/* Sensirion SHT3x-DIS humidity and temperature sensor driver.
 * The SHT3x comes in many different versions, this driver is for the
 * I2C version only.
 *
 * Copyright (C) 2016 Sensirion AG, Switzerland
 * Author: David Frey <david.frey@sensirion.com>
 * Author: Pascal Sachs <pascal.sachs@sensirion.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#include <asm/page.h>
#include <linux/crc8.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/jiffies.h>
#include <linux/platform_data/sht3x.h>

/* commands (high precision mode) */
static const unsigned char sht3x_cmd_measure_blocking_hpm[]    = { 0x2c, 0x06 };
static const unsigned char sht3x_cmd_measure_nonblocking_hpm[] = { 0x24, 0x00 };

/* commands (low power mode) */
static const unsigned char sht3x_cmd_measure_blocking_lpm[]    = { 0x2c, 0x10 };
static const unsigned char sht3x_cmd_measure_nonblocking_lpm[] = { 0x24, 0x16 };

/* commands for periodic mode */
static const unsigned char sht3x_cmd_measure_periodic_mode[]   = { 0xe0, 0x00 };
static const unsigned char sht3x_cmd_break[]                   = { 0x30, 0x93 };

/* commands for heater control */
static const unsigned char sht3x_cmd_heater_on[]               = { 0x30, 0x6d };
static const unsigned char sht3x_cmd_heater_off[]              = { 0x30, 0x66 };

/* other commands */
static const unsigned char sht3x_cmd_read_status_reg[]         = { 0xf3, 0x2d };
static const unsigned char sht3x_cmd_clear_status_reg[]        = { 0x30, 0x41 };

/* delays for non-blocking i2c commands, both in us */
#define SHT3X_NONBLOCKING_WAIT_TIME_HPM  15000
#define SHT3X_NONBLOCKING_WAIT_TIME_LPM   4000

#define SHT3X_WORD_LEN         2
#define SHT3X_CMD_LENGTH       2
#define SHT3X_CRC8_LEN         1
#define SHT3X_RESPONSE_LENGTH  6
#define SHT3X_CRC8_POLYNOMIAL  0x31
#define SHT3X_CRC8_INIT        0xFF
#define SHT3X_MIN_TEMPERATURE  -45000
#define SHT3X_MAX_TEMPERATURE  130000
#define SHT3X_MIN_HUMIDITY     0
#define SHT3X_MAX_HUMIDITY     100000

enum sht3x_chips {
        sht3x,
        sts3x,
};

enum sht3x_limits {
        limit_max = 0,
        limit_max_hyst,
        limit_min,
        limit_min_hyst,
};

DECLARE_CRC8_TABLE(sht3x_crc8_table);

/* periodic measure commands (high precision mode) */
static const char periodic_measure_commands_hpm[][SHT3X_CMD_LENGTH] = {
        /* 0.5 measurements per second */
        {0x20, 0x32},
        /* 1 measurements per second */
        {0x21, 0x30},
        /* 2 measurements per second */
        {0x22, 0x36},
        /* 4 measurements per second */
        {0x23, 0x34},
        /* 10 measurements per second */
        {0x27, 0x37},
};

/* periodic measure commands (low power mode) */
static const char periodic_measure_commands_lpm[][SHT3X_CMD_LENGTH] = {
        /* 0.5 measurements per second */
        {0x20, 0x2f},
        /* 1 measurements per second */
        {0x21, 0x2d},
        /* 2 measurements per second */
        {0x22, 0x2b},
        /* 4 measurements per second */
        {0x23, 0x29},
        /* 10 measurements per second */
        {0x27, 0x2a},
};

struct sht3x_limit_commands {
        const char read_command[SHT3X_CMD_LENGTH];
        const char write_command[SHT3X_CMD_LENGTH];
};

static const struct sht3x_limit_commands limit_commands[] = {
        /* temp1_max, humidity1_max */
        [limit_max] = { {0xe1, 0x1f}, {0x61, 0x1d} },
        /* temp_1_max_hyst, humidity1_max_hyst */
        [limit_max_hyst] = { {0xe1, 0x14}, {0x61, 0x16} },
        /* temp1_min, humidity1_min */
        [limit_min] = { {0xe1, 0x02}, {0x61, 0x00} },
        /* temp_1_min_hyst, humidity1_min_hyst */
        [limit_min_hyst] = { {0xe1, 0x09}, {0x61, 0x0B} },
};

#define SHT3X_NUM_LIMIT_CMD  ARRAY_SIZE(limit_commands)

static const u16 mode_to_update_interval[] = {
           0,
        2000,
        1000,
         500,
         250,
         100,
};

struct sht3x_data {
        struct i2c_client *client;
        struct mutex i2c_lock; /* lock for sending i2c commands */
        struct mutex data_lock; /* lock for updating driver data */

        u8 mode;
        const unsigned char *command;
        u32 wait_time;                  /* in us*/
        unsigned long last_update;      /* last update in periodic mode*/

        struct sht3x_platform_data setup;

        /*
         * cached values for temperature and humidity and limits
         * the limits arrays have the following order:
         * max, max_hyst, min, min_hyst
         */
        int temperature;
        int temperature_limits[SHT3X_NUM_LIMIT_CMD];
        u32 humidity;
        u32 humidity_limits[SHT3X_NUM_LIMIT_CMD];
};

static u8 get_mode_from_update_interval(u16 value)
{
        size_t index;
        u8 number_of_modes = ARRAY_SIZE(mode_to_update_interval);

        if (value == 0)
                return 0;

        /* find next faster update interval */
        for (index = 1; index < number_of_modes; index++) {
                if (mode_to_update_interval[index] <= value)
                        return index;
        }

        return number_of_modes - 1;
}

static int sht3x_read_from_command(struct i2c_client *client,
                                   struct sht3x_data *data,
                                   const char *command,
                                   char *buf, int length, u32 wait_time)
{
        int ret;

        mutex_lock(&data->i2c_lock);
        ret = i2c_master_send(client, command, SHT3X_CMD_LENGTH);

        if (ret != SHT3X_CMD_LENGTH) {
                ret = ret < 0 ? ret : -EIO;
                goto out;
        }

        if (wait_time)
                usleep_range(wait_time, wait_time + 1000);

        ret = i2c_master_recv(client, buf, length);
        if (ret != length) {
                ret = ret < 0 ? ret : -EIO;
                goto out;
        }

        ret = 0;
out:
        mutex_unlock(&data->i2c_lock);
        return ret;
}

static int sht3x_extract_temperature(u16 raw)
{
        /*
         * From datasheet:
         * T = -45 + 175 * ST / 2^16
         * Adapted for integer fixed point (3 digit) arithmetic.
         */
        return ((21875 * (int)raw) >> 13) - 45000;
}

static u32 sht3x_extract_humidity(u16 raw)
{
        /*
         * From datasheet:
         * RH = 100 * SRH / 2^16
         * Adapted for integer fixed point (3 digit) arithmetic.
         */
        return (12500 * (u32)raw) >> 13;
}

static struct sht3x_data *sht3x_update_client(struct device *dev)
{
        struct sht3x_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        u16 interval_ms = mode_to_update_interval[data->mode];
        unsigned long interval_jiffies = msecs_to_jiffies(interval_ms);
        unsigned char buf[SHT3X_RESPONSE_LENGTH];
        u16 val;
        int ret = 0;

        mutex_lock(&data->data_lock);
        /*
         * Only update cached readings once per update interval in periodic
         * mode. In single shot mode the sensor measures values on demand, so
         * every time the sysfs interface is called, a measurement is triggered.
         * In periodic mode however, the measurement process is handled
         * internally by the sensor and reading out sensor values only makes
         * sense if a new reading is available.
         */
        if (time_after(jiffies, data->last_update + interval_jiffies)) {
                ret = sht3x_read_from_command(client, data, data->command, buf,
                                              sizeof(buf), data->wait_time);
                if (ret)
                        goto out;

                val = be16_to_cpup((__be16 *)buf);
                data->temperature = sht3x_extract_temperature(val);
                val = be16_to_cpup((__be16 *)(buf + 3));
                data->humidity = sht3x_extract_humidity(val);
                data->last_update = jiffies;
        }

out:
        mutex_unlock(&data->data_lock);
        if (ret)
                return ERR_PTR(ret);

        return data;
}

/* sysfs attributes */
static ssize_t temp1_input_show(struct device *dev,
                                struct device_attribute *attr, char *buf)
{
        struct sht3x_data *data = sht3x_update_client(dev);

        if (IS_ERR(data))
                return PTR_ERR(data);

        return sprintf(buf, "%d\n", data->temperature);
}

static ssize_t humidity1_input_show(struct device *dev,
                                    struct device_attribute *attr, char *buf)
{
        struct sht3x_data *data = sht3x_update_client(dev);

        if (IS_ERR(data))
                return PTR_ERR(data);

        return sprintf(buf, "%u\n", data->humidity);
}

/*
 * limits_update must only be called from probe or with data_lock held
 */
static int limits_update(struct sht3x_data *data)
{
        int ret;
        u8 index;
        int temperature;
        u32 humidity;
        u16 raw;
        char buffer[SHT3X_RESPONSE_LENGTH];
        const struct sht3x_limit_commands *commands;
        struct i2c_client *client = data->client;

        for (index = 0; index < SHT3X_NUM_LIMIT_CMD; index++) {
                commands = &limit_commands[index];
                ret = sht3x_read_from_command(client, data,
                                              commands->read_command, buffer,
                                              SHT3X_RESPONSE_LENGTH, 0);

                if (ret)
                        return ret;

                raw = be16_to_cpup((__be16 *)buffer);
                temperature = sht3x_extract_temperature((raw & 0x01ff) << 7);
                humidity = sht3x_extract_humidity(raw & 0xfe00);
                data->temperature_limits[index] = temperature;
                data->humidity_limits[index] = humidity;
        }

        return ret;
}

static ssize_t temp1_limit_show(struct device *dev,
                                struct device_attribute *attr,
                                char *buf)
{
        struct sht3x_data *data = dev_get_drvdata(dev);
        u8 index = to_sensor_dev_attr(attr)->index;
        int temperature_limit = data->temperature_limits[index];

        return scnprintf(buf, PAGE_SIZE, "%d\n", temperature_limit);
}

static ssize_t humidity1_limit_show(struct device *dev,
                                    struct device_attribute *attr,
                                    char *buf)
{
        struct sht3x_data *data = dev_get_drvdata(dev);
        u8 index = to_sensor_dev_attr(attr)->index;
        u32 humidity_limit = data->humidity_limits[index];

        return scnprintf(buf, PAGE_SIZE, "%u\n", humidity_limit);
}

/*
 * limit_store must only be called with data_lock held
 */
static size_t limit_store(struct device *dev,
                          size_t count,
                          u8 index,
                          int temperature,
                          u32 humidity)
{
        char buffer[SHT3X_CMD_LENGTH + SHT3X_WORD_LEN + SHT3X_CRC8_LEN];
        char *position = buffer;
        int ret;
        u16 raw;
        struct sht3x_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        const struct sht3x_limit_commands *commands;

        commands = &limit_commands[index];

        memcpy(position, commands->write_command, SHT3X_CMD_LENGTH);
        position += SHT3X_CMD_LENGTH;
        /*
         * ST = (T + 45) / 175 * 2^16
         * SRH = RH / 100 * 2^16
         * adapted for fixed point arithmetic and packed the same as
         * in limit_show()
         */
        raw = ((u32)(temperature + 45000) * 24543) >> (16 + 7);
        raw |= ((humidity * 42950) >> 16) & 0xfe00;

        *((__be16 *)position) = cpu_to_be16(raw);
        position += SHT3X_WORD_LEN;
        *position = crc8(sht3x_crc8_table,
                         position - SHT3X_WORD_LEN,
                         SHT3X_WORD_LEN,
                         SHT3X_CRC8_INIT);

        mutex_lock(&data->i2c_lock);
        ret = i2c_master_send(client, buffer, sizeof(buffer));
        mutex_unlock(&data->i2c_lock);

        if (ret != sizeof(buffer))
                return ret < 0 ? ret : -EIO;

        data->temperature_limits[index] = temperature;
        data->humidity_limits[index] = humidity;
        return count;
}

static ssize_t temp1_limit_store(struct device *dev,
                                 struct device_attribute *attr,
                                 const char *buf,
                                 size_t count)
{
        int temperature;
        int ret;
        struct sht3x_data *data = dev_get_drvdata(dev);
        u8 index = to_sensor_dev_attr(attr)->index;

        ret = kstrtoint(buf, 0, &temperature);
        if (ret)
                return ret;

        temperature = clamp_val(temperature, SHT3X_MIN_TEMPERATURE,
                                SHT3X_MAX_TEMPERATURE);
        mutex_lock(&data->data_lock);
        ret = limit_store(dev, count, index, temperature,
                          data->humidity_limits[index]);
        mutex_unlock(&data->data_lock);

        return ret;
}

static ssize_t humidity1_limit_store(struct device *dev,
                                     struct device_attribute *attr,
                                     const char *buf,
                                     size_t count)
{
        u32 humidity;
        int ret;
        struct sht3x_data *data = dev_get_drvdata(dev);
        u8 index = to_sensor_dev_attr(attr)->index;

        ret = kstrtou32(buf, 0, &humidity);
        if (ret)
                return ret;

        humidity = clamp_val(humidity, SHT3X_MIN_HUMIDITY, SHT3X_MAX_HUMIDITY);
        mutex_lock(&data->data_lock);
        ret = limit_store(dev, count, index, data->temperature_limits[index],
                          humidity);
        mutex_unlock(&data->data_lock);

        return ret;
}

static void sht3x_select_command(struct sht3x_data *data)
{
        /*
         * In blocking mode (clock stretching mode) the I2C bus
         * is blocked for other traffic, thus the call to i2c_master_recv()
         * will wait until the data is ready. For non blocking mode, we
         * have to wait ourselves.
         */
        if (data->mode > 0) {
                data->command = sht3x_cmd_measure_periodic_mode;
                data->wait_time = 0;
        } else if (data->setup.blocking_io) {
                data->command = data->setup.high_precision ?
                                sht3x_cmd_measure_blocking_hpm :
                                sht3x_cmd_measure_blocking_lpm;
                data->wait_time = 0;
        } else {
                if (data->setup.high_precision) {
                        data->command = sht3x_cmd_measure_nonblocking_hpm;
                        data->wait_time = SHT3X_NONBLOCKING_WAIT_TIME_HPM;
                } else {
                        data->command = sht3x_cmd_measure_nonblocking_lpm;
                        data->wait_time = SHT3X_NONBLOCKING_WAIT_TIME_LPM;
                }
        }
}

static int status_register_read(struct device *dev,
                                struct device_attribute *attr,
                                char *buffer, int length)
{
        int ret;
        struct sht3x_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;

        ret = sht3x_read_from_command(client, data, sht3x_cmd_read_status_reg,
                                      buffer, length, 0);

        return ret;
}

static ssize_t temp1_alarm_show(struct device *dev,
                                struct device_attribute *attr,
                                char *buf)
{
        char buffer[SHT3X_WORD_LEN + SHT3X_CRC8_LEN];
        int ret;

        ret = status_register_read(dev, attr, buffer,
                                   SHT3X_WORD_LEN + SHT3X_CRC8_LEN);
        if (ret)
                return ret;

        return scnprintf(buf, PAGE_SIZE, "%d\n", !!(buffer[0] & 0x04));
}

static ssize_t humidity1_alarm_show(struct device *dev,
                                    struct device_attribute *attr,
                                    char *buf)
{
        char buffer[SHT3X_WORD_LEN + SHT3X_CRC8_LEN];
        int ret;

        ret = status_register_read(dev, attr, buffer,
                                   SHT3X_WORD_LEN + SHT3X_CRC8_LEN);
        if (ret)
                return ret;

        return scnprintf(buf, PAGE_SIZE, "%d\n", !!(buffer[0] & 0x08));
}

static ssize_t heater_enable_show(struct device *dev,
                                  struct device_attribute *attr,
                                  char *buf)
{
        char buffer[SHT3X_WORD_LEN + SHT3X_CRC8_LEN];
        int ret;

        ret = status_register_read(dev, attr, buffer,
                                   SHT3X_WORD_LEN + SHT3X_CRC8_LEN);
        if (ret)
                return ret;

        return scnprintf(buf, PAGE_SIZE, "%d\n", !!(buffer[0] & 0x20));
}

static ssize_t heater_enable_store(struct device *dev,
                                   struct device_attribute *attr,
                                   const char *buf,
                                   size_t count)
{
        struct sht3x_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        int ret;
        bool status;

        ret = kstrtobool(buf, &status);
        if (ret)
                return ret;

        mutex_lock(&data->i2c_lock);

        if (status)
                ret = i2c_master_send(client, (char *)&sht3x_cmd_heater_on,
                                      SHT3X_CMD_LENGTH);
        else
                ret = i2c_master_send(client, (char *)&sht3x_cmd_heater_off,
                                      SHT3X_CMD_LENGTH);

        mutex_unlock(&data->i2c_lock);

        return ret;
}

static ssize_t update_interval_show(struct device *dev,
                                    struct device_attribute *attr,
                                    char *buf)
{
        struct sht3x_data *data = dev_get_drvdata(dev);

        return scnprintf(buf, PAGE_SIZE, "%u\n",
                         mode_to_update_interval[data->mode]);
}

static ssize_t update_interval_store(struct device *dev,
                                     struct device_attribute *attr,
                                     const char *buf,
                                     size_t count)
{
        u16 update_interval;
        u8 mode;
        int ret;
        const char *command;
        struct sht3x_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;

        ret = kstrtou16(buf, 0, &update_interval);
        if (ret)
                return ret;

        mode = get_mode_from_update_interval(update_interval);

        mutex_lock(&data->data_lock);
        /* mode did not change */
        if (mode == data->mode) {
                mutex_unlock(&data->data_lock);
                return count;
        }

        mutex_lock(&data->i2c_lock);
        /*
         * Abort periodic measure mode.
         * To do any changes to the configuration while in periodic mode, we
         * have to send a break command to the sensor, which then falls back
         * to single shot (mode = 0).
         */
        if (data->mode > 0) {
                ret = i2c_master_send(client, sht3x_cmd_break,
                                      SHT3X_CMD_LENGTH);
                if (ret != SHT3X_CMD_LENGTH)
                        goto out;
                data->mode = 0;
        }

        if (mode > 0) {
                if (data->setup.high_precision)
                        command = periodic_measure_commands_hpm[mode - 1];
                else
                        command = periodic_measure_commands_lpm[mode - 1];

                /* select mode */
                ret = i2c_master_send(client, command, SHT3X_CMD_LENGTH);
                if (ret != SHT3X_CMD_LENGTH)
                        goto out;
        }

        /* select mode and command */
        data->mode = mode;
        sht3x_select_command(data);

out:
        mutex_unlock(&data->i2c_lock);
        mutex_unlock(&data->data_lock);
        if (ret != SHT3X_CMD_LENGTH)
                return ret < 0 ? ret : -EIO;

        return count;
}

static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, temp1_input_show, NULL, 0);
static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, humidity1_input_show,
                          NULL, 0);
static SENSOR_DEVICE_ATTR(temp1_max, S_IRUGO | S_IWUSR,
                          temp1_limit_show, temp1_limit_store,
                          limit_max);
static SENSOR_DEVICE_ATTR(humidity1_max, S_IRUGO | S_IWUSR,
                          humidity1_limit_show, humidity1_limit_store,
                          limit_max);
static SENSOR_DEVICE_ATTR(temp1_max_hyst, S_IRUGO | S_IWUSR,
                          temp1_limit_show, temp1_limit_store,
                          limit_max_hyst);
static SENSOR_DEVICE_ATTR(humidity1_max_hyst, S_IRUGO | S_IWUSR,
                          humidity1_limit_show, humidity1_limit_store,
                          limit_max_hyst);
static SENSOR_DEVICE_ATTR(temp1_min, S_IRUGO | S_IWUSR,
                          temp1_limit_show, temp1_limit_store,
                          limit_min);
static SENSOR_DEVICE_ATTR(humidity1_min, S_IRUGO | S_IWUSR,
                          humidity1_limit_show, humidity1_limit_store,
                          limit_min);
static SENSOR_DEVICE_ATTR(temp1_min_hyst, S_IRUGO | S_IWUSR,
                          temp1_limit_show, temp1_limit_store,
                          limit_min_hyst);
static SENSOR_DEVICE_ATTR(humidity1_min_hyst, S_IRUGO | S_IWUSR,
                          humidity1_limit_show, humidity1_limit_store,
                          limit_min_hyst);
static SENSOR_DEVICE_ATTR(temp1_alarm, S_IRUGO, temp1_alarm_show, NULL, 0);
static SENSOR_DEVICE_ATTR(humidity1_alarm, S_IRUGO, humidity1_alarm_show,
                          NULL, 0);
static SENSOR_DEVICE_ATTR(heater_enable, S_IRUGO | S_IWUSR,
                          heater_enable_show, heater_enable_store, 0);
static SENSOR_DEVICE_ATTR(update_interval, S_IRUGO | S_IWUSR,
                          update_interval_show, update_interval_store, 0);

static struct attribute *sht3x_attrs[] = {
        &sensor_dev_attr_temp1_input.dev_attr.attr,
        &sensor_dev_attr_humidity1_input.dev_attr.attr,
        &sensor_dev_attr_temp1_max.dev_attr.attr,
        &sensor_dev_attr_temp1_max_hyst.dev_attr.attr,
        &sensor_dev_attr_humidity1_max.dev_attr.attr,
        &sensor_dev_attr_humidity1_max_hyst.dev_attr.attr,
        &sensor_dev_attr_temp1_min.dev_attr.attr,
        &sensor_dev_attr_temp1_min_hyst.dev_attr.attr,
        &sensor_dev_attr_humidity1_min.dev_attr.attr,
        &sensor_dev_attr_humidity1_min_hyst.dev_attr.attr,
        &sensor_dev_attr_temp1_alarm.dev_attr.attr,
        &sensor_dev_attr_humidity1_alarm.dev_attr.attr,
        &sensor_dev_attr_heater_enable.dev_attr.attr,
        &sensor_dev_attr_update_interval.dev_attr.attr,
        NULL
};

static struct attribute *sts3x_attrs[] = {
        &sensor_dev_attr_temp1_input.dev_attr.attr,
        NULL
};

ATTRIBUTE_GROUPS(sht3x);
ATTRIBUTE_GROUPS(sts3x);

static int sht3x_probe(struct i2c_client *client,
                       const struct i2c_device_id *id)
{
        int ret;
        struct sht3x_data *data;
        struct device *hwmon_dev;
        struct i2c_adapter *adap = client->adapter;
        struct device *dev = &client->dev;
        const struct attribute_group **attribute_groups;

        /*
         * we require full i2c support since the sht3x uses multi-byte read and
         * writes as well as multi-byte commands which are not supported by
         * the smbus protocol
         */
        if (!i2c_check_functionality(adap, I2C_FUNC_I2C))
                return -ENODEV;

        ret = i2c_master_send(client, sht3x_cmd_clear_status_reg,
                              SHT3X_CMD_LENGTH);
        if (ret != SHT3X_CMD_LENGTH)
                return ret < 0 ? ret : -ENODEV;

        data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        data->setup.blocking_io = false;
        data->setup.high_precision = true;
        data->mode = 0;
        data->last_update = jiffies - msecs_to_jiffies(3000);
        data->client = client;
        crc8_populate_msb(sht3x_crc8_table, SHT3X_CRC8_POLYNOMIAL);

        if (client->dev.platform_data)
                data->setup = *(struct sht3x_platform_data *)dev->platform_data;

        sht3x_select_command(data);

        mutex_init(&data->i2c_lock);
        mutex_init(&data->data_lock);

        /*
         * An attempt to read limits register too early
         * causes a NACK response from the chip.
         * Waiting for an empirical delay of 500 us solves the issue.
         */
        usleep_range(500, 600);

        ret = limits_update(data);
        if (ret)
                return ret;

        if (id->driver_data == sts3x)
                attribute_groups = sts3x_groups;
        else
                attribute_groups = sht3x_groups;

        hwmon_dev = devm_hwmon_device_register_with_groups(dev,
                                                           client->name,
                                                           data,
                                                           attribute_groups);

        if (IS_ERR(hwmon_dev))
                dev_dbg(dev, "unable to register hwmon device\n");

        return PTR_ERR_OR_ZERO(hwmon_dev);
}

/* device ID table */
static const struct i2c_device_id sht3x_ids[] = {
        {"sht3x", sht3x},
        {"sts3x", sts3x},
        {}
};

MODULE_DEVICE_TABLE(i2c, sht3x_ids);

static struct i2c_driver sht3x_i2c_driver = {
        .driver.name = "sht3x",
        .probe       = sht3x_probe,
        .id_table    = sht3x_ids,
};

module_i2c_driver(sht3x_i2c_driver);

MODULE_AUTHOR("David Frey <david.frey@sensirion.com>");
MODULE_AUTHOR("Pascal Sachs <pascal.sachs@sensirion.com>");
MODULE_DESCRIPTION("Sensirion SHT3x humidity and temperature sensor driver");
MODULE_LICENSE("GPL");