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303 lines
7.2 KiB
303 lines
7.2 KiB
// 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 <[email protected]> |
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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_HPM 8200 /* see t_MEAS,h in datasheet */ |
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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 successful, -ERRNO 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; |
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u8 cmd[SHT4X_CMD_LEN] = {SHT4X_CMD_MEASURE_HPM}; |
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u8 raw_data[SHT4X_RESPONSE_LENGTH]; |
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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_before_eq(jiffies, next_update)) |
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goto unlock; |
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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_HPM, SHT4X_MEAS_DELAY_HPM + 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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ret = 0; |
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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, INT_MAX); |
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return 0; |
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} |
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/* sht4x_interval_read() - read the minimum poll interval in milliseconds */ |
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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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/* sht4x_temperature1_read() - read the temperature in millidegrees */ |
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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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/* sht4x_humidity1_read() - read a relative humidity in millipercent */ |
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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 const struct of_device_id sht4x_of_match[] = { |
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{ .compatible = "sensirion,sht4x" }, |
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{ } |
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}; |
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MODULE_DEVICE_TABLE(of, sht4x_of_match); |
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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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.of_match_table = sht4x_of_match, |
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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 <[email protected]>"); |
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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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