linux-kernel - Re: [RFC] add pwmlib support

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Date:	Sat, 29 Jan 2011 21:53:50 +0100
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Sascha Hauer <s.hauer@...gutronix.de>
CC:	linux-kernel@...r.kernel.org, Eric Miao <eric.miao@...aro.org>,
	Ben Dooks <ben-linux@...ff.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Hemanth V <hemanthv@...com>, Jean Delvare <khali@...ux-fr.org>,
	linux-arm-kernel@...ts.infradead.org,
	Uwe Kleine-Koenig <u.kleine-koenig@...gutronix.de>,
	Shawn Guo <shawn.guo@...escale.com>,
	Arun Murthy <arun.murthy@...ricsson.com>,
	Bill Gatliff <bgat@...lgatliff.com>
Subject: Re: [RFC] add pwmlib support

On 01/28/2011 01:21 PM, Sascha Hauer wrote:
> Hi all,
> 
> While implementing just another pwm driver I thought it's time to implement
> generic pwm support. The following series adds drivers/pwm/pwmlib.c and
> a i.MX23/28 pwm driver which serves as a usage example for pwmlib. The
> code is inspired by gpiolib support and tested using the backlight pwm
> driver by Eric Miao.
> 
> Currently the pwm_request, pwm_add, pwm_remove and pwm_free operations are
> protected with a single mutex wherea the pwm_enable, pwm_disable and
> pwm_config operations are unlocked. It is assumed that the owners of the
> pwm handle the serialization of the pwm accesses. This may not be enough, so
> i'd like to discuss the locking (and type of locking) here.
> 
> I Cced the people working with PWMs in the kernel in the hope that they can
> give input on what's missing / wrong in this implementation
> 
> Sascha
> 

Hi

There have been two other proposals for a generic PWM api during the last year.
You might want to take a look at them.

https://lkml.org/lkml/2010/2/9/275
https://lkml.org/lkml/2010/9/28/107

I've added Bill Gatliff and Arun Murthy to Cc.

- Lars
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