Re: /proc/acpi/video

[Volkan YAZICI <yazicivo@ttmail.com>]

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.

--8<---------------cut here---------------start------------->8---
$ ls -l /sys/class/backlight/
total 0
lrwxrwxrwx 1 root root 0 Oct 29 21:48 acpi_video0 -> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/acpi_video0/

$ ls -l /sys/class/backlight/acpi_video0/
total 0
-r--r--r-- 1 root root 4096 Oct 29 21:48 actual_brightness
-rw-r--r-- 1 root root 4096 Oct 30 17:32 bl_power
-rw-r--r-- 1 root root 4096 Oct 30 17:32 brightness
lrwxrwxrwx 1 root root    0 Oct 30 17:32 device -> ../../../0000:01:00.0/
-r--r--r-- 1 root root 4096 Oct 30 17:32 max_brightness
drwxr-xr-x 2 root root    0 Oct 30 17:32 power/
lrwxrwxrwx 1 root root    0 Oct 29 21:48 subsystem -> ../../../../../../class/backlight/
-r--r--r-- 1 root root 4096 Oct 30 17:32 type
-rw-r--r-- 1 root root 4096 Oct 29 21:48 uevent

$ cat /sys/class/backlight/acpi_video0/brightness
7

$ cat /sys/class/backlight/acpi_video0/max_brightness
7
--8<---------------cut here---------------end--------------->8---

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.

--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.