linux-kernel - Re: [PATCH v8 2/2] iio: adc: ad7173: add AD7173 driver

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Message-ID: <ZXm-hf8UQ3VEyP-2@smile.fi.intel.com>
Date:   Wed, 13 Dec 2023 16:24:05 +0200
From:   Andy Shevchenko <andy@...nel.org>
To:     Dumitru Ceclan <mitrutzceclan@...il.com>
Cc:     linus.walleij@...aro.org, brgl@...ev.pl,
        linux-gpio@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>,
        Jonathan Cameron <jic23@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Michael Walle <michael@...le.cc>,
        Arnd Bergmann <arnd@...db.de>,
        ChiaEn Wu <chiaen_wu@...htek.com>,
        Niklas Schnelle <schnelle@...ux.ibm.com>,
        Leonard Göhrs <l.goehrs@...gutronix.de>,
        Mike Looijmans <mike.looijmans@...ic.nl>,
        Haibo Chen <haibo.chen@....com>,
        Hugo Villeneuve <hvilleneuve@...onoff.com>,
        Ceclan Dumitru <dumitru.ceclan@...log.com>,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 2/2] iio: adc: ad7173: add AD7173 driver

On Tue, Dec 12, 2023 at 12:44:36PM +0200, Dumitru Ceclan wrote:
> The AD7173 family offer a complete integrated Sigma-Delta ADC solution
> which can be used in high precision, low noise single channel
> applications or higher speed multiplexed applications. The Sigma-Delta
> ADC is intended primarily for measurement of signals close to DC but also
> delivers outstanding performance with input bandwidths out to ~10kHz.

I do not see any major problem in the code,
Reviewed-by: Andy Shevchenko <andy@...nel.org>

Some nit-picks below, but it's fine if it get addressed later on. Up to you
and Jonathan.

...

> +static const unsigned int ad7173_sinc5_data_rates[] = {
> +	6211000, 6211000, 6211000, 6211000, 6211000, 6211000, 5181000, 4444000,
> +	3115000, 2597000, 1007000, 503800,  381000,  200300,  100500,  59520,
> +	49680,	 20010,	  16333,   10000,   5000,    2500,    1250,
> +};
> +
> +static const unsigned int ad7175_sinc5_data_rates[] = {
> +	50000000, 41667000, 31250000, 27778000, 20833000, 17857000, 12500000,

I would add a comment with offsets, like

	... /* 0-6 */

But better to make it power of two, like each 4 on one line or 8.

> +	10000000, 5000000,  2500000,  1000000,	500000,	  397500,   200000,
> +	100000,	  59920,    49960,    20000,	16666,	  10000,    5000,
> +};

Not that I insist, just consider readability of these tables.

...

> +		if (chan->type == IIO_TEMP) {
> +			temp = ((u32)AD7173_VOLTAGE_INT_REF_uV) * MILLI;

Hmm... Is the casting mandatory here?

> +			temp /= AD7173_TEMP_SENSIIVITY_uV_per_C;
> +			*val = temp;
> +			*val2 = chan->scan_type.realbits;
> +		} else {
> +			*val = ad7173_get_ref_voltage_milli(st, ch->cfg.ref_sel);
> +			*val2 = chan->scan_type.realbits - !!(ch->cfg.bipolar);
> +		}

...

> +		if (chan->type == IIO_TEMP)
> +			*val = -874379; //-milli_kelvin_to_millicelsius(0)/scale

Hmm... Besides C99 comment format, can we actually use the mentioned API?
In such a case the comment won't be needed and the value semantics is better
to get.

> +		else
> +			*val = -BIT(chan->scan_type.realbits - 1);

...

> +static int ad7173_debug_reg_access(struct iio_dev *indio_dev, unsigned int reg,
> +				   unsigned int writeval, unsigned int *readval)
> +{
> +	struct ad7173_state *st = iio_priv(indio_dev);
> +	u8 reg_size;
> +
> +	if (reg == 0)

0 does not have its definition, does it?

> +		reg_size = 1;
> +	else if (reg == AD7173_REG_CRC || reg == AD7173_REG_DATA ||
> +		 reg >= AD7173_REG_OFFSET(0))
> +		reg_size = 3;
> +	else
> +		reg_size = 2;
> +
> +	if (readval)
> +		return ad_sd_read_reg(&st->sd, reg, reg_size, readval);
> +
> +	return ad_sd_write_reg(&st->sd, reg, reg_size, writeval);
> +}

...

> +	channels_st_priv_arr = devm_kcalloc(dev, num_channels,
> +					    sizeof(*channels_st_priv_arr),
> +					    GFP_KERNEL);
> +	if (!channels_st_priv_arr)
> +		return -ENOMEM;

The variable name can be made shorter and hence the above will take less LoCs.

-- 
With Best Regards,
Andy Shevchenko