linux-kernel - Re: [PATCH v2 4/4] iio: adc: ad7768-1: add support for ADAQ776x-1 ADC Family

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Message-ID: <aK50KITsXoPTkRbA@JSANTO12-L01.ad.analog.com>
Date: Tue, 26 Aug 2025 23:57:44 -0300
From: Jonathan Santos <jonath4nns@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Jonathan Santos <Jonathan.Santos@...log.com>,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, Michael.Hennerich@...log.com,
	lars@...afoo.de, dlechner@...libre.com, nuno.sa@...log.com,
	andy@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, marcelo.schmitt1@...il.com
Subject: Re: [PATCH v2 4/4] iio: adc: ad7768-1: add support for ADAQ776x-1
 ADC Family

On 08/25, Jonathan Cameron wrote:
> On Sun, 24 Aug 2025 01:10:13 -0300
> Jonathan Santos <Jonathan.Santos@...log.com> wrote:
> 
> > Add support for ADAQ7767/68/69-1 series, which includes PGIA and
> > Anti-aliasing filter (AAF) gains. Unlike the AD7768-1, they do not
> > provide a VCM regulator interface.
> > 
> > The PGA gain is configured in run-time through the scale attribute,
> > if supported by the device. PGA is enabled and controlled by the GPIO
> > controller (GPIOs 0, 1 and 2) provided by the device with the SPI
> > interface.
> > 
> > The AAF gain is defined by hardware connections and should be specified
> > in device tree.
> > 
> > Signed-off-by: Jonathan Santos <Jonathan.Santos@...log.com>
> Hi Jonathan
> 
> Various minor comments inline.
> 
> Thanks,
> 
> Jonathan
> 
...
> >  	/* Register VCM output regulator */
> > -	ret = ad7768_register_regulators(&spi->dev, st, indio_dev);
> > -	if (ret)
> > -		return ret;
> > +	if (st->chip->has_vcm_regulator) {
> > +		ret = ad7768_register_regulators(&spi->dev, st, indio_dev);
> > +		if (ret)
> > +			return ret;
> > +	}
> > +
> > +	st->aaf_gain = AD7768_AAF_IN1;
> > +	ret = device_property_read_u32(&spi->dev, "adi,gain-milli", &val);
> > +	if (ret && st->chip->has_variable_aaf)
> > +		dev_warn(&spi->dev, "AAF gain not specified, using default\n");
> > +
> > +	if (!ret && !st->chip->has_variable_aaf)
> > +		dev_warn(&spi->dev, "AAF gain not supported for %s\n", st->chip->name);
> 
> I'm confused.  If you hit this warn, you then go ahead and set it anyway. How does that
> work?
> 

I would be setting a variable that will not be used, so no functional impact.
I could add another condition to avoid assigning it, or do you believe it
is better to return error like before? 

> > +
> > +	if (!ret) {
> use a local bool for ret here with a suitable name. Carrying on using ret is
> fragile against later code changes where someone doesn't realise it is still in use.
> 

Maybe it is better to handle this in a helper function and apply the
suggestion.

> > +		/* If provided, validate and set the gain */
> > +		switch (val) {
> > +		case 1000:
> > +			st->aaf_gain = AD7768_AAF_IN1;
> > +			break;
> > +		case 364:
> > +			st->aaf_gain = AD7768_AAF_IN2;
> > +			break;
> > +		case 143:
> > +			st->aaf_gain = AD7768_AAF_IN3;
> > +			break;
> > +		default:
> > +			return dev_err_probe(&spi->dev, -EINVAL,
> > +					     "Invalid firmware provided AAF gain\n");
> > +		}
> > +	}

Regards,
Jonathan S.