linux-kernel - Re: [PATCH 4/6] input: cyapa: enable/disable trackpad device based on LID state

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Message-ID: <20140520152551.GB9444@core.coreip.homeip.net>
Date:	Tue, 20 May 2014 08:25:51 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Dudley Du <dudl@...ress.com>, Benson Leung <bleung@...gle.com>,
	Daniel Kurtz <djkurtz@...gle.com>,
	David Solda <dso@...ress.com>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/6] input: cyapa: enable/disable trackpad device based
 on LID state

On Tue, May 20, 2014 at 02:40:12PM +0200, Rafael J. Wysocki wrote:
> On Monday, May 19, 2014 08:43:02 PM Dmitry Torokhov wrote:
> > Hi Dudley,
> > 
> > On Wed, Apr 16, 2014 at 08:39:34AM +0000, Dudley Du wrote:
> > > Rely on EV_SW and SW_LID bits to identify a LID device, and hook
> > > up our filter to listen for SW_LID events to enable/disable touchpad when
> > > LID is open/closed.
> > > TEST=test on Chomebooks.
> > 
> > This is a policy and it does not belong in the kernel. Please work with
> > Rafael to establish generic interface to put devices into low power mode
> > (like accelerating runtime PM idle timeout)
> 
> I'm not really sure what you mean here, care to be more specific?

I think we chatted about this before - we need a uniform interface for
userspace to put devices into low power mode on demand. As
implementation detail I thought we could require runtime PM for that and
simply pretend that the PM timeout expired early when userspace invokes
that API.

> 
> > and use it when userspace detects that lid is closed.
> 
> I guess we get an event then, don't we?

Right, userspace gets EV_SW/SW_LID input event and needs to react. In
this particular case the desire is to power down touchpad (since it is
unaccessible). I am not sure why system suspend (which I expect happen
in reaction to lid closing) is not enough, but that's question for
Dudley.

Thanks.

-- 
Dmitry
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