[ltp] W520: Battery-mode-Brightness-Problem

[KASSBOHM]

Hi,

I am running ubuntu-11.04 on a W520. Most things work perfectly -
except that I can't use it in battery-mode, i.e. unplugged to AC. And
I can't control the brightness of the screen.

Whenever I try to work on battery, the computer freezes and I can't do
anything but shut down by pressing the power-key.

Whenever (plugged in AC, i.e. not on battery) and I use the special
keys to reduce the brightness of the screen, after one minute or so
the computer also freezes and I have to shut down.

So that my guess is, that screen brightness adjustment is a problem...

#dmesg shows:
...
[   16.942616] thinkpad_acpi: ThinkPad ACPI Extras v0.24
[   16.942617] thinkpad_acpi: http://ibm-acpi.sf.net/
[   16.942618] thinkpad_acpi: ThinkPad BIOS 8BET41WW (1.21 ), EC unknown
[   16.942620] thinkpad_acpi: Lenovo ThinkPad W520, model 428449G
[   16.943440] thinkpad_acpi: detected a 8-level brightness capable ThinkPad
...

#cat /sys/class/backlight/acpi_video0/max_brightness shows:
15

Does anybody have an idea how to track down the problem and eventually solve it?

Regards,
Sven