LXR linux/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
  44static 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
  92static 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
 105static const struct iio_info si7020_info = {
 106        .read_raw = si7020_read_raw,
 107        .driver_module = THIS_MODULE,
 108};
 109
 110static 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(*client));
 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
 146static const struct i2c_device_id si7020_id[] = {
 147        { "si7020", 0 },
 148        { }
 149};
 150MODULE_DEVICE_TABLE(i2c, si7020_id);
 151
 152static struct i2c_driver si7020_driver = {
 153        .driver.name    = "si7020",
 154        .probe          = si7020_probe,
 155        .id_table       = si7020_id,
 156};
 157
 158module_i2c_driver(si7020_driver);
 159MODULE_DESCRIPTION("Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors");
 160MODULE_AUTHOR("David Barksdale <dbarksdale@uplogix.com>");
 161MODULE_LICENSE("GPL");
 162