From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754222Ab2DIUmL (ORCPT ); Mon, 9 Apr 2012 16:42:11 -0400 Received: from mail-pz0-f52.google.com ([209.85.210.52]:61070 "EHLO mail-pz0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752046Ab2DIUmJ (ORCPT ); Mon, 9 Apr 2012 16:42:09 -0400 Date: Mon, 9 Apr 2012 13:42:02 -0700 From: Dmitry Torokhov To: Shuah Khan Cc: Andrew Morton , neilb@suse.de, rpurdie@linux.intel.com, LKML Subject: Re: [PATCH RESEND] LEDS-One-Shot-Timer-Trigger-implementation Message-ID: <20120409204202.GC18542@core.coreip.homeip.net> References: <1333310039.2879.4.camel@lorien2> <20120406165353.ab667eb0.akpm@linux-foundation.org> <1333808024.2728.39.camel@lorien2> <20120407215641.GA4539@core.coreip.homeip.net> <1333990549.2871.10.camel@lorien2> <20120409173703.GA18542@core.coreip.homeip.net> <1333995365.2871.17.camel@lorien2> <20120409184558.GB18542@core.coreip.homeip.net> <1334002847.2871.26.camel@lorien2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1334002847.2871.26.camel@lorien2> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 09, 2012 at 02:20:47PM -0600, Shuah Khan wrote: > On Mon, 2012-04-09 at 11:45 -0700, Dmitry Torokhov wrote: > > On Mon, Apr 09, 2012 at 12:16:05PM -0600, Shuah Khan wrote: > > > On Mon, 2012-04-09 at 10:37 -0700, Dmitry Torokhov wrote: > > > > On Mon, Apr 09, 2012 at 10:55:49AM -0600, Shuah Khan wrote: > > > > > On Sat, 2012-04-07 at 14:56 -0700, Dmitry Torokhov wrote: > > > > > > Hi Shuah, > > > > > > > > > > > > On Sat, Apr 07, 2012 at 08:13:44AM -0600, Shuah Khan wrote: > > > > > > > > > > > > > > > > +This feature will help implement vibrate functionality which requires one > > > > > > > > > +time activation of vibrate mode without a continuous vibrate on/off cycles. > > > > > > > > > > > > > > > > They make vibrating LED? ;) > > > > > > > > > > > > > > > > What's going on here? You're proposing to repurpose the LEDs code to > > > > > > > > drive vibration devices? Or some devices couple a LED with a vibration > > > > > > > > device? > > > > > > > > > > > > > > I owe you filling in the blanks type explanation. Let me describe the > > > > > > > use-case I am trying to address first. Vibrater function on phones is > > > > > > > implemented using PWM pins on SoC or PMIC. When there is no such > > > > > > > hardware present, a software solution is needed. Currently two drivers > > > > > > > timed-gpio and timed-output (under staging/android in Linux 3.3) > > > > > > > together implement the software vibrate feature. The main functionality > > > > > > > it implements is the one time enables of timer to prevent user space > > > > > > > crashes leaving the phone in vibrate mode causing the battery to drain. > > > > > > > leds as it is implemented currently, is not suitable to address this > > > > > > > use-case as it doesn't support one time enables. > > > > > > > > > > > > So why do not you use memoryless force feedback framework that other > > > > > > devices use (see drivers/input/misc/*vibra.c drivers). > > > > > > > > > > > > > > > > Dimitry, > > > > > > > > > > I took a look at these vibra* drivers. The three vibrate drivers are > > > > > chip-set specific. The use-case I have is a non-chip set approach to > > > > > address the use-case when vibrate hardware is not present. Are you > > > > > envisioning a generic approach using ff-memoryless infrastructure? > > > > > > > > Shuah, > > > > > > > > I guess I am confused now. You need some form of hardware to make your > > > > device to vibrate. > > > > > > > > What exactly are you trying to do? Are you trying to: > > > > > > > > 1. activate vibration on devices that can actually do it using LED > > > > interface, or > > > > > > > > 2. use LEDs as an alternative to vibrate on devices that can't > > > > physically vibrate? > > > > > > > > Thanks. > > > > > > What I meant by generic approach is a higher level interface that is not > > > tied too closely to the underlying hardware. Similar to the leds-pwm.c > > > and leds-gpio.c handle gpio and pwm based leds. The vibrate hardware in > > > my sue-case is a gpio based and could pwm based on some phones. > > > > Ok, so you need to add drivers/input/misc/gpio-vibrate.c and pwm-vibrate.c > > and then use FF to activate them. This way we have all vibrate > > implementation use one subsystem instead of splitting between > > input/led/whatever else people could come up with. > > > > Thanks. > > > > Dmitry, > > It is unfortunate that we have these two infrastructures evolve that has > a lot of overlap. Let me summarize the two alternatives first so we get > a feel for the work involved to address this use-case using ff and leds > frameworks: > > Alternative 1: using leds infrastructure > > Add new kernel interface to support one time enables. This will enable > existing gpio and pwm drivers to be used to implement vibrate. > > Alternative 2: using ff infrastructure > > Add new drivers gpio and pwm that use existing one time enable to > implement vibrate in a generic way. > > Does this sound right? From a quick glance it sounds like we can get to > the end goal quicker and in a simpler way with Alternative 1. However, I > might be missing longterm view. Any other alternatives we could explore? > For 1 you are forgetting "persuade current users of mainline vibrator drivers in kernel to adopt their drivers and userpace to LED framework" because we should try to provide single interface for a given function. Thanks. -- Dmitry