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

Andy Shevchenko
2023-12-13T14:24:15Z

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@kernel.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