From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alan Stern Subject: Re: [linux-pm] [RFC] input: syfs switches for SKE keypad Date: Wed, 13 Oct 2010 10:10:00 -0400 (EDT) Message-ID: References: <20101013095737.GI6424@rakim.wolfsonmicro.main> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: Received: from iolanthe.rowland.org ([192.131.102.54]:49648 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751936Ab0JMOKA (ORCPT ); Wed, 13 Oct 2010 10:10:00 -0400 In-Reply-To: <20101013095737.GI6424@rakim.wolfsonmicro.main> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Mark Brown Cc: Sundar R IYER , "samu.p.onkalo@nokia.com" , Linus WALLEIJ , Naveen Kumar GADDIPATI , Dmitry Torokhov , "linux-input@vger.kernel.org" , Linux-pm mailing list , Jayeeta BANDYOPADHYAY 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