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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 ...
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  1. #1
    Linux Engineer nujinini's Avatar
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    Continued Quest for Backlight Control


    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

    Code:
    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
    Code:
    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!
    nujinini
    Linux User #489667

  2. #2
    Linux Guru Rubberman's Avatar
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    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>
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  3. #3
    Linux Engineer nujinini's Avatar
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    Quote Originally Posted by Rubberman View Post
    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.

    Code:
    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]]
    nujinini
    Linux User #489667

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  5. #4
    Linux Guru Rubberman's Avatar
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    You were using the command argument 'vdefp', when it is supposed to be 'vbefp'. IE, sudo vbetool vbefp getbrightness
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  6. #5
    Linux Engineer nujinini's Avatar
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    Quote Originally Posted by Rubberman View Post
    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...:

    Code:
    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#
    nujinini
    Linux User #489667

  7. #6
    Linux Guru Rubberman's Avatar
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    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.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  8. #7
    Linux Engineer nujinini's Avatar
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    Quote Originally Posted by Rubberman View Post
    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!
    nujinini
    Linux User #489667

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