Re: [PATCH 2/2] iio: adc: ad4080: add support for AD4883

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] The `ad4080_get_scale` function calculates the fractional part of the scale in micro units but returns `IIO_VAL_INT_PLUS_NANO`, causing the userspace scale value to be off by a factor of 1000.
--

--- Patch [2]: [PATCH 2/2] iio: adc: ad4080: add support for AD4883 ---
commit 1f80e540484a260f71b5515f8af8d43748391d9e
Author: Antoniu Miclaus <antoniu.miclaus@analog.com>

iio: adc: ad4080: add support for AD4883

This commit adds support for the AD4883, a dual-channel, 16-bit, 40 MSPS
SAR ADC. It shares the register map and SPI interface with the AD4080
family and provides two independent ADC channels.

> diff --git a/drivers/iio/adc/ad4080.c b/drivers/iio/adc/ad4080.c
> index c7ecf6971be45..543728c7e88c0 100644
> --- a/drivers/iio/adc/ad4080.c
> +++ b/drivers/iio/adc/ad4080.c

[ ... ]

> @@ -646,6 +652,16 @@ static const struct ad4080_chip_info ad4880_chip_info = {
>  	.lvds_cnv_clk_cnt_max = AD4080_LVDS_CNV_CLK_CNT_MAX,
>  };
>  
> +static const struct ad4080_chip_info ad4883_chip_info = {
> +	.name = "ad4883",
> +	.product_id = AD4883_CHIP_ID,
> +	.scale_table = ad4080_scale_table,

[Severity: High]
This isn't a bug introduced by this patch, but looking at how the scale table
is used in ad4080_get_scale(), is there a mismatch in the units returned?

drivers/iio/adc/ad4080.c:ad4080_get_scale() {
	...
	tmp = (st->info->scale_table[0][0] * 1000000ULL) >>
		    st->info->channels[0].scan_type.realbits;
	*val = tmp / 1000000;
	*val2 = tmp % 1000000;

	return IIO_VAL_INT_PLUS_NANO;
}

Since the fractional part is calculated using modulo 1000000 (micro units)
but returned as IIO_VAL_INT_PLUS_NANO, the IIO core will format it as a
nano-scale value. Does this cause the scale exposed to userspace to be off
by a factor of 1000?

Should this return IIO_VAL_INT_PLUS_MICRO instead, or calculate with
1000000000ULL to match the NANO return type?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260720133707.103366-1-antoniu.miclaus@analog.com?part=2