// SPDX-License-Identifier: GPL-2.0-or-later
/*
* The driver for Measurement Specialties HTU31 Temperature and Humidity sensor.
*
* Copyright (C) 2025
* Author: Andrei Lalaev <andrey.lalaev@gmail.com>
*/
#include <linux/array_size.h>
#include <linux/cleanup.h>
#include <linux/crc8.h>
#include <linux/debugfs.h>
#include <linux/delay.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/module.h>
#define HTU31_READ_TEMP_HUM_CMD 0x00
#define HTU31_READ_SERIAL_CMD 0x0a
#define HTU31_CONVERSION_CMD 0x5e
#define HTU31_HEATER_OFF_CMD 0x02
#define HTU31_HEATER_ON_CMD 0x04
#define HTU31_TEMP_HUM_LEN 6
/* Conversion time for the highest resolution */
#define HTU31_HUMIDITY_CONV_TIME 10000
/* us */
#define HTU31_TEMPERATURE_CONV_TIME 15000
/* us */
#define HTU31_SERIAL_NUMBER_LEN 3
#define HTU31_SERIAL_NUMBER_CRC_LEN 1
#define HTU31_SERIAL_NUMBER_CRC_OFFSET 3
#define HTU31_CRC8_INIT_VAL 0
#define HTU31_CRC8_POLYNOMIAL 0x31
DECLARE_CRC8_TABLE(htu31_crc8_table);
/**
* struct htu31_data - all the data required to operate a HTU31 chip
* @client: the i2c client associated with the HTU31
* @lock: a mutex to prevent parallel access to the data
* @wait_time: the time needed by sensor to convert values
* @temperature: the latest temperature value in millidegrees
* @humidity: the latest relative humidity value in millipercent
* @serial_number: the serial number of the sensor
* @heater_enable: the internal state of the heater
*/
struct htu31_data {
struct i2c_client *client;
struct mutex lock;
/* Used to protect against parallel data updates */
long wait_time;
long temperature;
long humidity;
u8 serial_number[HTU31_SERIAL_NUMBER_LEN];
bool heater_enable;
};
static long htu31_temp_to_millicelsius(u16 val)
{
return -40000 + DIV_ROUND_CLOSEST_ULL(165000ULL * val, 65535);
}
static long htu31_relative_humidity(u16 val)
{
return DIV_ROUND_CLOSEST_ULL(100000ULL * val, 65535);
}
static int htu31_data_fetch_command(
struct htu31_data *data)
{
struct i2c_client *client = data->client;
u8 conversion_on = HTU31_CONVERSION_CMD;
u8 read_data_cmd = HTU31_READ_TEMP_HUM_CMD;
u8 t_h_buf[HTU31_TEMP_HUM_LEN] = {};
struct i2c_msg msgs[] = {
{
.addr = client->addr,
.flags = 0,
.len = 1,
.buf = &read_data_cmd,
},
{
.addr = client->addr,
.flags = I2C_M_RD,
.len =
sizeof(t_h_buf),
.buf = t_h_buf,
},
};
int ret;
u8 crc;
guard(mutex)(&data->lock);
ret = i2c_master_send(client, &conversion_on, 1);
if (ret != 1) {
ret = ret < 0 ? ret : -EIO;
dev_err(&client->dev,
"Conversion command is failed. Error code: %d\n", ret);
return ret;
}
fsleep(data->wait_time);
ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
if (ret != ARRAY_SIZE(msgs)) {
ret = ret < 0 ? ret : -EIO;
dev_err(&client->dev,
"T&H command is failed. Error code: %d\n", ret);
return ret;
}
crc = crc8(htu31_crc8_table, &t_h_buf[0], 2, HTU31_CRC8_INIT_VAL);
if (crc != t_h_buf[2]) {
dev_err(&client->dev,
"Temperature CRC mismatch\n");
return -EIO;
}
crc = crc8(htu31_crc8_table, &t_h_buf[3], 2, HTU31_CRC8_INIT_VAL);
if (crc != t_h_buf[5]) {
dev_err(&client->dev,
"Humidity CRC mismatch\n");
return -EIO;
}
data->temperature = htu31_temp_to_millicelsius(be16_to_cpup((__be16 *)&t_h_buf[0]));
data->humidity = htu31_relative_humidity(be16_to_cpup((__be16 *)&t_h_buf[3]));
return 0;
}
static umode_t htu31_is_visible(
const void *data,
enum hwmon_sensor_types type,
u32 attr,
int channel)
{
switch (type) {
case hwmon_temp:
case hwmon_humidity:
return 0444;
default:
return 0;
}
}
static int htu31_read(
struct device *dev,
enum hwmon_sensor_types type,
u32 attr,
int channel,
long *val)
{
struct htu31_data *data = dev_get_drvdata(dev);
int ret;
ret = htu31_data_fetch_command(data);
if (ret < 0)
return ret;
switch (type) {
case hwmon_temp:
if (attr != hwmon_temp_input)
return -EINVAL;
*val = data->temperature;
break;
case hwmon_humidity:
if (attr != hwmon_humidity_input)
return -EINVAL;
*val = data->humidity;
break;
default:
return -EOPNOTSUPP;
}
return 0;
}
static int htu31_read_serial_number(
struct htu31_data *data)
{
struct i2c_client *client = data->client;
u8 read_sn_cmd = HTU31_READ_SERIAL_CMD;
u8 sn_buf[HTU31_SERIAL_NUMBER_LEN + HTU31_SERIAL_NUMBER_CRC_LEN];
struct i2c_msg msgs[] = {
{
.addr = client->addr,
.flags = 0,
.len = 1,
.buf = &read_sn_cmd,
},
{
.addr = client->addr,
.flags = I2C_M_RD,
.len =
sizeof(sn_buf),
.buf = sn_buf,
},
};
int ret;
u8 crc;
ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
if (ret < 0)
return ret;
crc = crc8(htu31_crc8_table, sn_buf, HTU31_SERIAL_NUMBER_LEN, HTU31_CRC8_INIT_VAL);
if (crc != sn_buf[HTU31_SERIAL_NUMBER_CRC_OFFSET]) {
dev_err(&client->dev,
"Serial number CRC mismatch\n");
return -EIO;
}
memcpy(data->serial_number, sn_buf, HTU31_SERIAL_NUMBER_LEN);
return 0;
}
static ssize_t heater_enable_show(
struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct htu31_data *data = dev_get_drvdata(dev);
return sysfs_emit(buf,
"%d\n", data->heater_enable);
}
static ssize_t heater_enable_store(
struct device *dev,
struct device_attribute *attr,
const char *buf,
size_t count)
{
struct htu31_data *data = dev_get_drvdata(dev);
u8 heater_cmd;
bool status;
int ret;
ret = kstrtobool(buf, &status);
if (ret)
return ret;
heater_cmd = status ? HTU31_HEATER_ON_CMD : HTU31_HEATER_OFF_CMD;
guard(mutex)(&data->lock);
ret = i2c_master_send(data->client, &heater_cmd, 1);
if (ret < 0)
return ret;
data->heater_enable = status;
return count;
}
static DEVICE_ATTR_RW(heater_enable);
static int serial_number_show(
struct seq_file *seq_file,
void *unused)
{
struct htu31_data *data = seq_file->
private;
seq_printf(seq_file,
"%X%X%X\n", data->serial_number[0],
data->serial_number[1], data->serial_number[2]);
return 0;
}
DEFINE_SHOW_ATTRIBUTE(serial_number);
static struct attribute *htu31_attrs[] = {
&dev_attr_heater_enable.attr,
NULL
};
ATTRIBUTE_GROUPS(htu31);
static const struct hwmon_channel_info *
const htu31_info[] = {
HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT),
NULL
};
static const struct hwmon_ops htu31_hwmon_ops = {
.is_visible = htu31_is_visible,
.read = htu31_read,
};
static const struct hwmon_chip_info htu31_chip_info = {
.info = htu31_info,
.ops = &htu31_hwmon_ops,
};
static int htu31_probe(
struct i2c_client *client)
{
struct device *dev = &client->dev;
struct device *hwmon_dev;
struct htu31_data *data;
int ret;
data = devm_kzalloc(dev,
sizeof(*data), GFP_KERNEL);
if (!data)
return -ENOMEM;
data->client = client;
data->wait_time = HTU31_TEMPERATURE_CONV_TIME + HTU31_HUMIDITY_CONV_TIME;
ret = devm_mutex_init(dev, &data->lock);
if (ret)
return ret;
crc8_populate_msb(htu31_crc8_table, HTU31_CRC8_POLYNOMIAL);
ret = htu31_read_serial_number(data);
if (ret) {
dev_err(dev,
"Failed to read serial number\n");
return ret;
}
debugfs_create_file(
"serial_number",
0444,
client->debugfs,
data,
&serial_number_fops);
hwmon_dev = devm_hwmon_device_register_with_info(dev,
client->name,
data,
&htu31_chip_info,
htu31_groups);
return PTR_ERR_OR_ZERO(hwmon_dev);
}
static const struct i2c_device_id htu31_id[] = {
{
"htu31" },
{ }
};
MODULE_DEVICE_TABLE(i2c, htu31_id);
#if IS_ENABLED(CONFIG_OF)
static const struct of_device_id htu31_of_match[] = {
{ .compatible =
"meas,htu31" },
{ }
};
MODULE_DEVICE_TABLE(of, htu31_of_match);
#endif
static struct i2c_driver htu31_driver = {
.driver = {
.name =
"htu31",
.of_match_table = of_match_ptr(htu31_of_match),
},
.probe = htu31_probe,
.id_table = htu31_id,
};
module_i2c_driver(htu31_driver);
MODULE_AUTHOR(
"Andrei Lalaev ");
MODULE_DESCRIPTION(
"HTU31 Temperature and Humidity sensor driver");
MODULE_LICENSE(
"GPL");
