brightness control on Dell Studio 1558
I am having problems in adjusting the screen brightness on Dell Studio 1558 laptop with Debian Squeeze and intel graphics. Pressing the corresponding Fn keys doesn't change the brightness and gives the following error:
[ 833.240055] ACPI: Failed to switch the brightness
[ 833.616022] ACPI: Failed to switch the brightness
[ 2182.884115] ACPI: Failed to switch the brightness
[ 2183.107576] ACPI: Failed to switch the brightness
I've tried "echo 10 > /sys/devices/virtual/backlight/dell_backlight/brightness" without result. The same with other values.
The file /proc/acpi/video/GFX0/DD01/brightness contains the line "<not supported>".
There is a patch offered there but I couldn't make it work on latest stable kernel from kernel.org
and there are no instructions available.
Thanks in advance