diff options
Diffstat (limited to 'drivers/hwmon/hih6130.c')
| -rw-r--r-- | drivers/hwmon/hih6130.c | 267 |
1 files changed, 267 insertions, 0 deletions
diff --git a/drivers/hwmon/hih6130.c b/drivers/hwmon/hih6130.c new file mode 100644 index 000000000..0ae1ee1db --- /dev/null +++ b/drivers/hwmon/hih6130.c @@ -0,0 +1,267 @@ +/* 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 + * @client: pointer to I2C client device + * @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"); |