+++ /dev/null
-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.
+++ /dev/null
-/*
- * 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");
projects / cascardo / linux.git / commitdiff