/* Honeywell HIH-6130/HIH-6131 humidity and temperature sensor driver
*
* Copyright (C) 2012 Iain Paton <ipaton0@gmail.com>
*
* heavily based on the sht21 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 sheets available (2012-06-22) at
* http://sensing.honeywell.com/index.php?ci_id=3106&la_id=1&defId=44872
*/
#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/delay.h>
#include <linux/jiffies.h>
/**
* struct hih6130 - HIH-6130 device specific data
* @hwmon_dev: device registered with hwmon
* @lock: mutex to protect measurement values
* @valid: only false before first measurement is taken
* @last_update: time of last update (jiffies)
* @temperature: cached temperature measurement value
* @humidity: cached humidity measurement value
* @write_length: length for I2C measurement request
*/
struct hih6130 {
struct i2c_client *client;
struct mutex lock;
bool valid;
unsigned long last_update;
int temperature;
int humidity;
size_t write_length;
};
/**
* hih6130_temp_ticks_to_millicelsius() - convert raw temperature ticks to
* milli celsius
* @ticks: temperature ticks value received from sensor
*/
static inline int hih6130_temp_ticks_to_millicelsius(int ticks)
{
ticks = ticks >> 2;
/*
* from data sheet section 5.0
* Formula T = ( ticks / ( 2^14 - 2 ) ) * 165 -40
*/
return (DIV_ROUND_CLOSEST(ticks * 1650, 16382) - 400) * 100;
}
/**
* hih6130_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 hih6130_rh_ticks_to_per_cent_mille(int ticks)
{
ticks &= ~0xC000; /* clear status bits */
/*
* from data sheet section 4.0
* Formula RH = ( ticks / ( 2^14 -2 ) ) * 100
*/
return DIV_ROUND_CLOSEST(ticks * 1000, 16382) * 100;
}
/**
* hih6130_update_measurements() - get updated measurements from device
* @dev: device
*
* Returns 0 on success, else negative errno.
*/
static int hih6130_update_measurements(struct device *dev)
{
struct hih6130 *hih6130 = dev_get_drvdata(dev);
struct i2c_client *client = hih6130->client;
int ret = 0;
int t;
unsigned char tmp[4];
struct i2c_msg msgs[1] = {
{
.addr = client->addr,
.flags = I2C_M_RD,
.len = 4,
.buf = tmp,
}
};
mutex_lock(&hih6130->lock);
/*
* While the measurement can be completed in ~40ms the sensor takes
* much longer to react to a change in external conditions. How quickly
* it reacts depends on airflow and other factors outwith our control.
* The datasheet specifies maximum 'Response time' for humidity at 8s
* and temperature at 30s under specified conditions.
* We therefore choose to only read the sensor at most once per second.
* This trades off pointless activity polling the sensor much faster
* than it can react against better response times in conditions more
* favourable than specified in the datasheet.
*/
if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) {
/*
* Write to slave address to request a measurement.
* According with the datasheet it should be with no data, but
* for systems with I2C bus drivers that do not allow zero
* length packets we write one dummy byte to allow sensor
* measurements on them.
*/
tmp[0] = 0;
ret = i2c_master_send(client, tmp, hih6130->write_length);
if (ret < 0)
goto out;
/* measurement cycle time is ~36.65msec */
msleep(40);
ret = i2c_transfer(client->adapter, msgs, 1);
if (ret < 0)
goto out;
if ((tmp[0] & 0xC0) != 0) {
dev_err(&client->dev, "Error while reading measurement result\n");
ret = -EIO;
goto out;
}
t = (tmp[0] << 8) + tmp[1];
hih6130->humidity = hih6130_rh_ticks_to_per_cent_mille(t);
t = (tmp[2] << 8) + tmp[3];
hih6130->temperature = hih6130_temp_ticks_to_millicelsius(t);
hih6130->last_update = jiffies;
hih6130->valid = true;
}
out:
mutex_unlock(&hih6130->lock);
return ret >= 0 ? 0 : ret;
}
/**
* hih6130_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 hih6130_show_temperature(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct hih6130 *hih6130 = dev_get_drvdata(dev);
int ret;
ret = hih6130_update_measurements(dev);
if (ret < 0)
return ret;
return sprintf(buf, "%d\n", hih6130->temperature);
}
/**
* hih6130_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 hih6130_show_humidity(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct hih6130 *hih6130 = dev_get_drvdata(dev);
int ret;
ret = hih6130_update_measurements(dev);
if (ret < 0)
return ret;
return sprintf(buf, "%d\n", hih6130->humidity);
}
/* sysfs attributes */
static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, hih6130_show_temperature,
NULL, 0);
static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, hih6130_show_humidity,
NULL, 0);
static struct attribute *hih6130_attrs[] = {
&sensor_dev_attr_temp1_input.dev_attr.attr,
&sensor_dev_attr_humidity1_input.dev_attr.attr,
NULL
};
ATTRIBUTE_GROUPS(hih6130);
static int hih6130_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct device *dev = &client->dev;
struct hih6130 *hih6130;
struct device *hwmon_dev;
if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
dev_err(&client->dev, "adapter does not support true I2C\n");
return -ENODEV;
}
hih6130 = devm_kzalloc(dev, sizeof(*hih6130), GFP_KERNEL);
if (!hih6130)
return -ENOMEM;
hih6130->client = client;
mutex_init(&hih6130->lock);
if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_QUICK))
hih6130->write_length = 1;
hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
hih6130,
hih6130_groups);
return PTR_ERR_OR_ZERO(hwmon_dev);
}
/* Device ID table */
static const struct i2c_device_id hih6130_id[] = {
{ "hih6130", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, hih6130_id);
static struct i2c_driver hih6130_driver = {
.driver.name = "hih6130",
.probe = hih6130_probe,
.id_table = hih6130_id,
};
module_i2c_driver(hih6130_driver);
MODULE_AUTHOR("Iain Paton <ipaton0@gmail.com>");
MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver");
MODULE_LICENSE("GPL");
