Message-Id: <1342789042-13433-1-git-send-email-johannes.winkelmann@sensirion.com>
Date:	Fri, 20 Jul 2012 14:57:22 +0200
From:	Johannes Winkelmann <johannes.winkelmann@...il.com>
To:	linux-kernel@...r.kernel.org, lm-sensors@...sensors.org
Cc:	Jean Delvare <khali@...ux-fr.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Johannes Winkelmann <johannes.winkelmann@...sirion.com>
Subject: [RFC][PATCH] hwmon: add support for Sensirion C1 sensor

this is an initial version of the driver for the upcoming Sensirion
SHT C1 humidity and temperature sensor. First hardware samples are
being tested by our key customers, and we'd therefore appreciate to
get feedback on the driver.

Datasheet URLs will be set as soon as there's a final version available.

Signed-off-by: Johannes Winkelmann <johannes.winkelmann@...sirion.com>
---
 Documentation/hwmon/shtc1           |   34 +++++
 drivers/hwmon/Kconfig               |   10 ++
 drivers/hwmon/Makefile              |    1 +
 drivers/hwmon/shtc1.c               |  282 +++++++++++++++++++++++++++++++++++
 include/linux/platform_data/shtc1.h |   24 +++
 5 files changed, 351 insertions(+)
 create mode 100644 Documentation/hwmon/shtc1
 create mode 100644 drivers/hwmon/shtc1.c
 create mode 100644 include/linux/platform_data/shtc1.h

diff --git a/Documentation/hwmon/shtc1 b/Documentation/hwmon/shtc1
new file mode 100644
index 0000000..ada89f5
--- /dev/null
+++ b/Documentation/hwmon/shtc1
@@ -0,0 +1,34 @@
+Kernel driver shtc1
+===================
+
+Supported chips:
+  * Sensirion SHTC1
+    Prefix: 'shtc1'
+    Addresses scanned: none
+    Datasheet: To be announced
+
+Author:
+  Johannes Winkelmann <johannes.winkelmann@...sirion.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.
+
+The device communicates with the I2C protocol. All sensors are set to the same
+I2C address 0x70, so an entry with I2C_BOARD_INFO("shtc1", 0x70) can be used
+in the board setup code.
+
+Furthermore, there are two configuration options by means of 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
+2. high or low accuracy. Using high accuracy is always recommended.
+
+sysfs-Interface
+---------------
+
+temp1_input - temperature input
+humidity1_input - humidity input
\ No newline at end of file
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 6f1d167..cd5dced 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -902,6 +902,16 @@ 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 SHTC1 humidity and temperature sensor."
+	depends on I2C
+	help
+	  If you say yes here you get support for the Sensiron SHTC1
+	  humidity and temperature sensor.
+
+	  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
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index e1eeac1..d6d11d4 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -107,6 +107,7 @@ 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
diff --git a/drivers/hwmon/shtc1.c b/drivers/hwmon/shtc1.c
new file mode 100644
index 0000000..b91d9ba
--- /dev/null
+++ b/drivers/hwmon/shtc1.c
@@ -0,0 +1,282 @@
+/* Sensirion SHTC1 humidity and temperature sensor driver
+ *
+ * Copyright (C) 2012 Sensirion AG, Switzerland
+ * Author: Johannes Winkelmann <johannes.winkelmann@...sirion.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.
+ *
+ * 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
+ *
+ * Data sheet available soon
+ *  TODO: add link
+ */
+
+#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 char shtc1_cmd_measure_blocking_hpm[]    = { 0x7C, 0xA2 };
+static const char shtc1_cmd_measure_nonblocking_hpm[] = { 0x78, 0x66 };
+
+/* commands (low precision mode) */
+static const char shtc1_cmd_measure_blocking_lpm[]    = { 0x64, 0x58 };
+static const char shtc1_cmd_measure_nonblocking_lpm[] = { 0x60, 0x9c };
+
+/* delays for non-blocking i2c commands */
+/* TODO: use max timings */
+static const int shtc1_nonblocking_wait_time_hpm = 10;
+static const int shtc1_nonblocking_wait_time_lpm =  1;
+
+
+#define SHTC1_CMD_LENGTH 2
+#define SHTC1_RESPONSE_LENGTH 6
+
+struct shtc1_data {
+	struct device *hwmon_dev;
+	struct mutex update_lock;
+	unsigned int valid:1;
+	unsigned long last_updated; /* In jiffies */
+
+	const char *command;
+	unsigned int nonblocking_wait_time;
+
+	struct shtc1_pdata setup;
+
+	int temperature;
+	int humidity;
+};
+
+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_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 < 0) {
+		dev_err(&client->dev, "failed to send command");
+		return -1;
+	}
+
+	/*
+	 * 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, thus the msleep()
+	 */
+	if (!data->setup.blocking_io)
+		msleep(data->nonblocking_wait_time);
+
+	ret = i2c_master_recv(client, buf, bufsize);
+	if (ret != bufsize) {
+		dev_err(&client->dev, "failed to read values: %d", ret);
+		return -1;
+	}
+
+	return 0;
+}
+
+/* sysfs attributes */
+static struct shtc1_data *shtc1_update_client(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct shtc1_data *data = i2c_get_clientdata(client);
+
+	char buf[SHTC1_RESPONSE_LENGTH];
+	int val;
+	int ret;
+
+	mutex_lock(&data->update_lock);
+
+	/*
+	 * initialize 'ret' in case we had a valid result before, but
+	 * read too quickly in which case we return the last values
+	 */
+	ret = !data->valid;
+
+	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 = -10 + 120 * SRH / 2^16
+		 *
+		 * Adapted for integer fixed point (3 digit) arithmetic
+		 */
+		val = (buf[0] << 8) | buf[1];
+		data->temperature = ((21875 * val) >> 13) - 45000;
+		val = (buf[3] << 8) | buf[4];
+		data->humidity = ((15000 * val) >> 13) - 10000;
+
+		data->last_updated = jiffies;
+		data->valid = 1;
+	}
+
+out:
+	mutex_unlock(&data->update_lock);
+
+	return ret == 0 ? data : NULL;
+}
+
+static ssize_t shtc1_show_temperature(struct device *dev,
+				      struct device_attribute *attr,
+				      char *buf)
+{
+	struct shtc1_data *data = shtc1_update_client(dev);
+	if (!data)
+		return -ENODEV;
+
+	return sprintf(buf, "%d\n", data->temperature);
+}
+
+static ssize_t shtc1_show_humidity(struct device *dev,
+				   struct device_attribute *attr,
+				   char *buf)
+{
+	struct shtc1_data *data = shtc1_update_client(dev);
+	if (!data)
+		return -ENODEV;
+
+	return sprintf(buf, "%d\n", data->humidity);
+}
+
+static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO,
+			  shtc1_show_temperature, NULL, 0);
+static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO,
+			  shtc1_show_humidity, NULL, 0);
+
+static struct attribute *shtc1_attributes[] = {
+	&sensor_dev_attr_temp1_input.dev_attr.attr,
+	&sensor_dev_attr_humidity1_input.dev_attr.attr,
+	NULL
+};
+
+static const struct attribute_group shtc1_attr_group = {
+	.attrs = shtc1_attributes,
+};
+
+
+
+static int __devinit shtc1_probe(struct i2c_client *client,
+				 const struct i2c_device_id *id)
+{
+	struct shtc1_data *data;
+	int err;
+
+	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;
+	}
+
+	data = devm_kzalloc(&client->dev, sizeof(struct shtc1_data),
+			    GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	/* defaults: blocking, high precision mode */
+	data->setup.blocking_io = 1;
+	data->setup.high_precision = 1;
+
+	if (client->dev.platform_data)
+		data->setup = *(struct shtc1_pdata *)client->dev.platform_data;
+	shtc1_select_command(data);
+
+	i2c_set_clientdata(client, data);
+	mutex_init(&data->update_lock);
+
+	err = sysfs_create_group(&client->dev.kobj, &shtc1_attr_group);
+	if (err) {
+		dev_dbg(&client->dev, "could not create sysfs files\n");
+		return err;
+	}
+	data->hwmon_dev = hwmon_device_register(&client->dev);
+	if (IS_ERR(data->hwmon_dev)) {
+		dev_dbg(&client->dev, "unable to register hwmon device\n");
+		err = PTR_ERR(data->hwmon_dev);
+		goto fail_remove_sysfs;
+	}
+
+
+	dev_info(&client->dev, "initialized\n");
+
+	return 0;
+
+fail_remove_sysfs:
+	sysfs_remove_group(&client->dev.kobj, &shtc1_attr_group);
+
+	return err;
+}
+
+
+/**
+ * shtc1_remove() - remove device
+ * @client: I2C client device
+ */
+static int __devexit shtc1_remove(struct i2c_client *client)
+{
+	struct shtc1_data *data = i2c_get_clientdata(client);
+
+	hwmon_device_unregister(data->hwmon_dev);
+	sysfs_remove_group(&client->dev.kobj, &shtc1_attr_group);
+
+	return 0;
+}
+
+/* Device ID table */
+static const struct i2c_device_id shtc1_id[] = {
+	{ "shtc1", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, c1_id);
+
+static struct i2c_driver shtc1_driver = {
+	.driver.name = "shtc1",
+	.probe       = shtc1_probe,
+	.remove      = __devexit_p(shtc1_remove),
+	.id_table    = shtc1_id,
+};
+
+module_i2c_driver(shtc1_driver);
+
+MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@...sirion.com>");
+MODULE_DESCRIPTION("Sensirion SHTC1 humidity and temperature sensor driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/platform_data/shtc1.h b/include/linux/platform_data/shtc1.h
new file mode 100644
index 0000000..3f83dce
--- /dev/null
+++ b/include/linux/platform_data/shtc1.h
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2012 Sensirion AG, Switzerland
+ * Author: Johannes Winkelmann <johannes.winkelmann@...sirion.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_pdata {
+	unsigned int blocking_io:1;
+	unsigned int high_precision:1;
+};
+
+#endif
-- 
1.7.9.5

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