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

[Henrique de Moraes Holschuh]

On Sun, 29 May 2011, KASSBOHM wrote:
> 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...

Which you might even find it is related to the video driver (kernel), or the
X.org/KMS drivers (GPU).

> [   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

What kernel is that?  It should get it right on 2.6.38+,  I think.

Anyway, disable brightness support on thinkpad-acpi using the
"brightness_enable=0" module parameter.  On your thinkpad, it is very likely
that brightness control is to be done either through generic ACPI, or
directly programmed in the GPU by kernel KMS (which might well mean "no
support").

Make sure you're using the latest BIOS, as well.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh