Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759900Ab0GBTX0 (ORCPT ); Fri, 2 Jul 2010 15:23:26 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:46753 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756662Ab0GBTXY (ORCPT ); Fri, 2 Jul 2010 15:23:24 -0400 From: "Rafael J. Wysocki" To: Pavel Machek Subject: Re: [PATCH] PM: Make it possible to avoid wakeup events from being lost Date: Fri, 2 Jul 2010 21:21:45 +0200 User-Agent: KMail/1.13.3 (Linux/2.6.35-rc3-rjw+; KDE/4.4.3; x86_64; ; ) Cc: linux-pm@lists.linux-foundation.org, Alan Stern , Linux Kernel Mailing List , Neil Brown , Matthew Garrett , mark gross <640e9920@gmail.com>, "Arve Hj??nnev??g" , Dmitry Torokhov , Florian Mickler , linux-pci@vger.kernel.org, Jesse Barnes References: <201006261514.13491.rjw@sisk.pl> <201007012102.27495.rjw@sisk.pl> <20100702181449.GC16577@elf.ucw.cz> In-Reply-To: <20100702181449.GC16577@elf.ucw.cz> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201007022121.45640.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1884 Lines: 43 On Friday, July 02, 2010, Pavel Machek wrote: > On Thu 2010-07-01 21:02:27, Rafael J. Wysocki wrote: > > On Thursday, July 01, 2010, Pavel Machek wrote: > > > Hi! > > > > > > > @@ -114,3 +114,17 @@ Description: > > > > if this file contains "1", which is the default. It may be > > > > disabled by writing "0" to this file, in which case all devices > > > > will be suspended and resumed synchronously. > > > > + > > > > +What: /sys/power/wakeup_count > > > > +Date: July 2010 > > > > +Contact: Rafael J. Wysocki > > > > +Description: > > > > + The /sys/power/wakeup_count file allows user space to avoid > > > > + losing wakeup events when transitioning the system into a sleep > > > > + state. Reading from it returns the current number of registered > > > > + wakeup events and it blocks if some wakeup events are being > > > > + processed at the time the file is read from. Writing to it > > > > + will only succeed if the current number of wakeup events is > > > > + equal to the written value and, if successful, will make the > > > > + kernel abort a subsequent transition to a sleep state if any > > > > + wakeup events are reported after the write has returned. > > > > > > I assume that second suspend always succeeds? > > > > The mechanism is one-shot if that's what you're asking for. > > Yep, it would be nice to document it. > > Plus maybe... should there be way to clear the wakeup_count? For > example when userspace decides that battery is low and that it wants > to go to sleep now? You don't need to clear it, just don't write to it before writing to /sys/power/state. Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/