the Power Management Daemon

Richard Hughes hughsient at
Mon Apr 2 19:14:19 EDT 2007

On Mon, 2007-04-02 at 16:56 -0600, Jordan Crouse wrote:
> Hi Richard -
> Power management is proceeding along nicely, and we're finally to the
> point where we can start to discuss the design and implementation of the
> OLPC Power Management Daemon.

Cool, cheers for the email.

Have you guys checked out the OHM (open hardware manager) presentation
[0] I did at FOSDEM this year? It touched on some nice use-cases for
embedded stuff. I don't know how much code you've written for PMD, but
I've got a load of demo code for OHM that might be useful.

> We should start to discuss how to go about implementing these in the power
> manager - we have a bunch of eager B2 owners out there ready to start saving
> power!  :)

You guys need to decide on the session/system/kernel split points. For
gnome-power-manager the split is very session-heavy, but embedded is
very much the other way. You probably want to see the work we've been
doing on the session power-management-spec [1] which would pretty much
be a drop in python file (tiny!) for the session aspect. This would give
you guys a "just works" session API that could be extended using extra
OLPC specific interfaces.

There's also the widget interface I'm using with g-p-m present, which
might also be interesting for you.

> Everybody, please feel free to comment on the page I linked above - we've
> only defined those scenarios that are currently within our reach, but there
> are others that we eventually want to support.

Sure. There's lots of crazy ideas like the self-battery-profiling code
that is being used in g-p-m trunk that may be of interest to you guys.
See my blog posts [2] for some of the discussion. The profiling code in
particular is *stonkingly* good at profiling old and broken batteries
discharge and charge rates and giving an accurate time to charge and

I'll add some stuff to the wiki tmw. Cheers,


[0] and

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