Re: [RFC] input: syfs switches for SKE keypad

Alan Stern
2010-10-13T14:10:00Z

On Wed, 13 Oct 2010, Mark Brown wrote:

> On Wed, Oct 13, 2010 at 08:16:20AM +0200, Sundar R IYER wrote:
>
> > >> This isn't *really* about saving power in the individual device; it's
> > >> more about stopping the device generating events that disrupt the rest
> > >> of the system. Suspending the device can be one way of doing that and
> > >> is useful if it can be done but is not really the immediate goal here.
>
> > >Runtime PM is _not_ a reliable way of preventing a device from
> > >generating events. It is meant for saving energy, nothing else.
>
> > >If that's what this is about, then the answer is simple: Don't use
> > >runtime PM to try to suppress events.
>
> > I think it is unfair to discriminate here about saving power and turning off
> > events. I believe putting the device into power save leads to, if device permits
> > preventing generating events is valid to hook up run time PM.
>
> This is the opposite way around to expectations - the expectation is
> that runtime power management will flow from the device becoming idle
> enough to turn off rather than the other way around.

Absolutely. Another point worth mentioning is that a device in
runtime-suspend can be resumed at any time, for a variety of reasons
unconnected with anything the user does. While it is back at full
power, there is nothing to stop it from generating events.

Alan Stern