From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759090AbZFCPiv (ORCPT ); Wed, 3 Jun 2009 11:38:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758237AbZFCPif (ORCPT ); Wed, 3 Jun 2009 11:38:35 -0400 Received: from wa-out-1112.google.com ([209.85.146.181]:44623 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758589AbZFCPie convert rfc822-to-8bit (ORCPT ); Wed, 3 Jun 2009 11:38:34 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=vcLO8A8YnGK6UlAlBcF0WiUMsQo6SERiJ4vWX8fAekROZFiLuTqeEd0QYTbE3fTJC2 Ad8G9ah9R9AeuJGj0wFCKlsNpGenAuk+4B1kvxUtCPyoBPkuB+dW0EgQgRMcw9XfcZL2 I8wRfFS/0doRBuz3aDZZJB6IZyUbJ3zlGNNXc= MIME-Version: 1.0 In-Reply-To: <20090603132217.GA18353@oksana.dev.rtsoft.ru> References: <4A255B21.8040002@gersys.de> <20090602171527.GA8745@oksana.dev.rtsoft.ru> <4A266FB2.2040902@gersys.de> <20090603132217.GA18353@oksana.dev.rtsoft.ru> Date: Wed, 3 Jun 2009 11:38:35 -0400 Message-ID: <9e4733910906030838o7313c311je3545cd974d3edd5@mail.gmail.com> Subject: Re: PWM class? (was: Re: MPC52xx simple GPIO support) From: Jon Smirl To: avorontsov@ru.mvista.com Cc: Stefan Strobl , ppc-dev , linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 3, 2009 at 9:22 AM, Anton Vorontsov wrote: > On Wed, Jun 03, 2009 at 02:42:26PM +0200, Stefan Strobl wrote: > [...] >> The led class provides support for setting the brightness, which >> obviously the gpio driver doesn't support. The hardware (mpc52xx_gpt) >> would support it in PWM mode though. I'm now wandering how this could be >> best implemented. >> >> 1) - Create some PWM class similar to the GPIO class >>    - Add support for PWM mode in mpc52xx_gpt.c that uses that PWM class >>    - And add an interface for the LED to use the PWM class >> >> 2) - Create an LED driver that accesses the mpc52xx_gpt directly. >> >> I think I would be overwhelmed trying to implement (1) but am confident >> to do (2). What do you think is the right approach? > > I'd suggest creating a generic PWM class, i.e. PWMLIB, alike to > GPIOLIB. (2) can be an acceptable approach for now, but for the > long-term solution (1) is the way to go. What happened to this one? http://ozlabs.org/pipermail/linuxppc-dev/2008-October/063562.html > > The non-lib PWM API is already there, see include/linux/pwm.h, > and arch/arm/mach-pxa/pwm.c as an implementation example. > > Note that PXA implementation is SOC-specific, which is not very > good. > > So I'd suggest creating drivers/pwm/pwmlib.c, borrowing > ideas from gpiolib. And then we can reuse drivers/leds/leds-pwm.c > driver (of course, after adding appropriate OF code into it). > > Sure, as you've said, it could be quite boringly to implement, > could take quite some time to pass all review cycles etc. > But someday someone will have to do this. :-) > > -- > Anton Vorontsov > email: cbouatmailru@gmail.com > irc://irc.freenode.net/bd2 > -- > 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/ > -- Jon Smirl jonsmirl@gmail.com