linux-kernel - Re: [PATCH v3 04/10] iio: adc: ad4170: Add support for calibration bias

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Message-ID: <b198ab8bcae5e9a31164bb565a089d14ff297b81.camel@gmail.com>
Date: Mon, 26 May 2025 11:27:02 +0100
From: Nuno Sá <noname.nuno@...il.com>
To: Marcelo Schmitt <marcelo.schmitt@...log.com>, linux-iio@...r.kernel.org,
 	devicetree@...r.kernel.org, linux-gpio@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Cc: jic23@...nel.org, lars@...afoo.de, Michael.Hennerich@...log.com, 
	dlechner@...libre.com, nuno.sa@...log.com, andy@...nel.org,
 robh@...nel.org, 	krzk+dt@...nel.org, conor+dt@...nel.org,
 linus.walleij@...aro.org, brgl@...ev.pl, 	marcelo.schmitt1@...il.com
Subject: Re: [PATCH v3 04/10] iio: adc: ad4170: Add support for calibration
 bias

On Tue, 2025-05-13 at 09:34 -0300, Marcelo Schmitt wrote:
> Add support for ADC calibration bias/offset configuration.
> 
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
> ---
> Change log v2 -> v3
> - New patch spun out of the base driver patch.
> 
>  drivers/iio/adc/ad4170.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/drivers/iio/adc/ad4170.c b/drivers/iio/adc/ad4170.c
> index 1df214f7fdec..b02fdd25b4c8 100644
> --- a/drivers/iio/adc/ad4170.c
> +++ b/drivers/iio/adc/ad4170.c
> @@ -643,6 +643,7 @@ static const struct iio_chan_spec ad4170_channel_template
> = {
>  	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
>  			      BIT(IIO_CHAN_INFO_SCALE) |
>  			      BIT(IIO_CHAN_INFO_OFFSET) |
> +			      BIT(IIO_CHAN_INFO_CALIBBIAS) |
>  			      BIT(IIO_CHAN_INFO_CALIBSCALE),
>  	.info_mask_separate_available = BIT(IIO_CHAN_INFO_SCALE),
>  	.scan_type = {
> @@ -954,6 +955,9 @@ static int ad4170_read_raw(struct iio_dev *indio_dev,
>  		pga = FIELD_GET(AD4170_AFE_PGA_GAIN_MSK, setup->afe);
>  		*val = chan_info->offset_tbl[pga];
>  		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_CALIBBIAS:
> +		*val = setup->offset;

same nit...

> +		return IIO_VAL_INT;
>  	case IIO_CHAN_INFO_CALIBSCALE:
>  		*val = setup->gain;
>  		return IIO_VAL_INT;
> @@ -1083,6 +1087,25 @@ static int ad4170_set_pga(struct ad4170_state *st,
>  	return 0;
>  }
>  
> +static int ad4170_set_calib_offset(struct ad4170_state *st,
> +				   struct iio_chan_spec const *chan, int val)
> +{
> +	struct ad4170_chan_info *chan_info = &st->chan_infos[chan->address];
> +	struct ad4170_setup *setup = &chan_info->setup;
> +	u32 old_offset;
> +	int ret;
> +
> +	guard(mutex)(&st->lock);
> +	old_offset = setup->offset;
> +	setup->offset = val;

Why doing the above dance?

> +
> +	ret = ad4170_write_channel_setup(st, chan->address, false);
> +	if (ret)
> +		setup->offset = old_offset;
> +

We could update the value in here.

> +	return ret;

I guess ret > 0 is not a thing? I find it more readable:

return 0;

It makes it clear we got success :)

- Nuno Sá

> +}
> +
>  static int ad4170_set_calib_gain(struct ad4170_state *st,
>  				 struct iio_chan_spec const *chan, int val)
>  {
> @@ -1111,6 +1134,8 @@ static int __ad4170_write_raw(struct iio_dev *indio_dev,
>  	switch (info) {
>  	case IIO_CHAN_INFO_SCALE:
>  		return ad4170_set_pga(st, chan, val, val2);
> +	case IIO_CHAN_INFO_CALIBBIAS:
> +		return ad4170_set_calib_offset(st, chan, val);
>  	case IIO_CHAN_INFO_CALIBSCALE:
>  		return ad4170_set_calib_gain(st, chan, val);
>  	default:
> @@ -1139,6 +1164,7 @@ static int ad4170_write_raw_get_fmt(struct iio_dev
> *indio_dev,
>  	switch (info) {
>  	case IIO_CHAN_INFO_SCALE:
>  		return IIO_VAL_INT_PLUS_NANO;
> +	case IIO_CHAN_INFO_CALIBBIAS:
>  	case IIO_CHAN_INFO_CALIBSCALE:
>  		return IIO_VAL_INT;
>  	default: