linux-kernel - Re: [PATCH v2 2/2] iio: adc: ad9467: support write/read offset

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Message-ID: <5d343af235c499382bd2eac987357e857865b457.camel@gmail.com>
Date: Tue, 02 Dec 2025 13:47:33 +0000
From: Nuno Sá <noname.nuno@...il.com>
To: Tomas Melin <tomas.melin@...sala.com>, Lars-Peter Clausen
 <lars@...afoo.de>,  Michael Hennerich <Michael.Hennerich@...log.com>, Nuno
 Sa <nuno.sa@...log.com>, Jonathan Cameron <jic23@...nel.org>,  David
 Lechner <dlechner@...libre.com>, Andy Shevchenko <andy@...nel.org>,
 Alexandru Ardelean	 <alexandru.ardelean@...log.com>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 linux-iio@...r.kernel.org, 	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] iio: adc: ad9467: support write/read offset

On Tue, 2025-12-02 at 12:53 +0000, Tomas Melin wrote:
> Support configuring output calibration value. Among the devices
> currently supported by this driver, this setting is specific to
> ad9434. The offset can be used to calibrate the output against
> a known input. The register is called offset, but the procedure
> is best mapped internally with calibbias operation.
> 
> Signed-off-by: Tomas Melin <tomas.melin@...sala.com>
> ---
>  drivers/iio/adc/ad9467.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 59 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/adc/ad9467.c b/drivers/iio/adc/ad9467.c
> index 2d8f8da3671dac61994a1864a82cdbef7f54c1af..c3cf7ae977d4279ce5e80a7c956c3844483eb8bd 100644
> --- a/drivers/iio/adc/ad9467.c
> +++ b/drivers/iio/adc/ad9467.c
> @@ -145,6 +145,7 @@ struct ad9467_chip_info {
>  	unsigned int num_lanes;
>  	unsigned int dco_en;
>  	unsigned int test_points;
> +	const int *offset_range;
>  	/* data clock output */
>  	bool has_dco;
>  	bool has_dco_invert;
> @@ -234,6 +235,10 @@ static int ad9467_reg_access(struct iio_dev *indio_dev, unsigned int reg,
>  	return 0;
>  }
>  
> +static const int ad9434_offset_range[] = {
> +	-128, 1, 127,
> +};
> +
>  static const unsigned int ad9265_scale_table[][2] = {
>  	{1250, 0x00}, {1500, 0x40}, {1750, 0x80}, {2000, 0xC0},
>  };
> @@ -298,7 +303,24 @@ static void __ad9467_get_scale(struct ad9467_state *st, int index,
>  }
>  
>  static const struct iio_chan_spec ad9434_channels[] = {
> -	AD9467_CHAN(0, BIT(IIO_CHAN_INFO_SCALE), 0, 12, 's'),
> +	{
> +		.type = IIO_VOLTAGE,
> +		.indexed = 1,
> +		.channel = 0,
> +		.info_mask_shared_by_type =
> +		BIT(IIO_CHAN_INFO_SCALE) |
> +		BIT(IIO_CHAN_INFO_SAMP_FREQ) |
> +		BIT(IIO_CHAN_INFO_CALIBBIAS),
> +		.info_mask_shared_by_type_available =
> +		BIT(IIO_CHAN_INFO_SCALE) |
> +		BIT(IIO_CHAN_INFO_CALIBBIAS),

Odd style for info_mask_shared_by_type_available and info_mask_shared_by_type. Seems we have
more line breaks than needed.


> +		.scan_index = 0,
> +		.scan_type = {
> +			.sign = 's',
> +			.realbits = 12,
> +			.storagebits = 16,
> +		},
> +	},
>  };
>  
>  static const struct iio_chan_spec ad9467_channels[] = {
> @@ -367,6 +389,7 @@ static const struct ad9467_chip_info ad9434_chip_tbl = {
>  	.default_output_mode = AD9434_DEF_OUTPUT_MODE,
>  	.vref_mask = AD9434_REG_VREF_MASK,
>  	.num_lanes = 6,
> +	.offset_range = ad9434_offset_range,
>  };
>  
>  static const struct ad9467_chip_info ad9265_chip_tbl = {
> @@ -499,6 +522,33 @@ static int ad9467_set_scale(struct ad9467_state *st, int val, int val2)
>  	return -EINVAL;
>  }
>  
> +static int ad9467_get_offset(struct ad9467_state *st, int *val)
> +{
> +	int ret;
> +
> +	ret = ad9467_spi_read(st, AN877_ADC_REG_OFFSET);
> +	if (ret < 0)
> +		return ret;
> +	*val = ret;
> +
> +	return IIO_VAL_INT;
> +}
> +
> +static int ad9467_set_offset(struct ad9467_state *st, int val)
> +{
> +	int ret;
> +
> +	if (val < st->info->offset_range[0] || val > st->info->offset_range[2])
> +		return -EINVAL;
> +
> +	ret = ad9467_spi_write(st, AN877_ADC_REG_OFFSET, val);
> +	if (ret < 0)
> +		return ret;
> +	/* Sync registers */

I think this is not what David meant by adding a comment. IMHO, the comment as-is does not
bring any added value.

- Nuno Sá