linux-kernel - Re: [PATCH 00/14] misc/ep93xx_pwm: cleanup driver for conversion to PWM framework

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Date:	Tue, 28 May 2013 13:42:05 +0200
From:	Lars Poeschel <poeschel@...onage.de>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	H Hartley Sweeten <hartleys@...ionengravers.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	Ryan Mallon <rmallon@...il.com>,
	"mcrapet@...il.com" <mcrapet@...il.com>
Subject: Re: [PATCH 00/14] misc/ep93xx_pwm: cleanup driver for conversion to PWM framework

On Tuesday 28 May 2013 at 13:00:12, Thierry Reding wrote:
> On Mon, May 27, 2013 at 07:12:08PM +0200, Arnd Bergmann wrote:
> > On Monday 27 May 2013, H Hartley Sweeten wrote:
> > > Also, I have a question about the conversion.
> > > 
> > > If I strip the sysfs support out of this driver the conversion is
> > > quite simple. But, my use for this driver requires user space
> > > control of the PWM.
> > > 
> > > Should I:
> > > 1) convert the driver to the PWM framework and leave the sysfs stuff
> > > in it 2) work out a generic sysfs support for the PWM framework and
> > > then
> > > 
> > >     convert the driver
> > > 
> > > 3) other...
> > > 
> > > I've been looking at 2) by doing something like how gpiolib does it.
> > > Do you think that would be acceptable?
> > 
> > That would be for Thierry to decide. It does sound better to me than
> > the 1) and I don't have a better idea for 3).
> > 
> > I wonder how the arbitration between in-kernel and user-space
> > consumers of the pwm lines would work though.
> 
> I've added Lars Poeschel on Cc, who's done some work on a sysfs
> interface for the PWM subsystem already. It's undergone some review
> already[0] and I think he's working on a v2 now.
> 
> Thierry
> 
> [0]: http://marc.info/?l=linux-kernel&m=136499756101273&w=2

I currently do not have the time to work on a v2 of the pwm sysfs patch but 
I will do it as soon as possible - if not someone else will do. 
Unfortunately my current involvements in other project will not allow me to 
do so for at least next two months.
I received some off-list reactions to my patches from users asking for pwm 
sysfs, so there is definitely a need for it!
If you decide to take attempt 2) (which is preferable) I recommend you to 
take a look at what I have done and Thierrys review comments. I took the 
gpiolib way and the result got rejected for very good reasons.

Regards,
Lars
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