# [solved] Why doesn't the 2.6.21 kernel have ACPI_VIDEO?

## RayDude

I'm running 2.6.21-suspend2-r6 on an HP DV9000Z.

I'd like to control my lcd backlight but the suspend2 sources don't have ACPI_VIDEO as an option.

Well. It doesn't seem to have it anyway. 2.6.20 suspend2 has it though. I can't run that because my laptop requires some of the drivers found only in 2.6.21.

Any suggestions?

Raydude

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## didymos

It does, but only if X86/IA64 is set.

Here's the full dependency line for that option:

```

!X86_VOYAGER && !X86_NUMAQ && !X86_VISWS && !IA64_HP_SIM && (IA64 || X86) && PM && ACPI && X86 && BACKLIGHT_CLASS_DEVICE

```

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## RayDude

 *didymos wrote:*   

> It does, but only if X86/IA64 is set.
> 
> Here's the full dependency line for that option:
> 
> ```
> ...

 

Why not for x86_64?

Should I ask the kernel guys?

Raydude

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## didymos

 *RayDude wrote:*   

> 
> 
> Why not for x86_64?
> 
> 

 

I have no idea.

 *Quote:*   

> 
> 
> Should I ask the kernel guys?
> 
> 

 

Maybe.  I'd try searching lkml first.  It might be in the kernel docs directory somewhere, or even in the code comments.

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## RayDude

Okay I figured it out: 2.6.21 requires the nvidia graphics module to be loaded:

```

  │ │    <*> nVidia Framebuffer Support                                   │ │

  │ │    [*]   Enable DDC Support                                         │ │

  │ │    [*]   Support for backlight control (NEW)                        │ │
```

Or one of the laptop modules (I have an HP and it doesn't have a module).

Raydude

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## RayDude

Unfortunately that didn't fix the problem. the nvidiafb driver conflicts with nvidia X driver. So I made it a module.

But then the /proc/acpi/video/VGA/LCD... stuff does not work.

So I'm still stuck.

Raydude

Update: trying this next:

```
  │ │    --- Backlight & LCD device support                               │ │

  │ │    <*>   Lowlevel Backlight controls                                │ │

  │ │    <*>   Lowlevel LCD controls                                      │ │
```

This works! I can set the brightness level. the info file doesn't look legit but it works.

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## madCoder|GN

How exactly did you use those once you compiled them into your kernel?  I have a Compaq, not an HP, but they're the same company now.  I have the class compiled into the kernel, but I don't know where to find the "info" file you're talking about, or how to control the brightness once it's in the kernel.  Are you also using some other kernel module to expose the brightness controls?

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## RayDude

 *madCoder|GN wrote:*   

> How exactly did you use those once you compiled them into your kernel?  I have a Compaq, not an HP, but they're the same company now.  I have the class compiled into the kernel, but I don't know where to find the "info" file you're talking about, or how to control the brightness once it's in the kernel.  Are you also using some other kernel module to expose the brightness controls?

 

Once you get it all compiled and working you will get a kernel device to set the brightness level:

```
cat /proc/acpi/video/VGA/LCD/brightness

levels:  92 42 20 24 28 33 38 42 48 56 66 78 92

current: 92
```

That will tell you the valid settings.

Then to set the brightness all you do is:

```
echo 38 > /proc/acpi/video/VGA/LCD/brightness
```

Also, please note the [FN] f7 and f8 keys work as well.

I have not found an application that will control LCD brightness. It really needs to be added to klaptop.

Raydude

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## madCoder|GN

 *RayDude wrote:*   

> Once you get it all compiled and working you will get a kernel device to set the brightness level:
> 
> ```
> cat /proc/acpi/video/VGA/LCD/brightness
> 
> ...

  That's what I was getting at, regarding why it doesn't show up.  In the gentoo-sources kernel, I found no reference to the ACPI_VIDEO config option, thus I had no /proc/acpi/video entry.

Note that compiling in the support that you quoted above for the low-level LCD & Brightness support, does NOT add that ACPI video support.  I switched to suspend2 sources, and that kernel did give me the option to compile the video support in, and then I did get the brightness controls you're talking about.  Although the Fn keys still did not affect it.

Thanks for the response though.

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