hwmon: (htu21) Add Measurement Specialties HTU21D support
authorWilliam Markezana <william.markezana@meas-spec.com>
Thu, 29 Aug 2013 11:51:42 +0000 (13:51 +0200)
committerGuenter Roeck <linux@roeck-us.net>
Thu, 29 Aug 2013 16:09:12 +0000 (09:09 -0700)
Signed-off-by: William Markezana <william.markezana@meas-spec.com>
[Guenter Roeck - minor formatting changes]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Documentation/hwmon/htu21 [new file with mode: 0644]
drivers/hwmon/Kconfig
drivers/hwmon/Makefile
drivers/hwmon/htu21.c [new file with mode: 0644]

diff --git a/Documentation/hwmon/htu21 b/Documentation/hwmon/htu21
new file mode 100644 (file)
index 0000000..f39a215
--- /dev/null
@@ -0,0 +1,46 @@
+Kernel driver htu21
+===================
+
+Supported chips:
+  * Measurement Specialties HTU21D
+    Prefix: 'htu21'
+    Addresses scanned: none
+    Datasheet: Publicly available at the Measurement Specialties website
+    http://www.meas-spec.com/downloads/HTU21D.pdf
+
+
+Author:
+  William Markezana <william.markezana@meas-spec.com>
+
+Description
+-----------
+
+The HTU21D is a humidity and temperature sensor in a DFN package of
+only 3 x 3 mm footprint and 0.9 mm height.
+
+The devices communicate with the I2C protocol. All sensors are set to the
+same I2C address 0x40, so an entry with I2C_BOARD_INFO("htu21", 0x40) can
+be used in the board setup code.
+
+This driver does not auto-detect devices. You will have to instantiate the
+devices explicitly. Please see Documentation/i2c/instantiating-devices
+for details.
+
+sysfs-Interface
+---------------
+
+temp1_input - temperature input
+humidity1_input - humidity input
+
+Notes
+-----
+
+The driver uses the default resolution settings of 12 bit for humidity and 14
+bit for temperature, which results in typical measurement times of 11 ms for
+humidity and 44 ms for temperature. To keep self heating below 0.1 degree
+Celsius, the device should not be active for more than 10% of the time. For
+this reason, the driver performs no more than two measurements per second and
+reports cached information if polled more frequently.
+
+Different resolutions, the on-chip heater, using the CRC checksum and reading
+the serial number are not supported yet.
index 0ff09d8d987beb02c165bde92678a0f4ba49229f..b3ab9d43bb3e8591c7d43c8728e5a3493f7b710e 100644 (file)
@@ -511,6 +511,16 @@ config SENSORS_HIH6130
          This driver can also be built as a module.  If so, the module
          will be called hih6130.
 
+config SENSORS_HTU21
+       tristate "Measurement Specialties HTU21D humidity/temperature sensors"
+       depends on I2C
+       help
+         If you say yes here you get support for the Measurement Specialties
+         HTU21D humidity and temperature sensors.
+
+         This driver can also be built as a module.  If so, the module
+         will be called htu21.
+
 config SENSORS_CORETEMP
        tristate "Intel Core/Core2/Atom temperature sensor"
        depends on X86
index 4f0fb5235f42933fc16ec59e1b7371dac0505af4..ec7cde06eb52bb628e1eb67d661d3d652ee91d97 100644 (file)
@@ -65,6 +65,7 @@ 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-$(CONFIG_SENSORS_HTU21)    += htu21.o
 obj-$(CONFIG_SENSORS_ULTRA45)  += ultra45_env.o
 obj-$(CONFIG_SENSORS_I5K_AMB)  += i5k_amb.o
 obj-$(CONFIG_SENSORS_IBMAEM)   += ibmaem.o
diff --git a/drivers/hwmon/htu21.c b/drivers/hwmon/htu21.c
new file mode 100644 (file)
index 0000000..839086e
--- /dev/null
@@ -0,0 +1,199 @@
+/*
+ * Measurement Specialties HTU21D humidity and temperature sensor driver
+ *
+ * Copyright (C) 2013 William Markezana <william.markezana@meas-spec.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.
+ *
+ */
+
+#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/jiffies.h>
+
+/* HTU21 Commands */
+#define HTU21_T_MEASUREMENT_HM 0xE3
+#define HTU21_RH_MEASUREMENT_HM        0xE5
+
+struct htu21 {
+       struct device *hwmon_dev;
+       struct mutex lock;
+       bool valid;
+       unsigned long last_update;
+       int temperature;
+       int humidity;
+};
+
+static inline int htu21_temp_ticks_to_millicelsius(int ticks)
+{
+       ticks &= ~0x0003; /* clear status bits */
+       /*
+        * Formula T = -46.85 + 175.72 * ST / 2^16 from datasheet p14,
+        * optimized for integer fixed point (3 digits) arithmetic
+        */
+       return ((21965 * ticks) >> 13) - 46850;
+}
+
+static inline int htu21_rh_ticks_to_per_cent_mille(int ticks)
+{
+       ticks &= ~0x0003; /* clear status bits */
+       /*
+        * Formula RH = -6 + 125 * SRH / 2^16 from datasheet p14,
+        * optimized for integer fixed point (3 digits) arithmetic
+        */
+       return ((15625 * ticks) >> 13) - 6000;
+}
+
+static int htu21_update_measurements(struct i2c_client *client)
+{
+       int ret = 0;
+       struct htu21 *htu21 = i2c_get_clientdata(client);
+
+       mutex_lock(&htu21->lock);
+
+       if (time_after(jiffies, htu21->last_update + HZ / 2) ||
+           !htu21->valid) {
+               ret = i2c_smbus_read_word_swapped(client,
+                                                 HTU21_T_MEASUREMENT_HM);
+               if (ret < 0)
+                       goto out;
+               htu21->temperature = htu21_temp_ticks_to_millicelsius(ret);
+               ret = i2c_smbus_read_word_swapped(client,
+                                                 HTU21_RH_MEASUREMENT_HM);
+               if (ret < 0)
+                       goto out;
+               htu21->humidity = htu21_rh_ticks_to_per_cent_mille(ret);
+               htu21->last_update = jiffies;
+               htu21->valid = true;
+       }
+out:
+       mutex_unlock(&htu21->lock);
+
+       return ret >= 0 ? 0 : ret;
+}
+
+static ssize_t htu21_show_temperature(struct device *dev,
+                                     struct device_attribute *attr, char *buf)
+{
+       struct i2c_client *client = to_i2c_client(dev);
+       struct htu21 *htu21 = i2c_get_clientdata(client);
+       int ret = htu21_update_measurements(client);
+       if (ret < 0)
+               return ret;
+       return sprintf(buf, "%d\n", htu21->temperature);
+}
+
+static ssize_t htu21_show_humidity(struct device *dev,
+                                  struct device_attribute *attr, char *buf)
+{
+       struct i2c_client *client = to_i2c_client(dev);
+       struct htu21 *htu21 = i2c_get_clientdata(client);
+       int ret = htu21_update_measurements(client);
+       if (ret < 0)
+               return ret;
+       return sprintf(buf, "%d\n", htu21->humidity);
+}
+
+static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO,
+                         htu21_show_temperature, NULL, 0);
+static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO,
+                         htu21_show_humidity, NULL, 0);
+
+static struct attribute *htu21_attributes[] = {
+       &sensor_dev_attr_temp1_input.dev_attr.attr,
+       &sensor_dev_attr_humidity1_input.dev_attr.attr,
+       NULL
+};
+
+static const struct attribute_group htu21_group = {
+       .attrs = htu21_attributes,
+};
+
+static int htu21_probe(struct i2c_client *client,
+                      const struct i2c_device_id *id)
+{
+       struct htu21 *htu21;
+       int err;
+
+       if (!i2c_check_functionality(client->adapter,
+                                    I2C_FUNC_SMBUS_READ_WORD_DATA)) {
+               dev_err(&client->dev,
+                       "adapter does not support SMBus word transactions\n");
+               return -ENODEV;
+       }
+
+       htu21 = devm_kzalloc(&client->dev, sizeof(*htu21), GFP_KERNEL);
+       if (!htu21)
+               return -ENOMEM;
+
+       i2c_set_clientdata(client, htu21);
+
+       mutex_init(&htu21->lock);
+
+       err = sysfs_create_group(&client->dev.kobj, &htu21_group);
+       if (err) {
+               dev_dbg(&client->dev, "could not create sysfs files\n");
+               return err;
+       }
+       htu21->hwmon_dev = hwmon_device_register(&client->dev);
+       if (IS_ERR(htu21->hwmon_dev)) {
+               dev_dbg(&client->dev, "unable to register hwmon device\n");
+               err = PTR_ERR(htu21->hwmon_dev);
+               goto error;
+       }
+
+       dev_info(&client->dev, "initialized\n");
+
+       return 0;
+
+error:
+       sysfs_remove_group(&client->dev.kobj, &htu21_group);
+       return err;
+}
+
+static int htu21_remove(struct i2c_client *client)
+{
+       struct htu21 *htu21 = i2c_get_clientdata(client);
+
+       hwmon_device_unregister(htu21->hwmon_dev);
+       sysfs_remove_group(&client->dev.kobj, &htu21_group);
+
+       return 0;
+}
+
+static const struct i2c_device_id htu21_id[] = {
+       { "htu21", 0 },
+       { }
+};
+MODULE_DEVICE_TABLE(i2c, htu21_id);
+
+static struct i2c_driver htu21_driver = {
+       .class = I2C_CLASS_HWMON,
+       .driver = {
+               .name   = "htu21",
+       },
+       .probe       = htu21_probe,
+       .remove      = htu21_remove,
+       .id_table    = htu21_id,
+};
+
+module_i2c_driver(htu21_driver);
+
+MODULE_AUTHOR("William Markezana <william.markezana@meas-spec.com>");
+MODULE_DESCRIPTION("MEAS HTU21D humidity and temperature sensor driver");
+MODULE_LICENSE("GPL");