Hi all!
Scenario: Slackware 13.0 and laptop Sony Vaio VGN-NS21Z.
Some time ago, while installing a new kernel (2.6.32.7) on my notebook, I noticed something strange that later on convinced me to get back to the default Slackware kernel (2.6.29.6): it was not possibile to set the brightness as there was no subsystem suitable to that goal.
In a nutshell: with the default Slack kernel I got this command:

echo "5" > /sys/class/backlight/sony/brightness

Now, there's nothing similar because, as far as I know, all Linux kernels from 2.6.30.* on don't create the directory /sys/class/backlight/sony/.
In 2.6.32 kernel config there's a significant module, though, sony_laptop.
It all seems strange to me: are we talking about a bug or has it been implemented a new feature to handle the problem?
Thanks in advance,

Burroughs from Italy.

I sympathise. sony_laptop replaced something that did work with my vaio (VGN-FS415M) about 2 years ago.

sony_laptop doesn't seem to work at all well: the battery is monitored OK, but none of the function-keys for brightness / volume / etc work.

So I have work-arounds: the volume control is on my panel, and brightness I can set with nvidia-settings