drivers/iio/humidity/si7020.c

   1 /*
   2  * si7020.c - Silicon Labs Si7013/20/21 Relative Humidity and Temp Sensors
   3  * Copyright (c) 2013,2014  Uplogix, Inc.
   4  * David Barksdale <dbarksdale@uplogix.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms and conditions of the GNU General Public License,
   8  * version 2, as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  */
  15
  16 /*
  17  * The Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors
  18  * are i2c devices which have an identical programming interface for
  19  * measuring relative humidity and temperature. The Si7013 has an additional
  20  * temperature input which this driver does not support.
  21  *
  22  * Data Sheets:
  23  *   Si7013: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7013.pdf
  24  *   Si7020: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7020.pdf
  25  *   Si7021: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7021.pdf
  26  */
  27
  28 #include <linux/delay.h>
  29 #include <linux/i2c.h>
  30 #include <linux/module.h>
  31 #include <linux/slab.h>
  32 #include <linux/sysfs.h>
  33
  34 #include <linux/iio/iio.h>
  35 #include <linux/iio/sysfs.h>
  36
  37 /* Measure Relative Humidity, Hold Master Mode */
  38 #define SI7020CMD_RH_HOLD       0xE5
  39 /* Measure Temperature, Hold Master Mode */
  40 #define SI7020CMD_TEMP_HOLD     0xE3
  41 /* Software Reset */
  42 #define SI7020CMD_RESET         0xFE
  43
  44 static int si7020_read_raw(struct iio_dev *indio_dev,
  45                            struct iio_chan_spec const *chan, int *val,
  46                            int *val2, long mask)
  47 {
  48         struct i2c_client **client = iio_priv(indio_dev);
  49         int ret;
  50
  51         switch (mask) {
  52         case IIO_CHAN_INFO_RAW:
  53                 ret = i2c_smbus_read_word_data(*client,
  54                                                chan->type == IIO_TEMP ?
  55                                                SI7020CMD_TEMP_HOLD :
  56                                                SI7020CMD_RH_HOLD);
  57                 if (ret < 0)
  58                         return ret;
  59                 *val = ret >> 2;
  60                 if (chan->type == IIO_HUMIDITYRELATIVE)
  61                         *val &= GENMASK(11, 0);
  62                 return IIO_VAL_INT;
  63         case IIO_CHAN_INFO_SCALE:
  64                 if (chan->type == IIO_TEMP)
  65                         *val = 175720; /* = 175.72 * 1000 */
  66                 else
  67                         *val = 125 * 1000;
  68                 *val2 = 65536 >> 2;
  69                 return IIO_VAL_FRACTIONAL;
  70         case IIO_CHAN_INFO_OFFSET:
  71                 /*
  72                  * Since iio_convert_raw_to_processed_unlocked assumes offset
  73                  * is an integer we have to round these values and lose
  74                  * accuracy.
  75                  * Relative humidity will be 0.0032959% too high and
  76                  * temperature will be 0.00277344 degrees too high.
  77                  * This is no big deal because it's within the accuracy of the
  78                  * sensor.
  79                  */
  80                 if (chan->type == IIO_TEMP)
  81                         *val = -4368; /* = -46.85 * (65536 >> 2) / 175.72 */
  82                 else
  83                         *val = -786; /* = -6 * (65536 >> 2) / 125 */
  84                 return IIO_VAL_INT;
  85         default:
  86                 break;
  87         }
  88
  89         return -EINVAL;
  90 }
  91
  92 static const struct iio_chan_spec si7020_channels[] = {
  93         {
  94                 .type = IIO_HUMIDITYRELATIVE,
  95                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
  96                         BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
  97         },
  98         {
  99                 .type = IIO_TEMP,
 100                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
 101                         BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
 102         }
 103 };
 104
 105 static const struct iio_info si7020_info = {
 106         .read_raw = si7020_read_raw,
 107         .driver_module = THIS_MODULE,
 108 };
 109
 110 static int si7020_probe(struct i2c_client *client,
 111                         const struct i2c_device_id *id)
 112 {
 113         struct iio_dev *indio_dev;
 114         struct i2c_client **data;
 115         int ret;
 116
 117         if (!i2c_check_functionality(client->adapter,
 118                                      I2C_FUNC_SMBUS_WRITE_BYTE |
 119                                      I2C_FUNC_SMBUS_READ_WORD_DATA))
 120                 return -ENODEV;
 121
 122         /* Reset device, loads default settings. */
 123         ret = i2c_smbus_write_byte(client, SI7020CMD_RESET);
 124         if (ret < 0)
 125                 return ret;
 126         /* Wait the maximum power-up time after software reset. */
 127         msleep(15);
 128
 129         indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
 130         if (!indio_dev)
 131                 return -ENOMEM;
 132
 133         data = iio_priv(indio_dev);
 134         *data = client;
 135
 136         indio_dev->dev.parent = &client->dev;
 137         indio_dev->name = dev_name(&client->dev);
 138         indio_dev->modes = INDIO_DIRECT_MODE;
 139         indio_dev->info = &si7020_info;
 140         indio_dev->channels = si7020_channels;
 141         indio_dev->num_channels = ARRAY_SIZE(si7020_channels);
 142
 143         return devm_iio_device_register(&client->dev, indio_dev);
 144 }
 145
 146 static const struct i2c_device_id si7020_id[] = {
 147         { "si7020", 0 },
 148         { }
 149 };
 150 MODULE_DEVICE_TABLE(i2c, si7020_id);
 151
 152 static struct i2c_driver si7020_driver = {
 153         .driver.name    = "si7020",
 154         .probe          = si7020_probe,
 155         .id_table       = si7020_id,
 156 };
 157
 158 module_i2c_driver(si7020_driver);
 159 MODULE_DESCRIPTION("Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors");
 160 MODULE_AUTHOR("David Barksdale <dbarksdale@uplogix.com>");
 161 MODULE_LICENSE("GPL");