linux-kernel - RE: [PATCHv6 1/4] pwm: Add Freescale FTM PWM driver support

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Date:	Fri, 13 Dec 2013 09:30:09 +0000
From:	"Li.Xiubo@...escale.com" <Li.Xiubo@...escale.com>
To:	Thierry Reding <thierry.reding@...il.com>
CC:	Shawn Guo <Shawn.Guo@...escale.com>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	"t.figa@...sung.com" <t.figa@...sung.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>,
	"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>,
	Huan Wang <Huan.Wang@...escale.com>,
	"Jingchang Lu" <jingchang.lu@...escale.com>
Subject: RE: [PATCHv6 1/4] pwm: Add Freescale FTM PWM driver support


> > +	struct fsl_pwm_chip *fpc;
> > +
> > +	fpc = to_fsl_chip(chip);
> > +
> > +	period_cycles = fsl_rate_to_cycles(fpc, period_ns);
> > +	if (period_cycles > 0xFFFF) {
> > +		dev_err(chip->dev, "required PWM period cycles(%lu) overflow "
> > +				"16-bits counter!\n", period_cycles);
> > +		return -EINVAL;
> > +	}
> > +
> > +	duty_cycles = fsl_rate_to_cycles(fpc, duty_ns);
> > +	if (duty_cycles >= 0xFFFF) {
> > +		dev_err(chip->dev, "required PWM duty cycles(%lu) overflow "
> > +				"16-bits counter!\n", duty_cycles);
> > +		return -EINVAL;
> > +	}
> 
> I'm not sure the error messages are all that useful. A -EINVAL error code
> should make it pretty clear what the problem is.
> 

Yes, it is.

But for the pwm leds, there hasn't any check about the return values, if
there is something wrong, we cannot get any information about this.

So I think this error messages are useful for this case.


--
Xiubo
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