max5432.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * Maxim Integrated MAX5432-MAX5435 digital potentiometer driver
  4 * Copyright (C) 2019 Martin Kaiser <martin@kaiser.cx>
  5 *
  6 * Datasheet:
  7 * https://datasheets.maximintegrated.com/en/ds/MAX5432-MAX5435.pdf
  8 */
  9
 10#include <linux/i2c.h>
 11#include <linux/iio/iio.h>
 12#include <linux/limits.h>
 13#include <linux/module.h>
 14#include <linux/mod_devicetable.h>
 15#include <linux/property.h>
 16
 17/* All chip variants have 32 wiper positions. */
 18#define MAX5432_MAX_POS 31
 19
 20#define MAX5432_OHM_50K   (50  * 1000)
 21#define MAX5432_OHM_100K  (100 * 1000)
 22
 23/* Update the volatile (currently active) setting. */
 24#define MAX5432_CMD_VREG  0x11
 25
 26struct max5432_data {
 27	struct i2c_client *client;
 28	unsigned long ohm;
 29};
 30
 31static const struct iio_chan_spec max5432_channels[] = {
 32	{
 33		.type = IIO_RESISTANCE,
 34		.indexed = 1,
 35		.output = 1,
 36		.channel = 0,
 37		.address = MAX5432_CMD_VREG,
 38		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
 39		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
 40	}
 41};
 42
 43static int max5432_read_raw(struct iio_dev *indio_dev,
 44			struct iio_chan_spec const *chan,
 45			int *val, int *val2, long mask)
 46{
 47	struct max5432_data *data = iio_priv(indio_dev);
 48
 49	if (mask != IIO_CHAN_INFO_SCALE)
 50		return -EINVAL;
 51
 52	if (unlikely(data->ohm > INT_MAX))
 53		return -ERANGE;
 54
 55	*val = data->ohm;
 56	*val2 = MAX5432_MAX_POS;
 57
 58	return IIO_VAL_FRACTIONAL;
 59}
 60
 61static int max5432_write_raw(struct iio_dev *indio_dev,
 62			struct iio_chan_spec const *chan,
 63			int val, int val2, long mask)
 64{
 65	struct max5432_data *data = iio_priv(indio_dev);
 66	u8 data_byte;
 67
 68	if (mask != IIO_CHAN_INFO_RAW)
 69		return -EINVAL;
 70
 71	if (val < 0 || val > MAX5432_MAX_POS)
 72		return -EINVAL;
 73
 74	if (val2 != 0)
 75		return -EINVAL;
 76
 77	/* Wiper position is in bits D7-D3. (D2-D0 are don't care bits.) */
 78	data_byte = val << 3;
 79	return i2c_smbus_write_byte_data(data->client, chan->address,
 80			data_byte);
 81}
 82
 83static const struct iio_info max5432_info = {
 84	.read_raw = max5432_read_raw,
 85	.write_raw = max5432_write_raw,
 86};
 87
 88static int max5432_probe(struct i2c_client *client)
 89{
 90	struct device *dev = &client->dev;
 91	struct iio_dev *indio_dev;
 92	struct max5432_data *data;
 93
 94	indio_dev = devm_iio_device_alloc(dev, sizeof(struct max5432_data));
 95	if (!indio_dev)
 96		return -ENOMEM;
 97
 98	i2c_set_clientdata(client, indio_dev);
 99
100	data = iio_priv(indio_dev);
101	data->client = client;
102	data->ohm = (unsigned long)device_get_match_data(dev);
103
104	indio_dev->info = &max5432_info;
105	indio_dev->channels = max5432_channels;
106	indio_dev->num_channels = ARRAY_SIZE(max5432_channels);
107	indio_dev->name = client->name;
108
109	return devm_iio_device_register(dev, indio_dev);
110}
111
112static const struct of_device_id max5432_dt_ids[] = {
113	{ .compatible = "maxim,max5432", .data = (void *)MAX5432_OHM_50K  },
114	{ .compatible = "maxim,max5433", .data = (void *)MAX5432_OHM_100K },
115	{ .compatible = "maxim,max5434", .data = (void *)MAX5432_OHM_50K  },
116	{ .compatible = "maxim,max5435", .data = (void *)MAX5432_OHM_100K },
117	{ }
118};
119MODULE_DEVICE_TABLE(of, max5432_dt_ids);
120
121static struct i2c_driver max5432_driver = {
122	.driver = {
123		.name = "max5432",
124		.of_match_table = max5432_dt_ids,
125	},
126	.probe = max5432_probe,
127};
128
129module_i2c_driver(max5432_driver);
130
131MODULE_AUTHOR("Martin Kaiser <martin@kaiser.cx>");
132MODULE_DESCRIPTION("max5432-max5435 digital potentiometers");
133MODULE_LICENSE("GPL v2");