drivers/iio/potentiometer/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
  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                 const struct i2c_device_id *id)
  90 {
  91         struct device *dev = &client->dev;
  92         struct iio_dev *indio_dev;
  93         struct max5432_data *data;
  94
  95         indio_dev = devm_iio_device_alloc(dev, sizeof(struct max5432_data));
  96         if (!indio_dev)
  97                 return -ENOMEM;
  98
  99         i2c_set_clientdata(client, indio_dev);
 100
 101         data = iio_priv(indio_dev);
 102         data->client = client;
 103         data->ohm = (unsigned long)device_get_match_data(dev);
 104
 105         indio_dev->info = &max5432_info;
 106         indio_dev->channels = max5432_channels;
 107         indio_dev->num_channels = ARRAY_SIZE(max5432_channels);
 108         indio_dev->name = client->name;
 109
 110         return devm_iio_device_register(dev, indio_dev);
 111 }
 112
 113 static const struct of_device_id max5432_dt_ids[] = {
 114         { .compatible = "maxim,max5432", .data = (void *)MAX5432_OHM_50K  },
 115         { .compatible = "maxim,max5433", .data = (void *)MAX5432_OHM_100K },
 116         { .compatible = "maxim,max5434", .data = (void *)MAX5432_OHM_50K  },
 117         { .compatible = "maxim,max5435", .data = (void *)MAX5432_OHM_100K },
 118         { /* sentinel */ }
 119 };
 120 MODULE_DEVICE_TABLE(of, max5432_dt_ids);
 121
 122 static struct i2c_driver max5432_driver = {
 123         .driver = {
 124                 .name = "max5432",
 125                 .of_match_table = max5432_dt_ids,
 126         },
 127         .probe = max5432_probe,
 128 };
 129
 130 module_i2c_driver(max5432_driver);
 131
 132 MODULE_AUTHOR("Martin Kaiser <martin@kaiser.cx>");
 133 MODULE_DESCRIPTION("max5432-max5435 digital potentiometers");
 134 MODULE_LICENSE("GPL v2");