Continued Quest for Backlight Control

[nujinini]

Hello Everyone!

The icon for the backlight control of my laptop shows everytime I use hotkeys but the actual brightness does not change.

In my continued quest for backlight control of my laptop, I have tried the following

jun@jun-laptop:/$ cd /proc/acpi/video/GFX0/DD02
jun@jun-laptop:/proc/acpi/video/GFX0/DD02$ ls
brightness  EDID  info  state
jun@jun-laptop:/proc/acpi/video/GFX0/DD02$ cat brightness
levels:  5 15 25 35 45 55 65 75 85 95 100
current: 100

jun@jun-laptop:/$ echo 5 >brightness
bash: brightness: Permission denied
jun@jun-laptop:/$ sudo echo 5 >brightness
bash: brightness: Permission denied
jun@jun-laptop:/$ sudo su
[sudo] password for jun: 
root@jun-laptop:/# echo 5 >brightness
root@jun-laptop:/# exit
jun@jun-laptop:/$ cat brightness
5
jun@jun-laptop:/$

If you may notice, I was able to change the levels from 100 to 5. However, the backlight does not seem to have changed, at least from a level: 100 to the new level: 5

In my continued quest for a more effective solution I stumbled upon this thread:

[ubuntu] [SOLVED] Backlight control from the command line - Ubuntu Forums

May I ask if this solution can also apply to what I am trying to to please? And if yes, I hope it would not be too much of a request to ask if you can "walk through" with me.

Thank you very much!

[Rubberman]

Well, the vbetool is a tool that allows you to access real-mode bios functions. Unfortunately, it might not work for you, depending upon how your system is configured. You can at least try it. Open a command line window and execute the command: sudo vbetool vbefp getbrightness
That will either return the current brightness setting that the BIOS knows about, or return the error "Real mode call failed". If it succeeds, then you can try the command: sudo vbetool vbefp setbrightness <level>

[nujinini]

Well, the vbetool is a tool that allows you to access real-mode bios functions. Unfortunately, it might not work for you, depending upon how your system is configured. You can at least try it. Open a command line window and execute the command: sudo vbetool vbefp getbrightness
That will either return the current brightness setting that the BIOS knows about, or return the error "Real mode call failed". If it succeeds, then you can try the command: sudo vbetool vbefp setbrightness <level>

Hi Rubberman!

Thank you for your response. Anyway, I gave it a try, several times as you may see. I think there might still be a missing switch? I'm not really sure.

jun@jun-laptop:~$ sudo vbetool vdefp getbrightness
[sudo] password for jun: 
vbetool: Usage vbetool [[vbestate save|restore]|[vbemode set|get]|[vgamode]|[dpms on|off|standby|suspend|reduced]|[post [romfile]]|[vgastate on|off]|[vbefp panelid|panelsize|getbrightness|setbrightness|invert]]

jun@jun-laptop:~$ sudo vbetool vdefp | getbrightness
vbetool: Usage vbetool [[vbestate save|restore]|[vbemode set|get]|[vgamode]|[dpms on|off|standby|suspend|reduced]|[post [romfile]]|[vgastate on|off]|[vbefp panelid|panelsize|getbrightness|setbrightness|invert]]
getbrightness: command not found

jun@jun-laptop:~$ sudo vbetool vdefp setbrightness
vbetool: Usage vbetool [[vbestate save|restore]|[vbemode set|get]|[vgamode]|[dpms on|off|standby|suspend|reduced]|[post [romfile]]|[vgastate on|off]|[vbefp panelid|panelsize|getbrightness|setbrightness|invert]]

jun@jun-laptop:~$ sudo vbetool vdefp | setbrightness
vbetool: Usage vbetool [[vbestate save|restore]|[vbemode set|get]|[vgamode]|[dpms on|off|standby|suspend|reduced]|[post [romfile]]|[vgastate on|off]|[vbefp panelid|panelsize|getbrightness|setbrightness|invert]]
setbrightness: command not found

jun@jun-laptop:~$ sudo su
root@jun-laptop:/home/jun# sudo vbetool vdefp getbrightness
vbetool: Usage vbetool [[vbestate save|restore]|[vbemode set|get]|[vgamode]|[dpms on|off|standby|suspend|reduced]|[post [romfile]]|[vgastate on|off]|[vbefp panelid|panelsize|getbrightness|setbrightness|invert]]

root@jun-laptop:/home/jun# sudo vbetool vdefp getbrightness
vbetool: Usage vbetool [[vbestate save|restore]|[vbemode set|get]|[vgamode]|[dpms on|off|standby|suspend|reduced]|[post [romfile]]|[vgastate on|off]|[vbefp panelid|panelsize|getbrightness|setbrightness|invert]]

[Rubberman]

You were using the command argument 'vdefp', when it is supposed to be 'vbefp'. IE, sudo vbetool vbefp getbrightness

[nujinini]

You were using the command argument 'vdefp', when it is supposed to be 'vbefp'. IE, sudo vbetool vbefp getbrightness

Ooopss... Sorry about that. My eyes have starting to play tricks on me again.

Anyway, here is my output...:

jun@jun-laptop:~$ sudo vbetool vbefp getbrightness
[sudo] password for jun: 
Real mode call failed
jun@jun-laptop:~$ sudo su
root@jun-laptop:/home/jun# vbetool vbefp getbrightness
Real mode call failed
root@jun-laptop:/home/jun#

[Rubberman]

That's what happened to me, but I ran it on my desktop and it is only supposed to work on laptop displays. What it is supposed to do is make a real-mode call into the bios to do a vesa (generic video) driver call to change the backlight intensity. However, it isn't guaranteed to work... apparently.

At this point, I don't know what to suggest. You might change your video driver to vesa (it won't handle the high resolutions) and see if the keyboard fn-* keys work that way. If so, then it is a driver problem.

[nujinini]

That's what happened to me, but I ran it on my desktop and it is only supposed to work on laptop displays. What it is supposed to do is make a real-mode call into the bios to do a vesa (generic video) driver call to change the backlight intensity. However, it isn't guaranteed to work... apparently.

At this point, I don't know what to suggest. You might change your video driver to vesa (it won't handle the high resolutions) and see if the keyboard fn-* keys work that way. If so, then it is a driver problem.

Okidoki. Thank you very much. I really appreciate it Rubberman!