linux-kernel - Re: [PATCH v2 2/2] iio: magnetometer: add ti tmag5273 driver

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Message-ID: <Y3vGNVZcSuILCHxW@smile.fi.intel.com>
Date:   Mon, 21 Nov 2022 20:40:53 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Gerald Loacker <gerald.loacker@...fvision.net>
Cc:     linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Nikita Yushchenko <nikita.yoush@...entembedded.com>,
        Jakob Hauser <jahau@...ketmail.com>,
        Michael Riesch <michael.riesch@...fvision.net>
Subject: Re: [PATCH v2 2/2] iio: magnetometer: add ti tmag5273 driver

On Mon, Nov 21, 2022 at 06:24:18PM +0100, Gerald Loacker wrote:
> Am 21.11.2022 um 15:04 schrieb Andy Shevchenko:
> > On Mon, Nov 21, 2022 at 01:35:42PM +0100, Gerald Loacker wrote:

...

> >> +	if (!device_property_read_string(data->dev, "ti,angle-measurement",
> >> +					 &angle_measurement)) {
> >> +		if (!strcmp(angle_measurement, "off"))
> >> +			data->angle_measurement = TMAG5273_ANGLE_EN_OFF;
> >> +		else if (!strcmp(angle_measurement, "x-y"))
> >> +			data->angle_measurement = TMAG5273_ANGLE_EN_X_Y;
> >> +		else if (!strcmp(angle_measurement, "y-z"))
> >> +			data->angle_measurement = TMAG5273_ANGLE_EN_Y_Z;
> >> +		else if (!strcmp(angle_measurement, "x-z"))
> >> +			data->angle_measurement = TMAG5273_ANGLE_EN_X_Z;
> >> +		else
> >> +			dev_warn(data->dev,
> >> +				 "failed to read angle-measurement\n");
> > 
> > Can't you use match_string()?
> > 
> 
> Yes, I will use match_string().
> 
> > And you actually can do a bit differently, can you?
> > 
> > 	angle_measurement = "...default...";
> > 	if (device_property_...)
> > 		dev_warn(data->dev, "failed to read angle-measurement\n");
> 
> I think we shouldn't warn here, as angle_measurement isn't a required
> property. Besides that I will do it this way.
> 
> > 	ret = match_string();
> > 	if (ret < 0)
> > 		dev_warn(data->dev, "invalid angle-measurement value\n");
> > 	else
> > 		data->angle_measurement = ret;
> > 
> >> +	}

After looking into DT patch I think you can even use
device_property_match_string(),

...

> >> +		snprintf(data->name, sizeof(data->name), "tmag5273x%1u",
> > 
> > There is a difference between %1u and %.1u. And I believe you wanted the
> > latter, but...
> 
> %1u works fine for me. Can you point me to the documentation for %.1u?

man printf(3)

It was a surprise to me that many developers don't know the difference here.
The %NNNNu defines the _minimum_ digits to print, while the %.NNNu defines
the _exact_ amount of digits to print (NNN -- a number).

> >> +			 data->version);

-- 
With Best Regards,
Andy Shevchenko