Re: Backlight mystery - anyone shed light? some progress

[Camaleón <noelamac@gmail.com>]

On Sun, 24 Apr 2011 10:49:26 +0100, Anthony Campbell wrote:

> On 23 Apr 2011, Camaleón wrote:
 
>> Also, check for a BIOS update, most of these "ACPI things" are usually
>> fixed after updating to the latest BIOS.
>> 
>> 
> Thanks, Camaleon. I found a lot of people using the same laptop with
> Windows who have the same problem. In some cases a bios upgrade fixed
> it, in others not. I tried to do this but it requires using an .exe
> file, and though I could do this with both wine and dosemu I couldn't
> obtain a suitable iso file to do the upgrade. (Also, I was a little
> afraid of ending up with an unbootable machine, which a few people
> report as happening.)

Don't be afraid of a BIOS update. Laptops need this piece of code to be 
updated more often than desktops machines due to buggy firmware and 
notebook's embedded nature.

What happens here is that manufacturers do not always provide a utility 
to extract the update file in order you can put it into a USB/CD-ROM to 
run the update and sadly the complete procedure needs to be done in a 
windows environment.

(That's one of the reasons why it is a good idea to do not remove the 
windows partition although you don't use it on your day work :-/)

> BUT I have found that by unloading and reloading the video module
> (and/or the radeon module) I can sometimes obtain the requisite
> backlight file in /sys/devices/virtual .., after which the screen either
> becomes bright automatically or I can do it manually. So it seems to be
> something to do with the order in which the modules are loaded, though I
> can't figure out what. The effect is unpredictable - sometimes it works,
> sometimes not.

If you can wait with that bypass, msot sure is that any kernel update 
will solve the problem as you seemed to experience with 2.6.37 and 2.6.38 
branches.

Greetings,

-- 
Camaleón