linux-kernel - Re: [PATCHv2 1/4] pwm: Add Freescale FTM PWM driver support

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Date:	Mon, 2 Sep 2013 10:56:31 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Xiubo Li-B47053 <B47053@...escale.com>
Cc:	Guo Shawn-R65073 <r65073@...escale.com>,
	"thierry.reding@...il.com" <thierry.reding@...il.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"rob@...dley.net" <rob@...dley.net>,
	"ian.campbell@...rix.com" <ian.campbell@...rix.com>,
	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Lu Jingchang-B35083 <B35083@...escale.com>
Subject: Re: [PATCHv2 1/4] pwm: Add Freescale FTM PWM driver support

On Mon, Sep 02, 2013 at 03:33:37AM +0000, Xiubo Li-B47053 wrote:
> 
> > > +static void fsl_pwm_free(struct pwm_chip *chip, struct pwm_device
> > > +*pwm) {
> > > +	struct fsl_pwm_chip *fpc;
> > > +	struct fsl_pwm_data *pwm_data;
> > > +
> > > +	fpc = to_fsl_chip(chip);
> > > +
> > > +	pwm_data = pwm_get_chip_data(pwm);
> > > +	if (!pwm_data)
> > > +		return;
> > 
> > THis check seems unnecessary.
> > 
> 
> But if do not check it here, I must check it in the following code.
> 
> > > +
> > > +	if (pwm_data->available != FSL_AVAILABLE)
> > > +		return;
> > > +
> 
> So the ' struct fsl_pwm_data' may be removed in the future.
> 
> > 
> > > +
> > > +
> > > +	pwm_data->period_cycles = period_cycles;
> > > +	pwm_data->duty_cycles = duty_cycles;
> > 
> > These fields are set but never read. Please drop them.
> > 
> > If you drop the 'available' field also the you can drop chip_data
> > completely.
> > 
> 
> I think I may move the 'available' field to the PWM driver data struct.

You simply don't need the available field. You don't need to track
whether they are available. If a user enables a pwm which is not routed
out of the SoC (disabled in the iomux) simply nothing will happen except
for a slightly increased power consumption.

Sascha


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