diff options
Diffstat (limited to 'drivers/hwmon/hih6130.c')
| -rw-r--r-- | drivers/hwmon/hih6130.c | 293 |
1 files changed, 293 insertions, 0 deletions
diff --git a/drivers/hwmon/hih6130.c b/drivers/hwmon/hih6130.c new file mode 100644 index 000000000000..e8ee75f55472 --- /dev/null +++ b/drivers/hwmon/hih6130.c @@ -0,0 +1,293 @@ +/* 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> + +/** + * 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 + */ +struct hih6130 { + struct device *hwmon_dev; + struct mutex lock; + bool valid; + unsigned long last_update; + int temperature; + int humidity; +}; + +/** + * 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 + * @client: I2C client device + * + * Returns 0 on success, else negative errno. + */ +static int hih6130_update_measurements(struct i2c_client *client) +{ + int ret = 0; + int t; + struct hih6130 *hih6130 = i2c_get_clientdata(client); + 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, no data, to request a measurement */ + ret = i2c_master_send(client, tmp, 0); + 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 i2c_client *client = to_i2c_client(dev); + struct hih6130 *hih6130 = i2c_get_clientdata(client); + int ret = hih6130_update_measurements(client); + 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 i2c_client *client = to_i2c_client(dev); + struct hih6130 *hih6130 = i2c_get_clientdata(client); + int ret = hih6130_update_measurements(client); + 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_attributes[] = { + &sensor_dev_attr_temp1_input.dev_attr.attr, + &sensor_dev_attr_humidity1_input.dev_attr.attr, + NULL +}; + +static const struct attribute_group hih6130_attr_group = { + .attrs = hih6130_attributes, +}; + +/** + * hih6130_probe() - probe device + * @client: I2C client device + * @id: device ID + * + * Called by the I2C core when an entry in the ID table matches a + * device's name. + * Returns 0 on success. + */ +static int __devinit hih6130_probe(struct i2c_client *client, + const struct i2c_device_id *id) +{ + struct hih6130 *hih6130; + int err; + + 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(&client->dev, sizeof(*hih6130), GFP_KERNEL); + if (!hih6130) + return -ENOMEM; + + i2c_set_clientdata(client, hih6130); + + mutex_init(&hih6130->lock); + + err = sysfs_create_group(&client->dev.kobj, &hih6130_attr_group); + if (err) { + dev_dbg(&client->dev, "could not create sysfs files\n"); + return err; + } + + hih6130->hwmon_dev = hwmon_device_register(&client->dev); + if (IS_ERR(hih6130->hwmon_dev)) { + dev_dbg(&client->dev, "unable to register hwmon device\n"); + err = PTR_ERR(hih6130->hwmon_dev); + goto fail_remove_sysfs; + } + + return 0; + +fail_remove_sysfs: + sysfs_remove_group(&client->dev.kobj, &hih6130_attr_group); + return err; +} + +/** + * hih6130_remove() - remove device + * @client: I2C client device + */ +static int __devexit hih6130_remove(struct i2c_client *client) +{ + struct hih6130 *hih6130 = i2c_get_clientdata(client); + + hwmon_device_unregister(hih6130->hwmon_dev); + sysfs_remove_group(&client->dev.kobj, &hih6130_attr_group); + + return 0; +} + +/* 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, + .remove = __devexit_p(hih6130_remove), + .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"); |