--- /dev/null
+// 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 <navin@linumiz.com>
+ */
+
+#include <linux/crc8.h>
+#include <linux/delay.h>
+#include <linux/hwmon.h>
+#include <linux/i2c.h>
+#include <linux/jiffies.h>
+#include <linux/module.h>
+
+/*
+ * 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 <navin@linumiz.com>");
+MODULE_DESCRIPTION("Sensirion SHT4x humidity and temperature sensor driver");
+MODULE_LICENSE("GPL v2");
projects / platform / kernel / linux-rpi.git / commitdiff