A friend of mine has Fujitsu Siemens Amilo laptop and is full time using his computer with Slackware Linux.
He is quite happy with Slackware Linux 13.37 on the laptop, but unfortunately sometimes his screen brightness lowers. One example when the screen gets darkened is when he switch the computer on without being plugged in the electricity grid. This lowered brightness makes the screen un-user friendly and is quite tiring for the eye …
By default the laptop has the usual function keys and in theory pressing Function (fn) + F8 / F7 – should increase / decrease the brightness with no problems, however on Slackware Linux (and probably on other Linuxes too?), the function keys are not properly recognized and not responding whilst pressed.
I used to have brigtness issues on my Lenovo notebook too and remember how irritating this was.
After a bit of recalling memories on how I solved this brightness issues I remembered the screen brigthness on Linux is tunable through /proc virtual (memory) filesystem.
The laptop (Amilo) Fujitsu Siemens video card is:
lspci |grep -i vga
00:02.0 VGA compatible controller: Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller (primary) (rev 03)
I took a quick look in /proc and found few files called brightness:
- /proc/acpi/video/GFX0/DD01/brightness
- /proc/acpi/video/GFX0/DD02/brightness
- /proc/acpi/video/GFX0/DD03/brightness
- /proc/acpi/video/GFX0/DD04/brightness
- /proc/acpi/video/GFX0/DD05/brightness
cat-ting /proc/acpi/video/GFX0/DD01/brightness, /proc/acpi/video/GFX0/DD03/brightness, /proc/acpi/video/GFX0/DD04/brightness all shows not supported and therefore, they cannot be used to modify brightness:
bash-4.1# for i in $(/proc/acpi/video/GFX0/DD0{1,3,4,5}/brightness); do \
cat $i;
done
<not supported>
<not supported>
<not supported>
<not supported>
After a bit of testing I finally succeeded in increasing the brightness.
Increasing the brightness on the notebook Intel GM965 video card model is done, through file:
/proc/acpi/video/GFX0/DD02/brightness
To see all the brightness levels the Fujitsu LCD display supports:
bash-4.1# cat /proc/acpi/video/GFX0/DD02/brightness
levels: 13 25 38 50 63 75 88 100
current: 25
As you can see the dark screen was caused cause the current: brightness is set to a low value of 25.
To light up the LCD screen and make the screen display fine again, I increased the brightness to the maximum level 100, e.g.:
bash-4.1# echo '100' > /proc/acpi/video/GFX0/DD02/brigthness
Just for the fun, I've written also a two lines script which gradually increases LCDs brightness 
bash-4.1# echo '13' > /proc/acpi/video/GFX0/DD02/brightness;
bash-4.1# for i in \
$(cat /proc/acpi/video/GFX0/DD02/brightness|grep 'levels'|sed -e 's#levels:##g'); do \
echo $i > /proc/acpi/video/GFX0/DD02/brightness; sleep 1; \done
fujitsu_siemens_brightness_fun.sh script is fun to observe in changing the LCD screen gradually in one second intervals
Here is also a tiny program that reduces and increases the notebook laptop brightness written in C. My friend Dido, coded it in just few minutes just for the fun
To permanently solve the issues with darkened screen on boot time it is a good idea to include echo '100' > /proc/acpi/video/GFX0/DD02/brigthness in /etc/rc.local:
bash-4.1# echo '100' > /proc/acpi/video/GFX0/DD02/brigthness
I've also written another Universal Linux Increase laptop screen brightness Shell script which should be presumable also working for all Laptop models running Linux
My maximize_all_linux_laptops_brightness.sh "universal increase Linux brightness" script is here
I'll be glad to hear from people who had tested the script on other laptops and can confirm it works fine for them.
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