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hwmon: (sht4x) Add support for Sensirion STS4x temperature sensors

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The Sensirion STS4x series is the temperature-only variant of the
SHT4x family. It shares the same I2C command set, conversion formulas,
CRC checksum, and timing with the SHT4x, but only returns temperature
data (3 bytes: 2 data bytes + 1 CRC byte).

Add support for the STS4x series by dynamically adjusting the read
response length, suppressing humidity channel attributes when probed
as STS4x, and omitting heater sysfs attributes.

Link: https://sensirion.com/resource/datasheet/sts4x
Signed-off-by: Alessandro Zini <alessandro.zini@siemens.com>
Link: https://patch.msgid.link/20260821091924.18975-3-alessandro.zini@siemens.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Alessandro Zini 2026-08-21 11:19:24 +02:00 committed by Guenter Roeck
parent 961fa6fa65
commit e9e597193e
2 changed files with 61 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
Documentation/hwmon/sht4x.rst
View File

@ -15,6 +15,16 @@ Supported Chips:
English: https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/2_Humidity_Sensors/Datasheets/Sensirion_Humidity_Sensors_SHT4x_Datasheet.pdf
* Sensirion STS4X
Prefix: 'sts4x'
Addresses scanned: None
Datasheet:
English: https://sensirion.com/resource/datasheet/sts4x
Author: Navin Sankar Velliangiri <navin@linumiz.com>
@ -22,9 +32,10 @@ Description
-----------
This driver implements support for the Sensirion SHT4x chip, a humidity
and temperature sensor. Temperature is measured in degree celsius, relative
humidity is expressed as a percentage. In sysfs interface, all values are
scaled by 1000, i.e. the value for 31.5 degrees celsius is 31500.
and temperature sensor, and the Sensirion STS4x chip, a temperature sensor.
Temperature is measured in degree celsius, relative humidity is expressed as a
percentage (on SHT4x only). In sysfs interface, all values are scaled by 1000,
i.e. the value for 31.5 degrees celsius is 31500.
Usage Notes
-----------

66
drivers/hwmon/sht4x.c
View File

@ -43,6 +43,7 @@
#define SHT4X_CRC8_LEN 1
#define SHT4X_WORD_LEN 2
#define SHT4X_RESPONSE_LENGTH 6
#define STS4X_RESPONSE_LENGTH 3
#define SHT4X_CRC8_POLYNOMIAL 0x31
#define SHT4X_CRC8_INIT 0xff
#define SHT4X_MIN_TEMPERATURE -45000
@ -52,9 +53,15 @@
DECLARE_CRC8_TABLE(sht4x_crc8_table);
enum sht4x_chips {
sht4x,
sts4x,
};
/**
* struct sht4x_data - All the data required to operate an SHT4X chip
* @client: the i2c client associated with the SHT4X
* @chip_id: the chip type (sht4x or sts4x)
* @heating_complete: the time that the last heating finished
* @data_pending: true if and only if there are measurements to retrieve after heating
* @heater_power: the power at which the heater will be started
@ -67,6 +74,7 @@ DECLARE_CRC8_TABLE(sht4x_crc8_table);
*/
struct sht4x_data {
struct i2c_client *client;
enum sht4x_chips chip_id;
u64 heating_complete; /* in jiffies */
bool data_pending;
u32 heater_power; /* in milli-watts */
@ -92,11 +100,15 @@ static int sht4x_read_values(struct sht4x_data *data)
u8 crc;
u8 cmd[SHT4X_CMD_LEN] = {SHT4X_CMD_MEASURE_HPM};
u8 raw_data[SHT4X_RESPONSE_LENGTH];
u64 curr_jiffies;
size_t response_length = data->chip_id == sts4x ?
STS4X_RESPONSE_LENGTH : SHT4X_RESPONSE_LENGTH;
curr_jiffies = get_jiffies_64();
if (time_before64(curr_jiffies, data->heating_complete))
msleep(jiffies_to_msecs(data->heating_complete - curr_jiffies));
if (data->chip_id != sts4x) {
u64 curr_jiffies = get_jiffies_64();
if (time_before64(curr_jiffies, data->heating_complete))
msleep(jiffies_to_msecs(data->heating_complete - curr_jiffies));
}
if (data->data_pending &&
time_before64(get_jiffies_64(), data->heating_complete + data->update_interval)) {
@ -115,15 +127,14 @@ static int sht4x_read_values(struct sht4x_data *data)
usleep_range(SHT4X_MEAS_DELAY_HPM, SHT4X_MEAS_DELAY_HPM + SHT4X_DELAY_EXTRA);
}
ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH);
if (ret != SHT4X_RESPONSE_LENGTH) {
ret = i2c_master_recv(client, raw_data, response_length);
if (ret != response_length) {
if (ret >= 0)
ret = -ENODATA;
return ret;
}
t_ticks = raw_data[0] << 8 | raw_data[1];
rh_ticks = raw_data[3] << 8 | raw_data[4];
crc = crc8(sht4x_crc8_table, &raw_data[0], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
if (crc != raw_data[2]) {
@ -131,14 +142,19 @@ static int sht4x_read_values(struct sht4x_data *data)
return -EIO;
}
crc = crc8(sht4x_crc8_table, &raw_data[3], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
if (crc != raw_data[5]) {
dev_err(&client->dev, "data integrity check failed\n");
return -EIO;
data->temperature = ((21875 * (int32_t)t_ticks) >> 13) - 45000;
if (data->chip_id != sts4x) {
rh_ticks = raw_data[3] << 8 | raw_data[4];
crc = crc8(sht4x_crc8_table, &raw_data[3], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
if (crc != raw_data[5]) {
dev_err(&client->dev, "data integrity check failed\n");
return -EIO;
}
data->humidity = ((15625 * (int32_t)rh_ticks) >> 13) - 6000;
}
data->temperature = ((21875 * (int32_t)t_ticks) >> 13) - 45000;
data->humidity = ((15625 * (int32_t)rh_ticks) >> 13) - 6000;
data->last_updated = jiffies;
data->valid = true;
return 0;
@ -190,9 +206,14 @@ static umode_t sht4x_hwmon_visible(const void *data,
enum hwmon_sensor_types type,
u32 attr, int channel)
{
const struct sht4x_data *chip_data = data;
switch (type) {
case hwmon_temp:
return 0444;
case hwmon_humidity:
if (chip_data->chip_id == sts4x)
return 0;
return 0444;
case hwmon_chip:
return 0644;
@ -392,6 +413,7 @@ static const struct hwmon_chip_info sht4x_chip_info = {
static int sht4x_probe(struct i2c_client *client)
{
const struct attribute_group **groups = NULL;
struct device *device = &client->dev;
struct device *hwmon_dev;
struct sht4x_data *data;
@ -410,11 +432,15 @@ static int sht4x_probe(struct i2c_client *client)
if (!data)
return -ENOMEM;
data->chip_id = (uintptr_t)i2c_get_match_data(client);
data->update_interval = SHT4X_MIN_POLL_INTERVAL;
data->client = client;
data->heater_power = 200;
data->heater_time = 1000;
data->heating_complete = get_jiffies_64();
if (data->chip_id != sts4x) {
data->heater_power = 200;
data->heater_time = 1000;
data->heating_complete = get_jiffies_64();
groups = sht4x_groups;
}
crc8_populate_msb(sht4x_crc8_table, SHT4X_CRC8_POLYNOMIAL);
@ -428,19 +454,21 @@ static int sht4x_probe(struct i2c_client *client)
client->name,
data,
&sht4x_chip_info,
sht4x_groups);
groups);
return PTR_ERR_OR_ZERO(hwmon_dev);
}
static const struct i2c_device_id sht4x_id[] = {
{ .name = "sht4x" },
{ .name = "sht4x", .driver_data = sht4x },
{ .name = "sts4x", .driver_data = sts4x },
{ }
};
MODULE_DEVICE_TABLE(i2c, sht4x_id);
static const struct of_device_id sht4x_of_match[] = {
{ .compatible = "sensirion,sht4x" },
{ .compatible = "sensirion,sht4x", .data = (void *)sht4x },
{ .compatible = "sensirion,sts40", .data = (void *)sts4x },
{ }
};
MODULE_DEVICE_TABLE(of, sht4x_of_match);