1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Sensirion SHT21 humidity and temperature sensor driver
14 #include <linux/hwmon-sysfs.h>
29  * struct sht21 - SHT21 device specific data
34  * @humidity: cached humidity measurement value
43 	int humidity;  member
49  * sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to
51  * @ticks: temperature ticks value received from sensor
57 	 * Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2,  in sht21_temp_ticks_to_millicelsius()
60 	return ((21965 * ticks) >> 13) - 46850;  in sht21_temp_ticks_to_millicelsius()
64  * sht21_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to
65  * one-thousandths of a percent relative humidity
66  * @ticks: humidity ticks value received from sensor
72 	 * Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1,  in sht21_rh_ticks_to_per_cent_mille()
75 	return ((15625 * ticks) >> 13) - 6000;  in sht21_rh_ticks_to_per_cent_mille()
79  * sht21_update_measurements() - get updated measurements from device
88 	struct i2c_client *client = sht21->client;  in sht21_update_measurements()
90 	mutex_lock(&sht21->lock);  in sht21_update_measurements()
93 	 * SHT2x should not be active for more than 10% of the time - e.g.  in sht21_update_measurements()
96 	if (time_after(jiffies, sht21->last_update + HZ / 2) || !sht21->valid) {  in sht21_update_measurements()
101 		sht21->temperature = sht21_temp_ticks_to_millicelsius(ret);  in sht21_update_measurements()
106 		sht21->humidity = sht21_rh_ticks_to_per_cent_mille(ret);  in sht21_update_measurements()
107 		sht21->last_update = jiffies;  in sht21_update_measurements()
108 		sht21->valid = true;  in sht21_update_measurements()
111 	mutex_unlock(&sht21->lock);  in sht21_update_measurements()
117  * sht21_temperature_show() - show temperature measurement value in sysfs
135 	return sprintf(buf, "%d\n", sht21->temperature);  in sht21_temperature_show()
139  * sht21_humidity_show() - show humidity measurement value in sysfs
156 	return sprintf(buf, "%d\n", sht21->humidity);  in sht21_humidity_show()
161 	struct i2c_client *client = sht21->client;  in eic_read()
167 			.addr = client->addr,  in eic_read()
173 			.addr = client->addr,  in eic_read()
183 	ret = i2c_transfer(client->adapter, msgs, 2);  in eic_read()
194 	ret = i2c_transfer(client->adapter, msgs, 2);  in eic_read()
202 	ret = snprintf(sht21->eic, sizeof(sht21->eic), "%8phN\n", eic);  in eic_read()
205 		sht21->eic[0] = 0;  in eic_read()
211  * eic_show() - show Electronic Identification Code in sysfs
226 	ret = sizeof(sht21->eic) - 1;  in eic_show()
227 	mutex_lock(&sht21->lock);  in eic_show()
228 	if (!sht21->eic[0])  in eic_show()
231 		memcpy(buf, sht21->eic, ret);  in eic_show()
232 	mutex_unlock(&sht21->lock);  in eic_show()
252 	struct device *dev = &client->dev;  in sht21_probe()
256 	if (!i2c_check_functionality(client->adapter,  in sht21_probe()
258 		dev_err(&client->dev,  in sht21_probe()
260 		return -ENODEV;  in sht21_probe()
265 		return -ENOMEM;  in sht21_probe()
267 	sht21->client = client;  in sht21_probe()
269 	mutex_init(&sht21->lock);  in sht21_probe()
271 	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,  in sht21_probe()
292 MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver");