Suggestion for underlying design of power settings infrastructure (was: Re: Power Management and OpenMoko - third power setting)

[Andy Green]

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Somebody in the thread at some point said:

> What I'd really like to see is a flexible power setting system which
> allows for an arbitrary number of modes and complete flexibility
> regarding what is or isn't powered in each mode, and what causes each
> mode to be entered or exited.
> 
> I don't expect this to be a menu option (frankly I don't care about
> menus at all), but I strongly urge that the underlying infrastructure
> will be designed in a completely unrestrictive manner.

Currently is is so unrestricted that you can write your own code :-)
Just kidding.

There's a larger issue here of granularity that plugs into boot time
issues as well.  For example we sit through bluetooth startup in
initscripts even if we don't use bluetooth.  Bluetooth is also powered
whether we like it or not then.

The real one big win that we have on our side is the full suspend, that
is not granular at all because it turns off the CPU core then.  I think
instead of exposing a whole 1950s style control panel of options it
means we just need to keep things turned off until we need them and as
soon as we are done with them, and keep the whole phone in suspend the
vast bulk of the time.  All the other options won't make any real
difference I think because I just look at the backlight consumption and
the rest is largely insignificant.

> Don't do my thinking for me. If I wanted that, I'd use one of those
> other two operating systems. I came to Linux to think for myself.
> 
> I hope it's not too late.

Well on the one hand we need to match the hardware to the goal where
possible, after that we have to match performance to the hardware.  In
this case getting the backlight off as soon as possible and the thing to
slip into sleep as soon as possible when on battery without any UI is
optimal I think.  Maybe there is some way it can adjust the timing for
those based on what app has focus, eg, if he just selected a web page
keep the backlight up a bit longer because he probably reads it.

- -Andy
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