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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 09 Sep 2015 22:35:12 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Alan Stern <stern@...land.harvard.edu>,
	Octavian Purdila <octavian.purdila@...el.com>,
	"Tirdea, Irina" <irina.tirdea@...el.com>
Cc:	"Rafael J. Wysocki" <rafael@...nel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Oliver Neukum <oneukum@...e.com>,
	"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>, Pavel Machek <pavel@....cz>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>
Subject: Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend

On Wednesday, September 09, 2015 11:20:25 AM Alan Stern wrote:
> On Wed, 9 Sep 2015, Rafael J. Wysocki wrote:
> 
> > > The best example and actually the very specific problem we want to
> > > solve is handling touchscreens on a phone / tablet. When the screen is
> > > turned off, it is ideal to suspend the touchscreen for two reasons: to
> > > lower the power consumption as much as possible and to prevent
> > > interrupts to wake-up the CPU when the user touches the device, and
> > > thus save even more power as we allow the CPU to stay in deep idle
> > > states for longer periods.
> > >
> > > Note that when the screen is turned-on again, we want to resume the
> > > touchscreen so that it can send events again.
> > 
> > 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?).

Right.

> 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?

Honestly, I don't know.

Octavian, Irina, any reasons why things can't be done as Alan is suggesting?

Thanks,
Rafael

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/