drivers/hwmon/sht21.c - kernel/msm-4.9 - Gitiles

 /* Sensirion SHT21 humidity and temperature sensor driver
  *
  * Copyright (C) 2010 Urs Fleisch <urs.fleisch@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.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA
  *
  * Data sheet available (5/2010) at
  * http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT21.pdf
  */

 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/i2c.h>
 #include <linux/hwmon.h>
 #include <linux/hwmon-sysfs.h>
 #include <linux/err.h>
 #include <linux/mutex.h>
 #include <linux/device.h>
 #include <linux/jiffies.h>

 /* I2C command bytes */
 #define SHT21_TRIG_T_MEASUREMENT_HM  0xe3
 #define SHT21_TRIG_RH_MEASUREMENT_HM 0xe5

 /**
  * struct sht21 - SHT21 device specific data
  * @hwmon_dev: device registered with hwmon
  * @lock: mutex to protect measurement values
  * @valid: only 0 before first measurement is taken
  * @last_update: time of last update (jiffies)
  * @temperature: cached temperature measurement value
  * @humidity: cached humidity measurement value
  */
 struct sht21 {
 	struct i2c_client *client;
 	struct mutex lock;
 	char valid;
 	unsigned long last_update;
 	int temperature;
 	int humidity;
 };

 /**
  * sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to
  * milli celsius
  * @ticks: temperature ticks value received from sensor
  */
 static inline int sht21_temp_ticks_to_millicelsius(int ticks)
 {
 	ticks &= ~0x0003; /* clear status bits */
 	/*
 	 * Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2,
 	 * optimized for integer fixed point (3 digits) arithmetic
 	 */
 	return ((21965 * ticks) >> 13) - 46850;
 }

 /**
  * sht21_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to
  * one-thousandths of a percent relative humidity
  * @ticks: humidity ticks value received from sensor
  */
 static inline int sht21_rh_ticks_to_per_cent_mille(int ticks)
 {
 	ticks &= ~0x0003; /* clear status bits */
 	/*
 	 * Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1,
 	 * optimized for integer fixed point (3 digits) arithmetic
 	 */
 	return ((15625 * ticks) >> 13) - 6000;
 }

 /**
  * sht21_update_measurements() - get updated measurements from device
  * @dev: device
  *
  * Returns 0 on success, else negative errno.
  */
 static int sht21_update_measurements(struct device *dev)
 {
 	int ret = 0;
 	struct sht21 *sht21 = dev_get_drvdata(dev);
 	struct i2c_client *client = sht21->client;

 	mutex_lock(&sht21->lock);
 	/*
 	 * Data sheet 2.4:
 	 * SHT2x should not be active for more than 10% of the time - e.g.
 	 * maximum two measurements per second at 12bit accuracy shall be made.
 	 */
 	if (time_after(jiffies, sht21->last_update + HZ / 2) || !sht21->valid) {
 		ret = i2c_smbus_read_word_swapped(client,
 						  SHT21_TRIG_T_MEASUREMENT_HM);
 		if (ret < 0)
 			goto out;
 		sht21->temperature = sht21_temp_ticks_to_millicelsius(ret);
 		ret = i2c_smbus_read_word_swapped(client,
 						  SHT21_TRIG_RH_MEASUREMENT_HM);
 		if (ret < 0)
 			goto out;
 		sht21->humidity = sht21_rh_ticks_to_per_cent_mille(ret);
 		sht21->last_update = jiffies;
 		sht21->valid = 1;
 	}
 out:
 	mutex_unlock(&sht21->lock);

 	return ret >= 0 ? 0 : ret;
 }

 /**
  * sht21_show_temperature() - show temperature measurement value in sysfs
  * @dev: device
  * @attr: device attribute
  * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
  *
  * Will be called on read access to temp1_input sysfs attribute.
  * Returns number of bytes written into buffer, negative errno on error.
  */
 static ssize_t sht21_show_temperature(struct device *dev,
 	struct device_attribute *attr,
 	char *buf)
 {
 	struct sht21 *sht21 = dev_get_drvdata(dev);
 	int ret;

 	ret = sht21_update_measurements(dev);
 	if (ret < 0)
 		return ret;
 	return sprintf(buf, "%d\n", sht21->temperature);
 }

 /**
  * sht21_show_humidity() - show humidity measurement value in sysfs
  * @dev: device
  * @attr: device attribute
  * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
  *
  * Will be called on read access to humidity1_input sysfs attribute.
  * Returns number of bytes written into buffer, negative errno on error.
  */
 static ssize_t sht21_show_humidity(struct device *dev,
 	struct device_attribute *attr,
 	char *buf)
 {
 	struct sht21 *sht21 = dev_get_drvdata(dev);
 	int ret;

 	ret = sht21_update_measurements(dev);
 	if (ret < 0)
 		return ret;
 	return sprintf(buf, "%d\n", sht21->humidity);
 }

 /* sysfs attributes */
 static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, sht21_show_temperature,
 	NULL, 0);
 static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, sht21_show_humidity,
 	NULL, 0);

 static struct attribute *sht21_attrs[] = {
 	&sensor_dev_attr_temp1_input.dev_attr.attr,
 	&sensor_dev_attr_humidity1_input.dev_attr.attr,
 	NULL
 };

 ATTRIBUTE_GROUPS(sht21);

 static int sht21_probe(struct i2c_client *client,
 	const struct i2c_device_id *id)
 {
 	struct device *dev = &client->dev;
 	struct device *hwmon_dev;
 	struct sht21 *sht21;

 	if (!i2c_check_functionality(client->adapter,
 				     I2C_FUNC_SMBUS_WORD_DATA)) {
 		dev_err(&client->dev,
 			"adapter does not support SMBus word transactions\n");
 		return -ENODEV;
 	}

 	sht21 = devm_kzalloc(dev, sizeof(*sht21), GFP_KERNEL);
 	if (!sht21)
 		return -ENOMEM;

 	sht21->client = client;

 	mutex_init(&sht21->lock);

 	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
 							   sht21, sht21_groups);
 	return PTR_ERR_OR_ZERO(hwmon_dev);
 }

 /* Device ID table */
 static const struct i2c_device_id sht21_id[] = {
 	{ "sht21", 0 },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, sht21_id);

 static struct i2c_driver sht21_driver = {
 	.driver.name = "sht21",
 	.probe       = sht21_probe,
 	.id_table    = sht21_id,
 };

 module_i2c_driver(sht21_driver);

 MODULE_AUTHOR("Urs Fleisch <urs.fleisch@sensirion.com>");
 MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver");
 MODULE_LICENSE("GPL");
	/* Sensirion SHT21 humidity and temperature sensor driver
	*
	* Copyright (C) 2010 Urs Fleisch <urs.fleisch@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.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA
	*
	* Data sheet available (5/2010) at
	* http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT21.pdf
	*/

	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/slab.h>
	#include <linux/i2c.h>
	#include <linux/hwmon.h>
	#include <linux/hwmon-sysfs.h>
	#include <linux/err.h>
	#include <linux/mutex.h>
	#include <linux/device.h>
	#include <linux/jiffies.h>

	/* I2C command bytes */
	#define SHT21_TRIG_T_MEASUREMENT_HM 0xe3
	#define SHT21_TRIG_RH_MEASUREMENT_HM 0xe5

	/**
	* struct sht21 - SHT21 device specific data
	* @hwmon_dev: device registered with hwmon
	* @lock: mutex to protect measurement values
	* @valid: only 0 before first measurement is taken
	* @last_update: time of last update (jiffies)
	* @temperature: cached temperature measurement value
	* @humidity: cached humidity measurement value
	*/
	struct sht21 {
	struct i2c_client *client;
	struct mutex lock;
	char valid;
	unsigned long last_update;
	int temperature;
	int humidity;
	};

	/**
	* sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to
	* milli celsius
	* @ticks: temperature ticks value received from sensor
	*/
	static inline int sht21_temp_ticks_to_millicelsius(int ticks)
	{
	ticks &= ~0x0003; /* clear status bits */
	/*
	* Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2,
	* optimized for integer fixed point (3 digits) arithmetic
	*/
	return ((21965 * ticks) >> 13) - 46850;
	}

	/**
	* sht21_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to
	* one-thousandths of a percent relative humidity
	* @ticks: humidity ticks value received from sensor
	*/
	static inline int sht21_rh_ticks_to_per_cent_mille(int ticks)
	{
	ticks &= ~0x0003; /* clear status bits */
	/*
	* Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1,
	* optimized for integer fixed point (3 digits) arithmetic
	*/
	return ((15625 * ticks) >> 13) - 6000;
	}

	/**
	* sht21_update_measurements() - get updated measurements from device
	* @dev: device
	*
	* Returns 0 on success, else negative errno.
	*/
	static int sht21_update_measurements(struct device *dev)
	{
	int ret = 0;
	struct sht21 *sht21 = dev_get_drvdata(dev);
	struct i2c_client *client = sht21->client;

	mutex_lock(&sht21->lock);
	/*
	* Data sheet 2.4:
	* SHT2x should not be active for more than 10% of the time - e.g.
	* maximum two measurements per second at 12bit accuracy shall be made.
	*/
	if (time_after(jiffies, sht21->last_update + HZ / 2) \|\| !sht21->valid) {
	ret = i2c_smbus_read_word_swapped(client,
	SHT21_TRIG_T_MEASUREMENT_HM);
	if (ret < 0)
	goto out;
	sht21->temperature = sht21_temp_ticks_to_millicelsius(ret);
	ret = i2c_smbus_read_word_swapped(client,
	SHT21_TRIG_RH_MEASUREMENT_HM);
	if (ret < 0)
	goto out;
	sht21->humidity = sht21_rh_ticks_to_per_cent_mille(ret);
	sht21->last_update = jiffies;
	sht21->valid = 1;
	}
	out:
	mutex_unlock(&sht21->lock);

	return ret >= 0 ? 0 : ret;
	}

	/**
	* sht21_show_temperature() - show temperature measurement value in sysfs
	* @dev: device
	* @attr: device attribute
	* @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
	*
	* Will be called on read access to temp1_input sysfs attribute.
	* Returns number of bytes written into buffer, negative errno on error.
	*/
	static ssize_t sht21_show_temperature(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	struct sht21 *sht21 = dev_get_drvdata(dev);
	int ret;

	ret = sht21_update_measurements(dev);
	if (ret < 0)
	return ret;
	return sprintf(buf, "%d\n", sht21->temperature);
	}

	/**
	* sht21_show_humidity() - show humidity measurement value in sysfs
	* @dev: device
	* @attr: device attribute
	* @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
	*
	* Will be called on read access to humidity1_input sysfs attribute.
	* Returns number of bytes written into buffer, negative errno on error.
	*/
	static ssize_t sht21_show_humidity(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	struct sht21 *sht21 = dev_get_drvdata(dev);
	int ret;

	ret = sht21_update_measurements(dev);
	if (ret < 0)
	return ret;
	return sprintf(buf, "%d\n", sht21->humidity);
	}

	/* sysfs attributes */
	static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, sht21_show_temperature,
	NULL, 0);
	static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, sht21_show_humidity,
	NULL, 0);

	static struct attribute *sht21_attrs[] = {
	&sensor_dev_attr_temp1_input.dev_attr.attr,
	&sensor_dev_attr_humidity1_input.dev_attr.attr,
	NULL
	};

	ATTRIBUTE_GROUPS(sht21);

	static int sht21_probe(struct i2c_client *client,
	const struct i2c_device_id *id)
	{
	struct device *dev = &client->dev;
	struct device *hwmon_dev;
	struct sht21 *sht21;

	if (!i2c_check_functionality(client->adapter,
	I2C_FUNC_SMBUS_WORD_DATA)) {
	dev_err(&client->dev,
	"adapter does not support SMBus word transactions\n");
	return -ENODEV;
	}

	sht21 = devm_kzalloc(dev, sizeof(*sht21), GFP_KERNEL);
	if (!sht21)
	return -ENOMEM;

	sht21->client = client;

	mutex_init(&sht21->lock);

	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
	sht21, sht21_groups);
	return PTR_ERR_OR_ZERO(hwmon_dev);
	}

	/* Device ID table */
	static const struct i2c_device_id sht21_id[] = {
	{ "sht21", 0 },
	{ }
	};
	MODULE_DEVICE_TABLE(i2c, sht21_id);

	static struct i2c_driver sht21_driver = {
	.driver.name = "sht21",
	.probe = sht21_probe,
	.id_table = sht21_id,
	};

	module_i2c_driver(sht21_driver);

	MODULE_AUTHOR("Urs Fleisch <urs.fleisch@sensirion.com>");
	MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver");
	MODULE_LICENSE("GPL");