Bug#489495:

[Michel Dänzer <daenzer@debian.org>]

On Wed, 2009-11-04 at 22:13 +0100, Thomas Champagne wrote: 
> 
> The different power-manager like gnome-power-manager for Gnome or
> Powerdevil for Kde call the same method that this command : 
> xset dpms force off
> So, they use DPMS to switch off the screen.
> But, when you check the xorg.0.log, you can see this line : 
> "No DPMS capabilities specified; RGB/Color Display". 
> 
> So, on Ibook, it isn't possible to switch off the screen with DPMS. 
> The power screen is managed by the Power Management Unit (PMU). 

BTW, this may be true for your iBook model, but I suspect it isn't for
all iBooks. It certainly isn't for the PowerBook I'm writing this on.


> I have created bug reports in Gnome power management : 
> https://bugzilla.gnome.org/show_bug.cgi?id=550524
> There is also a bug report for the radeon driver : 
> http://bugs.freedesktop.org/show_bug.cgi?id=19168
> And in launchpad for ubuntu : 
> https://bugs.launchpad.net/debian/+source/xserver-xorg-video-ati/+bug/249568
> https://bugs.launchpad.net/ubuntu/+source/gnome-power-manager/+bug/117836
> 
> You can read this reports and tell me if you have an idea to solve this
> bug. 

I think it would definitely be good to fix the DPMS functionality in the
video drivers. This might be easier to achieve with kernel modesetting
(KMS) available for Radeons in current upstream kernels.

That said, I don't think it would be unreasonable for the power
management daemons to also try disabling the backlight via the kernel
backlight interfaces.


-- 
Earthling Michel Dänzer           |                http://www.vmware.com
Libre software enthusiast         |          Debian, X and DRI developer