From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Torokhov Subject: Re: [PATCH] - race-free suspend. Was: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8) Date: Fri, 4 Jun 2010 00:14:45 -0700 Message-ID: <20100604071445.GG21239@core.coreip.homeip.net> References: <20100601122012.1edeaf48@notabene.brown> <20100602153235.340a7852@notabene.brown> <20100602180614.729246ea@notabene.brown> <20100602210224.6ae2333f@notabene.brown> <20100602210521.54b9cd9b@schatten.dmk.lab> <20100602233243.GA27666@core.coreip.homeip.net> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Arve =?iso-8859-1?B?SGr4bm5lduVn?= Cc: Florian Mickler , Neil Brown , Thomas Gleixner , "Rafael J. Wysocki" , Alan Stern , Felipe Balbi , Peter Zijlstra , "Paul@smtp1.linux-foundation.org" , LKML , Linux OMAP Mailing List , Linux PM , Alan Cox , James Bottomley List-Id: linux-omap@vger.kernel.org On Wed, Jun 02, 2010 at 07:44:59PM -0700, Arve Hj=F8nnev=E5g wrote: > On Wed, Jun 2, 2010 at 4:32 PM, Dmitry Torokhov > wrote: > > On Wed, Jun 02, 2010 at 09:05:21PM +0200, Florian Mickler wrote: > >> On Wed, 2 Jun 2010 21:02:24 +1000 > >> Neil Brown wrote: > >> > > >> > And this decision (to block suspend) really needs to be made in = the driver, > >> > not in userspace? > >> > >> Well, it fits. The requirement is a direct consequence of the inti= mate > >> knowledge the driver has about the driven devices. > > > > That is not really true. A driver does have intimate knowledge of t= he > > device, however it does not necessarily have an idea about the data= read > > from the device. Consider the gpio_matrix driver: Arve says that it= has > > to continue scanning matrix once first interrupt arrvies. But it re= ally > > depends on what key has been pressed - if user pressed KEY_SUSPEND = or > > KEY_POWER it cmight be better if we did not wait for key release bu= t > > initiated the action right away. The decision on how system reacts = to a > > key press does not belong to the driver but really to userspace. >=20 > If we just suspend while the keypad scan is active, a second press of > KEY_POWER would not be able wake the device up. The gpio keypad matri= x > driver has two operating modes. No keys are pressed: all the outputs > are active so a key press will generate an interrupt in one of the > inputs. Keys are pressed: Activate a single output at a time so we ca= n > determine which keys are pressed. The second mode is entered when the > driver gets an interrupt in the first mode. The first mode is entered > if the scan detected that no keys are pressed. The driver could be > modified to stop the scan on suspend and forcibly put the device back > in no-keys-pressed state, but pressing additional keys connected to > the same input can no longer generate any events (the input does not > change). Would that be still the case if you reprogram the device as wakeup source while suspending? Anyway, it does not really matter. Your case (current suspend blockers) would delay putting device to sleep till you release all the keys, including KEY_POWER. If you delegate the decision to userspace it would have an _option_ of putting the device to sleep earlier, however in bot= h cases user has to release all keys before the device can be resumed. --=20 Dmitry