hwmon: (htu21) Add Measurement Specialties HTU21D support

Signed-off-by: William Markezana <william.markezana@meas-spec.com>
[Guenter Roeck - minor formatting changes]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

3 files changed, 210 insertions, 0 deletions

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 0ff09d8d987b..b3ab9d43bb3e 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -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
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 4f0fb5235f42..ec7cde06eb52 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -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
index 000000000000..839086e0e951
--- /dev/null
+++ b/drivers/hwmon/htu21.c
@@ -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");