hwmon: Honeywell Humidicon HIH-6130/HIH-6131 humidity and temperature sensor driver

This is a new driver for the Honeywell Humidicon HIH-6130/HIH-6131 humidity sensor.

The driver is based on the existing Sensiron sht21 driver with the necessary changes
to the probe, update_measurements and conversion functions necessary to use the
Honeywell sensors.

There's no difference between the 6130 & 6131 other than the 6131 having an external
condensation filter attached.
Signed-off-by: NIain Paton <ipaton0@gmail.com>
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>

Documentation/hwmon/hih6130

+Kernel driver hih6130
+=====================
+
+Supported chips:
+  * Honeywell HIH-6130 / HIH-6131
+    Prefix: 'hih6130'
+    Addresses scanned: none
+    Datasheet: Publicly available at the Honeywell website
+    http://sensing.honeywell.com/index.php?ci_id=3106&la_id=1&defId=44872
+
+Author:
+  Iain Paton <ipaton0@gmail.com>
+
+Description
+-----------
+
+The HIH-6130 & HIH-6131 are humidity and temperature sensors in a SO8 package.
+The difference between the two devices is that the HIH-6131 has a condensation
+filter.
+
+The devices communicate with the I2C protocol. All sensors are set to the same
+I2C address 0x27 by default, so an entry with I2C_BOARD_INFO("hih6130", 0x27)
+can be used in the board setup code.
+
+Please see Documentation/i2c/instantiating-devices for details on how to
+instantiate I2C devices.
+
+sysfs-Interface
+---------------
+
+temp1_input - temperature input
+humidity1_input - humidity input
+
+Notes
+-----
+
+Command mode and alarms are not currently supported.

drivers/hwmon/Kconfig

@@ -443,6 +443,16 @@ config SENSORS_GPIO_FAN
 	  This driver can also be built as a module.  If so, the module
 	  will be called gpio-fan.
 
+config SENSORS_HIH6130
+	tristate "Honeywell Humidicon HIH-6130 humidity/temperature sensor"
+	depends on I2C && EXPERIMENTAL
+	help
+	  If you say yes here you get support for Honeywell Humidicon
+	  HIH-6130 and HIH-6131 Humidicon humidity sensors.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called hih6130.
+
 config SENSORS_CORETEMP
 	tristate "Intel Core/Core2/Atom temperature sensor"
 	depends on X86 && PCI && EXPERIMENTAL

drivers/hwmon/Makefile

@@ -59,6 +59,7 @@ obj-$(CONFIG_SENSORS_G760A)	+= g760a.o
 obj-$(CONFIG_SENSORS_GL518SM)	+= gl518sm.o
 obj-$(CONFIG_SENSORS_GL520SM)	+= gl520sm.o
 obj-$(CONFIG_SENSORS_GPIO_FAN)	+= gpio-fan.o
+obj-$(CONFIG_SENSORS_HIH6130)	+= hih6130.o
 obj-$(CONFIG_SENSORS_ULTRA45)	+= ultra45_env.o
 obj-$(CONFIG_SENSORS_I5K_AMB)	+= i5k_amb.o
 obj-$(CONFIG_SENSORS_IBMAEM)	+= ibmaem.o

drivers/hwmon/hih6130.c

+/* 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");