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

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Message-ID: <20160412141718.5fe4cf24@bbrezillon>
Date:	Tue, 12 Apr 2016 14:17:18 +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>,
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	linux-input@...r.kernel.org, Bryan Wu <cooloney@...il.com>,
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	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, 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)?

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