drivers/hwmon/sht21.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* Sensirion SHT21 humidity and temperature sensor driver
  *
  * Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com>
  *
  * Data sheet available at https://www.sensirion.com/file/datasheet_sht21
  */

 #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
 #define SHT21_READ_SNB_CMD1 0xFA
 #define SHT21_READ_SNB_CMD2 0x0F
 #define SHT21_READ_SNAC_CMD1 0xFC
 #define SHT21_READ_SNAC_CMD2 0xC9

 /**
  * struct sht21 - SHT21 device specific data
  * @client: I2C client device
  * @lock: mutex to protect measurement values
  * @last_update: time of last update (jiffies)
  * @temperature: cached temperature measurement value
  * @humidity: cached humidity measurement value
  * @valid: only 0 before first measurement is taken
  * @eic: cached electronic identification code text
  */
 struct sht21 {
 	struct i2c_client *client;
 	struct mutex lock;
 	unsigned long last_update;
 	int temperature;
 	int humidity;
 	bool valid;
 	char eic[18];
 };

 /**
  * 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 = true;
 	}
 out:
 	mutex_unlock(&sht21->lock);

 	return ret >= 0 ? 0 : ret;
 }

 /**
  * sht21_temperature_show() - 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_temperature_show(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_humidity_show() - 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_humidity_show(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);
 }

 static ssize_t eic_read(struct sht21 *sht21)
 {
 	struct i2c_client *client = sht21->client;
 	u8 tx[2];
 	u8 rx[8];
 	u8 eic[8];
 	struct i2c_msg msgs[2] = {
 		{
 			.addr = client->addr,
 			.flags = 0,
 			.len = 2,
 			.buf = tx,
 		},
 		{
 			.addr = client->addr,
 			.flags = I2C_M_RD,
 			.len = 8,
 			.buf = rx,
 		},
 	};
 	int ret;

 	tx[0] = SHT21_READ_SNB_CMD1;
 	tx[1] = SHT21_READ_SNB_CMD2;
 	ret = i2c_transfer(client->adapter, msgs, 2);
 	if (ret < 0)
 		goto out;
 	eic[2] = rx[0];
 	eic[3] = rx[2];
 	eic[4] = rx[4];
 	eic[5] = rx[6];

 	tx[0] = SHT21_READ_SNAC_CMD1;
 	tx[1] = SHT21_READ_SNAC_CMD2;
 	msgs[1].len = 6;
 	ret = i2c_transfer(client->adapter, msgs, 2);
 	if (ret < 0)
 		goto out;
 	eic[0] = rx[3];
 	eic[1] = rx[4];
 	eic[6] = rx[0];
 	eic[7] = rx[1];

 	ret = snprintf(sht21->eic, sizeof(sht21->eic), "%8phN\n", eic);
 out:
 	if (ret < 0)
 		sht21->eic[0] = 0;

 	return ret;
 }

 /**
  * eic_show() - show Electronic Identification Code in sysfs
  * @dev: device
  * @attr: device attribute
  * @buf: sysfs buffer (PAGE_SIZE) where EIC is written
  *
  * Will be called on read access to eic sysfs attribute.
  * Returns number of bytes written into buffer, negative errno on error.
  */
 static ssize_t eic_show(struct device *dev,
 	struct device_attribute *attr,
 	char *buf)
 {
 	struct sht21 *sht21 = dev_get_drvdata(dev);
 	int ret;

 	ret = sizeof(sht21->eic) - 1;
 	mutex_lock(&sht21->lock);
 	if (!sht21->eic[0])
 		ret = eic_read(sht21);
 	if (ret > 0)
 		memcpy(buf, sht21->eic, ret);
 	mutex_unlock(&sht21->lock);
 	return ret;
 }

 /* sysfs attributes */
 static SENSOR_DEVICE_ATTR_RO(temp1_input, sht21_temperature, 0);
 static SENSOR_DEVICE_ATTR_RO(humidity1_input, sht21_humidity, 0);
 static DEVICE_ATTR_RO(eic);

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

 ATTRIBUTE_GROUPS(sht21);

 static int sht21_probe(struct i2c_client *client)
 {
 	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" },
 	{ }
 };
 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");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/* Sensirion SHT21 humidity and temperature sensor driver
	*
	* Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com>
	*
	* Data sheet available at https://www.sensirion.com/file/datasheet_sht21
	*/

	#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
	#define SHT21_READ_SNB_CMD1 0xFA
	#define SHT21_READ_SNB_CMD2 0x0F
	#define SHT21_READ_SNAC_CMD1 0xFC
	#define SHT21_READ_SNAC_CMD2 0xC9

	/**
	* struct sht21 - SHT21 device specific data
	* @client: I2C client device
	* @lock: mutex to protect measurement values
	* @last_update: time of last update (jiffies)
	* @temperature: cached temperature measurement value
	* @humidity: cached humidity measurement value
	* @valid: only 0 before first measurement is taken
	* @eic: cached electronic identification code text
	*/
	struct sht21 {
	struct i2c_client *client;
	struct mutex lock;
	unsigned long last_update;
	int temperature;
	int humidity;
	bool valid;
	char eic[18];
	};

	/**
	* 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 = true;
	}
	out:
	mutex_unlock(&sht21->lock);

	return ret >= 0 ? 0 : ret;
	}

	/**
	* sht21_temperature_show() - 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_temperature_show(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_humidity_show() - 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_humidity_show(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);
	}

	static ssize_t eic_read(struct sht21 *sht21)
	{
	struct i2c_client *client = sht21->client;
	u8 tx[2];
	u8 rx[8];
	u8 eic[8];
	struct i2c_msg msgs[2] = {
	{
	.addr = client->addr,
	.flags = 0,
	.len = 2,
	.buf = tx,
	},
	{
	.addr = client->addr,
	.flags = I2C_M_RD,
	.len = 8,
	.buf = rx,
	},
	};
	int ret;

	tx[0] = SHT21_READ_SNB_CMD1;
	tx[1] = SHT21_READ_SNB_CMD2;
	ret = i2c_transfer(client->adapter, msgs, 2);
	if (ret < 0)
	goto out;
	eic[2] = rx[0];
	eic[3] = rx[2];
	eic[4] = rx[4];
	eic[5] = rx[6];

	tx[0] = SHT21_READ_SNAC_CMD1;
	tx[1] = SHT21_READ_SNAC_CMD2;
	msgs[1].len = 6;
	ret = i2c_transfer(client->adapter, msgs, 2);
	if (ret < 0)
	goto out;
	eic[0] = rx[3];
	eic[1] = rx[4];
	eic[6] = rx[0];
	eic[7] = rx[1];

	ret = snprintf(sht21->eic, sizeof(sht21->eic), "%8phN\n", eic);
	out:
	if (ret < 0)
	sht21->eic[0] = 0;

	return ret;
	}

	/**
	* eic_show() - show Electronic Identification Code in sysfs
	* @dev: device
	* @attr: device attribute
	* @buf: sysfs buffer (PAGE_SIZE) where EIC is written
	*
	* Will be called on read access to eic sysfs attribute.
	* Returns number of bytes written into buffer, negative errno on error.
	*/
	static ssize_t eic_show(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	struct sht21 *sht21 = dev_get_drvdata(dev);
	int ret;

	ret = sizeof(sht21->eic) - 1;
	mutex_lock(&sht21->lock);
	if (!sht21->eic[0])
	ret = eic_read(sht21);
	if (ret > 0)
	memcpy(buf, sht21->eic, ret);
	mutex_unlock(&sht21->lock);
	return ret;
	}

	/* sysfs attributes */
	static SENSOR_DEVICE_ATTR_RO(temp1_input, sht21_temperature, 0);
	static SENSOR_DEVICE_ATTR_RO(humidity1_input, sht21_humidity, 0);
	static DEVICE_ATTR_RO(eic);

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

	ATTRIBUTE_GROUPS(sht21);

	static int sht21_probe(struct i2c_client *client)
	{
	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" },
	{ }
	};
	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");