linux-kernel - Re: [PATCH 11/11] iio: pressure-core: st: Provide correct regulator support

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Message-ID: <20130904132439.GA10155@sirena.org.uk>
Date:	Wed, 4 Sep 2013 14:24:39 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Mark Rutland <mark.rutland@....com>
Cc:	Lee Jones <lee.jones@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jic23@....ac.uk" <jic23@....ac.uk>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	"linus.walleij@...aro.org" <linus.walleij@...aro.org>,
	"denis.ciocca@...com" <denis.ciocca@...com>,
	"arnd@...db.de" <arnd@...db.de>
Subject: Re: [PATCH 11/11] iio: pressure-core: st: Provide correct regulator
 support

On Wed, Sep 04, 2013 at 02:11:11PM +0100, Mark Rutland wrote:
> On Wed, Sep 04, 2013 at 10:31:43AM +0100, Lee Jones wrote:

> > +	/* Regulator not mandatory, but if requested we should enable it. */
> > +	pdata->regulator = regulator_get(&indio_dev->dev, "vdd");
> > +	if (!IS_ERR_OR_NULL(pdata->regulator)) {

> Can regulator_get return NULL? As far as I can see, it either returns a
> valid reulator pointer or an ERR_PTR value.

Yes, NULL is a valid regulator.

> When you say "if requested", do you mean "if described in the dt"? If
> so, the above doesn't distunguish between a regulator not being listed
> and one failing to be got (e.g. if we got EPROBE_DEFER from
> regulator_get).

> I think this would be better handled with something like Mark Brown's
> suggested regulator_get_optional [1,2].

If the regulator may genuinely be absent from the system then it should
be being requested using regulator_get_optional().  Otherwise it should
be being requested using regulator_get().  In both cases it is important 
that the driver pays attention to errors.

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