linux-kernel - Re: [PATCH 2/3] iio: light: lm3533-als: Print error message on invalid resistance

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Message-ID: <20151028183750.GB24668@usrtlx11787.corpusers.net>
Date:	Wed, 28 Oct 2015 11:37:50 -0700
From:	Bjorn Andersson <bjorn.andersson@...ymobile.com>
To:	Joe Perches <joe@...ches.com>
CC:	Jonathan Cameron <jic23@...nel.org>,
	Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Johan Hovold <jhovold@...il.com>,
	Peter Meerwald <pmeerw@...erw.net>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/3] iio: light: lm3533-als: Print error message on
 invalid resistance

On Tue 27 Oct 12:18 PDT 2015, Joe Perches wrote:

> On Sun, 2015-10-25 at 11:09 -0700, Bjorn Andersson wrote:
> > Print an error message to indicate that invalid configuration data was
> > provided in the platform_data, rather than just aborting initialization.
> 
> Perhaps it'd be nicer to show the 3 values.
> 

I do agree that it would be helpful to hint the developer about the
expected range. The problem I see here though is that, in the case of
devicetree we've now moved from resistance to a register value.

E.g. specifying 500kOhm in dt would make this piece complain about a
resistance of 0 being invalid and I would have to read the code and/or
datasheet anyways to find the valid range.

The reason I did not put this error print in the dt parser was that I
did not want to replicate the resistor limits and I figured it would be
useful for platform_data users as well. But if this is going to be
informative I think I need to move it.

So would you be okay with not improving the message? Or would you like
me to just move it into the code in patch 1 - and leave the
platform_data case as it was (with a silent failure)?

> > diff --git a/drivers/iio/light/lm3533-als.c b/drivers/iio/light/lm3533-als.c
> []
> > @@ -743,8 +743,10 @@ static int lm3533_als_set_resistor(struct lm3533_als *als, u8 val)
> >  {
> >  	int ret;
> >  
> > -	if (val < LM3533_ALS_RESISTOR_MIN || val > LM3533_ALS_RESISTOR_MAX)
> > +	if (val < LM3533_ALS_RESISTOR_MIN || val > LM3533_ALS_RESISTOR_MAX) {
> > +		dev_err(&als->pdev->dev, "invalid resistor value\n");
> >  		return -EINVAL;
> > +	};
> >  

Regards,
Bjorn
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