diff options
Diffstat (limited to 'drivers/hwmon/htu21.c')
| -rw-r--r-- | drivers/hwmon/htu21.c | 174 |
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"); |