/*
 * Maxim Integrated DS1803 digital potentiometer driver
 * Copyright (c) 2016 Slawomir Stepien
 *
 * Datasheet: https://datasheets.maximintegrated.com/en/ds/DS1803.pdf
 *
 * DEVID	#Wipers	#Positions	Resistor Opts (kOhm)	i2c address
 * ds1803	2	256		10, 50, 100		0101xxx
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 */

#include <linux/err.h>
#include <linux/export.h>
#include <linux/i2c.h>
#include <linux/iio/iio.h>
#include <linux/module.h>
#include <linux/of.h>

#define DS1803_MAX_POS		255
#define DS1803_WRITE(chan)	(0xa8 | ((chan) + 1))

enum ds1803_type {
	DS1803_010,
	DS1803_050,
	DS1803_100,
};

struct ds1803_cfg {
	int kohms;
};

static const struct ds1803_cfg ds1803_cfg[] = {
	[DS1803_010] = { .kohms =  10, },
	[DS1803_050] = { .kohms =  50, },
	[DS1803_100] = { .kohms = 100, },
};

struct ds1803_data {
	struct i2c_client *client;
	const struct ds1803_cfg *cfg;
};

#define DS1803_CHANNEL(ch) {					\
	.type = IIO_RESISTANCE,					\
	.indexed = 1,						\
	.output = 1,						\
	.channel = (ch),					\
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
}

static const struct iio_chan_spec ds1803_channels[] = {
	DS1803_CHANNEL(0),
	DS1803_CHANNEL(1),
};

static int ds1803_read_raw(struct iio_dev *indio_dev,
			    struct iio_chan_spec const *chan,
			    int *val, int *val2, long mask)
{
	struct ds1803_data *data = iio_priv(indio_dev);
	int pot = chan->channel;
	int ret;
	u8 result[ARRAY_SIZE(ds1803_channels)];

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		ret = i2c_master_recv(data->client, result,
				indio_dev->num_channels);
		if (ret < 0)
			return ret;

		*val = result[pot];
		return IIO_VAL_INT;

	case IIO_CHAN_INFO_SCALE:
		*val = 1000 * data->cfg->kohms;
		*val2 = DS1803_MAX_POS;
		return IIO_VAL_FRACTIONAL;
	}

	return -EINVAL;
}

static int ds1803_write_raw(struct iio_dev *indio_dev,
			     struct iio_chan_spec const *chan,
			     int val, int val2, long mask)
{
	struct ds1803_data *data = iio_priv(indio_dev);
	int pot = chan->channel;

	if (val2 != 0)
		return -EINVAL;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		if (val > DS1803_MAX_POS || val < 0)
			return -EINVAL;
		break;
	default:
		return -EINVAL;
	}

	return i2c_smbus_write_byte_data(data->client, DS1803_WRITE(pot), val);
}

static const struct iio_info ds1803_info = {
	.read_raw = ds1803_read_raw,
	.write_raw = ds1803_write_raw,
};

static int ds1803_probe(struct i2c_client *client,
			 const struct i2c_device_id *id)
{
	struct device *dev = &client->dev;
	struct ds1803_data *data;
	struct iio_dev *indio_dev;

	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
	if (!indio_dev)
		return -ENOMEM;

	i2c_set_clientdata(client, indio_dev);

	data = iio_priv(indio_dev);
	data->client = client;
	data->cfg = &ds1803_cfg[id->driver_data];

	indio_dev->dev.parent = dev;
	indio_dev->info = &ds1803_info;
	indio_dev->channels = ds1803_channels;
	indio_dev->num_channels = ARRAY_SIZE(ds1803_channels);
	indio_dev->name = client->name;

	return devm_iio_device_register(dev, indio_dev);
}

#if defined(CONFIG_OF)
static const struct of_device_id ds1803_dt_ids[] = {
	{ .compatible = "maxim,ds1803-010", .data = &ds1803_cfg[DS1803_010] },
	{ .compatible = "maxim,ds1803-050", .data = &ds1803_cfg[DS1803_050] },
	{ .compatible = "maxim,ds1803-100", .data = &ds1803_cfg[DS1803_100] },
	{}
};
MODULE_DEVICE_TABLE(of, ds1803_dt_ids);
#endif /* CONFIG_OF */

static const struct i2c_device_id ds1803_id[] = {
	{ "ds1803-010", DS1803_010 },
	{ "ds1803-050", DS1803_050 },
	{ "ds1803-100", DS1803_100 },
	{}
};
MODULE_DEVICE_TABLE(i2c, ds1803_id);

static struct i2c_driver ds1803_driver = {
	.driver = {
		.name	= "ds1803",
		.of_match_table = of_match_ptr(ds1803_dt_ids),
	},
	.probe		= ds1803_probe,
	.id_table	= ds1803_id,
};

module_i2c_driver(ds1803_driver);

MODULE_AUTHOR("Slawomir Stepien <sst@poczta.fm>");
MODULE_DESCRIPTION("DS1803 digital potentiometer");
MODULE_LICENSE("GPL v2");