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62cfc05763
This patch enables automatic loading of the sht4x module via a device tree table entry. Signed-off-by: David Mosberger-Tang <davidm@egauge.net> Link: https://lore.kernel.org/r/20211121160637.2312106-1-davidm@egauge.net Signed-off-by: Guenter Roeck <linux@roeck-us.net>
304 lines
7.2 KiB
C
304 lines
7.2 KiB
C
// 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_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, UINT_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 <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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