/* 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");
