 3.10 suiting to your 64 or 32 processor :

sudo dpkg -i linux-*.deb

Sorry - now have seen that there is an extra package besides xrandr - it is called xbacklight

It is not installed by default:

sudo apt-get install xbacklight

xbacklight -get

delivers the current set value.

According to man xbacklight you can set it with:

xbacklight -set (here decimal value in percent !)

There is a special brightness for xbacklight to be set with:

xbacklight -inc (here decimal value increases in percent !)

and

xbacklight -dec (here decimal value decreases in persent !)

lowers the value down again - in case value was set too high.

Is your question answered ? - Let me know !

I created a temporally bash script to adjust brightness level. Then I create 2 sortcuts at keyboard mapping settings to set up CTRL + Brightness UP or CTRL + Brightness Down with this script:

#!/bin/bash

# Step brightness value
STEP=2
# Max brightness value (defult 100)
MAX=100
# Min brightness value (defult 0)
MIN=0

COMMAND=$(xrandr --verbose | grep -i brightness | cut -f2 -d':' | tr -d "[:space:]")
ACTUAL=$(bc -l <<< $COMMAND*100 | cut -f1 -d'.')

while getopts ": u d" input
do
    case $input in
    u)  if [ $ACTUAL -lt $MAX ];then
                TOTAL=$(bc -l <<< $(($ACTUAL+$STEP))/100)
                $(xrandr --output DP-0 --brightness $TOTAL)
        fi;;
    d)  if [ $ACTUAL -gt $MIN ];then
                TOTAL=$(bc -l <<< $(($ACTUAL-$STEP))/100)
                $(xrandr --output DP-0 --brightness $TOTAL)
        fi;;
    ?)  printf "Usage: brightness [OPTION]\n"
        printf "Increase or decrease birghtness on Ubuntu Xorg.\n" 
        printf "WAYLAND MUST BE DISABLED\n\n"
        printf "  -u\t Increases brightness\n"
        printf "  -d\t Decreases brightness\n"
        exit 2;;
    esac
done

And in set custom shortcut I added this