linux-kernel - Re: [PATCH v5 05/46] pwm: introduce the pwm

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Message-ID: <20160412145511.2f13d24f@bbrezillon>
Date:	Tue, 12 Apr 2016 14:55:11 +0200
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	linux-pwm@...r.kernel.org,
	Mike Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>, linux-clk@...r.kernel.org,
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	Jean Delvare <jdelvare@...e.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-input@...r.kernel.org, Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>,
	Jacek Anaszewski <j.anaszewski@...sung.com>,
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	Alexander Shiyan <shc_work@...l.ru>, Milo Kim <milo.kim@...com>
Subject: Re: [PATCH v5 05/46] pwm: introduce the pwm_args concept

On Tue, 12 Apr 2016 14:20:29 +0200
Thierry Reding <thierry.reding@...il.com> wrote:

> On Tue, Apr 12, 2016 at 02:04:12PM +0200, Boris Brezillon wrote:
> > On Tue, 12 Apr 2016 13:39:12 +0200
> > Thierry Reding <thierry.reding@...il.com> wrote:
> > 
> > > On Wed, Mar 30, 2016 at 10:03:28PM +0200, Boris Brezillon wrote:
> > > > Currently the PWM core mixes the current PWM state with the per-platform
> > > > reference config (specified through the PWM lookup table, DT definition or
> > > > directly hardcoded in PWM drivers).
> > > > 
> > > > Create a pwm_args struct to store this reference config, so that PWM users
> > > > can differentiate the current config from the reference one.
> > > > 
> > > > Patch all places where pwm->args should be initialized. We keep the
> > > > pwm_set_polarity/period() calls until all PWM users are patched to
> > > > use pwm_args instead of pwm_get_period/polarity().
> > > 
> > > Perhaps a helper would be useful? Something like:
> > > 
> > > 	static inline void
> > > 	pwm_apply_args(struct pwm_device *pwm, const struct pwm_args *args)
> > > 	{
> > > 		pwm_set_duty_cycle(pwm, args->duty_cycle);
> > > 		pwm_set_period(pwm, args->period);
> > > 	}
> > > 
> > > ? That would make it slightly easier to get rid of it again after all
> > > clients have been converted.
> > 
> > Sure. I'll add this helper.
> > 
> > > 
> > > With the exception of pwm-clps711x all of these args are set at of_xlate
> > > time (for DT) or from the lookup table in pwm_get() (for non-DT), so it
> > > might even be possible to move this call to the core, so that removal of
> > > it will be a one-liner.
> > 
> > Not sure I get that one. Some drivers are implementing their own
> > ->of_xlate() method, how would you get rid of this pwm_apply_args() in
> > those custom implementations?
> 
> I was proposing to have pwm_apply_args() called from the core.
> of_pwm_get() is where ->of_xlate() is called from, and the lookup table
> arguments would be applied in pwm_get(). Taking into account clps711x,
> which sets the arguments in ->request() it might be possible to simply
> call pwm_apply_args() from pwm_device_request(), since that's also
> called by all other request functions, even the legacy ones.
> 
> That said, the amount of code to modify isn't that large, so I'm fine if
> you want to keep sprinkling the calls across multiple files, especially
> since it's temporary.

No, I'm fine addressing that, but I just don't get where you'd get the
pwm_args to apply. Do you suggest to pass 'struct pwm_args *' to the
->of_xlate() and ->request() methods?

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com