linux/drivers/hwmon/sht21.c
Thomas Gleixner fd534e9b5f treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 102
Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license as published by
  the free software foundation either version 2 of the license or at
  your option any later version this program is distributed in the
  hope that it will be useful but without any warranty without even
  the implied warranty of merchantability or fitness for a particular
  purpose see the gnu general public license for more details you
  should have received a copy of the gnu general public license along
  with this program if not write to the free software foundation inc
  51 franklin st fifth floor boston ma 02110 1301 usa

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 50 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190523091649.499889647@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-24 17:39:00 +02:00

298 lines
7.4 KiB
C

// 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:
* SHT2x should not be active for more than 10% of the time - e.g.
* maximum two measurements per second at 12bit accuracy shall be made.
*/
if (time_after(jiffies, sht21->last_update + HZ / 2) || !sht21->valid) {
ret = i2c_smbus_read_word_swapped(client,
SHT21_TRIG_T_MEASUREMENT_HM);
if (ret < 0)
goto out;
sht21->temperature = sht21_temp_ticks_to_millicelsius(ret);
ret = i2c_smbus_read_word_swapped(client,
SHT21_TRIG_RH_MEASUREMENT_HM);
if (ret < 0)
goto out;
sht21->humidity = sht21_rh_ticks_to_per_cent_mille(ret);
sht21->last_update = jiffies;
sht21->valid = 1;
}
out:
mutex_unlock(&sht21->lock);
return ret >= 0 ? 0 : ret;
}
/**
* sht21_show_temperature() - 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)
{
struct sht21 *sht21 = dev_get_drvdata(dev);
int ret;
ret = sht21_update_measurements(dev);
if (ret < 0)
return ret;
return sprintf(buf, "%d\n", sht21->temperature);
}
/**
* sht21_show_humidity() - 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)
{
struct sht21 *sht21 = dev_get_drvdata(dev);
int ret;
ret = sht21_update_measurements(dev);
if (ret < 0)
return ret;
return sprintf(buf, "%d\n", sht21->humidity);
}
static ssize_t eic_read(struct sht21 *sht21)
{
struct i2c_client *client = sht21->client;
u8 tx[2];
u8 rx[8];
u8 eic[8];
struct i2c_msg msgs[2] = {
{
.addr = client->addr,
.flags = 0,
.len = 2,
.buf = tx,
},
{
.addr = client->addr,
.flags = I2C_M_RD,
.len = 8,
.buf = rx,
},
};
int ret;
tx[0] = SHT21_READ_SNB_CMD1;
tx[1] = SHT21_READ_SNB_CMD2;
ret = i2c_transfer(client->adapter, msgs, 2);
if (ret < 0)
goto out;
eic[2] = rx[0];
eic[3] = rx[2];
eic[4] = rx[4];
eic[5] = rx[6];
tx[0] = SHT21_READ_SNAC_CMD1;
tx[1] = SHT21_READ_SNAC_CMD2;
msgs[1].len = 6;
ret = i2c_transfer(client->adapter, msgs, 2);
if (ret < 0)
goto out;
eic[0] = rx[3];
eic[1] = rx[4];
eic[6] = rx[0];
eic[7] = rx[1];
ret = snprintf(sht21->eic, sizeof(sht21->eic),
"%02x%02x%02x%02x%02x%02x%02x%02x\n",
eic[0], eic[1], eic[2], eic[3],
eic[4], eic[5], eic[6], eic[7]);
out:
if (ret < 0)
sht21->eic[0] = 0;
return ret;
}
/**
* 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)
{
struct sht21 *sht21 = dev_get_drvdata(dev);
int ret;
ret = sizeof(sht21->eic) - 1;
mutex_lock(&sht21->lock);
if (!sht21->eic[0])
ret = eic_read(sht21);
if (ret > 0)
memcpy(buf, sht21->eic, ret);
mutex_unlock(&sht21->lock);
return ret;
}
/* 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[] = {
&sensor_dev_attr_temp1_input.dev_attr.attr,
&sensor_dev_attr_humidity1_input.dev_attr.attr,
&dev_attr_eic.attr,
NULL
};
ATTRIBUTE_GROUPS(sht21);
static int sht21_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct device *dev = &client->dev;
struct device *hwmon_dev;
struct sht21 *sht21;
if (!i2c_check_functionality(client->adapter,
I2C_FUNC_SMBUS_WORD_DATA)) {
dev_err(&client->dev,
"adapter does not support SMBus word transactions\n");
return -ENODEV;
}
sht21 = devm_kzalloc(dev, sizeof(*sht21), GFP_KERNEL);
if (!sht21)
return -ENOMEM;
sht21->client = client;
mutex_init(&sht21->lock);
hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
sht21, sht21_groups);
return PTR_ERR_OR_ZERO(hwmon_dev);
}
/* Device ID table */
static const struct i2c_device_id sht21_id[] = {
{ "sht21", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, sht21_id);
static struct i2c_driver sht21_driver = {
.driver.name = "sht21",
.probe = sht21_probe,
.id_table = sht21_id,
};
module_i2c_driver(sht21_driver);
MODULE_AUTHOR("Urs Fleisch <urs.fleisch@sensirion.com>");
MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver");
MODULE_LICENSE("GPL");