linux-imx

// SPDX-License-Identifier: GPL-2.0-or-later

/* Sensirion SHT21 humidity and temperature sensor driver

 *

 * Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com>

 *

 * Data sheet available at http://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  0xe3

#define SHT21_TRIG_RH_MEASUREMENT_HM 0xe5

#define SHT21_READ_SNB_CMD1 0xFA

#define SHT21_READ_SNB_CMD2 0x0F

#define SHT21_READ_SNAC_CMD1 0xFC

#define SHT21_READ_SNAC_CMD2 0xC9

​

/**

 * 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 {

    struct i2c_client *client;

    struct mutex lock;

    unsigned long last_update;

    int temperature;

    int humidity;

    char valid;

    char eic[18];

};

​

/**

 * 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)

{

    ticks &= ~0x0003; /* clear status bits */

    /*

     * Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2,

     * optimized for integer fixed point (3 digits) arithmetic

     */

    return ((21965 * ticks) >> 13) - 46850;

}

​

/**

 * 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)

{

    ticks &= ~0x0003; /* clear status bits */

    /*

     * Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1,

     * optimized for integer fixed point (3 digits) arithmetic

     */

    return ((15625 * ticks) >> 13) - 6000;

}

​

/**

 * 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)

{

    int ret = 0;

    struct sht21 *sht21 = dev_get_drvdata(dev);

    struct i2c_client *client = sht21->client;

​

    mutex_lock(&sht21->lock);

    /*

     * Data sheet 2.4: