linux-kernel - Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend

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Date:	Mon, 21 Sep 2015 10:38:46 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Pavel Machek <pavel@....cz>
cc:	"Rafael J. Wysocki" <rafael@...nel.org>,
	Octavian Purdila <octavian.purdila@...el.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	"Tirdea, Irina" <irina.tirdea@...el.com>,
	Oliver Neukum <oneukum@...e.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Brown, Len" <len.brown@...el.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>
Subject: Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing
 runtime suspend

On Mon, 21 Sep 2015, Pavel Machek wrote:

> > > In fact, then, what you need seems to be the feature discussed by Alan
> > > and me some time ago allowing remote wakeup do be disabled for runtime
> > > PM from user space as that in combination with autosuspend should
> > > address your use case.
> > 
> > That, plus they want the touchscreen to go into runtime suspend 
> > whenever the screen is off (was this not the main reason for the 
> > patch?).
> > 
> > It seems to me that it should be possible to arrange for this to happen 
> > simply by making userspace close the touchscreen device when the screen 
> > is turned off.  Or am I missing something?
> 
> Well... that's not what existing userspace expects. Your X windows
> server will not close the touchscreen.

Surely that's a userspace issue, rather than a kernel problem?  The X
server does have some notion of power management and power savings; why
not extend that notion to include touchscreens?

> ..and it would be nice to have enough hardware abstraction in the
> kernel so that X can be used on phones...

What -- not Wayland?!  :-)

Alan Stern

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