--- /dev/null
+/* 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");
Code Review / kvmfornfv.git / blobdiff