[Kde-hardware-devel] Missing powermanagement features in Solid

[Sebastian Kügler]

On Monday 18 June 2007 20:14:24 Kevin Ottens wrote:
> Le samedi 16 juin 2007, Sebastian Kügler a écrit :

> > > > While hacking on a Plasma::DataEngine that can potentially provide
> > > > the necessary information for a battery applet, I found that some
> > > > functionality is missing for the things I'd like to see implemented
> > > > at some point.
> > > >
> > > > More specific, I'd like to see the following provided by Solid:
> > > >
> > > > - Time remaining until battery completely empty
> > > > - Time remaining until battery is fully charged
> > >
> > > Not provided yet, actually I'm not sure where it's best to implement
> > > this since this kind of information is completely unreliable, and
> > > requires some learning on the battery behavior (which would be weird to
> > > do in a lib imo).
> >
> > Well, HAL has those and I found it quite useful (gets us rid of the
> > policy stuff, provides consistency for those that are running various
> > powermanagement tools at the same time). GNOME's powermanager actually
> > has some advanced heuristics to collect this data, I'm not sure if that's
> > what we want. See for example http://hughsient.livejournal.com/28386.html
>
> Well, those heuristics are here because the HAL information is
> (understandably) unreliable.

The information is quite useful for me. While it might not be reliable, it's 
still a hint, and it's much more readable for the human mind as well. This 
information should IMO be provided by Solid, the 'reliability' issue should 
IMO be fixed in HAL. 

How about exposing this from HAL for the short term and keep in mind that we 
want to make this a bit smarter?

> > Anyway, being able to get this information from HAL would be a good first
> > step, one could drop in a better implementation of the remaining time
> > some time in the future. The information itself is essential. Most users
> > don't care about the percentage, that's battery dependant, they want to
> > know how much time's left.
>
> Well, I'm sort of reluctant to provide such unreliable information, hoping
> that it'll get magically sorted... in the meantime you have applications
> taking decision using bogus information.

I don't see a clear way of getting features such as "suspend when 3 minutes of 
battery life" are reached. The remaining battery capacity suffers from the 
same problem if I understand you correctly (It also decreases quicker when 
you start tuxracer).

> Moreover, looking at the kind of application you're working on, you're not
> interested in having this information for a particular battery, but need to
> compute it for all the batteries in the system. That's why I'd advise to
> introduce this in Solid::Control::PowerManager first, since it'll be used
> by a couple of applications only, knowing the issue at hand, then when we
> get it right we'll be able to migrate the relevant parts in kdelibs, on
> Solid::Battery itself (the method on Solid::Control::PowerManager would
> then use that instead of a specific implementation).

Sounds sensible to me.

> Is it fine for you? Willing to work on it?

I've written in total no more than 1 KLOC C++, I doubt you would want me to do 
it. :D
-- 
sebas

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