Update on Ubuntu 11.10 (Oneiric)
Hi there,
   just a quick update on screen brightness issue status, for the Vaio Y series.
The problem seems related to gnome-power-manager & intel 915 driver... Kamal 
Mostafa has released a path that should be already present in Ubuntu 11.10.
I don't know if this due to the Kamal patch (but I think so), but now it is 
possible to control our (sony Y) brightness through: 
/sys/class/backlight/intel_backlight/brightness

Anyway, the gnome-power-manager links to 
/sys/class/backlight/acpi_video0/
in order to read/set backlight. Unfortunately, this control is completely void 
and does not produce any effect.
A suggested workaround is to start linux with boot parameter:
acpi_backlight=vendor

This produce the desired effect: /sys/class/backlight/acpi_video0/ disappears, 
BUT the sony_laptop module, as does not found acpi support to brightness, takes 
in care brightness management creating its own sony brightness device... and 
yes, gnome-power-manager prefers it than our beloved intel_backlight.
Unfortunately, we NEED sony_laptop module, because takes care of the fn keys 
bindings.
So, two ways are available:
1) modify and recompile sony_laptop module in order to ignore brightness 
control + acpi_backlight=vendor on boot
2) The old and still pretty good acpi event management through custom scripts

Solution 2 is easier and less intrusive, so I have updated the brightness 
scripts, in order to adopt the new brightness control interface and sync with 
the "void" acpi_video0 control when pressing brightness up and down keys.
The install script is now a little smarter, doing checks in order to prevent 
installation where not needed.

I leave here a copy of the patch, hoping could be of help

Cheers

Francesco


** Attachment added: "sonyY_patch3.tar.gz"
   
https://bugs.launchpad.net/ubuntu/+source/gnome-power-manager/+bug/524967/+attachment/2733058/+files/sonyY_patch3.tar.gz

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https://bugs.launchpad.net/bugs/524967

Title:
  Screen brightness doesn't work on Vaio Y

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