iio: potentiometer: add a driver for Maxim 5432-5435

	  To compile this driver as a module, choose M here: the

	  module will be called ds1803.

config MAX5432

	tristate "Maxim MAX5432-MAX5435 Digital Potentiometer driver"

	depends on I2C

	help

	  Say yes here to build support for the Maxim

	  MAX5432, MAX5433, MAX5434 and MAX5435 digital

	  potentiometer chips.

	  To compile this driver as a module, choose M here: the

	  module will be called max5432.

config MAX5481

	tristate "Maxim MAX5481-MAX5484 Digital Potentiometer driver"

	depends on SPI

# When adding new entries keep the list in alphabetical order

obj-$(CONFIG_AD5272) += ad5272.o

obj-$(CONFIG_DS1803) += ds1803.o

obj-$(CONFIG_MAX5432) += max5432.o

obj-$(CONFIG_MAX5481) += max5481.o

obj-$(CONFIG_MAX5487) += max5487.o

obj-$(CONFIG_MCP4018) += mcp4018.o

// SPDX-License-Identifier: GPL-2.0-or-later

/*

 * Maxim Integrated MAX5432-MAX5435 digital potentiometer driver

 * Copyright (C) 2019 Martin Kaiser <martin@kaiser.cx>

 *

 * Datasheet:

 * https://datasheets.maximintegrated.com/en/ds/MAX5432-MAX5435.pdf

 */

#include <linux/i2c.h>

#include <linux/iio/iio.h>

#include <linux/limits.h>

#include <linux/module.h>

#include <linux/of.h>

#include <linux/of_device.h>

/* All chip variants have 32 wiper positions. */

#define MAX5432_MAX_POS 31

#define MAX5432_OHM_50K   (50  * 1000)

#define MAX5432_OHM_100K  (100 * 1000)

/* Update the volatile (currently active) setting. */

#define MAX5432_CMD_VREG  0x11

struct max5432_data {

	struct i2c_client *client;

	unsigned long ohm;

};

static const struct iio_chan_spec max5432_channels[] = {

	{

		.type = IIO_RESISTANCE,

		.indexed = 1,

		.output = 1,

		.channel = 0,

		.address = MAX5432_CMD_VREG,

		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),

		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),

	}

};

static int max5432_read_raw(struct iio_dev *indio_dev,

			struct iio_chan_spec const *chan,

			int *val, int *val2, long mask)

{

	struct max5432_data *data = iio_priv(indio_dev);

	if (mask != IIO_CHAN_INFO_SCALE)

		return -EINVAL;

	if (unlikely(data->ohm > INT_MAX))

		return -ERANGE;

	*val = data->ohm;

	*val2 = MAX5432_MAX_POS;

	return IIO_VAL_FRACTIONAL;

}

static int max5432_write_raw(struct iio_dev *indio_dev,

			struct iio_chan_spec const *chan,

			int val, int val2, long mask)

{

	struct max5432_data *data = iio_priv(indio_dev);

	u8 data_byte;

	if (mask != IIO_CHAN_INFO_RAW)

		return -EINVAL;

	if (val < 0 || val > MAX5432_MAX_POS)

		return -EINVAL;

	if (val2 != 0)

		return -EINVAL;

	/* Wiper position is in bits D7-D3. (D2-D0 are don't care bits.) */

	data_byte = val << 3;

	return i2c_smbus_write_byte_data(data->client, chan->address,

			data_byte);

}

static const struct iio_info max5432_info = {

	.read_raw = max5432_read_raw,

	.write_raw = max5432_write_raw,

};

static int max5432_probe(struct i2c_client *client,

		const struct i2c_device_id *id)

{

	struct device *dev = &client->dev;

	struct iio_dev *indio_dev;

	struct max5432_data *data;

	indio_dev = devm_iio_device_alloc(dev, sizeof(struct max5432_data));

	if (!indio_dev)

		return -ENOMEM;

	i2c_set_clientdata(client, indio_dev);

	data = iio_priv(indio_dev);

	data->client = client;

	data->ohm = (unsigned long)of_device_get_match_data(dev);

	indio_dev->dev.parent = dev;

	indio_dev->info = &max5432_info;

	indio_dev->channels = max5432_channels;

	indio_dev->num_channels = ARRAY_SIZE(max5432_channels);

	indio_dev->name = client->name;

	return devm_iio_device_register(dev, indio_dev);

}

static const struct of_device_id max5432_dt_ids[] = {

	{ .compatible = "maxim,max5432", .data = (void *)MAX5432_OHM_50K  },

	{ .compatible = "maxim,max5433", .data = (void *)MAX5432_OHM_100K },

	{ .compatible = "maxim,max5434", .data = (void *)MAX5432_OHM_50K  },

	{ .compatible = "maxim,max5435", .data = (void *)MAX5432_OHM_100K },

	{ /* sentinel */ }

};

MODULE_DEVICE_TABLE(of, max5432_dt_ids);

static struct i2c_driver max5432_driver = {

	.driver = {

		.name = "max5432",

		.of_match_table = of_match_ptr(max5432_dt_ids),

	},

	.probe = max5432_probe,

};

module_i2c_driver(max5432_driver);

MODULE_AUTHOR("Martin Kaiser <martin@kaiser.cx>");

MODULE_DESCRIPTION("max5432-max5435 digital potentiometers");

MODULE_LICENSE("GPL v2");