Intel graphics card brightness control issue

[Matthias Petermann]

Hi Ethan,

Zitat von "Ethan W. House" <ehouse at csh.rit.edu>:

> What could be causing my brightness control to not work on my Intel
> graphics card. The acpi values change but no effect takes place.
>
> ehouse at derpy ~ $ sudo sysctl hw.acpi.video.lcd0.brightness=50
> hw.acpi.video.lcd0.brightness: 100 -> 50
> ehouse at derpy ~ $ sudo sysctl hw.acpi.video.lcd0.active=1
> hw.acpi.video.lcd0.active: 0 -> 0
>
> I also have an issue were upon resume by machine reboots. I believe the two
> might be related but I am not sure.
>
> I found a couple of other email chains with similar issues but most of them
> have been inactive for more then a year.

Which Laptop model do you have? This issue appears a bit familiar to  
me[1] - I have the same on my Thinkpad. As a workaround you could try  
to change the brightness by direct ACPI calls.

Preparation:

* install sysutils/acpi_call
* kldload acpi_call

Change brightness:

* acpi_call -p '\VBRU'   (Brightness Up)
* acpi_call -p '\VBRD'   (Brightness Down)

It might be that these calls are specific to Thinkpads, not sure if  
they work with others. You can try to find out with acpidump[1].

Kind regards,
Matthias

[1] http://www.freebsd.org/cgi/query-pr.cgi?pr=amd64/181357
[2] http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/acpi-debug.html
-- 
Matthias Petermann <matthias at petermann-it.de>
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