linux/drivers/hwmon/sht21.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* Sensirion SHT21 humidity and temperature sensor driver
 *
 * Copyright (C) 2010 Urs Fleisch <[email protected]>
 *
 * Data sheet available at https://www.sensirion.com/file/datasheet_sht21
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/err.h>
#include <linux/mutex.h>
#include <linux/device.h>
#include <linux/jiffies.h>

/* I2C command bytes */
#define SHT21_TRIG_T_MEASUREMENT_HM …
#define SHT21_TRIG_RH_MEASUREMENT_HM …
#define SHT21_READ_SNB_CMD1 …
#define SHT21_READ_SNB_CMD2 …
#define SHT21_READ_SNAC_CMD1 …
#define SHT21_READ_SNAC_CMD2 …

/**
 * struct sht21 - SHT21 device specific data
 * @client: I2C client device
 * @lock: mutex to protect measurement values
 * @last_update: time of last update (jiffies)
 * @temperature: cached temperature measurement value
 * @humidity: cached humidity measurement value
 * @valid: only 0 before first measurement is taken
 * @eic: cached electronic identification code text
 */
struct sht21 { … };

/**
 * sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to
 * milli celsius
 * @ticks: temperature ticks value received from sensor
 */
static inline int sht21_temp_ticks_to_millicelsius(int ticks)
{ … }

/**
 * sht21_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to
 * one-thousandths of a percent relative humidity
 * @ticks: humidity ticks value received from sensor
 */
static inline int sht21_rh_ticks_to_per_cent_mille(int ticks)
{ … }

/**
 * sht21_update_measurements() - get updated measurements from device
 * @dev: device
 *
 * Returns 0 on success, else negative errno.
 */
static int sht21_update_measurements(struct device *dev)
{ … }

/**
 * sht21_temperature_show() - show temperature measurement value in sysfs
 * @dev: device
 * @attr: device attribute
 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
 *
 * Will be called on read access to temp1_input sysfs attribute.
 * Returns number of bytes written into buffer, negative errno on error.
 */
static ssize_t sht21_temperature_show(struct device *dev,
				      struct device_attribute *attr,
				      char *buf)
{ … }

/**
 * sht21_humidity_show() - show humidity measurement value in sysfs
 * @dev: device
 * @attr: device attribute
 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
 *
 * Will be called on read access to humidity1_input sysfs attribute.
 * Returns number of bytes written into buffer, negative errno on error.
 */
static ssize_t sht21_humidity_show(struct device *dev,
				   struct device_attribute *attr, char *buf)
{ … }

static ssize_t eic_read(struct sht21 *sht21)
{ … }

/**
 * eic_show() - show Electronic Identification Code in sysfs
 * @dev: device
 * @attr: device attribute
 * @buf: sysfs buffer (PAGE_SIZE) where EIC is written
 *
 * Will be called on read access to eic sysfs attribute.
 * Returns number of bytes written into buffer, negative errno on error.
 */
static ssize_t eic_show(struct device *dev,
	struct device_attribute *attr,
	char *buf)
{ … }

/* sysfs attributes */
static SENSOR_DEVICE_ATTR_RO(temp1_input, sht21_temperature, 0);
static SENSOR_DEVICE_ATTR_RO(humidity1_input, sht21_humidity, 0);
static DEVICE_ATTR_RO(eic);

static struct attribute *sht21_attrs[] = …;

ATTRIBUTE_GROUPS(…);

static int sht21_probe(struct i2c_client *client)
{ … }

/* Device ID table */
static const struct i2c_device_id sht21_id[] = …;
MODULE_DEVICE_TABLE(i2c, sht21_id);

static struct i2c_driver sht21_driver = …;

module_i2c_driver(…) …;

MODULE_AUTHOR(…) …;
MODULE_DESCRIPTION(…) …;
MODULE_LICENSE(…) …;