# LCD brightness control on samsung Q45 does not work

## hans_da

In short, the LCD brightness control of Samsung Q45 does not work on my box. System is x86_64, kernel 2.6.24-gentoo-r8.

Several things.

1. The brightness control keys of Q45 is Fn+Up and Fn+Down. When I pressed these two, the dmesg told me:

atkbd.c: Unknown key pressed (translated set 2, code 0x88 on isa0060/serio0).

atkbd.c: Use 'setkeycodes e008 <keycode>' to make it known.

atkbd.c: Unknown key pressed (translated set 2, code 0x89 on isa0060/serio0).

atkbd.c: Use 'setkeycodes e009 <keycode>' to make it known.

2. According to the http://gentoo-wiki.com/HOWTO_Power_Management#Adjust_LCD_brightness I should compile the ACPI/Video module. But this option simply does not exist in menuconfig. Does the new kernel changed something?

3. When start the X, xorg.0.log reports:

expected keysym, got XF86KbdLightOnOff: line 70 of pc

expected keysym, got XF86KbdBrightnessDown: line 71 of pc

expected keysym, got XF86KbdBrightnessUp: line 72 of pc

The XKEYBOARD keymap compiler (xkbcomp) reports:

> Warning:          Type "ONE_LEVEL" has 1 levels, but <RALT> has 2 symbols

>                   Ignoring extra symbols

Errors from xkbcomp are not fatal to the X server

For me, it seems that 1. the kernel support for the backlight has some problem and 2. the key pressing is not recognized properly. Any suggestion would be very helpful!

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## carpman

I have one these arriving tomorrow so have been checking up on it and linux, i have read that you can loose this feature in x but drop to console and it work!

Worth trying to see if if this is so?

cheers

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## hans_da

Switching to console also does not help. I think the center problem is that there is NO kernel module to support changing the LCD brightness. As I said there is no such ACPI kernel option in kernel 2.6.24. I don't know why. Perhaps it is moved to somewhere else?

I also read about that switching to console problem. This problem only applies to Q45 with nvidia cards. In my case I am using the intel X3100.

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## pappy_mcfae

There is kernel support, you just have to know where to look for it. Also, the referenced document is just a wee bit out of date. To be able to control the LCD brightness, you need to select:

```
Graphics support --> 

[*]Backlight & LCD device support --> 

Lowlevel Backlight controls [*]

Lowlevel LCD controls[*] 
```

From my experience, it's best to just use the function keys to get the job done. Having Linux do the job leads to some pretty serious annoyances.

Good luck.

Blessed be!

Pappy

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## hans_da

 *pappy_mcfae wrote:*   

> 
> 
> From my experience, it's best to just use the function keys to get the job done. Having Linux do the job leads to some pretty serious annoyances.
> 
> 

 

I totally agree! 

But then how to let  the Fn keys do the job? When still in the grub, the Fn keys function nicely to regulate the bightness. But as soon as the kernel is started, the Fn key does not work anymore. Should I try just disable all the LCD control drivers in the kernel?

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## hans_da

Just tried out. This does not help.

There are at least three combinations not working:

Fn + F5 : turn on/off the LCD backlight

Fn + Up/Down : change the backlight brightness

All these keys are working nicely just in the grub stage. Just when the kernel is loaded, all keys stop to function. I think the functionality of these keys is directly related to the BIOS, while the linux kernel has somehow stopped passing the right signal to the BIOS.

I will try to dig a little bit on this:

http://gunnarwrobel.de/wiki/Linux-and-the-keyboard.html

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## hans_da

a little bit search gives the following:

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/216436

I think the problem is that the new linux kernel can sense and intercept these special keyboard signals. The keyboard signal does not reach the BIOS, thus no reaction to the LCD. Of course one can still try to catch the signal and do all the job with ACPI or HAL or whatever, but this is a completely different story, and it is also not preferable.

Well, any walk around? Or where should I report in upstream if this is really a problem?

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## pappy_mcfae

I honestly don't know. I guess I dodged another bullet. This system doesn't suffer that problem. 

What might help is to look through my kernel .config and compare it with yours. Since everything works on my system, you might be able to use some of my settings to fix yours.

Good luck.

Blessed be!

Pappy

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## carpman

 *pappy_mcfae wrote:*   

> I honestly don't know. I guess I dodged another bullet. This system doesn't suffer that problem. 
> 
> What might help is to look through my kernel .config and compare it with yours. Since everything works on my system, you might be able to use some of my settings to fix yours.
> 
> Good luck.
> ...

 

I am planning Q45 install and was looking through your config and see you did use mcore2 but pentiumM as cpu choice, i take this because it is a mobile cpu?

Do they not do mcore2 for mobile cpu?

cheers

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## pappy_mcfae

Yes, this machine has a P-IV Celeron M, and no, I don't think they shave the CPU settings that closely. However, you can always do a bit of experimentation.

Blessed be!

Pappy

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## carpman

 *pappy_mcfae wrote:*   

> Yes, this machine has a P-IV Celeron M, and no, I don't think they shave the CPU settings that closely. However, you can always do a bit of experimentation.
> 
> Blessed be!
> 
> Pappy

 

Ok, so with my Intel Core 2 Duo 7100 i would choose mcore2?

You say every thing else is working on you q45 does this include web cam and modem?

cheers

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## pappy_mcfae

I'm sorry. I misunderstood you. I only offer my config as a general setup for yours. My system is a Compaq C504US. The settings (apart from the hardware) allow me to use my keyboard to its fullest, and it allows me to set my LCD brightness. If you follow the basics in my kernel, you should be able to use the keyboard to change brightness after kernel initialization.

Once again, I apologize for being inaccurate. That was my fault and I apologize if I confused you. My .config is to be a guide, since I can control my LCD screen. 

Also, if you'd like, I can set up a kernel for you. Just post your .config and the results of lspci.

Blessed be!

Pappy

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## carpman

 *pappy_mcfae wrote:*   

> I'm sorry. I misunderstood you. I only offer my config as a general setup for yours. My system is a Compaq C504US. The settings (apart from the hardware) allow me to use my keyboard to its fullest, and it allows me to set my LCD brightness. If you follow the basics in my kernel, you should be able to use the keyboard to change brightness after kernel initialization.
> 
> Once again, I apologize for being inaccurate. That was my fault and I apologize if I confused you. My .config is to be a guide, since I can control my LCD screen. 
> 
> Also, if you'd like, I can set up a kernel for you. Just post your .config and the results of lspci.
> ...

 

Hello, sorry i thought you posting config for q45, thanks for the offer though but will do it myself after some research.

cheers

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