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Commit 2ff44072 authored by Guenter Roeck's avatar Guenter Roeck
Browse files

hwmon: (htu21) Remove driver 



HTU21 is now supported by IIO, and can be instantiated as hwmon driver
using the iio-hwmon bridge. An explicit hwmon driver is no longer needed.

Cc: William Markezana <william.markezana@meas-spec.com>
Cc: Ludovic Tancerel <ludovic.tancerel@maplehightech.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Reviewed-by: default avatarJean Delvare <jdelvare@suse.de>
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent a3a316cf

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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@@ -859,16 +859,6 @@ config SENSORS_MAX31790 
	  This driver can also be built as a module.  If so, the module

	  will be called max31790.



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_MCP3021

	tristate "Microchip MCP3021 and compatibles"

	depends on I2C

drivers/hwmon/Makefile

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@@ -68,7 +68,6 @@ 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_I5500)	+= i5500_temp.o

obj-$(CONFIG_SENSORS_I5K_AMB)	+= i5k_amb.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 i2c_client *client;

	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 device *dev)

{

	struct htu21 *htu21 = dev_get_drvdata(dev);

	struct i2c_client *client = htu21->client;

	int ret = 0;



	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 htu21 *htu21 = dev_get_drvdata(dev);

	int ret;



	ret = htu21_update_measurements(dev);

	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 htu21 *htu21 = dev_get_drvdata(dev);

	int ret;



	ret = htu21_update_measurements(dev);

	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_attrs[] = {

	&sensor_dev_attr_temp1_input.dev_attr.attr,

	&sensor_dev_attr_humidity1_input.dev_attr.attr,

	NULL

};



ATTRIBUTE_GROUPS(htu21);



static int htu21_probe(struct i2c_client *client,

		       const struct i2c_device_id *id)

{

	struct device *dev = &client->dev;

	struct htu21 *htu21;

	struct device *hwmon_dev;



	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(dev, sizeof(*htu21), GFP_KERNEL);

	if (!htu21)

		return -ENOMEM;



	htu21->client = client;

	mutex_init(&htu21->lock);



	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,

							   htu21,

							   htu21_groups);

	return PTR_ERR_OR_ZERO(hwmon_dev);

}



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,

	.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");