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hwmon: add support for Sensirion SHTC1 sensor

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Add support for Sensirion SHTC1 and compatible temperature and humidity
sensors.

Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Tomas Pop 2014-06-05 15:24:19 -07:00 committed by Guenter Roeck
parent 31e3879127
commit 1a539d372e
5 changed files with 328 additions and 0 deletions
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43
Documentation/hwmon/shtc1 Normal file
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Kernel driver shtc1
===================
Supported chips:
* Sensirion SHTC1
Prefix: 'shtc1'
Addresses scanned: none
Datasheet: http://www.sensirion.com/file/datasheet_shtc1
* Sensirion SHTW1
Prefix: 'shtw1'
Addresses scanned: none
Datasheet: Not publicly available
Author:
Johannes Winkelmann <johannes.winkelmann@sensirion.com>
Description
-----------
This driver implements support for the Sensirion SHTC1 chip, a humidity and
temperature sensor. Temperature is measured in degrees celsius, relative
humidity is expressed as a percentage. Driver can be used as well for SHTW1
chip, which has the same electrical interface.
The device communicates with the I2C protocol. All sensors are set to I2C
address 0x70. See Documentation/i2c/instantiating-devices for methods to
instantiate the device.
There are two options configurable by means of shtc1_platform_data:
1. blocking (pull the I2C clock line down while performing the measurement) or
non-blocking mode. Blocking mode will guarantee the fastest result but
the I2C bus will be busy during that time. By default, non-blocking mode
is used. Make sure clock-stretching works properly on your device if you
want to use blocking mode.
2. high or low accuracy. High accuracy is used by default and using it is
strongly recommended.
sysfs-Interface
---------------
temp1_input - temperature input
humidity1_input - humidity input

10
drivers/hwmon/Kconfig
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@ -1124,6 +1124,16 @@ config SENSORS_SHT21
This driver can also be built as a module. If so, the module
will be called sht21.
config SENSORS_SHTC1
tristate "Sensiron humidity and temperature sensors. SHTC1 and compat."
depends on I2C
help
If you say yes here you get support for the Sensiron SHTC1 and SHTW1
humidity and temperature sensors.
This driver can also be built as a module. If so, the module
will be called shtc1.
config SENSORS_S3C
tristate "Samsung built-in ADC"
depends on S3C_ADC

1
drivers/hwmon/Makefile
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@ -126,6 +126,7 @@ obj-$(CONFIG_SENSORS_SCH5627) += sch5627.o
obj-$(CONFIG_SENSORS_SCH5636) += sch5636.o
obj-$(CONFIG_SENSORS_SHT15) += sht15.o
obj-$(CONFIG_SENSORS_SHT21) += sht21.o
obj-$(CONFIG_SENSORS_SHTC1) += shtc1.o
obj-$(CONFIG_SENSORS_SIS5595) += sis5595.o
obj-$(CONFIG_SENSORS_SMM665) += smm665.o
obj-$(CONFIG_SENSORS_SMSC47B397)+= smsc47b397.o

251
drivers/hwmon/shtc1.c Normal file
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/* Sensirion SHTC1 humidity and temperature sensor driver
*
* Copyright (C) 2014 Sensirion AG, Switzerland
* Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
*
* 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.
*
*/
#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/delay.h>
#include <linux/platform_data/shtc1.h>
/* commands (high precision mode) */
static const unsigned char shtc1_cmd_measure_blocking_hpm[] = { 0x7C, 0xA2 };
static const unsigned char shtc1_cmd_measure_nonblocking_hpm[] = { 0x78, 0x66 };
/* commands (low precision mode) */
static const unsigned char shtc1_cmd_measure_blocking_lpm[] = { 0x64, 0x58 };
static const unsigned char shtc1_cmd_measure_nonblocking_lpm[] = { 0x60, 0x9c };
/* command for reading the ID register */
static const unsigned char shtc1_cmd_read_id_reg[] = { 0xef, 0xc8 };
/* constants for reading the ID register */
#define SHTC1_ID 0x07
#define SHTC1_ID_REG_MASK 0x1f
/* delays for non-blocking i2c commands, both in us */
#define SHTC1_NONBLOCKING_WAIT_TIME_HPM 14400
#define SHTC1_NONBLOCKING_WAIT_TIME_LPM 1000
#define SHTC1_CMD_LENGTH 2
#define SHTC1_RESPONSE_LENGTH 6
struct shtc1_data {
struct i2c_client *client;
struct mutex update_lock;
bool valid;
unsigned long last_updated; /* in jiffies */
const unsigned char *command;
unsigned int nonblocking_wait_time; /* in us */
struct shtc1_platform_data setup;
int temperature; /* 1000 * temperature in dgr C */
int humidity; /* 1000 * relative humidity in %RH */
};
static int shtc1_update_values(struct i2c_client *client,
struct shtc1_data *data,
char *buf, int bufsize)
{
int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
if (ret != SHTC1_CMD_LENGTH) {
dev_err(&client->dev, "failed to send command: %d\n", ret);
return ret < 0 ? ret : -EIO;
}
/*
* In blocking mode (clock stretching mode) the I2C bus
* is blocked for other traffic, thus the call to i2c_master_recv()
* will wait until the data is ready. For non blocking mode, we
* have to wait ourselves.
*/
if (!data->setup.blocking_io)
usleep_range(data->nonblocking_wait_time,
data->nonblocking_wait_time + 1000);
ret = i2c_master_recv(client, buf, bufsize);
if (ret != bufsize) {
dev_err(&client->dev, "failed to read values: %d\n", ret);
return ret < 0 ? ret : -EIO;
}
return 0;
}
/* sysfs attributes */
static struct shtc1_data *shtc1_update_client(struct device *dev)
{
struct shtc1_data *data = dev_get_drvdata(dev);
struct i2c_client *client = data->client;
unsigned char buf[SHTC1_RESPONSE_LENGTH];
int val;
int ret = 0;
mutex_lock(&data->update_lock);
if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
ret = shtc1_update_values(client, data, buf, sizeof(buf));
if (ret)
goto out;
/*
* From datasheet:
* T = -45 + 175 * ST / 2^16
* RH = 100 * SRH / 2^16
*
* Adapted for integer fixed point (3 digit) arithmetic.
*/
val = be16_to_cpup((__be16 *)buf);
data->temperature = ((21875 * val) >> 13) - 45000;
val = be16_to_cpup((__be16 *)(buf + 3));
data->humidity = ((12500 * val) >> 13);
data->last_updated = jiffies;
data->valid = true;
}
out:
mutex_unlock(&data->update_lock);
return ret == 0 ? data : ERR_PTR(ret);
}
static ssize_t temp1_input_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct shtc1_data *data = shtc1_update_client(dev);
if (IS_ERR(data))
return PTR_ERR(data);
return sprintf(buf, "%d\n", data->temperature);
}
static ssize_t humidity1_input_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct shtc1_data *data = shtc1_update_client(dev);
if (IS_ERR(data))
return PTR_ERR(data);
return sprintf(buf, "%d\n", data->humidity);
}
static DEVICE_ATTR_RO(temp1_input);
static DEVICE_ATTR_RO(humidity1_input);
static struct attribute *shtc1_attrs[] = {
&dev_attr_temp1_input.attr,
&dev_attr_humidity1_input.attr,
NULL
};
ATTRIBUTE_GROUPS(shtc1);
static void shtc1_select_command(struct shtc1_data *data)
{
if (data->setup.high_precision) {
data->command = data->setup.blocking_io ?
shtc1_cmd_measure_blocking_hpm :
shtc1_cmd_measure_nonblocking_hpm;
data->nonblocking_wait_time = SHTC1_NONBLOCKING_WAIT_TIME_HPM;
} else {
data->command = data->setup.blocking_io ?
shtc1_cmd_measure_blocking_lpm :
shtc1_cmd_measure_nonblocking_lpm;
data->nonblocking_wait_time = SHTC1_NONBLOCKING_WAIT_TIME_LPM;
}
}
static int shtc1_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
int ret;
char id_reg[2];
struct shtc1_data *data;
struct device *hwmon_dev;
struct i2c_adapter *adap = client->adapter;
struct device *dev = &client->dev;
if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
dev_err(dev, "plain i2c transactions not supported\n");
return -ENODEV;
}
ret = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
if (ret != SHTC1_CMD_LENGTH) {
dev_err(dev, "could not send read_id_reg command: %d\n", ret);
return ret < 0 ? ret : -ENODEV;
}
ret = i2c_master_recv(client, id_reg, sizeof(id_reg));
if (ret != sizeof(id_reg)) {
dev_err(dev, "could not read ID register: %d\n", ret);
return -ENODEV;
}
if ((id_reg[1] & SHTC1_ID_REG_MASK) != SHTC1_ID) {
dev_err(dev, "ID register doesn't match\n");
return -ENODEV;
}
data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
if (!data)
return -ENOMEM;
data->setup.blocking_io = false;
data->setup.high_precision = true;
data->client = client;
if (client->dev.platform_data)
data->setup = *(struct shtc1_platform_data *)dev->platform_data;
shtc1_select_command(data);
mutex_init(&data->update_lock);
hwmon_dev = devm_hwmon_device_register_with_groups(dev,
client->name,
data,
shtc1_groups);
if (IS_ERR(hwmon_dev))
dev_dbg(dev, "unable to register hwmon device\n");
return PTR_ERR_OR_ZERO(hwmon_dev);
}
/* device ID table */
static const struct i2c_device_id shtc1_id[] = {
{ "shtc1", 0 },
{ "shtw1", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, shtc1_id);
static struct i2c_driver shtc1_i2c_driver = {
.driver.name = "shtc1",
.probe = shtc1_probe,
.id_table = shtc1_id,
};
module_i2c_driver(shtc1_i2c_driver);
MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.com>");
MODULE_DESCRIPTION("Sensirion SHTC1 humidity and temperature sensor driver");
MODULE_LICENSE("GPL");

23
include/linux/platform_data/shtc1.h Normal file
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@ -0,0 +1,23 @@
/*
* Copyright (C) 2014 Sensirion AG, Switzerland
* Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* 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.
*
*/
#ifndef __SHTC1_H_
#define __SHTC1_H_
struct shtc1_platform_data {
bool blocking_io;
bool high_precision;
};
#endif /* __SHTC1_H_ */