# [SOLVED] LCD brightness buttons don't work.

## shlape

Having installed Gentoo 2008.0 on my new Vostro 1710 I noticed the brightness controls don't work as they did on my old Latitude D800 laptop. Before hassling Dell about the possibility that there was a problem with the laptop itself, I booted an Ubuntu live CD and found it worked perfectly.

Before anyone diverts this topic to "why don't you just install Ubuntu", I'll mention briefly that I think Ubuntu is a great Linux distro but my preference is Gentoo.

I believe the problem may be an incorrect kernel configuration. Any ideas?Last edited by shlape on Sat Apr 04, 2009 12:28 am; edited 2 times in total

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## avieth

 *shlape wrote:*   

> Before anyone diverts this topic to "why don't you just install Ubuntu"

 

 :Surprised:  That would never happen here!

I googled and found this page. There's some good information on there that you can try on your system, like the echo -n # /proc/acpi/video/VGA/LCD/brightness . Half way down there are a couple scripts that are offered up to replace some apparently useless acpi files, you should try that.

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## shlape

 *avieth wrote:*   

> 
> 
> I googled and found this page. There's some good information on there that you can try on your system, like the echo -n # /proc/acpi/video/VGA/LCD/brightness . Half way down there are a couple scripts that are offered up to replace some apparently useless acpi files, you should try that.

 

Yeah, Google gave me results like that too. UnfortunatelyI have no "video" in my /proc/acpi directory.

The thing that has me believing it may be a kernel config problem is, after booting the Ubuntu live CD, I can see a /proc/acpi/video/...

While in Ubuntu, I copied the lsmod output to see what modules *may* be added, but instead of mindlessly adding modules which I'm not sure of, I'm hoping someone can direct me down a wiser path. 

...or maybe I'm off in the wrong direction?

*help*

 :Confused: 

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## shlape

I guess it's always useful to provide a 'how did I do it' after marking the post as SOLVED, so here it goes....

After finding out that the Ubuntu live CD was succeeding in configuring the laptop to use the brightness keys I thought I'd have a look at the .config it was using.

I found that CONFIG_ACPI_VIDEO was set, but in my kernel config it was no where to be found. Instead of doing a nasty cut-n-past to my .config file

I looked around and found this:

http://www.nabble.com/T61-Brightness-keys-with-2.6.26-not-working-(NVIDIA)-td18577619.html"

(sorry, the URL function just wasn't working for me this morning)   :Embarassed: 

More importantly...

 *Quote:*   

> In 2.6.26 the dependencies for video.c changed. please make sure you have
> 
> CONFIG_ACPI_VIDEO enabled (i think it requires CONFIG_VIDEO_OUTPUT_CONTROL
> 
> now). 

 

and

 *Quote:*   

> Previously I could not enable CONFIG_ACPI_VIDEO because it wasn't displayed in
> 
> menuconfig. After I enabled CONFIG_VIDEO_OUTPUT_CONTROL I finally could select it. 

 

After doing this, and a quick reboot... problem solved.

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## pilla

Moved from Installing Gentoo to Kernel & Hardware.

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## durand101

shlape, thanks for posting the solution!

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## piponazo

My eyes will be grateful to you forever   :Laughing: . This solution works.

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