Re: /proc/acpi/video

[Camaleón <noelamac@gmail.com>]

On Sun, 30 Oct 2011 17:38:41 +0200, Volkan YAZICI wrote:

> On Sat, 29 Oct 2011 20:31:03 +0000 (UTC), Camaleón writes:
>> What's the output of "ls -l /sys/class/backlight"?
>>
>> If I follow the instructions of the section named "The /sys/class/
>> backlight interface" I can indeed see and set the backlight values as
>> stated. For instance, to put the backlight at its maximum value, as
>> root I can run:
>>
>> echo 10 > /sys/class/backlight/acpi_video0/brightness
> 
> My configurations are as follows.

(...)

> First, I tried to alter the "brightness":
> 
> --8<---------------cut here---------------start------------->8--- 
> $ echo 1 | sudo tee /sys/class/backlight/acpi_video0/brightness 
> 1
> 
> $ cat /sys/class/backlight/acpi_video0/brightness 
> 1
> --8<---------------cut here---------------end--------------->8---
> 
> Nothing happens.

That's bad. Reducing the value of brightness has to be applied in real 
time, at least that's what happens here. I'm using an intel card/driver, 
what's yours?

> --8<---------------cut here---------------start------------->8--- 
> $ echo 1 | sudo tee /sys/class/backlight/acpi_video0/actual_brightness 
> tee: /sys/class/backlight/acpi_video0/actual_brightness: Permission denied 
> 1
> --8<---------------cut here---------------end--------------->8---
> 
> Still nothing happens.

That's normal. "actual_brightness" file is not writeable by root user, just 
read only.

Greetings,

-- 
Camaleón