252 lines
6.9 KiB
C
252 lines
6.9 KiB
C
/* Sensirion SHTC1 humidity and temperature sensor driver
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*
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* Copyright (C) 2014 Sensirion AG, Switzerland
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* Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/i2c.h>
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#include <linux/hwmon.h>
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#include <linux/hwmon-sysfs.h>
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#include <linux/err.h>
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#include <linux/delay.h>
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#include <linux/platform_data/shtc1.h>
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/* commands (high precision mode) */
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static const unsigned char shtc1_cmd_measure_blocking_hpm[] = { 0x7C, 0xA2 };
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static const unsigned char shtc1_cmd_measure_nonblocking_hpm[] = { 0x78, 0x66 };
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/* commands (low precision mode) */
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static const unsigned char shtc1_cmd_measure_blocking_lpm[] = { 0x64, 0x58 };
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static const unsigned char shtc1_cmd_measure_nonblocking_lpm[] = { 0x60, 0x9c };
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/* command for reading the ID register */
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static const unsigned char shtc1_cmd_read_id_reg[] = { 0xef, 0xc8 };
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/* constants for reading the ID register */
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#define SHTC1_ID 0x07
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#define SHTC1_ID_REG_MASK 0x1f
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/* delays for non-blocking i2c commands, both in us */
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#define SHTC1_NONBLOCKING_WAIT_TIME_HPM 14400
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#define SHTC1_NONBLOCKING_WAIT_TIME_LPM 1000
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#define SHTC1_CMD_LENGTH 2
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#define SHTC1_RESPONSE_LENGTH 6
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struct shtc1_data {
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struct i2c_client *client;
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struct mutex update_lock;
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bool valid;
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unsigned long last_updated; /* in jiffies */
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const unsigned char *command;
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unsigned int nonblocking_wait_time; /* in us */
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struct shtc1_platform_data setup;
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int temperature; /* 1000 * temperature in dgr C */
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int humidity; /* 1000 * relative humidity in %RH */
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};
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static int shtc1_update_values(struct i2c_client *client,
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struct shtc1_data *data,
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char *buf, int bufsize)
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{
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int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
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if (ret != SHTC1_CMD_LENGTH) {
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dev_err(&client->dev, "failed to send command: %d\n", ret);
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return ret < 0 ? ret : -EIO;
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}
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/*
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* In blocking mode (clock stretching mode) the I2C bus
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* is blocked for other traffic, thus the call to i2c_master_recv()
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* will wait until the data is ready. For non blocking mode, we
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* have to wait ourselves.
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*/
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if (!data->setup.blocking_io)
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usleep_range(data->nonblocking_wait_time,
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data->nonblocking_wait_time + 1000);
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ret = i2c_master_recv(client, buf, bufsize);
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if (ret != bufsize) {
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dev_err(&client->dev, "failed to read values: %d\n", ret);
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return ret < 0 ? ret : -EIO;
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}
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return 0;
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}
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/* sysfs attributes */
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static struct shtc1_data *shtc1_update_client(struct device *dev)
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{
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struct shtc1_data *data = dev_get_drvdata(dev);
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struct i2c_client *client = data->client;
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unsigned char buf[SHTC1_RESPONSE_LENGTH];
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int val;
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int ret = 0;
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mutex_lock(&data->update_lock);
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if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
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ret = shtc1_update_values(client, data, buf, sizeof(buf));
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if (ret)
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goto out;
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/*
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* From datasheet:
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* T = -45 + 175 * ST / 2^16
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* RH = 100 * SRH / 2^16
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*
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* Adapted for integer fixed point (3 digit) arithmetic.
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*/
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val = be16_to_cpup((__be16 *)buf);
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data->temperature = ((21875 * val) >> 13) - 45000;
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val = be16_to_cpup((__be16 *)(buf + 3));
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data->humidity = ((12500 * val) >> 13);
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data->last_updated = jiffies;
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data->valid = true;
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}
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out:
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mutex_unlock(&data->update_lock);
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return ret == 0 ? data : ERR_PTR(ret);
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}
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static ssize_t temp1_input_show(struct device *dev,
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struct device_attribute *attr,
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char *buf)
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{
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struct shtc1_data *data = shtc1_update_client(dev);
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if (IS_ERR(data))
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return PTR_ERR(data);
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return sprintf(buf, "%d\n", data->temperature);
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}
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static ssize_t humidity1_input_show(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct shtc1_data *data = shtc1_update_client(dev);
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if (IS_ERR(data))
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return PTR_ERR(data);
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return sprintf(buf, "%d\n", data->humidity);
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}
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static DEVICE_ATTR_RO(temp1_input);
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static DEVICE_ATTR_RO(humidity1_input);
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static struct attribute *shtc1_attrs[] = {
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&dev_attr_temp1_input.attr,
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&dev_attr_humidity1_input.attr,
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NULL
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};
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ATTRIBUTE_GROUPS(shtc1);
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static void shtc1_select_command(struct shtc1_data *data)
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{
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if (data->setup.high_precision) {
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data->command = data->setup.blocking_io ?
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shtc1_cmd_measure_blocking_hpm :
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shtc1_cmd_measure_nonblocking_hpm;
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data->nonblocking_wait_time = SHTC1_NONBLOCKING_WAIT_TIME_HPM;
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} else {
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data->command = data->setup.blocking_io ?
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shtc1_cmd_measure_blocking_lpm :
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shtc1_cmd_measure_nonblocking_lpm;
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data->nonblocking_wait_time = SHTC1_NONBLOCKING_WAIT_TIME_LPM;
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}
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}
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static int shtc1_probe(struct i2c_client *client,
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const struct i2c_device_id *id)
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{
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int ret;
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char id_reg[2];
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struct shtc1_data *data;
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struct device *hwmon_dev;
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struct i2c_adapter *adap = client->adapter;
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struct device *dev = &client->dev;
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if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
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dev_err(dev, "plain i2c transactions not supported\n");
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return -ENODEV;
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}
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ret = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
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if (ret != SHTC1_CMD_LENGTH) {
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dev_err(dev, "could not send read_id_reg command: %d\n", ret);
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return ret < 0 ? ret : -ENODEV;
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}
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ret = i2c_master_recv(client, id_reg, sizeof(id_reg));
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if (ret != sizeof(id_reg)) {
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dev_err(dev, "could not read ID register: %d\n", ret);
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return -ENODEV;
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}
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if ((id_reg[1] & SHTC1_ID_REG_MASK) != SHTC1_ID) {
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dev_err(dev, "ID register doesn't match\n");
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return -ENODEV;
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}
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data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
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if (!data)
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return -ENOMEM;
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data->setup.blocking_io = false;
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data->setup.high_precision = true;
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data->client = client;
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if (client->dev.platform_data)
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data->setup = *(struct shtc1_platform_data *)dev->platform_data;
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shtc1_select_command(data);
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mutex_init(&data->update_lock);
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hwmon_dev = devm_hwmon_device_register_with_groups(dev,
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client->name,
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data,
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shtc1_groups);
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if (IS_ERR(hwmon_dev))
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dev_dbg(dev, "unable to register hwmon device\n");
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return PTR_ERR_OR_ZERO(hwmon_dev);
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}
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/* device ID table */
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static const struct i2c_device_id shtc1_id[] = {
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{ "shtc1", 0 },
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{ "shtw1", 0 },
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{ }
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};
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MODULE_DEVICE_TABLE(i2c, shtc1_id);
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static struct i2c_driver shtc1_i2c_driver = {
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.driver.name = "shtc1",
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.probe = shtc1_probe,
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.id_table = shtc1_id,
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};
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module_i2c_driver(shtc1_i2c_driver);
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MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.com>");
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MODULE_DESCRIPTION("Sensirion SHTC1 humidity and temperature sensor driver");
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MODULE_LICENSE("GPL");
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