From 505c2549373f3aa9ee16493f872e57876ffb70b1 Mon Sep 17 00:00:00 2001 From: Navin Sankar Velliangiri Date: Mon, 24 May 2021 19:50:38 +0530 Subject: 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 [groeck: dropped unnecessary empty line and continuation lines] Signed-off-by: Guenter Roeck --- drivers/hwmon/sht4x.c | 301 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 301 insertions(+) create mode 100644 drivers/hwmon/sht4x.c (limited to 'drivers/hwmon/sht4x.c') diff --git a/drivers/hwmon/sht4x.c b/drivers/hwmon/sht4x.c new file mode 100644 index 000000000000..1dc51ee2a72b --- /dev/null +++ b/drivers/hwmon/sht4x.c @@ -0,0 +1,301 @@ +// SPDX-License-Identifier: GPL-2.0-only + +/* + * Copyright (c) Linumiz 2021 + * + * sht4x.c - Linux hwmon driver for SHT4x Temperature and Humidity sensor + * + * Author: Navin Sankar Velliangiri + */ + +#include +#include +#include +#include +#include +#include + +/* + * Poll intervals (in milliseconds) + */ +#define SHT4X_MIN_POLL_INTERVAL 2000 + +/* + * I2C command delays (in microseconds) + */ +#define SHT4X_MEAS_DELAY 1000 +#define SHT4X_DELAY_EXTRA 10000 + +/* + * Command Bytes + */ +#define SHT4X_CMD_MEASURE_HPM 0b11111101 +#define SHT4X_CMD_RESET 0b10010100 + +#define SHT4X_CMD_LEN 1 +#define SHT4X_CRC8_LEN 1 +#define SHT4X_WORD_LEN 2 +#define SHT4X_RESPONSE_LENGTH 6 +#define SHT4X_CRC8_POLYNOMIAL 0x31 +#define SHT4X_CRC8_INIT 0xff +#define SHT4X_MIN_TEMPERATURE -45000 +#define SHT4X_MAX_TEMPERATURE 125000 +#define SHT4X_MIN_HUMIDITY 0 +#define SHT4X_MAX_HUMIDITY 100000 + +DECLARE_CRC8_TABLE(sht4x_crc8_table); + +/** + * struct sht4x_data - All the data required to operate an SHT4X chip + * @client: the i2c client associated with the SHT4X + * @lock: a mutex that is used to prevent parallel access to the i2c client + * @update_interval: the minimum poll interval + * @last_updated: the previous time that the SHT4X was polled + * @temperature: the latest temperature value received from the SHT4X + * @humidity: the latest humidity value received from the SHT4X + */ +struct sht4x_data { + struct i2c_client *client; + struct mutex lock; /* atomic read data updates */ + bool valid; /* validity of fields below */ + long update_interval; /* in milli-seconds */ + long last_updated; /* in jiffies */ + s32 temperature; + s32 humidity; +}; + +/** + * sht4x_read_values() - read and parse the raw data from the SHT4X + * @sht4x_data: the struct sht4x_data to use for the lock + * Return: 0 if succesfull, 1 if not + */ +static int sht4x_read_values(struct sht4x_data *data) +{ + int ret = 0; + u16 t_ticks, rh_ticks; + unsigned long next_update; + struct i2c_client *client = data->client; + u8 crc, raw_data[SHT4X_RESPONSE_LENGTH], + cmd[] = {SHT4X_CMD_MEASURE_HPM}; + + mutex_lock(&data->lock); + next_update = data->last_updated + + msecs_to_jiffies(data->update_interval); + if (!data->valid || time_after(jiffies, next_update)) { + ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN); + if (ret < 0) + goto unlock; + + usleep_range(SHT4X_MEAS_DELAY, + SHT4X_MEAS_DELAY + SHT4X_DELAY_EXTRA); + + ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH); + if (ret != SHT4X_RESPONSE_LENGTH) { + if (ret >= 0) + ret = -ENODATA; + + goto unlock; + } + + 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]) { + dev_err(&client->dev, "data integrity check failed\n"); + ret = -EIO; + goto unlock; + } + + 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"); + ret = -EIO; + goto unlock; + } + + 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; + } + +unlock: + mutex_unlock(&data->lock); + return ret; +} + +static ssize_t sht4x_interval_write(struct sht4x_data *data, long val) +{ + data->update_interval = clamp_val(val, SHT4X_MIN_POLL_INTERVAL, UINT_MAX); + + return 0; +} + +/** + * sht4x_interval_read() - read the minimum poll interval + * in milliseconds + */ +static size_t sht4x_interval_read(struct sht4x_data *data, long *val) +{ + *val = data->update_interval; + return 0; +} + +/** + * sht4x_temperature1_read() - read the temperature in millidegrees + */ +static int sht4x_temperature1_read(struct sht4x_data *data, long *val) +{ + int ret; + + ret = sht4x_read_values(data); + if (ret < 0) + return ret; + + *val = data->temperature; + + return 0; +} + +/** + * sht4x_humidity1_read() - read a relative humidity in millipercent + */ +static int sht4x_humidity1_read(struct sht4x_data *data, long *val) +{ + int ret; + + ret = sht4x_read_values(data); + if (ret < 0) + return ret; + + *val = data->humidity; + + return 0; +} + +static umode_t sht4x_hwmon_visible(const void *data, + enum hwmon_sensor_types type, + u32 attr, int channel) +{ + switch (type) { + case hwmon_temp: + case hwmon_humidity: + return 0444; + case hwmon_chip: + return 0644; + default: + return 0; + } +} + +static int sht4x_hwmon_read(struct device *dev, enum hwmon_sensor_types type, + u32 attr, int channel, long *val) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + + switch (type) { + case hwmon_temp: + return sht4x_temperature1_read(data, val); + case hwmon_humidity: + return sht4x_humidity1_read(data, val); + case hwmon_chip: + return sht4x_interval_read(data, val); + default: + return -EOPNOTSUPP; + } +} + +static int sht4x_hwmon_write(struct device *dev, enum hwmon_sensor_types type, + u32 attr, int channel, long val) +{ + struct sht4x_data *data = dev_get_drvdata(dev); + + switch (type) { + case hwmon_chip: + return sht4x_interval_write(data, val); + default: + return -EOPNOTSUPP; + } +} + +static const struct hwmon_channel_info *sht4x_info[] = { + HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL), + HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT), + HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT), + NULL, +}; + +static const struct hwmon_ops sht4x_hwmon_ops = { + .is_visible = sht4x_hwmon_visible, + .read = sht4x_hwmon_read, + .write = sht4x_hwmon_write, +}; + +static const struct hwmon_chip_info sht4x_chip_info = { + .ops = &sht4x_hwmon_ops, + .info = sht4x_info, +}; + +static int sht4x_probe(struct i2c_client *client, + const struct i2c_device_id *sht4x_id) +{ + struct device *device = &client->dev; + struct device *hwmon_dev; + struct sht4x_data *data; + u8 cmd[] = {SHT4X_CMD_RESET}; + int ret; + + /* + * we require full i2c support since the sht4x uses multi-byte read and + * writes as well as multi-byte commands which are not supported by + * the smbus protocol + */ + if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) + return -EOPNOTSUPP; + + data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL); + if (!data) + return -ENOMEM; + + data->update_interval = SHT4X_MIN_POLL_INTERVAL; + data->client = client; + + mutex_init(&data->lock); + + crc8_populate_msb(sht4x_crc8_table, SHT4X_CRC8_POLYNOMIAL); + + ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN); + if (ret < 0) + return ret; + if (ret != SHT4X_CMD_LEN) + return -EIO; + + hwmon_dev = devm_hwmon_device_register_with_info(device, + client->name, + data, + &sht4x_chip_info, + NULL); + + return PTR_ERR_OR_ZERO(hwmon_dev); +} + +static const struct i2c_device_id sht4x_id[] = { + { "sht4x", 0 }, + { }, +}; +MODULE_DEVICE_TABLE(i2c, sht4x_id); + +static struct i2c_driver sht4x_driver = { + .driver = { + .name = "sht4x", + }, + .probe = sht4x_probe, + .id_table = sht4x_id, +}; + +module_i2c_driver(sht4x_driver); + +MODULE_AUTHOR("Navin Sankar Velliangiri "); +MODULE_DESCRIPTION("Sensirion SHT4x humidity and temperature sensor driver"); +MODULE_LICENSE("GPL v2"); -- cgit v1.2.3