Re: [PATCH 2/2] iio: dac: ad5766: add driver support for AD5766

[Jonathan Cameron]

On Mon, 23 Nov 2020 16:50:42 +0200
Cristian Pop <cristian.pop@xxxxxxxxxx> wrote:

> The AD5766/AD5767 are 16-channel, 16-bit/12-bit, voltage output dense DACs
> Digital-to-Analog converters.
> 
> This change adds support for these DACs.
> 
> Link: https://www.analog.com/media/en/technical-documentation/data-sheets/ad5766-5767.pdf

Biggest thing in here is you are proposing new ABI, but I'm not seeing
the docs we'd need to properly discuss that.

Otherwise, some more minor bits inline.

Thanks,

Jonathan

> 
> Signed-off-by: Cristian Pop <cristian.pop@xxxxxxxxxx>
> ---
>  drivers/iio/dac/ad5766.c | 768 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 768 insertions(+)
>  create mode 100644 drivers/iio/dac/ad5766.c
> 
> diff --git a/drivers/iio/dac/ad5766.c b/drivers/iio/dac/ad5766.c
> new file mode 100644
> index 000000000000..feef78960990
> --- /dev/null
> +++ b/drivers/iio/dac/ad5766.c
> @@ -0,0 +1,768 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Analog Devices AD5766, AD5767
> + * Digital to Analog Converters driver
> + *
> + * Copyright 2019 Analog Devices Inc.

2019-2020 perhaps given making changes?

> + */
> +
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +#include <linux/iio/iio.h>
> +
> +#define AD5766_CMD_NOP_MUX_OUT			0x00
> +#define AD5766_CMD_SDO_CNTRL			0x01
> +#define AD5766_CMD_WR_IN_REG(x)			(0x10 | ((x) & 0xF))
> +#define AD5766_CMD_WR_DAC_REG(x)		(0x20 | ((x) & 0xF))
> +#define AD5766_CMD_SW_LDAC			0x30
> +#define AD5766_CMD_SPAN_REG			0x40
> +#define AD5766_CMD_WR_PWR_DITHER		0x51
> +#define AD5766_CMD_WR_DAC_REG_ALL		0x60
> +#define AD5766_CMD_SW_FULL_RESET		0x70
> +#define AD5766_CMD_READBACK_REG(x)		(0x80 | ((x) & 0xF))
> +#define AD5766_CMD_DITHER_SIG_1			0x90
> +#define AD5766_CMD_DITHER_SIG_2			0xA0
> +#define AD5766_CMD_INV_DITHER			0xB0
> +#define AD5766_CMD_DITHER_SCALE_1		0xC0
> +#define AD5766_CMD_DITHER_SCALE_2		0xD0
> +
> +#define AD5766_FULL_RESET_CODE			0x1234
> +
> +enum ad5766_type {
> +	ID_AD5766,
> +	ID_AD5767,
> +};
> +
> +static ssize_t ad5766_write_ext(struct iio_dev *indio_dev,
> +				 uintptr_t private,
> +				 const struct iio_chan_spec *chan,
> +				 const char *buf, size_t len);
> +static ssize_t ad5766_read_ext(struct iio_dev *indio_dev,
> +			       uintptr_t private,
> +			       const struct iio_chan_spec *chan,
> +			       char *buf);
> +
> +static int ad5766_get_dither_source(struct iio_dev *dev,
> +			     const struct iio_chan_spec *chan);
> +
> +static int ad5766_set_dither_source(struct iio_dev *dev,
> +			     const struct iio_chan_spec *chan,
> +			     unsigned int mode);
> +
> +static int ad5766_get_dither_scale(struct iio_dev *dev,
> +			     const struct iio_chan_spec *chan);
> +
> +static int ad5766_set_dither_scale(struct iio_dev *dev,
> +			     const struct iio_chan_spec *chan,
> +			     unsigned int mode);

I'd be looking to reorganize the code to avoid the need for
these forward definitions.  It's fairly rare that we actually need to do this.

> +
> +#define _AD5766_CHAN_EXT_INFO(_name, _what, _shared) { \
> +	.name = _name, \
> +	.read = ad5766_read_ext, \
> +	.write = ad5766_write_ext, \
> +	.private = _what, \
> +	.shared = _shared, \
> +}
> +
> +enum {
> +	AD5766_DITHER_PWR,
> +	AD5766_DITHER_INVERT
> +};
> +
> +static const char * const ad5766_dither_sources[] = {
> +	"NO_DITHER",

Definitely needs docs as I have no idea what this is!

> +	"N0",
> +	"N1",
> +};
> +
> +static const char * const ad5766_dither_scales[] = {
> +	"NO_SCALING",
> +	"75%_SCALING",
> +	"50%_SCALING",
> +	"25%_SCALING",

New ABI.... Docs?
This looks like it should be a well defined nummeric ABI, though
I don't understand it enough yet to know if there is a number that
corresponds to NO_SCALING?  If there isn't then split it into two
ABI elements, one to enable / disable and one for the scaling.



> +};
> +
> +static const struct iio_enum ad5766_dither_source_enum = {
> +	.items = ad5766_dither_sources,
> +	.num_items = ARRAY_SIZE(ad5766_dither_sources),
> +	.set = ad5766_set_dither_source,
> +	.get = ad5766_get_dither_source,
> +};
> +
> +static const struct iio_enum ad5766_dither_scale_enum = {
> +	.items = ad5766_dither_scales,
> +	.num_items = ARRAY_SIZE(ad5766_dither_scales),
> +	.set = ad5766_set_dither_scale,
> +	.get = ad5766_get_dither_scale,
> +};
> +
> +static const struct iio_chan_spec_ext_info ad5766_ext_info[] = {
> +
> +	_AD5766_CHAN_EXT_INFO("dither_pwr", AD5766_DITHER_PWR, IIO_SEPARATE),
> +	_AD5766_CHAN_EXT_INFO("dither_invert", AD5766_DITHER_INVERT,
> +			      IIO_SEPARATE),
> +	IIO_ENUM("dither_source", IIO_SEPARATE, &ad5766_dither_source_enum),
> +	IIO_ENUM_AVAILABLE_SHARED("dither_source",
> +				  IIO_SEPARATE,
> +				  &ad5766_dither_source_enum),
> +	IIO_ENUM("dither_scale", IIO_SEPARATE, &ad5766_dither_scale_enum),
> +	IIO_ENUM_AVAILABLE_SHARED("dither_scale",
> +				  IIO_SEPARATE,
> +				  &ad5766_dither_scale_enum),
> +	{}
> +};
> +
> +#define AD576x_CHANNEL(_chan, _bits) {					\
> +	.type = IIO_VOLTAGE,						\
> +	.indexed = 1,							\
> +	.output = 1,							\
> +	.channel = (_chan),						\
> +	.address = (_chan),						\
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_OFFSET) |		\
> +		BIT(IIO_CHAN_INFO_SCALE),				\
> +	.info_mask_shared_by_type_available =				\
> +		BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_SCALE),	\
> +	.scan_type = {							\
> +		.sign = 'u',						\
> +		.realbits = (_bits),					\
> +		.storagebits = 16,					\
> +		.shift = 16 - (_bits),					\
> +	},								\
> +	.ext_info = ad5766_ext_info,					\
> +}
> +
> +#define DECLARE_AD576x_CHANNELS(_name, _bits)			\
> +const struct iio_chan_spec _name[] = {				\
> +	AD576x_CHANNEL(0, (_bits)),				\
> +	AD576x_CHANNEL(1, (_bits)),				\
> +	AD576x_CHANNEL(2, (_bits)),				\
> +	AD576x_CHANNEL(3, (_bits)),				\
> +	AD576x_CHANNEL(4, (_bits)),				\
> +	AD576x_CHANNEL(5, (_bits)),				\
> +	AD576x_CHANNEL(6, (_bits)),				\
> +	AD576x_CHANNEL(7, (_bits)),				\
> +	AD576x_CHANNEL(8, (_bits)),				\
> +	AD576x_CHANNEL(9, (_bits)),				\
> +	AD576x_CHANNEL(10, (_bits)),				\
> +	AD576x_CHANNEL(11, (_bits)),				\
> +	AD576x_CHANNEL(12, (_bits)),				\
> +	AD576x_CHANNEL(13, (_bits)),				\
> +	AD576x_CHANNEL(14, (_bits)),				\
> +	AD576x_CHANNEL(15, (_bits)),				\
> +}
> +
> +enum ad5766_voltage_range {
> +	AD5766_VOLTAGE_RANGE_M20V_0V,
> +	AD5766_VOLTAGE_RANGE_M16V_to_0V,
> +	AD5766_VOLTAGE_RANGE_M10V_to_0V,
> +	AD5766_VOLTAGE_RANGE_M12V_to_14V,
> +	AD5766_VOLTAGE_RANGE_M16V_to_10V,
> +	AD5766_VOLTAGE_RANGE_M10V_to_6V,
> +	AD5766_VOLTAGE_RANGE_M5V_to_5V,
> +	AD5766_VOLTAGE_RANGE_M10V_to_10V,
> +	AD5766_VOLTAGE_RANGE_MAX,
> +};
> +
> +/**
> + * struct ad5766_chip_info - chip specific information
> + * @num_channels:	number of channels
> + * @channel:	        channel specification
> + */
> +
> +struct ad5766_chip_info {
> +	unsigned int			num_channels;
> +	const struct iio_chan_spec	*channels;
> +};
> +
> +/**
> + * struct ad5766_state - driver instance specific data
> + * @spi:		Spi device
SPI device
> + * @lock:		Mutex lock
> + * @chip_info:		Chip model specific constants
> + * @gpio_reset:		Reset gpio

Reset GPIO etc.

> + * @crt_range:		Current selected output range
> + * @cached_offset:	Cached range coresponding to the selected offset
> + * @dither_power_ctrl:	Power-down bit for each channel dither block (for
> + *			example, D15 = DAC 15,D8 = DAC 8, and D0 = DAC 0)
> + *			0 - Normal operation, 1 - Power down
> + * @dither_invert:	Inverts the dither signal applied to the selected DAC
> + *			outputs
> + * @dither_source:	Selects between 3 possible sources: No dither, N0, N1
> + * @dither_source:	Selects between 4 possible sources:
> + *			No scale, 75%, 50%, 25%
> + * @scale_avail:	Scale available table
> + * @offset_avail:	Offest available table
> + * @data:		Spi transfer buffers
> + */
> +
I would drop the blank line between comments for structures and the structure
starting. Helps the eye to group them when reading (slightly!)
> +struct ad5766_state {
> +	struct spi_device		*spi;
> +	struct mutex			lock;
> +	const struct ad5766_chip_info	*chip_info;
> +	struct gpio_desc		*gpio_reset;
> +	enum ad5766_voltage_range	crt_range;
> +	enum ad5766_voltage_range	cached_offset;
> +	u16		dither_power_ctrl;
> +	u16		dither_invert;
> +	u32		dither_source;
> +	u32		dither_scale;
> +	s32		scale_avail[AD5766_VOLTAGE_RANGE_MAX][2];
> +	s32		offset_avail[AD5766_VOLTAGE_RANGE_MAX][2];
> +	union {
> +		u32	d32;
> +		u16	w16[2];
> +		u8	b8[4];
> +	} data[3] ____cacheline_aligned;
> +};
> +
> +struct ad5766_span_tbl {
> +	int		min;
> +	int		max;
> +};
> +
> +static const struct ad5766_span_tbl ad5766_span_tbl[] = {
> +	[AD5766_VOLTAGE_RANGE_M20V_0V] = {
> +		.min = -20,
> +		.max = 0,
> +	},
> +	[AD5766_VOLTAGE_RANGE_M16V_to_0V] = {
> +		.min = -16,
> +		.max = 0,
> +	},
> +	[AD5766_VOLTAGE_RANGE_M10V_to_0V] = {
> +		.min = -10,
> +		.max = 0,
> +	},
> +	[AD5766_VOLTAGE_RANGE_M12V_to_14V] = {
> +		.min = -12,
> +		.max = 14,
> +	},
> +	[AD5766_VOLTAGE_RANGE_M16V_to_10V] = {
> +		.min = -16,
> +		.max = 10,
> +	},
> +	[AD5766_VOLTAGE_RANGE_M10V_to_6V] = {
> +		.min = -10,
> +		.max = 6,
> +	},
> +	[AD5766_VOLTAGE_RANGE_M5V_to_5V] = {
> +		.min = -5,
> +		.max = 5,
> +	},
> +	[AD5766_VOLTAGE_RANGE_M10V_to_10V] = {
> +		.min = -10,
> +		.max = 10,
> +	},
> +};
> +
> +static int ad5766_write_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int val,
> +			    int val2,
> +			    long info);
> +
> +static int ad5766_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan,
> +			   int *val,
> +			   int *val2,
> +			   long m);
> +
> +static int ad5766_read_avail(struct iio_dev *indio_dev,
> +				struct iio_chan_spec const *chan,
> +				const int **vals, int *type, int *length,
> +				long mask);
> +
> +static const struct iio_info ad5766_info = {
> +	.read_raw = ad5766_read_raw,
> +	.write_raw = ad5766_write_raw,
> +	.read_avail = ad5766_read_avail,
> +};

I'd move this down so you don't need the forward declarations.

> +
> +static DECLARE_AD576x_CHANNELS(ad5766_channels, 16);
> +static DECLARE_AD576x_CHANNELS(ad5767_channels, 12);
> +
> +static const struct ad5766_chip_info ad5766_chip_infos[] = {
> +	[ID_AD5766] = {
> +		.num_channels = ARRAY_SIZE(ad5766_channels),
> +		.channels = ad5766_channels,
> +	},
> +	[ID_AD5767] = {
> +		.num_channels = ARRAY_SIZE(ad5767_channels),
> +		.channels = ad5767_channels,
> +	},
> +};
> +
> +static int _ad5766_spi_write(struct ad5766_state *st,
> +			     u8 command,
> +			     u16 data)
> +{
> +	st->data[0].b8[0] = command;
> +	st->data[0].b8[1] = (data & 0xFF00) >> 8;
> +	st->data[0].b8[2] = (data & 0x00FF) >> 0;

Maybe an unaligned write would be easier to read?

> +
> +	return spi_write(st->spi, &st->data[0].b8[0], 3);
> +}
> +
> +static int ad5766_write(struct iio_dev *indio_dev, u8 dac, u16 data)
> +{
> +	struct ad5766_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	mutex_lock(&st->lock);
> +	ret = _ad5766_spi_write(st, AD5766_CMD_WR_DAC_REG(dac), data);
> +	mutex_unlock(&st->lock);
> +
> +	return ret;
> +}
> +
> +static void ad5766_init_scale_tables(struct ad5766_state *st)
> +{
> +	int i;
> +	s32 denom;
> +	s64 offset;
> +	u64 scale;
> +	u8 realbits = st->chip_info->channels[0].scan_type.realbits;
> +
> +	for (i = 0; i < AD5766_VOLTAGE_RANGE_MAX; i++) {
> +		offset = (1 << realbits) * ad5766_span_tbl[i].min;
> +		denom = ad5766_span_tbl[i].max - ad5766_span_tbl[i].min;
> +		offset = div_s64(offset * 1000000, denom);
> +		st->offset_avail[i][0] = div_s64(offset, 1000000);
> +		div_s64_rem(offset, 1000000, &st->offset_avail[i][1]);
> +
> +		scale = ad5766_span_tbl[i].max - ad5766_span_tbl[i].min;
> +		scale = div_u64((scale * 1000000000), (1 << realbits));
> +		st->scale_avail[i][0] = (int)div_u64(scale, 1000000);
> +		div_s64_rem(scale, 1000000, &st->scale_avail[i][1]);
> +	}
> +}
> +
> +static int ad5766_reset(struct ad5766_state *st)
> +{
> +	int ret = 0;
> +
> +	if (st->gpio_reset) {
> +		gpiod_set_value_cansleep(st->gpio_reset, 0);
> +		ndelay(100); /* t_reset >= 100ns */
> +		gpiod_set_value_cansleep(st->gpio_reset, 1);
> +	} else {
> +		ret = _ad5766_spi_write(st, AD5766_CMD_SW_FULL_RESET,
> +					AD5766_FULL_RESET_CODE);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	/*
> +	 * Minimum time between a reset and the subsequent successful write is
> +	 * typically 25 ns
> +	 */
> +	ndelay(25);
> +
> +	return 0;
> +}
> +
> +static int ad5766_default_setup(struct ad5766_state *st,
> +	enum ad5766_voltage_range range)
> +{
> +	int ret;
> +
> +	/* Always issue a software reset before writing to the span register. */
> +	ret = ad5766_reset(st);
> +	if (ret)
> +		return ret;
> +
> +	ret = _ad5766_spi_write(st, AD5766_CMD_SPAN_REG, range);
> +	if (ret)
> +		return ret;
> +
> +	st->crt_range = range;
> +	st->cached_offset = range;
> +
> +	st->dither_power_ctrl = 0;
> +	ret = _ad5766_spi_write(st, AD5766_CMD_WR_PWR_DITHER,
> +			     st->dither_power_ctrl);
> +	if (ret)
> +		return ret;
> +
> +	st->dither_source = 0;
> +	ret = _ad5766_spi_write(st, AD5766_CMD_DITHER_SIG_1,
> +			  st->dither_source & 0xFFFF);
> +	if (ret)
> +		return ret;
> +
> +	ret = _ad5766_spi_write(st, AD5766_CMD_DITHER_SIG_2,
> +			  (st->dither_source >> 16) & 0xFFFF);
> +	if (ret)
> +		return ret;
> +
> +	st->dither_scale = 0;
> +	ret = _ad5766_spi_write(st, AD5766_CMD_DITHER_SCALE_1,
> +			  st->dither_scale & 0xFFFF);
> +	if (ret)
> +		return ret;
> +
> +	ret = _ad5766_spi_write(st, AD5766_CMD_DITHER_SCALE_2,
> +			  (st->dither_scale >> 16) & 0xFFFF);
> +	if (ret)
> +		return ret;
> +
> +	st->dither_invert = 0;
> +	ret = _ad5766_spi_write(st, AD5766_CMD_INV_DITHER,
> +			     st->dither_invert);
> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +static int ad5766_set_offset(struct ad5766_state *st, int val, int val2)
> +{
> +	int i;
> +	s32 (*tbl)[AD5766_VOLTAGE_RANGE_MAX][2] = &(st->offset_avail);
> +
> +	for (i = 0; i < AD5766_VOLTAGE_RANGE_MAX; i++) {
> +		if ((*tbl)[i][0] == val && (*tbl)[i][1] == val2) {
> +			st->cached_offset = i;
> +			return 0;
> +		}
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int ad5766_set_scale(struct ad5766_state *st, int val, int val2)
> +{
> +	int i;
> +	enum ad5766_voltage_range offset_idx = st->cached_offset;
> +	s32 (*offset_tbl)[AD5766_VOLTAGE_RANGE_MAX][2] = &(st->offset_avail);
> +	s32 (*scale_tbl)[AD5766_VOLTAGE_RANGE_MAX][2] = &(st->scale_avail);
> +
> +	for (i = 0; i < AD5766_VOLTAGE_RANGE_MAX; i++) {
> +		if ((*scale_tbl)[i][0] != val || (*scale_tbl)[i][1] != val2)
> +			continue;
> +
> +		if ((*offset_tbl)[i][0] != (*offset_tbl)[offset_idx][0] ||
> +			(*offset_tbl)[i][1] != (*offset_tbl)[offset_idx][1])
> +			continue;
> +
> +		return ad5766_default_setup(st, i);
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int ad5766_write_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int val,
> +			    int val2,
> +			    long info)
> +{
> +	struct ad5766_state *st = iio_priv(indio_dev);
> +	const int max_val = (1 << chan->scan_type.realbits);

Only used in the INFO_RAW path so move it down there.

> +
> +	switch (info) {
> +	case IIO_CHAN_INFO_RAW:
> +		if (val >= max_val || val < 0)
> +			return -EINVAL;
> +		val <<= chan->scan_type.shift;
> +		return ad5766_write(indio_dev, chan->address, val);
> +	case IIO_CHAN_INFO_OFFSET:
> +		return ad5766_set_offset(st, val, val2);
> +	case IIO_CHAN_INFO_SCALE:
> +		return ad5766_set_scale(st, val, val2);
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int _ad5766_spi_read(struct ad5766_state *st, u8 dac, int *val)
> +{
> +	int ret;
> +	struct spi_transfer xfers[] = {
> +		{
> +			.tx_buf = &st->data[0].d32,
> +			.bits_per_word = 8,
> +			.len = 3,
> +			.cs_change = 1,
> +		}, {
> +			.tx_buf = &st->data[1].d32,
> +			.rx_buf = &st->data[2].d32,
> +			.bits_per_word = 8,
> +			.len = 3,
> +		},
> +	};
> +
> +	st->data[0].d32 = AD5766_CMD_READBACK_REG(dac);
> +	st->data[1].d32 = AD5766_CMD_NOP_MUX_OUT;
> +
> +	ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
> +

no blank line here.  Keep the error handling in the same visual block
as the call that returned the error.

> +	if (ret)
> +		return ret;
> +
> +	*val = st->data[2].w16[1];
> +
> +	return ret;
> +}
> +
> +static int ad5766_read(struct iio_dev *indio_dev, u8 dac, int *val)
> +{
> +	struct ad5766_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	mutex_lock(&st->lock);
> +	ret = _ad5766_spi_read(st, dac, val);
> +	mutex_unlock(&st->lock);
> +
> +	return ret;
> +}
> +
> +static ssize_t ad5766_write_ext(struct iio_dev *indio_dev,
> +				 uintptr_t private,
> +				 const struct iio_chan_spec *chan,
> +				 const char *buf, size_t len)
> +{
> +	bool readin;
> +	int ret;
> +	struct ad5766_state *st = iio_priv(indio_dev);
> +
> +	ret = kstrtobool(buf, &readin);
> +	if (ret)
> +		return ret;
> +
> +	switch ((u32)private) {
> +	case AD5766_DITHER_PWR:
> +		ret = kstrtobool(buf, &readin);
> +		if (ret)
> +			break;
> +		readin = !readin;
> +		st->dither_power_ctrl = (st->dither_power_ctrl &
> +					 ~BIT(chan->channel)) |
> +					 (readin << chan->channel);
> +		ret = ad5766_write(indio_dev, AD5766_CMD_WR_PWR_DITHER,
> +			     st->dither_power_ctrl);
> +		break;
> +	case AD5766_DITHER_INVERT:
> +		st->dither_invert = (st->dither_invert &
> +						~BIT(chan->channel)) |
> +						(readin << chan->channel);
> +		ret = ad5766_write(indio_dev, AD5766_CMD_INV_DITHER,
> +				st->dither_power_ctrl);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +		break;
> +	}
> +
> +	return ret ? ret : len;
> +}
> +
> +static int ad5766_get_dither_source(struct iio_dev *dev,
> +				    const struct iio_chan_spec *chan)
> +{
> +	struct ad5766_state *st = iio_priv(dev);
> +
> +	return (st->dither_source >> (chan->channel * 2) & 0x03);
> +}
> +
> +static int ad5766_set_dither_source(struct iio_dev *dev,
> +			  const struct iio_chan_spec *chan,
> +			  unsigned int mode)
> +{
> +	int ret;
> +	struct ad5766_state *st = iio_priv(dev);
> +
> +	st->dither_source = (st->dither_source & ~(0x03 << (chan->channel * 2)))
> +			    | (mode << (chan->channel * 2));
> +
> +	ret = ad5766_write(dev, AD5766_CMD_DITHER_SIG_1,
> +			  st->dither_source & 0xFFFF);
> +	if (ret)
> +		return ret;
> +
> +	return ad5766_write(dev, AD5766_CMD_DITHER_SIG_2,
> +			  (st->dither_source >> 16) & 0xFFFF);
> +}
> +
> +static int ad5766_get_dither_scale(struct iio_dev *dev,
> +				   const struct iio_chan_spec *chan)
> +{
> +	struct ad5766_state *st = iio_priv(dev);
> +
> +	return (st->dither_scale >> (chan->channel * 2) & 0x03);
> +}
> +
> +static int ad5766_set_dither_scale(struct iio_dev *dev,
> +			  const struct iio_chan_spec *chan,
> +			  unsigned int scale)
> +{
> +	int ret;
> +	struct ad5766_state *st = iio_priv(dev);
> +
> +	st->dither_scale = (st->dither_scale & ~(0x03 << (chan->channel * 2)))

0x03 looks like a mask?  If so define it as such with GENMASK()

> +			    | (scale << (chan->channel * 2));
> +
> +	ret = ad5766_write(dev, AD5766_CMD_DITHER_SCALE_1,
> +			  st->dither_scale & 0xFFFF);

Another mask, define it clearly with GENMASK() so that's self documenting.
Same in other places.
Looks like good places to use FIELD_PREP() etc.


> +	if (ret)
> +		return ret;
> +
> +	return ad5766_write(dev, AD5766_CMD_DITHER_SCALE_2,
> +			  (st->dither_scale >> 16) & 0xFFFF);
> +}
> +
> +static ssize_t ad5766_read_ext(struct iio_dev *indio_dev,
> +			       uintptr_t private,
> +			       const struct iio_chan_spec *chan,
> +			       char *buf)
> +{
> +	int ret;
> +	struct ad5766_state *st = iio_priv(indio_dev);
> +
> +	switch ((u32)private) {
> +	case AD5766_DITHER_PWR:
> +		return sprintf(buf, "%u\n", 0x01 &
> +			       ~(st->dither_power_ctrl >> chan->channel));
> +		break;
> +	case AD5766_DITHER_INVERT:
> +		return sprintf(buf, "%u\n", 0x01 &
> +			       (st->dither_invert >> chan->channel));
> +		break;
> +	default:
> +		ret = -EINVAL;
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
> +static int ad5766_read_avail(struct iio_dev *indio_dev,
> +				 struct iio_chan_spec const *chan,
> +				 const int **vals, int *type, int *length,
> +				 long mask)
> +{
> +	struct ad5766_state *st = iio_priv(indio_dev);
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SCALE:
> +		*vals = (int *)st->scale_avail;

int might not have the same size as s32 which would make this
exciting.  I'd change the definition of scale_avail to int [][]

> +		*type = IIO_VAL_INT_PLUS_MICRO;
> +		/* Values are stored in a 2D matrix  */
> +		*length = AD5766_VOLTAGE_RANGE_MAX * 2;
> +
> +		return IIO_AVAIL_LIST;
> +	case IIO_CHAN_INFO_OFFSET:
> +		*vals = (int *)st->offset_avail;
> +		*type = IIO_VAL_INT_PLUS_MICRO;
> +		/* Values are stored in a 2D matrix  */
> +		*length = AD5766_VOLTAGE_RANGE_MAX * 2;
> +
> +		return IIO_AVAIL_LIST;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int ad5766_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan,
> +			   int *val,
> +			   int *val2,
> +			   long m)
> +{
> +	int ret;
> +	struct ad5766_state *st = iio_priv(indio_dev);
> +
> +	switch (m) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = ad5766_read(indio_dev, chan->address, val);
> +		if (ret)
> +			return ret;
> +
> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = st->scale_avail[st->crt_range][0];
> +		*val2 = st->scale_avail[st->crt_range][1];
> +
> +		return IIO_VAL_INT_PLUS_MICRO;
> +
> +	case IIO_CHAN_INFO_OFFSET:
> +		*val = st->offset_avail[st->crt_range][0];
> +		*val2 = st->offset_avail[st->crt_range][1];
> +
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int ad5766_probe(struct spi_device *spi)
> +{
> +	enum ad5766_type type = spi_get_device_id(spi)->driver_data;

That spi_get_device_id is non trivial enough I'd prefer to see this
not hidden away in the declarations block.  Move it down to just above
where it is used perhaps?

> +	struct iio_dev *indio_dev;
> +	struct ad5766_state *st;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	st = iio_priv(indio_dev);
> +	spi_set_drvdata(spi, indio_dev);

Can't see where this is used.

> +
> +	mutex_init(&st->lock);
> +
> +	st->spi = spi;
> +	st->chip_info = &ad5766_chip_infos[type];
> +
> +	indio_dev->channels = st->chip_info->channels;
> +	indio_dev->num_channels = st->chip_info->num_channels;
> +	indio_dev->info = &ad5766_info;
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->dev.of_node = spi->dev.of_node;
> +	indio_dev->name = spi_get_device_id(spi)->name;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +
> +	st->gpio_reset = devm_gpiod_get_optional(&st->spi->dev, "reset",
> +						GPIOD_OUT_HIGH);
> +
> +	ad5766_init_scale_tables(st);
> +
> +	ret = ad5766_default_setup(st, AD5766_VOLTAGE_RANGE_M5V_to_5V);
> +	if (ret)
> +		return ret;
> +
> +	return devm_iio_device_register(&spi->dev, indio_dev);
> +}
> +
> +static const struct of_device_id ad5766_dt_match[] = {
> +	{ .compatible = "adi,ad5766" },
> +	{ .compatible = "adi,ad5767" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, ad5766_dt_match);
> +
> +static const struct spi_device_id ad5766_spi_ids[] = {
> +	{ "ad5766", ID_AD5766 },
> +	{ "ad5767", ID_AD5767 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(spi, ad5766_spi_ids);
> +
> +static struct spi_driver ad5766_driver = {
> +	.driver = {
> +		.name = "ad5766",
> +		.of_match_table = ad5766_dt_match,
> +	},
> +	.probe = ad5766_probe,
> +	.id_table = ad5766_spi_ids,
> +};
> +module_spi_driver(ad5766_driver);
> +
> +MODULE_AUTHOR("Denis-Gabriel Gheorghescu <denis.gheorghescu@xxxxxxxxxx>");
> +MODULE_DESCRIPTION("Analog Devices AD5766/AD5767 DACs");
> +MODULE_LICENSE("GPL v2");