hwmon: (htu21) Add Measurement Specialties HTU21D support (f060c658) · Commits · e / devices / android_kernel_xiaomi_markw

Documentation/hwmon/htu21

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		Kernel driver htu21
		===================

		Supported chips:
		* Measurement Specialties HTU21D
		Prefix: 'htu21'
		Addresses scanned: none
		Datasheet: Publicly available at the Measurement Specialties website
		http://www.meas-spec.com/downloads/HTU21D.pdf


		Author:
		William Markezana <william.markezana@meas-spec.com>

		Description
		-----------

		The HTU21D is a humidity and temperature sensor in a DFN package of
		only 3 x 3 mm footprint and 0.9 mm height.

		The devices communicate with the I2C protocol. All sensors are set to the
		same I2C address 0x40, so an entry with I2C_BOARD_INFO("htu21", 0x40) can
		be used in the board setup code.

		This driver does not auto-detect devices. You will have to instantiate the
		devices explicitly. Please see Documentation/i2c/instantiating-devices
		for details.

		sysfs-Interface
		---------------

		temp1_input - temperature input
		humidity1_input - humidity input

		Notes
		-----

		The driver uses the default resolution settings of 12 bit for humidity and 14
		bit for temperature, which results in typical measurement times of 11 ms for
		humidity and 44 ms for temperature. To keep self heating below 0.1 degree
		Celsius, the device should not be active for more than 10% of the time. For
		this reason, the driver performs no more than two measurements per second and
		reports cached information if polled more frequently.

		Different resolutions, the on-chip heater, using the CRC checksum and reading
		the serial number are not supported yet.

drivers/hwmon/Kconfig

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		@@ -511,6 +511,16 @@ config SENSORS_HIH6130
		This driver can also be built as a module. If so, the module
		will be called hih6130.

		config SENSORS_HTU21
		tristate "Measurement Specialties HTU21D humidity/temperature sensors"
		depends on I2C
		help
		If you say yes here you get support for the Measurement Specialties
		HTU21D humidity and temperature sensors.

		This driver can also be built as a module. If so, the module
		will be called htu21.

		config SENSORS_CORETEMP
		tristate "Intel Core/Core2/Atom temperature sensor"
		depends on X86

drivers/hwmon/Makefile

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		@@ -65,6 +65,7 @@ obj-$(CONFIG_SENSORS_GL518SM) += gl518sm.o
		obj-$(CONFIG_SENSORS_GL520SM) += gl520sm.o
		obj-$(CONFIG_SENSORS_GPIO_FAN) += gpio-fan.o
		obj-$(CONFIG_SENSORS_HIH6130) += hih6130.o
		obj-$(CONFIG_SENSORS_HTU21) += htu21.o
		obj-$(CONFIG_SENSORS_ULTRA45) += ultra45_env.o
		obj-$(CONFIG_SENSORS_I5K_AMB) += i5k_amb.o
		obj-$(CONFIG_SENSORS_IBMAEM) += ibmaem.o

drivers/hwmon/htu21.c

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		/*
		* Measurement Specialties HTU21D humidity and temperature sensor driver
		*
		* Copyright (C) 2013 William Markezana <william.markezana@meas-spec.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 <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>

		/* HTU21 Commands */
		#define HTU21_T_MEASUREMENT_HM 0xE3
		#define HTU21_RH_MEASUREMENT_HM 0xE5

		struct htu21 {
		struct device *hwmon_dev;
		struct mutex lock;
		bool valid;
		unsigned long last_update;
		int temperature;
		int humidity;
		};

		static inline int htu21_temp_ticks_to_millicelsius(int ticks)
		{
		ticks &= ~0x0003; /* clear status bits */
		/*
		* Formula T = -46.85 + 175.72 * ST / 2^16 from datasheet p14,
		* optimized for integer fixed point (3 digits) arithmetic
		*/
		return ((21965 * ticks) >> 13) - 46850;
		}

		static inline int htu21_rh_ticks_to_per_cent_mille(int ticks)
		{
		ticks &= ~0x0003; /* clear status bits */
		/*
		* Formula RH = -6 + 125 * SRH / 2^16 from datasheet p14,
		* optimized for integer fixed point (3 digits) arithmetic
		*/
		return ((15625 * ticks) >> 13) - 6000;
		}

		static int htu21_update_measurements(struct i2c_client *client)
		{
		int ret = 0;
		struct htu21 *htu21 = i2c_get_clientdata(client);

		mutex_lock(&htu21->lock);

		if (time_after(jiffies, htu21->last_update + HZ / 2) \|\|
		!htu21->valid) {
		ret = i2c_smbus_read_word_swapped(client,
		HTU21_T_MEASUREMENT_HM);
		if (ret < 0)
		goto out;
		htu21->temperature = htu21_temp_ticks_to_millicelsius(ret);
		ret = i2c_smbus_read_word_swapped(client,
		HTU21_RH_MEASUREMENT_HM);
		if (ret < 0)
		goto out;
		htu21->humidity = htu21_rh_ticks_to_per_cent_mille(ret);
		htu21->last_update = jiffies;
		htu21->valid = true;
		}
		out:
		mutex_unlock(&htu21->lock);

		return ret >= 0 ? 0 : ret;
		}

		static ssize_t htu21_show_temperature(struct device *dev,
		struct device_attribute attr, char buf)
		{
		struct i2c_client *client = to_i2c_client(dev);
		struct htu21 *htu21 = i2c_get_clientdata(client);
		int ret = htu21_update_measurements(client);
		if (ret < 0)
		return ret;
		return sprintf(buf, "%d\n", htu21->temperature);
		}

		static ssize_t htu21_show_humidity(struct device *dev,
		struct device_attribute attr, char buf)
		{
		struct i2c_client *client = to_i2c_client(dev);
		struct htu21 *htu21 = i2c_get_clientdata(client);
		int ret = htu21_update_measurements(client);
		if (ret < 0)
		return ret;
		return sprintf(buf, "%d\n", htu21->humidity);
		}

		static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO,
		htu21_show_temperature, NULL, 0);
		static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO,
		htu21_show_humidity, NULL, 0);

		static struct attribute *htu21_attributes[] = {
		&sensor_dev_attr_temp1_input.dev_attr.attr,
		&sensor_dev_attr_humidity1_input.dev_attr.attr,
		NULL
		};

		static const struct attribute_group htu21_group = {
		.attrs = htu21_attributes,
		};

		static int htu21_probe(struct i2c_client *client,
		const struct i2c_device_id *id)
		{
		struct htu21 *htu21;
		int err;

		if (!i2c_check_functionality(client->adapter,
		I2C_FUNC_SMBUS_READ_WORD_DATA)) {
		dev_err(&client->dev,
		"adapter does not support SMBus word transactions\n");
		return -ENODEV;
		}

		htu21 = devm_kzalloc(&client->dev, sizeof(*htu21), GFP_KERNEL);
		if (!htu21)
		return -ENOMEM;

		i2c_set_clientdata(client, htu21);

		mutex_init(&htu21->lock);

		err = sysfs_create_group(&client->dev.kobj, &htu21_group);
		if (err) {
		dev_dbg(&client->dev, "could not create sysfs files\n");
		return err;
		}
		htu21->hwmon_dev = hwmon_device_register(&client->dev);
		if (IS_ERR(htu21->hwmon_dev)) {
		dev_dbg(&client->dev, "unable to register hwmon device\n");
		err = PTR_ERR(htu21->hwmon_dev);
		goto error;
		}

		dev_info(&client->dev, "initialized\n");

		return 0;

		error:
		sysfs_remove_group(&client->dev.kobj, &htu21_group);
		return err;
		}

		static int htu21_remove(struct i2c_client *client)
		{
		struct htu21 *htu21 = i2c_get_clientdata(client);

		hwmon_device_unregister(htu21->hwmon_dev);
		sysfs_remove_group(&client->dev.kobj, &htu21_group);

		return 0;
		}

		static const struct i2c_device_id htu21_id[] = {
		{ "htu21", 0 },
		{ }
		};
		MODULE_DEVICE_TABLE(i2c, htu21_id);

		static struct i2c_driver htu21_driver = {
		.class = I2C_CLASS_HWMON,
		.driver = {
		.name = "htu21",
		},
		.probe = htu21_probe,
		.remove = htu21_remove,
		.id_table = htu21_id,
		};

		module_i2c_driver(htu21_driver);

		MODULE_AUTHOR("William Markezana <william.markezana@meas-spec.com>");
		MODULE_DESCRIPTION("MEAS HTU21D humidity and temperature sensor driver");
		MODULE_LICENSE("GPL");