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 
26 struct max5432_data {
27 	struct i2c_client *client;
28 	unsigned long ohm;
29 };
30 
31 static 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 
43 static 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 
61 static 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 
83 static const struct iio_info max5432_info = {
84 	.read_raw = max5432_read_raw,
85 	.write_raw = max5432_write_raw,
86 };
87 
88 static 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 
112 static 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 	{ /* sentinel */ }
118 };
119 MODULE_DEVICE_TABLE(of, max5432_dt_ids);
120 
121 static struct i2c_driver max5432_driver = {
122 	.driver = {
123 		.name = "max5432",
124 		.of_match_table = max5432_dt_ids,
125 	},
126 	.probe = max5432_probe,
127 };
128 
129 module_i2c_driver(max5432_driver);
130 
131 MODULE_AUTHOR("Martin Kaiser <martin@kaiser.cx>");
132 MODULE_DESCRIPTION("max5432-max5435 digital potentiometers");
133 MODULE_LICENSE("GPL v2");
134