1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Honeywell HIH-6130/HIH-6131 humidity and temperature sensor driver
9  * Data sheets available (2012-06-22) at
18 #include <linux/hwmon-sysfs.h>
26  * struct hih6130 - HIH-6130 device specific data
32  * @humidity: cached humidity measurement value
41 	int humidity;  member
46  * hih6130_temp_ticks_to_millicelsius() - convert raw temperature ticks to
48  * @ticks: temperature ticks value received from sensor
55 	 * Formula T = ( ticks / ( 2^14 - 2 ) ) * 165 -40  in hih6130_temp_ticks_to_millicelsius()
57 	return (DIV_ROUND_CLOSEST(ticks * 1650, 16382) - 400) * 100;  in hih6130_temp_ticks_to_millicelsius()
61  * hih6130_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to
62  * one-thousandths of a percent relative humidity
63  * @ticks: humidity ticks value received from sensor
70 	 * Formula RH = ( ticks / ( 2^14 -2 ) ) * 100  in hih6130_rh_ticks_to_per_cent_mille()
76  * hih6130_update_measurements() - get updated measurements from device
84 	struct i2c_client *client = hih6130->client;  in hih6130_update_measurements()
90 			.addr = client->addr,  in hih6130_update_measurements()
97 	mutex_lock(&hih6130->lock);  in hih6130_update_measurements()
100 	 * While the measurement can be completed in ~40ms the sensor takes  in hih6130_update_measurements()
103 	 * The datasheet specifies maximum 'Response time' for humidity at 8s  in hih6130_update_measurements()
105 	 * We therefore choose to only read the sensor at most once per second.  in hih6130_update_measurements()
106 	 * This trades off pointless activity polling the sensor much faster  in hih6130_update_measurements()
110 	if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) {  in hih6130_update_measurements()
116 		 * length packets we write one dummy byte to allow sensor  in hih6130_update_measurements()
120 		ret = i2c_master_send(client, tmp, hih6130->write_length);  in hih6130_update_measurements()
127 		ret = i2c_transfer(client->adapter, msgs, 1);  in hih6130_update_measurements()
132 			dev_err(&client->dev, "Error while reading measurement result\n");  in hih6130_update_measurements()
133 			ret = -EIO;  in hih6130_update_measurements()
138 		hih6130->humidity = hih6130_rh_ticks_to_per_cent_mille(t);  in hih6130_update_measurements()
141 		hih6130->temperature = hih6130_temp_ticks_to_millicelsius(t);  in hih6130_update_measurements()
143 		hih6130->last_update = jiffies;  in hih6130_update_measurements()
144 		hih6130->valid = true;  in hih6130_update_measurements()
147 	mutex_unlock(&hih6130->lock);  in hih6130_update_measurements()
153  * hih6130_temperature_show() - show temperature measurement value in sysfs
171 	return sprintf(buf, "%d\n", hih6130->temperature);  in hih6130_temperature_show()
175  * hih6130_humidity_show() - show humidity measurement value in sysfs
192 	return sprintf(buf, "%d\n", hih6130->humidity);  in hih6130_humidity_show()
209 	struct device *dev = &client->dev;  in hih6130_probe()
213 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {  in hih6130_probe()
214 		dev_err(&client->dev, "adapter does not support true I2C\n");  in hih6130_probe()
215 		return -ENODEV;  in hih6130_probe()
220 		return -ENOMEM;  in hih6130_probe()
222 	hih6130->client = client;  in hih6130_probe()
223 	mutex_init(&hih6130->lock);  in hih6130_probe()
225 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_QUICK))  in hih6130_probe()
226 		hih6130->write_length = 1;  in hih6130_probe()
228 	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,  in hih6130_probe()
259 MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver");