Update on DeviceKit

[David Zeuthen]

On Wed, 2008-05-07 at 18:59 +0200, Danny Kukawka wrote:
> On Mittwoch, 7. Mai 2008, David Zeuthen wrote:
> > On Wed, 2008-05-07 at 18:44 +0200, Danny Kukawka wrote:
> > > Nobody speak about a "new fancy backlight control daemon". It should
> > > simply go into a DeviceKit-powermanagement (or how ever you would like to
> > > call it) and should provice at least the same functionality as currently
> > > HAL. And because of this KDE or GNOME (or whatever) applications could
> > > use simply the new DBus interface instead of HAL. Thats much easier than
> > > do everything through X.
> >
> > Why is this easier than to use X? What happens if you attach a secondary
> > monitor? What about remote X displays?
> 
> 1) I would like to be able to change the brightness also if I'm on my laptop 
> on console and remove the AC plug (e.g. in a system wide policy daemon that 
> handle basic powermanagement if no desktop application handle it).

I think, for this fringe case, such a daemon could just as easily
use /sys/class/backlight directly.

> 2) It's part of powermanagement (at least on laptops) and we should have a 
> common interface for that. I don't like to call 3 or more different 
> interfaces to do simple powermanagement tasks (like get battery/AC info from 
> one, get/set brightness from another and call SetPowersave on an other 
> again ...). 

By the same token should we also care about voltage / power management
on the GPU etc? Of course, not, leave that to the _driver_. Which is X.

> 3) Provide X a DBus interface for this? If not: is this planed? You maybe 
> don't want to depend on X libraries. A DBus interface is more usefull and 
> independent (you don't need to link against a X lib, ...). 

(FWIW, I hear that some people wants even "console" sessions to use X as
the _display_ driver. Which I think makes a lot of sense for a lot of
other reasons too (acceleration, power management, DPMS, unifying
graphics driver code etc.).)

Omitting a backlight interface on o.fd.DeviceKit.Power also has a lot to
do with keeping things simple (or simpler) and make it easy for people
new to hacking on Linux on where to fix bugs / fix their system. It's
_confusing_ the way it is right now. And that confusion is hurting us
insofar that people wanting to contribute / fix their system waste time
looking in the wrong place.

     David