Re: [linux-pm] [PATCH v2 1/2] Input: gpio-keys - allow platform to specify exact irq flags

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On Sun, Dec 06, 2009 at 09:47:04AM +0100, Pavel Machek wrote:
> Hi!
> 
> 
> > But runtime-pm.txt says for example:
> > 
> >     Generally, remote wake-up should be enabled for all input devices
> >     put into a low power state at run time.
> > 
> > But in this case the requirement is to suppress input events from a
> > given device, effectively muting and putting it into low power state,
> > even though it's still open by some other parties.  Runtime PM, on the
> > other hand tries not to interfere with the normal usage of the device.
> > 
> > Later:
> > 
> > (3) ->runtime_idle() and ->runtime_suspend() can only be executed for a
> >     device the usage counter of which is equal to zero _and_ [...]
> > 
> > which underlines the difference again: the usage counter (defined by
> > common sense) won't be zero in our case, because the device is
> > constantly kept open, while we want to mute it, putting it into a low
> > power state. 
> ...
> > Actually, this could be implemented by the various users cooperating in
> > closing the device, letting it go to sleep automatically.  But this
> > requires strictly cooperating parties and is more complicated that
> > flipping some master switch of the device.  We're looking for this
> > master switch, before needlessly building our own.
> 
> Please just close the device properly. I do not think we want 100
> different 'please mute keys A and G', 'please mute middle mouse button',
> ... interfaces anywhere near mainline.
> 

I do not think it is practical to simply close the device, given that
there may be several applications that have it open. I constantly see
embedded guys adding custom knobs to the devices allowing them to shut
off the device when not in use. Kind of runtame PM but user-initiated.

I would really love to have it implemented in the driver core so the
interface is the same for all drivers (that support this future).

> Or just do it as local patch.

I also see that gpio-keys is quite different in the sence that it can
shut off buttons selectively. I fact, at the moment every button can be
considered a separate device... But that would be too much overhead.

They could probably split the keys into 2 groups (critical that should
be always active) and not critical, that could be shut off, but I think
they want teh flexibility of controlling this at runtime instead of
doing it in board data.

-- 
Dmitry
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