[PATCH 1/1] hwmon: add support for Sensirion SHT3x sensors
From: Pascal Sachs
Date: Thu Mar 10 2016 - 10:14:40 EST
From: David Frey <david.frey@xxxxxxxxxxxxx>
This driver implements support for the Sensirion SHT3x-DIS chip,
a humidity and temperature sensor. Temperature is measured
in degrees Celsius, relative humidity is expressed as a percentage.
In the sysfs interface, all values are scaled by 1000,
i.e. the value for 31.5 degrees Celsius is 31500.
Signed-off-by: Pascal Sachs <pascal.sachs@xxxxxxxxxxxxx>
---
Patch was generated against kernel v4.5-rc7
Documentation/hwmon/sht3x | 42 ++++
drivers/hwmon/Kconfig | 10 +
drivers/hwmon/Makefile | 1 +
drivers/hwmon/sht3x.c | 389 ++++++++++++++++++++++++++++++++++++
include/linux/platform_data/sht3x.h | 23 +++
5 files changed, 465 insertions(+)
create mode 100644 Documentation/hwmon/sht3x
create mode 100644 drivers/hwmon/sht3x.c
create mode 100644 include/linux/platform_data/sht3x.h
diff --git a/Documentation/hwmon/sht3x b/Documentation/hwmon/sht3x
new file mode 100644
index 0000000..6023862
--- /dev/null
+++ b/Documentation/hwmon/sht3x
@@ -0,0 +1,42 @@
+Kernel driver sht3x
+===================
+
+Supported chips:
+ * Sensirion SHT3x-DIS
+ Prefix: 'sht3x'
+ Addresses scanned: none
+ Datasheet: http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_Datasheet_SHT3x_DIS.pdf
+
+Author:
+ David Frey <david.frey@xxxxxxxxxxxxx>
+
+Description
+-----------
+
+This driver implements support for the Sensirion SHT3x-DIS chip, a humidity
+and temperature sensor. Temperature is measured in degrees celsius, relative
+humidity is expressed as a percentage. In the sysfs interface, all values are
+scaled by 1000, i.e. the value for 31.5 degrees celsius is 31500.
+
+The device communicates with the I2C protocol. Sensors can have the I2C
+addresses 0x44 or 0x45, depending on the wiring. See
+Documentation/i2c/instantiating-devices for methods to instantiate the device.
+
+There are two options configurable by means of sht3x_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
+high_alert_set: temperature and humidity at which to set the high alert
+high_alert_clear: temperature and humidity at which to clear the high alert
+low_alert_clear: temperature and humidity at which to clear the low alert
+low_alert_set: temperature and humidity at which to set the low alert
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 60fb80b..4722b76 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1235,6 +1235,16 @@ config SENSORS_SHTC1
This driver can also be built as a module. If so, the module
will be called shtc1.
+config SENSORS_SHT3x
+ tristate "Sensiron humidity and temperature sensors. SHT3x and compat."
+ depends on I2C
+ help
+ If you say yes here you get support for the Sensiron SHT30 and SHT31
+ humidity and temperature sensors.
+
+ This driver can also be built as a module. If so, the module
+ will be called sht3x.
+
config SENSORS_S3C
tristate "Samsung built-in ADC"
depends on S3C_ADC
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 30c94df..8f19eab 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -136,6 +136,7 @@ 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-$(CONFIG_SENSORS_SHT3x) += sht3x.o
obj-$(CONFIG_SENSORS_SIS5595) += sis5595.o
obj-$(CONFIG_SENSORS_SMM665) += smm665.o
obj-$(CONFIG_SENSORS_SMSC47B397)+= smsc47b397.o
diff --git a/drivers/hwmon/sht3x.c b/drivers/hwmon/sht3x.c
new file mode 100644
index 0000000..2e78c44
--- /dev/null
+++ b/drivers/hwmon/sht3x.c
@@ -0,0 +1,389 @@
+/* Sensirion SHT3x-DIS humidity and temperature sensor driver.
+ * The SHT3x comes in many different versions, this driver is for the
+ * I2C version only.
+ *
+ * Copyright (C) 2015 Sensirion AG, Switzerland
+ * Author: David Frey <david.frey@xxxxxxxxxxxxx>
+ *
+ * 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 <asm/page.h>
+#include <linux/crc8.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/platform_data/sht3x.h>
+
+/* commands (high precision mode) */
+static const unsigned char sht3x_cmd_measure_blocking_hpm[] = { 0x2c, 0x06 };
+static const unsigned char sht3x_cmd_measure_nonblocking_hpm[] = { 0x24, 0x00 };
+
+/* commands (low power mode) */
+static const unsigned char sht3x_cmd_measure_blocking_lpm[] = { 0x2c, 0x10 };
+static const unsigned char sht3x_cmd_measure_nonblocking_lpm[] = { 0x24, 0x16 };
+
+static const unsigned char sht3x_cmd_read_status_reg[] = { 0xF3, 0x2D };
+
+#define HIGH_ALERT_SET_NAME "high_alert_set"
+#define HIGH_ALERT_CLEAR_NAME "high_alert_clear"
+#define LOW_ALERT_SET_NAME "low_alert_set"
+#define LOW_ALERT_CLEAR_NAME "low_alert_clear"
+
+/* delays for non-blocking i2c commands, both in us */
+#define SHT3X_NONBLOCKING_WAIT_TIME_HPM 15000
+#define SHT3X_NONBLOCKING_WAIT_TIME_LPM 4000
+
+#define SHT3X_WORD_LEN 2
+#define SHT3X_CMD_LENGTH SHT3X_WORD_LEN
+#define SHT3X_CRC8_LEN 1
+#define SHT3X_RESPONSE_LENGTH 6
+#define SHT3X_THRESHOLD_LENGTH 2
+#define SHT3X_THRESHOLD_COUNT \
+ (sizeof(threshold_commands) / sizeof(struct sht3x_alert_commands))
+#define SHT3X_CRC8_LEN 1
+#define SHT3X_CRC8_POLYNOMIAL 0x31
+#define SHT3X_CRC8_INIT 0xFF
+
+DECLARE_CRC8_TABLE(sht3x_crc8_table);
+
+struct sht3x_alert_commands {
+ const char *threshold_name;
+ const char read_command[SHT3X_CMD_LENGTH];
+ const char write_command[SHT3X_CMD_LENGTH];
+};
+
+const struct sht3x_alert_commands threshold_commands[] = {
+ { HIGH_ALERT_SET_NAME, {0xe1, 0x1f}, {0x61, 0x1d} },
+ { HIGH_ALERT_CLEAR_NAME, {0xe1, 0x14}, {0x61, 0x16} },
+ { LOW_ALERT_SET_NAME, {0xe1, 0x02}, {0x61, 0x00} },
+ { LOW_ALERT_CLEAR_NAME, {0xe1, 0x09}, {0x61, 0x0B} },
+};
+
+struct sht3x_data {
+ struct i2c_client *client;
+ struct mutex update_lock;
+
+ const unsigned char *command;
+ unsigned int nonblocking_wait_time; /* in us */
+
+ struct sht3x_platform_data setup;
+
+ int temperature; /* 1000 * temperature in dgr C */
+ int humidity; /* 1000 * relative humidity in %RH */
+};
+
+
+static const struct sht3x_alert_commands*
+find_commands(const char *threshold_name)
+{
+ int i;
+
+ for (i = 0; i < SHT3X_THRESHOLD_COUNT; i++) {
+ if (strcmp(threshold_name, threshold_commands[i].threshold_name)
+ == 0)
+ return &threshold_commands[i];
+ }
+ return 0;
+}
+
+static int sht3x_read_from_command(struct i2c_client *client,
+ const char *command,
+ char *buf, int length,
+ unsigned int wait_time)
+{
+ int ret = i2c_master_send(client, command, SHT3X_CMD_LENGTH);
+
+ if (ret != SHT3X_CMD_LENGTH) {
+ dev_err(&client->dev, "failed to send command: %d\n", ret);
+ return ret < 0 ? ret : -EIO;
+ }
+
+ if (wait_time)
+ usleep_range(wait_time, wait_time + 1000);
+
+ ret = i2c_master_recv(client, buf, length);
+ if (ret != length) {
+ dev_err(&client->dev, "failed to read values: %d\n", ret);
+ return ret < 0 ? ret : -EIO;
+ }
+
+ return 0;
+}
+
+static int sht3x_extract_temperature(u16 raw)
+{
+ /*
+ * From datasheet:
+ * T = -45 + 175 * ST / 2^16
+ * Adapted for integer fixed point (3 digit) arithmetic.
+ */
+ return ((21875 * (int)raw) >> 13) - 45000;
+}
+
+static int sht3x_extract_humidity(u16 raw)
+{
+ /*
+ * From datasheet:
+ * RH = 100 * SRH / 2^16
+ * Adapted for integer fixed point (3 digit) arithmetic.
+ */
+ return ((12500 * (int)raw) >> 13);
+}
+
+/* sysfs attributes */
+static struct sht3x_data *sht3x_update_client(struct device *dev)
+{
+ struct sht3x_data *data = dev_get_drvdata(dev);
+ struct i2c_client *client = data->client;
+ unsigned char buf[SHT3X_RESPONSE_LENGTH];
+ u16 val;
+ int ret = 0;
+ /*
+ * 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.
+ */
+ unsigned int wait_time = data->setup.blocking_io ?
+ 0 : data->nonblocking_wait_time;
+
+ mutex_lock(&data->update_lock);
+
+ ret = sht3x_read_from_command(client, data->command,
+ buf, sizeof(buf), wait_time);
+ if (ret)
+ goto out;
+
+ val = be16_to_cpup((__be16 *) buf);
+ data->temperature = sht3x_extract_temperature(val);
+ val = be16_to_cpup((__be16 *) (buf + 3));
+ data->humidity = sht3x_extract_humidity(val);
+
+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 sht3x_data *data = sht3x_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 sht3x_data *data = sht3x_update_client(dev);
+
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
+ return sprintf(buf, "%d\n", data->humidity);
+}
+
+static ssize_t alert_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ char buffer[SHT3X_WORD_LEN];
+ u16 raw;
+ int temperature, humidity;
+ struct sht3x_data *data = dev_get_drvdata(dev);
+ struct i2c_client *client = data->client;
+ const struct sht3x_alert_commands *commands =
+ find_commands(attr->attr.name);
+
+ int ret = sht3x_read_from_command(client, commands->read_command,
+ buffer, sizeof(buffer), 0);
+ if (ret)
+ return ret;
+
+ raw = be16_to_cpup((__be16 *) buffer);
+ /*
+ * top 7 bits are the humidity MSB,
+ * lower 9 bits are temperature MSB
+ */
+ temperature = sht3x_extract_temperature((raw & 0x01ff) << 7);
+ humidity = sht3x_extract_humidity(raw & 0xfe00);
+
+ return scnprintf(buf, PAGE_SIZE, "%d %d\n", temperature, humidity);
+}
+
+static ssize_t alert_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf,
+ size_t count)
+{
+ char buffer[2 * SHT3X_WORD_LEN + SHT3X_CRC8_LEN];
+ char *position = buffer;
+ u16 raw;
+ int temperature, humidity;
+ struct sht3x_data *data = dev_get_drvdata(dev);
+ struct i2c_client *client = data->client;
+ const struct sht3x_alert_commands *commands =
+ find_commands(attr->attr.name);
+
+ int ret = sscanf(buf, "%d %d", &temperature, &humidity);
+
+ if (ret != SHT3X_THRESHOLD_LENGTH) {
+ dev_err(&client->dev, "wrong number of arguments: %d", ret);
+ return -EINVAL;
+ }
+ if (temperature < -45000 || temperature > 130000) {
+ dev_err(&client->dev, "temperature out of range");
+ return -EINVAL;
+ }
+ if (humidity < 0 || humidity > 100000) {
+ dev_err(&client->dev, "humidity out of range");
+ return -EINVAL;
+ }
+
+ memcpy(position, commands->write_command, SHT3X_CMD_LENGTH);
+ position += SHT3X_CMD_LENGTH;
+ /*
+ * ST = (T + 45) / 175 * 2^16
+ * SRH = RH / 100 * 2^16
+ * adapted for fixed point arithmetic and packed the same as
+ * in alert_show()
+ */
+ raw = ((temperature + 45000) * 24543) >> (16 + 7);
+ raw |= ((humidity * 42950) >> 16) & 0xfe00;
+ *(__be16 *)(position) = cpu_to_be16(raw);
+ position[SHT3X_WORD_LEN] = crc8(sht3x_crc8_table,
+ position, SHT3X_WORD_LEN,
+ SHT3X_CRC8_INIT);
+
+ ret = i2c_master_send(client, buffer, sizeof(buffer));
+ if (ret != sizeof(buffer)) {
+ dev_err(&client->dev, "failed to set alert threshold\n");
+ return ret < 0 ? ret : -EIO;
+ }
+ return count;
+}
+
+static DEVICE_ATTR_RO(temp1_input);
+static DEVICE_ATTR_RO(humidity1_input);
+static DEVICE_ATTR(high_alert_set, 0664, alert_show, alert_store);
+static DEVICE_ATTR(high_alert_clear, 0664, alert_show, alert_store);
+static DEVICE_ATTR(low_alert_set, 0664, alert_show, alert_store);
+static DEVICE_ATTR(low_alert_clear, 0664, alert_show, alert_store);
+
+static struct attribute *sht3x_attrs[] = {
+ &dev_attr_temp1_input.attr,
+ &dev_attr_humidity1_input.attr,
+ &dev_attr_high_alert_set.attr,
+ &dev_attr_high_alert_clear.attr,
+ &dev_attr_low_alert_set.attr,
+ &dev_attr_low_alert_clear.attr,
+ NULL
+};
+
+ATTRIBUTE_GROUPS(sht3x);
+
+static void sht3x_select_command(struct sht3x_data *data)
+{
+ if (data->setup.high_precision) {
+ data->command = data->setup.blocking_io ?
+ sht3x_cmd_measure_blocking_hpm :
+ sht3x_cmd_measure_nonblocking_hpm;
+ data->nonblocking_wait_time = SHT3X_NONBLOCKING_WAIT_TIME_HPM;
+
+ } else {
+ data->command = data->setup.blocking_io ?
+ sht3x_cmd_measure_blocking_lpm :
+ sht3x_cmd_measure_nonblocking_lpm;
+ data->nonblocking_wait_time = SHT3X_NONBLOCKING_WAIT_TIME_LPM;
+ }
+}
+
+static int sht3x_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ int ret;
+ char status_reg[2];
+ struct sht3x_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, sht3x_cmd_read_status_reg,
+ SHT3X_CMD_LENGTH);
+ if (ret != SHT3X_CMD_LENGTH) {
+ dev_err(dev, "could not send read_status_reg command: %d\n",
+ ret);
+ return ret < 0 ? ret : -ENODEV;
+ }
+ ret = i2c_master_recv(client, status_reg, sizeof(status_reg));
+ if (ret != sizeof(status_reg)) {
+ dev_err(dev, "could not read status register: %d\n", ret);
+ 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;
+ crc8_populate_msb(sht3x_crc8_table, SHT3X_CRC8_POLYNOMIAL);
+
+ if (client->dev.platform_data)
+ data->setup = *(struct sht3x_platform_data *)dev->platform_data;
+ sht3x_select_command(data);
+ mutex_init(&data->update_lock);
+
+ hwmon_dev = devm_hwmon_device_register_with_groups(dev,
+ client->name,
+ data, sht3x_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 sht3x_id[] = {
+ {"sht3x", 0},
+ {}
+};
+
+MODULE_DEVICE_TABLE(i2c, sht3x_id);
+
+static struct i2c_driver sht3x_i2c_driver = {
+ .driver.name = "sht3x",
+ .probe = sht3x_probe,
+ .id_table = sht3x_id,
+};
+
+module_i2c_driver(sht3x_i2c_driver);
+
+MODULE_AUTHOR("David Frey <david.frey@xxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Sensirion SHT3x humidity and temperature sensor driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/platform_data/sht3x.h b/include/linux/platform_data/sht3x.h
new file mode 100644
index 0000000..c8be876
--- /dev/null
+++ b/include/linux/platform_data/sht3x.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2015 Sensirion AG, Switzerland
+ * Author: David Frey <david.frey@xxxxxxxxxxxxx>
+ *
+ * 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 __SHT3X_H_
+#define __SHT3X_H_
+
+struct sht3x_platform_data {
+ bool blocking_io;
+ bool high_precision;
+};
+#endif /* __SHT3X_H_ */
--
1.9.1
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