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path: root/drivers/hwmon/htu21.c
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-rw-r--r--drivers/hwmon/htu21.c174
1 files changed, 174 insertions, 0 deletions
diff --git a/drivers/hwmon/htu21.c b/drivers/hwmon/htu21.c
new file mode 100644
index 000000000..4c3bbb72f
--- /dev/null
+++ b/drivers/hwmon/htu21.c
@@ -0,0 +1,174 @@
+/*
+ * 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 i2c_client *client;
+ 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 device *dev)
+{
+ struct htu21 *htu21 = dev_get_drvdata(dev);
+ struct i2c_client *client = htu21->client;
+ int ret = 0;
+
+ 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 htu21 *htu21 = dev_get_drvdata(dev);
+ int ret;
+
+ ret = htu21_update_measurements(dev);
+ 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 htu21 *htu21 = dev_get_drvdata(dev);
+ int ret;
+
+ ret = htu21_update_measurements(dev);
+ 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_attrs[] = {
+ &sensor_dev_attr_temp1_input.dev_attr.attr,
+ &sensor_dev_attr_humidity1_input.dev_attr.attr,
+ NULL
+};
+
+ATTRIBUTE_GROUPS(htu21);
+
+static int htu21_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct device *dev = &client->dev;
+ struct htu21 *htu21;
+ struct device *hwmon_dev;
+
+ 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(dev, sizeof(*htu21), GFP_KERNEL);
+ if (!htu21)
+ return -ENOMEM;
+
+ htu21->client = client;
+ mutex_init(&htu21->lock);
+
+ hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
+ htu21,
+ htu21_groups);
+ return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+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,
+ .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");