[ltp] ibm-acpi brightness problems on the X60

[Henrique de Moraes Holschuh]

On Wed, 19 Mar 2008, Hasso Tepper wrote:
> Do you happen to know how exactly this decision is made - whether an OS is 
> capable or not? AFAICS it decides so even without thinkpad and/or video acpi 
> modules loaded, so it must be something generic in acpica?

If the ACPI _BCM method is called, the OS is considered to be capable.
Thinkpad-acpi (recent versions) will do it.  ACPI video will also do it.

There is also a possibility of different behaviour if the ACPI informs the
OSI string "Linux", so check that *and report if you find it to be different
for backlight*, please.  See the documentation on the kernel parameters
(kernel command line) for how to enable/disable the OSI string.

But X.org on Intel GPUs can also tell the BIOS to hand's off the backlight,
so if you don't have thinkpad-acpi or ACPI video loaded, and things still
don't work, you have to check if it is not X.org's doing.

But even with X.org blocking it, AFAIK, it unblocks things when the user is
in a text-mode VT.  Just make sure you have the latest intel driver for
X.org.

-- 
  "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