Re: [PATCH v3 5/5] iio: adc: ad4080: add support for AD4880 dual-channel ADC

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 13 Feb 2026 16:47:37 +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>
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>

One small thing inline.

> @@ -617,13 +731,34 @@ 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);
> +	/* 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]);
>  
> -	st->info = spi_get_device_match_data(spi);
> -	if (!st->info)
> -		return -ENODEV;
> +	/* Setup ancillary SPI devices for additional channels */
> +	if (st->info->num_channels > 1) {
> +		u32 reg[AD4080_MAX_CHANNELS];
> +
> +		ret = device_property_read_u32_array(dev, "reg", reg,
> +						     st->info->num_channels);
Can we just use

		spi_get_chipselect(spi, 1) ?

I think the generic firmware parser will have already parsed the DT and filled
that in by this point.

> +		if (ret)
> +			return dev_err_probe(dev, ret,
> +					     "missing reg entries for multi-channel device\n");
> +
> +		for (int i = 1; i < st->info->num_channels; i++) {
> +			st->spi[i] = devm_spi_new_ancillary_device(spi, reg[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]);
> +		}
> +	}