Laptop Panel brightness control

Adam Jackson ajax at
Mon Jan 4 10:37:00 PST 2010

On Mon, 2009-12-28 at 15:59 +0100, Sylvain Defresne wrote:
> Hello,
> In 2006 a property laptop_panel.brightness_in_hardware was added to
> HAL [1] to inform client of different handling of the bightness
> control key by the BIOS (some BIOSes forward the event to the
> userspace, some handle them directly, some both handle them and
> forward them to userspace).

We've never used the HAL property for brightness control in X.

> However, now that HAL is currently deprecated in favor of DeviceKit,
> and XRandR for controlling the brightness, the difference of handling
> of the brightness control key is once more causing bug in userspace
> (see [2], [3] but it is not specific to gnome-power-manager, it also
> affect kde user). So there is a need to one more time address this
> issue by using a database to inform daemon of how the brightness event
> is handled by the BIOS.
> I'm willing to help with this issue as I've got one of the affected
> BIOS (MSI Wind U100). However I'm not familiar with DeviceKit nor
> XRandR, and don't know in which project I need to add this
> caracterisation of the BIOS and exposition of the equivalent of the
> laptop_panel.brightness_in_hardware property ?

The brightness control should be internally routed in the kernel to be a
DRM output property, which the X server then proxies through as a RANDR
output property.  DeviceKit doesn't get involved here, just make the
kernel do the right thing.

- ajax
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