Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932156Ab1F2Tsa (ORCPT ); Wed, 29 Jun 2011 15:48:30 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:49255 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932112Ab1F2Ts2 (ORCPT ); Wed, 29 Jun 2011 15:48:28 -0400 X-Greylist: delayed 86805 seconds by postgrey-1.27 at vger.kernel.org; Wed, 29 Jun 2011 15:48:28 EDT X-Originating-IP: 217.70.178.137 X-Originating-IP: 83.160.107.163 Date: Wed, 29 Jun 2011 21:47:22 +0200 From: Matthias Kaehlcke To: Sascha Hauer Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Arnd Bergmann , viresh kumar , Shawn Guo , Ryan Mallon , Kurt Van Dijck , Lothar =?iso-8859-1?Q?Wa=DFmann?= Subject: Re: [PATCH 1/2] PWM: add pwm framework support Message-ID: <20110629194722.GA10861@darwin> Mail-Followup-To: Matthias Kaehlcke , Sascha Hauer , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Arnd Bergmann , viresh kumar , Shawn Guo , Ryan Mallon , Kurt Van Dijck , Lothar =?iso-8859-1?Q?Wa=DFmann?= References: <1309338215-10702-1-git-send-email-s.hauer@pengutronix.de> <1309338215-10702-2-git-send-email-s.hauer@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1309338215-10702-2-git-send-email-s.hauer@pengutronix.de> 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 Content-Length: 2096 Lines: 46 El Wed, Jun 29, 2011 at 11:03:34AM +0200 Sascha Hauer ha dit: > This patch adds framework support for PWM (pulse width modulation) devices. > > The is a barebone PWM API already in the kernel under include/linux/pwm.h, > but it does not allow for multiple drivers as each of them implements the > pwm_*() functions. > > There are other PWM framework patches around from Bill Gatliff. Unlike > his framework this one does not change the existing API for PWMs so that > this framework can act as a drop in replacement for the existing API. > > Why another framework? > > Several people argue that there should not be another framework for PWMs > but they should be integrated into one of the existing frameworks like led > or hwmon. Unlike these frameworks the PWM framework is agnostic to the > purpose of the PWM. In fact, a PWM can drive a LED, but this makes the > LED framework a user of a PWM, like already done in leds-pwm.c. The gpio > framework also is not suitable for PWMs. Every gpio could be turned into > a PWM using timer based toggling, but on the other hand not every PWM hardware > device can be turned into a gpio due to the lack of hardware capabilities. > > This patch does not try to improve the PWM API yet, this could be done in > subsequent patches. > > Signed-off-by: Sascha Hauer Reviewed-by: Matthias Kaehlcke -- Matthias Kaehlcke Embedded Linux Developer Amsterdam You must have long-range goals to keep you from being frustrated by short-range failure .''`. using free software / Debian GNU/Linux | http://debian.org : :' : `. `'` gpg --keyserver pgp.mit.edu --recv-keys 47D8E5D4 `- -- 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/