[ltp] ACPI video module on Thinkpad R61 8918

[Henrique de Moraes Holschuh]

On Wed, 10 Oct 2007, Christian Birchinger wrote:
> ~$ cat /proc/acpi/video/VID/LCD0/brightness 
> levels:  100 100 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 100
> current: 85
> 
> First of all, what are the first 2 "100" entries? The others are
> the available 16 brightness levels.

Dumbness in the driver.  They are the levels used when on AC or battery (I
don't recall which is which.  Refer to ACPI v3.0a spec if you care, look for
the descprition of "_BCL".

> "current" does not get updated when the Fn+Home/End hotkeys or
> the special /proc/acpi/ibm/brightness from the thinkpad-acpi
> module gets used to adjust brightness. On boot it shows "0"
> but the display is not dark.

This is a bug somewhere, but it *could* be in the thinkpad firmware. Make
sure you are using the latest one.

> When echo-ing values to /proc/acpi/video/VID/LCD0/brightness the
> brightness level changes and "current" gets updated correct.
> 
> All listed levels except "100" can be set. An attempt to set
> "100" results in an "invalid" error.

Looks like a bug in the video driver.

-- 
  "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