htu31.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * The driver for Measurement Specialties HTU31 Temperature and Humidity sensor.
  4 *
  5 * Copyright (C) 2025
  6 * Author: Andrei Lalaev <andrey.lalaev@gmail.com>
  7 */
  8
  9#include <linux/array_size.h>
 10#include <linux/cleanup.h>
 11#include <linux/crc8.h>
 12#include <linux/debugfs.h>
 13#include <linux/delay.h>
 14#include <linux/hwmon.h>
 15#include <linux/hwmon-sysfs.h>
 16#include <linux/i2c.h>
 17#include <linux/init.h>
 18#include <linux/module.h>
 19
 20#define HTU31_READ_TEMP_HUM_CMD	0x00
 21#define HTU31_READ_SERIAL_CMD		0x0a
 22#define HTU31_CONVERSION_CMD		0x5e
 23#define HTU31_HEATER_OFF_CMD		0x02
 24#define HTU31_HEATER_ON_CMD		0x04
 25
 26#define HTU31_TEMP_HUM_LEN		6
 27
 28/* Conversion time for the highest resolution */
 29#define HTU31_HUMIDITY_CONV_TIME	10000 /* us */
 30#define HTU31_TEMPERATURE_CONV_TIME	15000 /* us */
 31
 32#define HTU31_SERIAL_NUMBER_LEN	3
 33#define HTU31_SERIAL_NUMBER_CRC_LEN	1
 34#define HTU31_SERIAL_NUMBER_CRC_OFFSET	3
 35
 36#define HTU31_CRC8_INIT_VAL		0
 37#define HTU31_CRC8_POLYNOMIAL		0x31
 38DECLARE_CRC8_TABLE(htu31_crc8_table);
 39
 40/**
 41 * struct htu31_data - all the data required to operate a HTU31 chip
 42 * @client: the i2c client associated with the HTU31
 43 * @lock: a mutex to prevent parallel access to the data
 44 * @wait_time: the time needed by sensor to convert values
 45 * @temperature: the latest temperature value in millidegrees
 46 * @humidity: the latest relative humidity value in millipercent
 47 * @serial_number: the serial number of the sensor
 48 * @heater_enable: the internal state of the heater
 49 */
 50struct htu31_data {
 51	struct i2c_client *client;
 52	struct mutex lock; /* Used to protect against parallel data updates */
 53	long wait_time;
 54	long temperature;
 55	long humidity;
 56	u8 serial_number[HTU31_SERIAL_NUMBER_LEN];
 57	bool heater_enable;
 58};
 59
 60static long htu31_temp_to_millicelsius(u16 val)
 61{
 62	return -40000 + DIV_ROUND_CLOSEST_ULL(165000ULL * val, 65535);
 63}
 64
 65static long htu31_relative_humidity(u16 val)
 66{
 67	return DIV_ROUND_CLOSEST_ULL(100000ULL * val, 65535);
 68}
 69
 70static int htu31_data_fetch_command(struct htu31_data *data)
 71{
 72	struct i2c_client *client = data->client;
 73	u8 conversion_on = HTU31_CONVERSION_CMD;
 74	u8 read_data_cmd = HTU31_READ_TEMP_HUM_CMD;
 75	u8 t_h_buf[HTU31_TEMP_HUM_LEN] = {};
 76	struct i2c_msg msgs[] = {
 77		{
 78			.addr = client->addr,
 79			.flags = 0,
 80			.len = 1,
 81			.buf = &read_data_cmd,
 82		},
 83		{
 84			.addr = client->addr,
 85			.flags = I2C_M_RD,
 86			.len = sizeof(t_h_buf),
 87			.buf = t_h_buf,
 88		},
 89	};
 90	int ret;
 91	u8 crc;
 92
 93	guard(mutex)(&data->lock);
 94
 95	ret = i2c_master_send(client, &conversion_on, 1);
 96	if (ret != 1) {
 97		ret = ret < 0 ? ret : -EIO;
 98		dev_err(&client->dev,
 99			"Conversion command is failed. Error code: %d\n", ret);
100		return ret;
101	}
102
103	fsleep(data->wait_time);
104
105	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
106	if (ret != ARRAY_SIZE(msgs)) {
107		ret = ret < 0 ? ret : -EIO;
108		dev_err(&client->dev,
109			"T&H command is failed. Error code: %d\n", ret);
110		return ret;
111	}
112
113	crc = crc8(htu31_crc8_table, &t_h_buf[0], 2, HTU31_CRC8_INIT_VAL);
114	if (crc != t_h_buf[2]) {
115		dev_err(&client->dev, "Temperature CRC mismatch\n");
116		return -EIO;
117	}
118
119	crc = crc8(htu31_crc8_table, &t_h_buf[3], 2, HTU31_CRC8_INIT_VAL);
120	if (crc != t_h_buf[5]) {
121		dev_err(&client->dev, "Humidity CRC mismatch\n");
122		return -EIO;
123	}
124
125	data->temperature = htu31_temp_to_millicelsius(be16_to_cpup((__be16 *)&t_h_buf[0]));
126	data->humidity = htu31_relative_humidity(be16_to_cpup((__be16 *)&t_h_buf[3]));
127
128	return 0;
129}
130
131static umode_t htu31_is_visible(const void *data, enum hwmon_sensor_types type,
132				u32 attr, int channel)
133{
134	switch (type) {
135	case hwmon_temp:
136	case hwmon_humidity:
137		return 0444;
138	default:
139		return 0;
140	}
141}
142
143static int htu31_read(struct device *dev, enum hwmon_sensor_types type,
144		      u32 attr, int channel, long *val)
145{
146	struct htu31_data *data = dev_get_drvdata(dev);
147	int ret;
148
149	ret = htu31_data_fetch_command(data);
150	if (ret < 0)
151		return ret;
152
153	switch (type) {
154	case hwmon_temp:
155		if (attr != hwmon_temp_input)
156			return -EINVAL;
157
158		*val = data->temperature;
159		break;
160	case hwmon_humidity:
161		if (attr != hwmon_humidity_input)
162			return -EINVAL;
163
164		*val = data->humidity;
165		break;
166	default:
167		return -EOPNOTSUPP;
168	}
169
170	return 0;
171}
172
173static int htu31_read_serial_number(struct htu31_data *data)
174{
175	struct i2c_client *client = data->client;
176	u8 read_sn_cmd = HTU31_READ_SERIAL_CMD;
177	u8 sn_buf[HTU31_SERIAL_NUMBER_LEN + HTU31_SERIAL_NUMBER_CRC_LEN];
178	struct i2c_msg msgs[] = {
179		{
180			.addr = client->addr,
181			.flags = 0,
182			.len = 1,
183			.buf = &read_sn_cmd,
184		},
185		{
186			.addr = client->addr,
187			.flags = I2C_M_RD,
188			.len = sizeof(sn_buf),
189			.buf = sn_buf,
190		},
191	};
192	int ret;
193	u8 crc;
194
195	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
196	if (ret < 0)
197		return ret;
198
199	crc = crc8(htu31_crc8_table, sn_buf, HTU31_SERIAL_NUMBER_LEN, HTU31_CRC8_INIT_VAL);
200	if (crc != sn_buf[HTU31_SERIAL_NUMBER_CRC_OFFSET]) {
201		dev_err(&client->dev, "Serial number CRC mismatch\n");
202		return -EIO;
203	}
204
205	memcpy(data->serial_number, sn_buf, HTU31_SERIAL_NUMBER_LEN);
206
207	return 0;
208}
209
210static ssize_t heater_enable_show(struct device *dev,
211				  struct device_attribute *attr,
212				  char *buf)
213{
214	struct htu31_data *data = dev_get_drvdata(dev);
215
216	return sysfs_emit(buf, "%d\n", data->heater_enable);
217}
218
219static ssize_t heater_enable_store(struct device *dev,
220				   struct device_attribute *attr,
221				   const char *buf,
222				   size_t count)
223{
224	struct htu31_data *data = dev_get_drvdata(dev);
225	u8 heater_cmd;
226	bool status;
227	int ret;
228
229	ret = kstrtobool(buf, &status);
230	if (ret)
231		return ret;
232
233	heater_cmd = status ? HTU31_HEATER_ON_CMD : HTU31_HEATER_OFF_CMD;
234
235	guard(mutex)(&data->lock);
236
237	ret = i2c_master_send(data->client, &heater_cmd, 1);
238	if (ret < 0)
239		return ret;
240
241	data->heater_enable = status;
242
243	return count;
244}
245
246static DEVICE_ATTR_RW(heater_enable);
247
248static int serial_number_show(struct seq_file *seq_file,
249			      void *unused)
250{
251	struct htu31_data *data = seq_file->private;
252
253	seq_printf(seq_file, "%X%X%X\n", data->serial_number[0],
254		   data->serial_number[1], data->serial_number[2]);
255	return 0;
256}
257
258DEFINE_SHOW_ATTRIBUTE(serial_number);
259
260static struct attribute *htu31_attrs[] = {
261	&dev_attr_heater_enable.attr,
262	NULL
263};
264
265ATTRIBUTE_GROUPS(htu31);
266
267static const struct hwmon_channel_info * const htu31_info[] = {
268	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
269	HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT),
270	NULL
271};
272
273static const struct hwmon_ops htu31_hwmon_ops = {
274	.is_visible = htu31_is_visible,
275	.read = htu31_read,
276};
277
278static const struct hwmon_chip_info htu31_chip_info = {
279	.info = htu31_info,
280	.ops = &htu31_hwmon_ops,
281};
282
283static int htu31_probe(struct i2c_client *client)
284{
285	struct device *dev = &client->dev;
286	struct device *hwmon_dev;
287	struct htu31_data *data;
288	int ret;
289
290	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
291	if (!data)
292		return -ENOMEM;
293
294	data->client = client;
295	data->wait_time = HTU31_TEMPERATURE_CONV_TIME + HTU31_HUMIDITY_CONV_TIME;
296
297	ret = devm_mutex_init(dev, &data->lock);
298	if (ret)
299		return ret;
300
301	crc8_populate_msb(htu31_crc8_table, HTU31_CRC8_POLYNOMIAL);
302
303	ret = htu31_read_serial_number(data);
304	if (ret) {
305		dev_err(dev, "Failed to read serial number\n");
306		return ret;
307	}
308
309	debugfs_create_file("serial_number",
310			    0444,
311			    client->debugfs,
312			    data,
313			    &serial_number_fops);
314
315	hwmon_dev = devm_hwmon_device_register_with_info(dev,
316							 client->name,
317							 data,
318							 &htu31_chip_info,
319							 htu31_groups);
320
321	return PTR_ERR_OR_ZERO(hwmon_dev);
322}
323
324static const struct i2c_device_id htu31_id[] = {
325	{ "htu31" },
326	{ }
327};
328MODULE_DEVICE_TABLE(i2c, htu31_id);
329
330#if IS_ENABLED(CONFIG_OF)
331static const struct of_device_id htu31_of_match[] = {
332	{ .compatible = "meas,htu31" },
333	{ }
334};
335MODULE_DEVICE_TABLE(of, htu31_of_match);
336#endif
337
338static struct i2c_driver htu31_driver = {
339	.driver = {
340		.name = "htu31",
341		.of_match_table = of_match_ptr(htu31_of_match),
342	},
343	.probe = htu31_probe,
344	.id_table = htu31_id,
345};
346module_i2c_driver(htu31_driver);
347
348MODULE_AUTHOR("Andrei Lalaev <andrey.lalaev@gmail.com>");
349MODULE_DESCRIPTION("HTU31 Temperature and Humidity sensor driver");
350MODULE_LICENSE("GPL");