hwmon: Add sht4x Temperature and Humidity Sensor Driver
This patch adds a hwmon driver for the SHT4x Temperature and Humidity sensor. Signed-off-by: Navin Sankar Velliangiri <navin@linumiz.com> [groeck: dropped unnecessary empty line and continuation lines] Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Navin Sankar Velliangiri
Guenter Roeck
parent
f20f7363e7
commit
505c254937
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@ -165,6 +165,7 @@ Hardware Monitoring Kernel Drivers
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sht15
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sht21
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sht3x
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sht4x
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shtc1
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sis5595
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sl28cpld
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@ -0,0 +1,45 @@
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.. SPDX-License-Identifier: GPL-2.0
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Kernel driver sht4x
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===================
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Supported Chips:
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* Sensirion SHT4X
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Prefix: 'sht4x'
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Addresses scanned: None
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Datasheet:
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English: https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/2_Humidity_Sensors/Datasheets/Sensirion_Humidity_Sensors_SHT4x_Datasheet.pdf
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Author: Navin Sankar Velliangiri <navin@linumiz.com>
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Description
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-----------
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This driver implements support for the Sensirion SHT4x chip, a humidity
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and temperature sensor. Temperature is measured in degree celsius, relative
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humidity is expressed as a percentage. In sysfs interface, all values are
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scaled by 1000, i.e. the value for 31.5 degrees celsius is 31500.
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Usage Notes
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-----------
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The device communicates with the I2C protocol. Sensors can have the I2C
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address 0x44. See Documentation/i2c/instantiating-devices.rst for methods
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to instantiate the device.
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Sysfs entries
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-------------
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=============== ============================================
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temp1_input Measured temperature in millidegrees Celcius
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humidity1_input Measured humidity in %H
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update_interval The minimum interval for polling the sensor,
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in milliseconds. Writable. Must be at least
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2000.
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============== =============================================
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@ -1583,6 +1583,17 @@ config SENSORS_SHT3x
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This driver can also be built as a module. If so, the module
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will be called sht3x.
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config SENSORS_SHT4x
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tristate "Sensiron humidity and temperature sensors. SHT4x and compat."
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depends on I2C
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select CRC8
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help
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If you say yes here you get support for the Sensiron SHT40, SHT41 and
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SHT45 humidity and temperature sensors.
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This driver can also be built as a module. If so, the module
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will be called sht4x.
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config SENSORS_SHTC1
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tristate "Sensiron humidity and temperature sensors. SHTC1 and compat."
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depends on I2C
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@ -171,6 +171,7 @@ obj-$(CONFIG_SENSORS_SL28CPLD) += sl28cpld-hwmon.o
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obj-$(CONFIG_SENSORS_SHT15) += sht15.o
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obj-$(CONFIG_SENSORS_SHT21) += sht21.o
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obj-$(CONFIG_SENSORS_SHT3x) += sht3x.o
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obj-$(CONFIG_SENSORS_SHT4x) += sht4x.o
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obj-$(CONFIG_SENSORS_SHTC1) += shtc1.o
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obj-$(CONFIG_SENSORS_SIS5595) += sis5595.o
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obj-$(CONFIG_SENSORS_SMM665) += smm665.o
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@ -0,0 +1,301 @@
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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (c) Linumiz 2021
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*
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* sht4x.c - Linux hwmon driver for SHT4x Temperature and Humidity sensor
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*
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* Author: Navin Sankar Velliangiri <navin@linumiz.com>
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*/
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#include <linux/crc8.h>
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#include <linux/delay.h>
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#include <linux/hwmon.h>
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#include <linux/i2c.h>
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#include <linux/jiffies.h>
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#include <linux/module.h>
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/*
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* Poll intervals (in milliseconds)
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*/
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#define SHT4X_MIN_POLL_INTERVAL 2000
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/*
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* I2C command delays (in microseconds)
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*/
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#define SHT4X_MEAS_DELAY 1000
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#define SHT4X_DELAY_EXTRA 10000
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/*
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* Command Bytes
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*/
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#define SHT4X_CMD_MEASURE_HPM 0b11111101
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#define SHT4X_CMD_RESET 0b10010100
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#define SHT4X_CMD_LEN 1
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#define SHT4X_CRC8_LEN 1
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#define SHT4X_WORD_LEN 2
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#define SHT4X_RESPONSE_LENGTH 6
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#define SHT4X_CRC8_POLYNOMIAL 0x31
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#define SHT4X_CRC8_INIT 0xff
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#define SHT4X_MIN_TEMPERATURE -45000
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#define SHT4X_MAX_TEMPERATURE 125000
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#define SHT4X_MIN_HUMIDITY 0
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#define SHT4X_MAX_HUMIDITY 100000
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DECLARE_CRC8_TABLE(sht4x_crc8_table);
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/**
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* struct sht4x_data - All the data required to operate an SHT4X chip
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* @client: the i2c client associated with the SHT4X
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* @lock: a mutex that is used to prevent parallel access to the i2c client
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* @update_interval: the minimum poll interval
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* @last_updated: the previous time that the SHT4X was polled
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* @temperature: the latest temperature value received from the SHT4X
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* @humidity: the latest humidity value received from the SHT4X
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*/
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struct sht4x_data {
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struct i2c_client *client;
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struct mutex lock; /* atomic read data updates */
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bool valid; /* validity of fields below */
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long update_interval; /* in milli-seconds */
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long last_updated; /* in jiffies */
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s32 temperature;
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s32 humidity;
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};
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/**
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* sht4x_read_values() - read and parse the raw data from the SHT4X
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* @sht4x_data: the struct sht4x_data to use for the lock
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* Return: 0 if succesfull, 1 if not
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*/
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static int sht4x_read_values(struct sht4x_data *data)
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{
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int ret = 0;
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u16 t_ticks, rh_ticks;
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unsigned long next_update;
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struct i2c_client *client = data->client;
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u8 crc, raw_data[SHT4X_RESPONSE_LENGTH],
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cmd[] = {SHT4X_CMD_MEASURE_HPM};
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mutex_lock(&data->lock);
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next_update = data->last_updated +
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msecs_to_jiffies(data->update_interval);
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if (!data->valid || time_after(jiffies, next_update)) {
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ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN);
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if (ret < 0)
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goto unlock;
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usleep_range(SHT4X_MEAS_DELAY,
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SHT4X_MEAS_DELAY + SHT4X_DELAY_EXTRA);
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ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH);
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if (ret != SHT4X_RESPONSE_LENGTH) {
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if (ret >= 0)
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ret = -ENODATA;
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goto unlock;
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}
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t_ticks = raw_data[0] << 8 | raw_data[1];
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rh_ticks = raw_data[3] << 8 | raw_data[4];
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crc = crc8(sht4x_crc8_table, &raw_data[0], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
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if (crc != raw_data[2]) {
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dev_err(&client->dev, "data integrity check failed\n");
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ret = -EIO;
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goto unlock;
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}
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crc = crc8(sht4x_crc8_table, &raw_data[3], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
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if (crc != raw_data[5]) {
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dev_err(&client->dev, "data integrity check failed\n");
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ret = -EIO;
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goto unlock;
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}
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data->temperature = ((21875 * (int32_t)t_ticks) >> 13) - 45000;
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data->humidity = ((15625 * (int32_t)rh_ticks) >> 13) - 6000;
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data->last_updated = jiffies;
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data->valid = true;
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}
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unlock:
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mutex_unlock(&data->lock);
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return ret;
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}
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static ssize_t sht4x_interval_write(struct sht4x_data *data, long val)
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{
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data->update_interval = clamp_val(val, SHT4X_MIN_POLL_INTERVAL, UINT_MAX);
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return 0;
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}
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/**
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* sht4x_interval_read() - read the minimum poll interval
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* in milliseconds
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*/
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static size_t sht4x_interval_read(struct sht4x_data *data, long *val)
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{
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*val = data->update_interval;
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return 0;
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}
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/**
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* sht4x_temperature1_read() - read the temperature in millidegrees
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*/
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static int sht4x_temperature1_read(struct sht4x_data *data, long *val)
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{
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int ret;
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ret = sht4x_read_values(data);
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if (ret < 0)
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return ret;
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*val = data->temperature;
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return 0;
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}
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/**
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* sht4x_humidity1_read() - read a relative humidity in millipercent
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*/
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static int sht4x_humidity1_read(struct sht4x_data *data, long *val)
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{
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int ret;
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ret = sht4x_read_values(data);
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if (ret < 0)
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return ret;
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*val = data->humidity;
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return 0;
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}
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static umode_t sht4x_hwmon_visible(const void *data,
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enum hwmon_sensor_types type,
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u32 attr, int channel)
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{
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switch (type) {
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case hwmon_temp:
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case hwmon_humidity:
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return 0444;
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case hwmon_chip:
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return 0644;
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default:
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return 0;
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}
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}
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static int sht4x_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
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u32 attr, int channel, long *val)
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{
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struct sht4x_data *data = dev_get_drvdata(dev);
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switch (type) {
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case hwmon_temp:
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return sht4x_temperature1_read(data, val);
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case hwmon_humidity:
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return sht4x_humidity1_read(data, val);
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case hwmon_chip:
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return sht4x_interval_read(data, val);
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default:
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return -EOPNOTSUPP;
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}
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}
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static int sht4x_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
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u32 attr, int channel, long val)
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{
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struct sht4x_data *data = dev_get_drvdata(dev);
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switch (type) {
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case hwmon_chip:
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return sht4x_interval_write(data, val);
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default:
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return -EOPNOTSUPP;
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}
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}
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static const struct hwmon_channel_info *sht4x_info[] = {
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HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
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HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
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HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT),
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NULL,
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};
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static const struct hwmon_ops sht4x_hwmon_ops = {
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.is_visible = sht4x_hwmon_visible,
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.read = sht4x_hwmon_read,
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.write = sht4x_hwmon_write,
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};
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static const struct hwmon_chip_info sht4x_chip_info = {
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.ops = &sht4x_hwmon_ops,
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.info = sht4x_info,
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};
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static int sht4x_probe(struct i2c_client *client,
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const struct i2c_device_id *sht4x_id)
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{
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struct device *device = &client->dev;
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struct device *hwmon_dev;
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struct sht4x_data *data;
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u8 cmd[] = {SHT4X_CMD_RESET};
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int ret;
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/*
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* we require full i2c support since the sht4x uses multi-byte read and
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* writes as well as multi-byte commands which are not supported by
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* the smbus protocol
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*/
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if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
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return -EOPNOTSUPP;
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data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL);
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if (!data)
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return -ENOMEM;
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data->update_interval = SHT4X_MIN_POLL_INTERVAL;
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data->client = client;
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mutex_init(&data->lock);
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crc8_populate_msb(sht4x_crc8_table, SHT4X_CRC8_POLYNOMIAL);
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ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN);
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if (ret < 0)
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return ret;
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if (ret != SHT4X_CMD_LEN)
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return -EIO;
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hwmon_dev = devm_hwmon_device_register_with_info(device,
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client->name,
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data,
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&sht4x_chip_info,
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NULL);
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return PTR_ERR_OR_ZERO(hwmon_dev);
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}
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static const struct i2c_device_id sht4x_id[] = {
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{ "sht4x", 0 },
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{ },
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};
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MODULE_DEVICE_TABLE(i2c, sht4x_id);
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static struct i2c_driver sht4x_driver = {
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.driver = {
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.name = "sht4x",
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},
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.probe = sht4x_probe,
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.id_table = sht4x_id,
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};
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module_i2c_driver(sht4x_driver);
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MODULE_AUTHOR("Navin Sankar Velliangiri <navin@linumiz.com>");
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MODULE_DESCRIPTION("Sensirion SHT4x humidity and temperature sensor driver");
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MODULE_LICENSE("GPL v2");
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