[linux-2.6-block.git] / drivers / hwmon / sht21.c

/* 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");
Commit	Line	Data
430400b8 UF	1	/* Sensirion SHT21 humidity and temperature sensor driver
	2	*
	3	* Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com>
	4	*
	5	* This program is free software; you can redistribute it and/or modify
	6	* it under the terms of the GNU General Public License as published by
	7	* the Free Software Foundation; either version 2 of the License, or
	8	* (at your option) any later version.
	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	* You should have received a copy of the GNU General Public License
	16	* along with this program; if not, write to the Free Software
	17	* Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA
	18	*
	19	* Data sheet available (5/2010) at
	20	* http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT21.pdf
	21	*/
	22
	23	#include <linux/module.h>
	24	#include <linux/init.h>
	25	#include <linux/slab.h>
	26	#include <linux/i2c.h>
	27	#include <linux/hwmon.h>
	28	#include <linux/hwmon-sysfs.h>
	29	#include <linux/err.h>
	30	#include <linux/mutex.h>
	31	#include <linux/device.h>
dcd8f392	32	#include <linux/jiffies.h>
430400b8 UF	33
	34	/* I2C command bytes */
	35	#define SHT21_TRIG_T_MEASUREMENT_HM 0xe3
	36	#define SHT21_TRIG_RH_MEASUREMENT_HM 0xe5
	37
	38	/**
	39	* struct sht21 - SHT21 device specific data
	40	* @hwmon_dev: device registered with hwmon
	41	* @lock: mutex to protect measurement values
	42	* @valid: only 0 before first measurement is taken
	43	* @last_update: time of last update (jiffies)
	44	* @temperature: cached temperature measurement value
	45	* @humidity: cached humidity measurement value
	46	*/
	47	struct sht21 {
b8d56898	48	struct i2c_client *client;
430400b8 UF	49	struct mutex lock;
	50	char valid;
	51	unsigned long last_update;
	52	int temperature;
	53	int humidity;
	54	};
	55
	56	/**
	57	* sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to
	58	* milli celsius
	59	* @ticks: temperature ticks value received from sensor
	60	*/
	61	static inline int sht21_temp_ticks_to_millicelsius(int ticks)
	62	{
	63	ticks &= ~0x0003; /* clear status bits */
	64	/*
	65	* Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2,
	66	* optimized for integer fixed point (3 digits) arithmetic
	67	*/
	68	return ((21965 * ticks) >> 13) - 46850;
	69	}
	70
	71	/**
	72	* sht21_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to
	73	* one-thousandths of a percent relative humidity
	74	* @ticks: humidity ticks value received from sensor
	75	*/
	76	static inline int sht21_rh_ticks_to_per_cent_mille(int ticks)
	77	{
	78	ticks &= ~0x0003; /* clear status bits */
	79	/*
	80	* Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1,
	81	* optimized for integer fixed point (3 digits) arithmetic
	82	*/
	83	return ((15625 * ticks) >> 13) - 6000;
	84	}
	85
430400b8 UF	86	/**
430400b8 UF	87	* sht21_update_measurements() - get updated measurements from device
b8d56898	88	* @dev: device
430400b8 UF	89	*
	90	* Returns 0 on success, else negative errno.
	91	*/
b8d56898	92	static int sht21_update_measurements(struct device *dev)
430400b8 UF	93	{
430400b8 UF	94	int ret = 0;
b8d56898 AL	95	struct sht21 *sht21 = dev_get_drvdata(dev);
b8d56898 AL	96	struct i2c_client *client = sht21->client;
430400b8 UF	97
	98	mutex_lock(&sht21->lock);
	99	/*
	100	* Data sheet 2.4:
	101	* SHT2x should not be active for more than 10% of the time - e.g.
	102	* maximum two measurements per second at 12bit accuracy shall be made.
	103	*/
	104	if (time_after(jiffies, sht21->last_update + HZ / 2) \|\| !sht21->valid) {
90f4102c JD	105	ret = i2c_smbus_read_word_swapped(client,
90f4102c JD	106	SHT21_TRIG_T_MEASUREMENT_HM);
430400b8 UF	107	if (ret < 0)
	108	goto out;
	109	sht21->temperature = sht21_temp_ticks_to_millicelsius(ret);
90f4102c JD	110	ret = i2c_smbus_read_word_swapped(client,
90f4102c JD	111	SHT21_TRIG_RH_MEASUREMENT_HM);
430400b8 UF	112	if (ret < 0)
	113	goto out;
	114	sht21->humidity = sht21_rh_ticks_to_per_cent_mille(ret);
	115	sht21->last_update = jiffies;
	116	sht21->valid = 1;
	117	}
	118	out:
	119	mutex_unlock(&sht21->lock);
	120
	121	return ret >= 0 ? 0 : ret;
	122	}
	123
	124	/**
	125	* sht21_show_temperature() - show temperature measurement value in sysfs
	126	* @dev: device
	127	* @attr: device attribute
	128	* @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
	129	*
	130	* Will be called on read access to temp1_input sysfs attribute.
	131	* Returns number of bytes written into buffer, negative errno on error.
	132	*/
	133	static ssize_t sht21_show_temperature(struct device *dev,
	134	struct device_attribute *attr,
	135	char *buf)
	136	{
b8d56898 AL	137	struct sht21 *sht21 = dev_get_drvdata(dev);
	138	int ret;
	139
	140	ret = sht21_update_measurements(dev);
430400b8 UF	141	if (ret < 0)
	142	return ret;
	143	return sprintf(buf, "%d\n", sht21->temperature);
	144	}
	145
	146	/**
	147	* sht21_show_humidity() - show humidity measurement value in sysfs
	148	* @dev: device
	149	* @attr: device attribute
	150	* @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
	151	*
	152	* Will be called on read access to humidity1_input sysfs attribute.
	153	* Returns number of bytes written into buffer, negative errno on error.
	154	*/
	155	static ssize_t sht21_show_humidity(struct device *dev,
	156	struct device_attribute *attr,
	157	char *buf)
	158	{
b8d56898 AL	159	struct sht21 *sht21 = dev_get_drvdata(dev);
	160	int ret;
	161
	162	ret = sht21_update_measurements(dev);
430400b8 UF	163	if (ret < 0)
	164	return ret;
	165	return sprintf(buf, "%d\n", sht21->humidity);
	166	}
	167
	168	/* sysfs attributes */
	169	static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, sht21_show_temperature,
	170	NULL, 0);
	171	static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, sht21_show_humidity,
	172	NULL, 0);
	173
b8d56898	174	static struct attribute *sht21_attrs[] = {
430400b8 UF	175	&sensor_dev_attr_temp1_input.dev_attr.attr,
	176	&sensor_dev_attr_humidity1_input.dev_attr.attr,
	177	NULL
	178	};
	179
b8d56898	180	ATTRIBUTE_GROUPS(sht21);
430400b8	181
6c931ae1	182	static int sht21_probe(struct i2c_client *client,
430400b8 UF	183	const struct i2c_device_id *id)
430400b8 UF	184	{
b8d56898 AL	185	struct device *dev = &client->dev;
b8d56898 AL	186	struct device *hwmon_dev;
430400b8	187	struct sht21 *sht21;
430400b8 UF	188
	189	if (!i2c_check_functionality(client->adapter,
	190	I2C_FUNC_SMBUS_WORD_DATA)) {
	191	dev_err(&client->dev,
	192	"adapter does not support SMBus word transactions\n");
	193	return -ENODEV;
	194	}
	195
b8d56898	196	sht21 = devm_kzalloc(dev, sizeof(*sht21), GFP_KERNEL);
a844af19	197	if (!sht21)
430400b8	198	return -ENOMEM;
a844af19	199
b8d56898	200	sht21->client = client;
430400b8 UF	201
	202	mutex_init(&sht21->lock);
	203
b8d56898 AL	204	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
	205	sht21, sht21_groups);
	206	return PTR_ERR_OR_ZERO(hwmon_dev);
430400b8 UF	207	}
	208
	209	/* Device ID table */
	210	static const struct i2c_device_id sht21_id[] = {
	211	{ "sht21", 0 },
	212	{ }
	213	};
	214	MODULE_DEVICE_TABLE(i2c, sht21_id);
	215
	216	static struct i2c_driver sht21_driver = {
	217	.driver.name = "sht21",
	218	.probe = sht21_probe,
430400b8 UF	219	.id_table = sht21_id,
	220	};
	221
f0967eea	222	module_i2c_driver(sht21_driver);
430400b8 UF	223
	224	MODULE_AUTHOR("Urs Fleisch <urs.fleisch@sensirion.com>");
	225	MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver");
	226	MODULE_LICENSE("GPL");