Re: [PATCH v4 5/5] iio: adc: ad4080: add support for AD4880 dual-channel ADC

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 23 Feb 2026 18:21:04 +0200
Antoniu Miclaus <antoniu.miclaus@analog.com> wrote:

> Add support for the AD4880, a dual-channel 20-bit 40MSPS SAR ADC with
> integrated fully differential amplifiers (FDA).
> 
> The AD4880 has two independent ADC channels, each with its own SPI
> configuration interface. The driver uses spi_new_ancillary_device() to
> create an additional SPI device for the second channel, allowing both
> channels to share the same SPI bus with different chip selects.
> 
> Reviewed-by: David Lechner <dlechner@baylibre.com>
> Reviewed-by: Nuno Sá <nuno.sa@analog.com>
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Hi Antoniu

One minor question / comment below. Not particularly important
but as you will be doing a v5 anyway, seems reasonable to aks the
question.

>  static int ad4080_properties_parse(struct ad4080_state *st)
>  {
> -	struct device *dev = regmap_get_device(st->regmap);
> +	struct device *dev = regmap_get_device(st->regmap[0]);
>  
>  	st->lvds_cnv_en = device_property_read_bool(dev, "adi,lvds-cnv-enable");
>  
> @@ -602,6 +711,7 @@ static int ad4080_probe(struct spi_device *spi)
>  	struct device *dev = &spi->dev;
>  	struct ad4080_state *st;
>  	struct clk *clk;
> +	unsigned int ch;
>  	int ret;
>  
>  	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> @@ -610,6 +720,10 @@ static int ad4080_probe(struct spi_device *spi)
>  
>  	st = iio_priv(indio_dev);
>  
> +	st->info = spi_get_device_match_data(spi);
> +	if (!st->info)
> +		return -ENODEV;
> +
>  	ret = devm_regulator_bulk_get_enable(dev,
>  					     ARRAY_SIZE(ad4080_power_supplies),
>  					     ad4080_power_supplies);
> @@ -617,13 +731,27 @@ static int ad4080_probe(struct spi_device *spi)
>  		return dev_err_probe(dev, ret,
>  				     "failed to get and enable supplies\n");
>  
> -	st->regmap = devm_regmap_init_spi(spi, &ad4080_regmap_config);
> -	if (IS_ERR(st->regmap))
> -		return PTR_ERR(st->regmap);
> -
> -	st->info = spi_get_device_match_data(spi);
> -	if (!st->info)
> -		return -ENODEV;

Moving this up doesn't seem to be necessary.  Am I missing a reason
st->info should be set earlier? If not I'd have left it down here simpl
to avoid the churn.

> +	/* Setup primary SPI device (channel 0) */
> +	st->spi[0] = spi;
> +	st->regmap[0] = devm_regmap_init_spi(spi, &ad4080_regmap_config);
> +	if (IS_ERR(st->regmap[0]))
> +		return PTR_ERR(st->regmap[0]);
> +
> +	/* Setup ancillary SPI devices for additional channels */
> +	if (st->info->num_channels > 1) {
> +		for (int i = 1; i < st->info->num_channels; i++) {
> +			st->spi[i] = devm_spi_new_ancillary_device(spi,
> +					spi_get_chipselect(spi, i));
> +			if (IS_ERR(st->spi[i]))
> +				return dev_err_probe(dev, PTR_ERR(st->spi[i]),
> +						     "failed to register ancillary device\n");
> +
> +			st->regmap[i] = devm_regmap_init_spi(st->spi[i],
> +							     &ad4080_regmap_config);
> +			if (IS_ERR(st->regmap[i]))
> +				return PTR_ERR(st->regmap[i]);
> +		}
> +	}