I have an Alienware M11X R2 notebook which is built on Nvidia's new "optimus" technology. There's quite a few problems supporting this hardware with the current drivers available for linux and Xorg, but I'm hoping this one is easy to fix. In my Xorg.log, I see this line: [ 1574.285] (II) intel(0): found backlight control interface /sys/class/backlight/acpi_video1 So, my FN keys which I've bound to the proper Xorg symbol do not work to control my LCD brightness. However, I fixed this problem by binding the keys to a script I wrote that uses the proper acpi_video device, which is /sys/class/backlight/acpi_video0/brightness My system has both an NV50 and i915 GPU. I'm hoping I can provide the necessary information so that Xorg will eventually be able to control my brightness natively. I have posted lspci information and a complete disassembly of my ACPI DSDT here: https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/312756/comments/208 Thank you!
Oops, sorry, I forgot to mention that I'm using X86_64 FEDORA release 13, with latest updates/kernels/drivers.
So it seems like both GPUs provide an ACPI interface to modify the brightness even though only one is connected. Currently the driver is quite naive and just tries a light of known interfaces and uses the first one that exists. I am not even sure if it is possible to ACPI video driver to recognise that it is not in control of any real hardware and so should not expose an interface. However, I have pushed one patch which looks right under normal circumstances which is to only hook up a backlight interface if it reports a non-zero max value. I am interested to know if this is sufficient or whether we have to dig deeper.
To use the latest drivers in Ubuntu, you can simply install them from the ppa:xorg-edgers. You may have to wait a day or so before the commit becomes available through that channel.
Or can you attach the results of reading /sys/class/backlight/acpi_video*/*?
The docs say that the brightness should be controlled via the IGP. But that still leaves the question of how identify which ACPI backlight connects to which GPU. Hmm.
Not the perfect solution, but a stop-gap: commit 414e87255cdee6eb556703ddefd194af71b985ed Author: Chris Wilson <chris@chris-wilson.co.uk> Date: Sun Aug 26 19:47:31 2012 +0100 Add Option "Backlight" to override the probed backlight control interface The automatic selection may not correspond with the correct backlight (such as in a multi-gpu, multi-panel device) or the user may simply prefer another control interface. This allows them to override the chosen interface using Option "Backlight" "my-backlight" to specify '/sys/class/backlight/my-backlight' as the interface to use instead. Suggested-by: Alon Levy <alevy@redhat.com> References: https://bugs.freedesktop.org/show_bug.cgi?id=29273 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
And for acpi in particular we use: commit 7d76eb155ed78343abfa15b7c8af87fc3d4211e4 Author: Chris Wilson <chris@chris-wilson.co.uk> Date: Fri Sep 7 18:06:25 2012 +0100 sna: First scan for a backlight associated with the device The goal is to find the right interface in a multi-GPU system. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.