linux-kernel - Re: [PATCH v5 15/46] pwm: introduce the pwm

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Date:	Tue, 12 Apr 2016 14:21:41 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.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>,
	linux-leds@...r.kernel.org,
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	Ryan Mallon <rmallon@...il.com>,
	Alexander Shiyan <shc_work@...l.ru>, Milo Kim <milo.kim@...com>
Subject: Re: [PATCH v5 15/46] pwm: introduce the pwm_state concept

On Tue, Apr 12, 2016 at 02:17:18PM +0200, Boris Brezillon wrote:
> On Tue, 12 Apr 2016 13:49:04 +0200
> Thierry Reding <thierry.reding@...il.com> wrote:
> 
> > On Wed, Mar 30, 2016 at 10:03:38PM +0200, Boris Brezillon wrote:
> > > The PWM state, represented by its period, duty_cycle and polarity,
> > > is currently directly stored in the PWM device.
> > > Declare a pwm_state structure embedding those field so that we can later
> > > use this struct to atomically update all the PWM parameters at once.
> > > 
> > > All pwm_get_xxx() helpers are now implemented as wrappers around
> > > pwm_get_state().
> > > 
> > > Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> > > ---
> > >  drivers/pwm/core.c  |  8 ++++----
> > >  include/linux/pwm.h | 54 +++++++++++++++++++++++++++++++++++++++++------------
> > >  2 files changed, 46 insertions(+), 16 deletions(-)
> > > 
> > > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> > > index 6433059..f3f91e7 100644
> > > --- a/drivers/pwm/core.c
> > > +++ b/drivers/pwm/core.c
> > > @@ -268,7 +268,7 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip,
> > >  		pwm->chip = chip;
> > >  		pwm->pwm = chip->base + i;
> > >  		pwm->hwpwm = i;
> > > -		pwm->polarity = polarity;
> > > +		pwm->state.polarity = polarity;
> > 
> > Would this not more correctly be assigned to pwm->args.polarity? After
> > all this is setting up the "initial" state, much like DT or the lookup
> > tables would for duty cycle and period.
> 
> Yes, I wasn't sure about the pwm_add_with_polarity() meaning. To me,
> all the reference info should be extracted from DT, PWM lookup table or
> driver specific ->request() implementation, but I can definitely
> initialize the args.polarity here too.
> 
> Should I keep the pwm->state.polarity assignment (to set the initial
> polarity when the driver does not support hardware readout)?

Wouldn't this work automatically as part of the pwm_apply_args() helper
if we extended it with this setting?

Thierry

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