linux-kernel - Re: [PATCH v4 05/11] pwm: pwm-tiecap: pinctrl support

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Message-ID: <20121123111811.GA5072@avionic-0098.adnet.avionic-design.de>
Date:	Fri, 23 Nov 2012 12:18:11 +0100
From:	Thierry Reding <thierry.reding@...onic-design.de>
To:	"Philip, Avinash" <avinashphilip@...com>
Cc:	"paul@...an.com" <paul@...an.com>,
	"tony@...mide.com" <tony@...mide.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"Cousson, Benoit" <b-cousson@...com>,
	"Hiremath, Vaibhav" <hvaibhav@...com>,
	"AnilKumar, Chimata" <anilkumar@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"Nori, Sekhar" <nsekhar@...com>,
	"Hebbar, Gururaja" <gururaja.hebbar@...com>,
	"Bedia, Vaibhav" <vaibhav.bedia@...com>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v4 05/11] pwm: pwm-tiecap: pinctrl support

On Fri, Nov 23, 2012 at 11:12:15AM +0000, Philip, Avinash wrote:
> On Fri, Nov 23, 2012 at 16:21:10, Thierry Reding wrote:
> > On Fri, Nov 23, 2012 at 10:34:02AM +0000, Philip, Avinash wrote:
> > > On Fri, Nov 23, 2012 at 02:29:44, Thierry Reding wrote:
> > > > On Wed, Nov 21, 2012 at 06:41:02PM +0530, Philip, Avinash wrote:
> > > > [...]
> > > > > +	pinctrl = devm_pinctrl_get_select_default(&pdev->dev);
> > > > > +	if (IS_ERR(pinctrl))
> > > > > +		dev_warn(&pdev->dev, "failed to configure pins from driver\n");
> > > > 
> > > > I think we already discussed this, but shouldn't this be a fatal error?
> > > 
> > > I had checked relevant discussion and found this can be warning message.
> > > This is because most boards don't have pinctrl implemented at this point,
> > > or may never have.
> > > 
> > > https://lkml.org/lkml/2012/9/11/369
> > > 
> > > Any way I will change to
> > > dev_warn(&pdev->dev, "unable to select pin group\n");
> > > as in other drivers.
> > 
> > But in case pinctrl isn't implemented, shouldn't the implementation of
> > devm_pinctrl_get_select_default() just be a no-op?
> 
> So driver can still exist but pin mux functionality missing. Then warning
> message will give hints.
> I am also ok with error message & failure of driver with EPROBE_DEFER,
> if you want?

Everybody seems to be doing it with a warning, so I guess that's fine
for now. I just find it strange that if you request the default pin
group to be selected when in fact the hardware doesn't support pinctrl
at all you shouldn't be getting an error either.

I'm adding LinusW on Cc, perhaps he can shed some light on it.

Thierry

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