/* 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");