[RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Tomas Pop]

One more time this patch sent with correct settings of my email client 
- I'm sorry for this.

This is a second version of the driver for Sensirion SHTC1 humidity and
temperature sensor. Initial version was submitted in July 2012.
http://www.gossamer-threads.com/lists/linux/kernel/1569130#1569130

We included suggested corrections formerly discussed in this list after
initial submission, but since it is quite a while, we are re-submitting
it again as a request for comments. Here is a list of important changes
to the initial version:

* returning real error codes instead of -1 or -ENODEV
* using boolean variables instead of bitmaps where possible
* macros be16_to_cpup used for conversion of indianneess
* corrected formula for decoding of humidity and temperature values
* documentation update

Patch was generated against kernel v3.15-rc3

Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
---
 Documentation/hwmon/shtc1           |  38 +++++
 drivers/hwmon/Kconfig               |  10 ++
 drivers/hwmon/Makefile              |   1 +
 drivers/hwmon/shtc1.c               | 323 ++++++++++++++++++++++++++++++++++++
 include/linux/platform_data/shtc1.h |  24 +++
 5 files changed, 396 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..6a72ae2d
--- /dev/null
+++ b/Documentation/hwmon/shtc1
@@ -0,0 +1,38 @@
+Kernel driver shtc1
+===================
+
+Supported chips:
+  * Sensirion SHTC1
+    Prefix: 'shtc1'
+    Addresses scanned: none
+    Datasheet: Publicly available at the Sensirion website
+    http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_SHTC1_Datasheet.pdf
+
+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, that has the same electrical interface, but datasheet has not been
+yet published.
+
+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. See Documentation/i2c/instantiating-devices for
+other methods to instantiate the device.
+
+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
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index bc196f4..4d58149 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1114,6 +1114,16 @@ 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 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 c48f987..1cc5273 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -125,6 +125,7 @@ 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..96d398b
--- /dev/null
+++ b/drivers/hwmon/shtc1.c
@@ -0,0 +1,323 @@
+/* Sensirion SHTC1 humidity and temperature sensor driver
+ *
+ * Copyright (C) 2012 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.
+ *
+ * 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 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 and constants for reading the ID register */
+static const unsigned char shtc1_cmd_read_id_reg[]	     = { 0xef, 0xc8 };
+static const unsigned char shtc1_id_reg_content = 0x07;
+static const unsigned char shtc1_id_reg_mask    = 0x1f;
+
+/* delays for non-blocking i2c commands */
+/* TODO: use max timings */
+#define SHTC1_NONBLOCKING_WAIT_TIME_HPM  10
+#define 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;
+	bool valid;
+	unsigned long last_updated; /* In jiffies */
+
+	const unsigned char *command;
+	unsigned int nonblocking_wait_time;
+
+	struct shtc1_platform_data 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: %d", ret);
+		return ret;
+	}
+
+	/*
+	* 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().
+	*
+	* TODO: consider usleep_range
+	*/
+	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 ret;
+	}
+
+	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);
+
+	unsigned 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 = 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 = 1;
+	}
+
+out:
+	mutex_unlock(&data->update_lock);
+
+	return ret == 0 ? data : ERR_PTR(ret);
+}
+
+static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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 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 shtc1_probe(struct i2c_client *client,
+				const struct i2c_device_id *id)
+{
+	struct shtc1_data *data;
+	int err;
+	struct i2c_adapter *adap = client->adapter;
+	char id_reg[2];
+
+	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
+		dev_err(&client->dev,
+			"adapter does not support plain i2c transactions\n");
+		return -ENODEV;
+	}
+
+	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
+
+	if (err < 0) {
+		dev_err(&client->dev, "could not send read command: %d\n", err);
+		return -ENODEV;
+	}
+	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
+	if (err != sizeof(id_reg)) {
+		dev_err(&client->dev, "could not read ID register: %d\n", err);
+		return -ENODEV;
+	}
+	if ((id_reg[1] & shtc1_id_reg_mask) != shtc1_id_reg_content) {
+		dev_err(&client->dev, "ID register doesn't match\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_platform_data *)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");
+		goto fail_free;
+		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);
+fail_free:
+	kfree(data);
+
+	return err;
+}
+
+/**
+ * shtc1_remove() - remove device
+ * @client: I2C client device
+ */
+static int 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, shtc1_id);
+
+static struct i2c_driver shtc1_i2c_driver = {
+	.driver.name = "shtc1",
+	.probe	= shtc1_probe,
+	.remove      = shtc1_remove,
+	.id_table    = shtc1_id,
+};
+
+/**
+ * shtc1_init() - initialize driver
+ *
+ * Called when kernel is booted or module is inserted.
+ * Returns 0 on success.
+ */
+static int __init shtc1_init(void)
+{
+	return i2c_add_driver(&shtc1_i2c_driver);
+}
+module_init(shtc1_init);
+
+/*
+ * shtc1_exit() - clean up driver
+ *
+ * Called when module is removed.
+ */
+static void __exit shtc1_exit(void)
+{
+	i2c_del_driver(&shtc1_i2c_driver);
+}
+
+module_exit(shtc1_exit);
+
+
+MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.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..4629364
--- /dev/null
+++ b/include/linux/platform_data/shtc1.h
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2012 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
-- 
1.8.3.2

[lm-sensors] [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Tomas Pop]

One more time this patch sent with correct settings of my email client 
- I'm sorry for this.

This is a second version of the driver for Sensirion SHTC1 humidity and
temperature sensor. Initial version was submitted in July 2012.
http://www.gossamer-threads.com/lists/linux/kernel/1569130#1569130

We included suggested corrections formerly discussed in this list after
initial submission, but since it is quite a while, we are re-submitting
it again as a request for comments. Here is a list of important changes
to the initial version:

* returning real error codes instead of -1 or -ENODEV
* using boolean variables instead of bitmaps where possible
* macros be16_to_cpup used for conversion of indianneess
* corrected formula for decoding of humidity and temperature values
* documentation update

Patch was generated against kernel v3.15-rc3

Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
---
 Documentation/hwmon/shtc1           |  38 +++++
 drivers/hwmon/Kconfig               |  10 ++
 drivers/hwmon/Makefile              |   1 +
 drivers/hwmon/shtc1.c               | 323 ++++++++++++++++++++++++++++++++++++
 include/linux/platform_data/shtc1.h |  24 +++
 5 files changed, 396 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..6a72ae2d
--- /dev/null
+++ b/Documentation/hwmon/shtc1
@@ -0,0 +1,38 @@
+Kernel driver shtc1
+=========+
+Supported chips:
+  * Sensirion SHTC1
+    Prefix: 'shtc1'
+    Addresses scanned: none
+    Datasheet: Publicly available at the Sensirion website
+    http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_SHTC1_Datasheet.pdf
+
+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, that has the same electrical interface, but datasheet has not been
+yet published.
+
+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. See Documentation/i2c/instantiating-devices for
+other methods to instantiate the device.
+
+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
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index bc196f4..4d58149 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1114,6 +1114,16 @@ 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 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 c48f987..1cc5273 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -125,6 +125,7 @@ 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..96d398b
--- /dev/null
+++ b/drivers/hwmon/shtc1.c
@@ -0,0 +1,323 @@
+/* Sensirion SHTC1 humidity and temperature sensor driver
+ *
+ * Copyright (C) 2012 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.
+ *
+ * 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 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 and constants for reading the ID register */
+static const unsigned char shtc1_cmd_read_id_reg[]	     = { 0xef, 0xc8 };
+static const unsigned char shtc1_id_reg_content = 0x07;
+static const unsigned char shtc1_id_reg_mask    = 0x1f;
+
+/* delays for non-blocking i2c commands */
+/* TODO: use max timings */
+#define SHTC1_NONBLOCKING_WAIT_TIME_HPM  10
+#define 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;
+	bool valid;
+	unsigned long last_updated; /* In jiffies */
+
+	const unsigned char *command;
+	unsigned int nonblocking_wait_time;
+
+	struct shtc1_platform_data 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: %d", ret);
+		return ret;
+	}
+
+	/*
+	* 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().
+	*
+	* TODO: consider usleep_range
+	*/
+	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 ret;
+	}
+
+	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);
+
+	unsigned 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 = 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 = 1;
+	}
+
+out:
+	mutex_unlock(&data->update_lock);
+
+	return ret = 0 ? data : ERR_PTR(ret);
+}
+
+static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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 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 shtc1_probe(struct i2c_client *client,
+				const struct i2c_device_id *id)
+{
+	struct shtc1_data *data;
+	int err;
+	struct i2c_adapter *adap = client->adapter;
+	char id_reg[2];
+
+	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
+		dev_err(&client->dev,
+			"adapter does not support plain i2c transactions\n");
+		return -ENODEV;
+	}
+
+	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
+
+	if (err < 0) {
+		dev_err(&client->dev, "could not send read command: %d\n", err);
+		return -ENODEV;
+	}
+	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
+	if (err != sizeof(id_reg)) {
+		dev_err(&client->dev, "could not read ID register: %d\n", err);
+		return -ENODEV;
+	}
+	if ((id_reg[1] & shtc1_id_reg_mask) != shtc1_id_reg_content) {
+		dev_err(&client->dev, "ID register doesn't match\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_platform_data *)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");
+		goto fail_free;
+		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);
+fail_free:
+	kfree(data);
+
+	return err;
+}
+
+/**
+ * shtc1_remove() - remove device
+ * @client: I2C client device
+ */
+static int 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, shtc1_id);
+
+static struct i2c_driver shtc1_i2c_driver = {
+	.driver.name = "shtc1",
+	.probe	= shtc1_probe,
+	.remove      = shtc1_remove,
+	.id_table    = shtc1_id,
+};
+
+/**
+ * shtc1_init() - initialize driver
+ *
+ * Called when kernel is booted or module is inserted.
+ * Returns 0 on success.
+ */
+static int __init shtc1_init(void)
+{
+	return i2c_add_driver(&shtc1_i2c_driver);
+}
+module_init(shtc1_init);
+
+/*
+ * shtc1_exit() - clean up driver
+ *
+ * Called when module is removed.
+ */
+static void __exit shtc1_exit(void)
+{
+	i2c_del_driver(&shtc1_i2c_driver);
+}
+
+module_exit(shtc1_exit);
+
+
+MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.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..4629364
--- /dev/null
+++ b/include/linux/platform_data/shtc1.h
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2012 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
-- 
1.8.3.2




_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

Re: [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Guenter Roeck]

On 05/01/2014 04:05 PM, Tomas Pop wrote:
> One more time this patch sent with correct settings of my email client
> - I'm sorry for this.
>
> This is a second version of the driver for Sensirion SHTC1 humidity and
> temperature sensor. Initial version was submitted in July 2012.
> http://www.gossamer-threads.com/lists/linux/kernel/1569130#1569130
>
> We included suggested corrections formerly discussed in this list after
> initial submission, but since it is quite a while, we are re-submitting
> it again as a request for comments. Here is a list of important changes
> to the initial version:
>
> * returning real error codes instead of -1 or -ENODEV
> * using boolean variables instead of bitmaps where possible
> * macros be16_to_cpup used for conversion of indianneess
> * corrected formula for decoding of humidity and temperature values
> * documentation update
>
> Patch was generated against kernel v3.15-rc3
>
> Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
> ---
>   Documentation/hwmon/shtc1           |  38 +++++
>   drivers/hwmon/Kconfig               |  10 ++
>   drivers/hwmon/Makefile              |   1 +
>   drivers/hwmon/shtc1.c               | 323 ++++++++++++++++++++++++++++++++++++
>   include/linux/platform_data/shtc1.h |  24 +++
>   5 files changed, 396 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..6a72ae2d
> --- /dev/null
> +++ b/Documentation/hwmon/shtc1
> @@ -0,0 +1,38 @@
> +Kernel driver shtc1
> +===================
> +
> +Supported chips:
> +  * Sensirion SHTC1
> +    Prefix: 'shtc1'
> +    Addresses scanned: none
> +    Datasheet: Publicly available at the Sensirion website
> +    http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_SHTC1_Datasheet.pdf

Ok to add SHTW1 here if it is known to work.
Just say:
	Datasheet: Not publicly available

> +
> +Author:
> +  Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> +
> +Description
> +-----------
> +
> +This driver implements support for the Sensirion  SHTC1 chip, a humidity and

Two spaces

> +temperature sensor. Temperature is measured in degrees celsius, relative
> +humidity is expressed as a percentage. Driver can be used as well for SHTW1
> +chip, that has the same electrical interface, but datasheet has not been

... for SHTW1, which has the same electrical interface.

> +yet published.
> +

Either add support for the second now, or don't mention it at all
(especially if the chip has a different ID and you don't want to add
that ID at this point for some reason).

> +The device communicates with the I2C protocol. All sensors are set to the same

... are set to I2C address 0x70.

> +I2C address 0x70, so an entry with I2C_BOARD_INFO("shtc1", 0x70) can be used
> +in the board setup code. See Documentation/i2c/instantiating-devices for
> +other methods to instantiate the device.
> +
I would suggest to just refer to the instantiating-devices document and drop
the I2C_BOARD_INFO example.

> +Furthermore, there are two configuration options by means of platform_data:

options configurable by means ...

> +1. blocking (pull the I2C clock line down while performing the measurement) or
> +   non-blocking, mode. Blocking mode will guarantee the fastest result, but

non-blocking mode (no comma)

> +   the I2C bus will be busy during that time

					that time.

> +2. high or low accuracy. Using high accuracy is always recommended.
> +
> +sysfs-Interface
> +---------------
> +
> +temp1_input - temperature input
> +humidity1_input - humidity input
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index bc196f4..4d58149 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1114,6 +1114,16 @@ 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 humidity

and SHTW1 ?

> +	  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 c48f987..1cc5273 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -125,6 +125,7 @@ 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..96d398b
> --- /dev/null
> +++ b/drivers/hwmon/shtc1.c
> @@ -0,0 +1,323 @@
> +/* Sensirion SHTC1 humidity and temperature sensor driver
> + *
> + * Copyright (C) 2012 Sensirion AG, Switzerland

2014 ?

> + * Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> + *
Is Johannes still involved ?

> + * 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.
> + *
> + * Data sheet available soon
> + *  TODO: add link

Datasheet is referenced in documentation, so you don't need the link here.
Better to keep it in one please, then there is only one place to change
if it needs to be updated.

> + */
> +
> +#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 and constants for reading the ID register */
> +static const unsigned char shtc1_cmd_read_id_reg[]	     = { 0xef, 0xc8 };
> +static const unsigned char shtc1_id_reg_content = 0x07;
> +static const unsigned char shtc1_id_reg_mask    = 0x1f;
> +
Please use defines here. There is no benefit to have one-byte constants.

If the W1 chip has a different ID, you might as well add it in now and detect it.

> +/* delays for non-blocking i2c commands */
> +/* TODO: use max timings */
> +#define SHTC1_NONBLOCKING_WAIT_TIME_HPM  10
> +#define SHTC1_NONBLOCKING_WAIT_TIME_LPM   1

	delay in what ? ms ? us ? seconds ?
	Please specify.

> +
> +#define SHTC1_CMD_LENGTH      2
> +#define SHTC1_RESPONSE_LENGTH 6
> +
> +struct shtc1_data {
> +	struct device *hwmon_dev;
> +	struct mutex update_lock;
> +	bool valid;
> +	unsigned long last_updated; /* In jiffies */
> +
> +	const unsigned char *command;
> +	unsigned int nonblocking_wait_time;
> +
> +	struct shtc1_platform_data 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;
> +	}
> +}
> +
Please move this function down, just before the probe function.

> +static int shtc1_update_values(struct i2c_client *client,
> +				struct shtc1_data *data,
> +				char *buf,
> +				int bufsize)

Please align continuation lines with (, and limit the number of continuation lines
where possible (eg, buf and bufsize fit into one line).

> +{
> +	int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "failed to send command: %d", ret);

Newline missing.

> +		return ret;
> +	}

There is another error condition: the function returns the number of bytes written,
which can be smaller than SHTC1_CMD_LENGTH.

> +
> +	/*
> +	* 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().
> +	*
> +	* TODO: consider usleep_range

Please do ... and fix all the other TODOs in case I missed any.

> +	*/
> +	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);

Newline.

The return value can be >= 0, meaning the calling code can get confused.
Please make sure that the function always returns a valid error code.

> +		return ret;
> +	}
> +
> +	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);
> +
> +	unsigned 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;

So ret gets pre-initialized with 1 if valid == 0. Doesn't really make sense.
Just initialize it with 0 above.

	int ret = 0;

> +
> +	if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
> +		ret = shtc1_update_values(client, data, buf, sizeof(buf));
> +
Unnecessary empty line.

> +		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));

	Spaces before and after '+'

Just wondering .. what is in buf[2] and buf[5] ?

> +		data->humidity = ((12500 * val) >> 13);
> +
> +		data->last_updated = jiffies;
> +		data->valid = 1;

			= true;

> +	}
> +
> +out:
> +	mutex_unlock(&data->update_lock);
> +
> +	return ret == 0 ? data : ERR_PTR(ret);
> +}
> +
> +static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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 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);

You don't need SENSOR_DEVICE_ATTR here. DEVICE_ATTR is sufficient.

Another option would be to store temperature and humidity in an array
and use the last parameter of SENSOR_DEVICE_ATTR to index the array.
This way you would only need a single show function. I'll leave
that up to you.

> +
> +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,
> +};

Please use ATTRIBUTE_GROUPS().

> +
> +static int shtc1_probe(struct i2c_client *client,
> +				const struct i2c_device_id *id)
> +{
> +	struct shtc1_data *data;

A local variable
	struct device *dev = &client->dev;
would save you a number of dereference operations.

> +	int err;
> +	struct i2c_adapter *adap = client->adapter;
> +	char id_reg[2];
> +
> +	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
> +		dev_err(&client->dev,
> +			"adapter does not support plain i2c transactions\n");
> +		return -ENODEV;
> +	}
> +
> +	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
> +
Please no empty lines before error checks.

> +	if (err < 0) {

Also err != SHTC1_CMD_LENGTH.

> +		dev_err(&client->dev, "could not send read command: %d\n", err);
> +		return -ENODEV;
> +	}
> +	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
> +	if (err != sizeof(id_reg)) {
> +		dev_err(&client->dev, "could not read ID register: %d\n", err);
> +		return -ENODEV;
> +	}
> +	if ((id_reg[1] & shtc1_id_reg_mask) != shtc1_id_reg_content) {
> +		dev_err(&client->dev, "ID register doesn't match\n");
> +		return -ENODEV;
> +	}
> +
> +	data = devm_kzalloc(&client->dev, sizeof(struct shtc1_data),

	sizeof(*data) is preferred.

> +				GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	/* defaults: blocking, high precision mode */
> +	data->setup.blocking_io = 1;
> +	data->setup.high_precision = 1;
> +
		= true;
for both.

> +	if (client->dev.platform_data)
> +		data->setup = *(struct shtc1_platform_data *)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");
> +		goto fail_free;
> +		return err;

goto or return, but not both (doesn't this create a warning about unreachable code ?).
goto is unnecessary, actually. return err is just fine.

> +	}
> +	data->hwmon_dev = hwmon_device_register(&client->dev);

Please use devm_hwmon_device_register_with_groups().

	struct device *hwmon_dev;
	...
	hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev, client->name,
							data, sht1c_groups);
	return PTR_ERR_OR_ZERO(hwmon_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;
> +	}
> +
> +
No more than one empty line, please.

> +	dev_info(&client->dev, "initialized\n");

Unnecessary noise.

> +
> +	return 0;
> +
> +fail_remove_sysfs:
> +	sysfs_remove_group(&client->dev.kobj, &shtc1_attr_group);
> +fail_free:
> +	kfree(data);

Unnecessary kfree.

> +
> +	return err;
> +}
> +
> +/**
> + * shtc1_remove() - remove device
> + * @client: I2C client device
> + */
> +static int 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;
> +}

You can drop this entire function with the new hwmon API.

> +
> +/* device ID table */
> +static const struct i2c_device_id shtc1_id[] = {
> +	{ "shtc1", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, shtc1_id);
> +
> +static struct i2c_driver shtc1_i2c_driver = {
> +	.driver.name = "shtc1",
> +	.probe	= shtc1_probe,
> +	.remove      = shtc1_remove,
> +	.id_table    = shtc1_id,
> +};
> +
> +/**
> + * shtc1_init() - initialize driver
> + *
> + * Called when kernel is booted or module is inserted.
> + * Returns 0 on success.
> + */
> +static int __init shtc1_init(void)
> +{
> +	return i2c_add_driver(&shtc1_i2c_driver);
> +}
> +module_init(shtc1_init);
> +
> +/*
> + * shtc1_exit() - clean up driver
> + *
> + * Called when module is removed.
> + */
> +static void __exit shtc1_exit(void)
> +{
> +	i2c_del_driver(&shtc1_i2c_driver);
> +}
> +
> +module_exit(shtc1_exit);

Please use module_i2c_driver().

> +
> +
> +MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.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..4629364
> --- /dev/null
> +++ b/include/linux/platform_data/shtc1.h
> @@ -0,0 +1,24 @@
> +/*
> + * Copyright (C) 2012 Sensirion AG, Switzerland

2014 ?

> + * 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;
> +};
> +

Please no empty line at the end.

Wondering ... do you plan to implement devicetree support (or have customers who need it) ?

I could imagine that a chip like this will be used, for example, on beagleboard, which would
require devicetree support.

Thanks,
Guenter

Re: [lm-sensors] [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Guenter Roeck]

On 05/01/2014 04:05 PM, Tomas Pop wrote:
> One more time this patch sent with correct settings of my email client
> - I'm sorry for this.
>
> This is a second version of the driver for Sensirion SHTC1 humidity and
> temperature sensor. Initial version was submitted in July 2012.
> http://www.gossamer-threads.com/lists/linux/kernel/1569130#1569130
>
> We included suggested corrections formerly discussed in this list after
> initial submission, but since it is quite a while, we are re-submitting
> it again as a request for comments. Here is a list of important changes
> to the initial version:
>
> * returning real error codes instead of -1 or -ENODEV
> * using boolean variables instead of bitmaps where possible
> * macros be16_to_cpup used for conversion of indianneess
> * corrected formula for decoding of humidity and temperature values
> * documentation update
>
> Patch was generated against kernel v3.15-rc3
>
> Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
> ---
>   Documentation/hwmon/shtc1           |  38 +++++
>   drivers/hwmon/Kconfig               |  10 ++
>   drivers/hwmon/Makefile              |   1 +
>   drivers/hwmon/shtc1.c               | 323 ++++++++++++++++++++++++++++++++++++
>   include/linux/platform_data/shtc1.h |  24 +++
>   5 files changed, 396 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..6a72ae2d
> --- /dev/null
> +++ b/Documentation/hwmon/shtc1
> @@ -0,0 +1,38 @@
> +Kernel driver shtc1
> +=========> +
> +Supported chips:
> +  * Sensirion SHTC1
> +    Prefix: 'shtc1'
> +    Addresses scanned: none
> +    Datasheet: Publicly available at the Sensirion website
> +    http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_SHTC1_Datasheet.pdf

Ok to add SHTW1 here if it is known to work.
Just say:
	Datasheet: Not publicly available

> +
> +Author:
> +  Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> +
> +Description
> +-----------
> +
> +This driver implements support for the Sensirion  SHTC1 chip, a humidity and

Two spaces

> +temperature sensor. Temperature is measured in degrees celsius, relative
> +humidity is expressed as a percentage. Driver can be used as well for SHTW1
> +chip, that has the same electrical interface, but datasheet has not been

... for SHTW1, which has the same electrical interface.

> +yet published.
> +

Either add support for the second now, or don't mention it at all
(especially if the chip has a different ID and you don't want to add
that ID at this point for some reason).

> +The device communicates with the I2C protocol. All sensors are set to the same

... are set to I2C address 0x70.

> +I2C address 0x70, so an entry with I2C_BOARD_INFO("shtc1", 0x70) can be used
> +in the board setup code. See Documentation/i2c/instantiating-devices for
> +other methods to instantiate the device.
> +
I would suggest to just refer to the instantiating-devices document and drop
the I2C_BOARD_INFO example.

> +Furthermore, there are two configuration options by means of platform_data:

options configurable by means ...

> +1. blocking (pull the I2C clock line down while performing the measurement) or
> +   non-blocking, mode. Blocking mode will guarantee the fastest result, but

non-blocking mode (no comma)

> +   the I2C bus will be busy during that time

					that time.

> +2. high or low accuracy. Using high accuracy is always recommended.
> +
> +sysfs-Interface
> +---------------
> +
> +temp1_input - temperature input
> +humidity1_input - humidity input
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index bc196f4..4d58149 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1114,6 +1114,16 @@ 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 humidity

and SHTW1 ?

> +	  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 c48f987..1cc5273 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -125,6 +125,7 @@ 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..96d398b
> --- /dev/null
> +++ b/drivers/hwmon/shtc1.c
> @@ -0,0 +1,323 @@
> +/* Sensirion SHTC1 humidity and temperature sensor driver
> + *
> + * Copyright (C) 2012 Sensirion AG, Switzerland

2014 ?

> + * Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> + *
Is Johannes still involved ?

> + * 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.
> + *
> + * Data sheet available soon
> + *  TODO: add link

Datasheet is referenced in documentation, so you don't need the link here.
Better to keep it in one please, then there is only one place to change
if it needs to be updated.

> + */
> +
> +#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 and constants for reading the ID register */
> +static const unsigned char shtc1_cmd_read_id_reg[]	     = { 0xef, 0xc8 };
> +static const unsigned char shtc1_id_reg_content = 0x07;
> +static const unsigned char shtc1_id_reg_mask    = 0x1f;
> +
Please use defines here. There is no benefit to have one-byte constants.

If the W1 chip has a different ID, you might as well add it in now and detect it.

> +/* delays for non-blocking i2c commands */
> +/* TODO: use max timings */
> +#define SHTC1_NONBLOCKING_WAIT_TIME_HPM  10
> +#define SHTC1_NONBLOCKING_WAIT_TIME_LPM   1

	delay in what ? ms ? us ? seconds ?
	Please specify.

> +
> +#define SHTC1_CMD_LENGTH      2
> +#define SHTC1_RESPONSE_LENGTH 6
> +
> +struct shtc1_data {
> +	struct device *hwmon_dev;
> +	struct mutex update_lock;
> +	bool valid;
> +	unsigned long last_updated; /* In jiffies */
> +
> +	const unsigned char *command;
> +	unsigned int nonblocking_wait_time;
> +
> +	struct shtc1_platform_data 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;
> +	}
> +}
> +
Please move this function down, just before the probe function.

> +static int shtc1_update_values(struct i2c_client *client,
> +				struct shtc1_data *data,
> +				char *buf,
> +				int bufsize)

Please align continuation lines with (, and limit the number of continuation lines
where possible (eg, buf and bufsize fit into one line).

> +{
> +	int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "failed to send command: %d", ret);

Newline missing.

> +		return ret;
> +	}

There is another error condition: the function returns the number of bytes written,
which can be smaller than SHTC1_CMD_LENGTH.

> +
> +	/*
> +	* 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().
> +	*
> +	* TODO: consider usleep_range

Please do ... and fix all the other TODOs in case I missed any.

> +	*/
> +	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);

Newline.

The return value can be >= 0, meaning the calling code can get confused.
Please make sure that the function always returns a valid error code.

> +		return ret;
> +	}
> +
> +	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);
> +
> +	unsigned 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;

So ret gets pre-initialized with 1 if valid = 0. Doesn't really make sense.
Just initialize it with 0 above.

	int ret = 0;

> +
> +	if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
> +		ret = shtc1_update_values(client, data, buf, sizeof(buf));
> +
Unnecessary empty line.

> +		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));

	Spaces before and after '+'

Just wondering .. what is in buf[2] and buf[5] ?

> +		data->humidity = ((12500 * val) >> 13);
> +
> +		data->last_updated = jiffies;
> +		data->valid = 1;

			= true;

> +	}
> +
> +out:
> +	mutex_unlock(&data->update_lock);
> +
> +	return ret = 0 ? data : ERR_PTR(ret);
> +}
> +
> +static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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 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);

You don't need SENSOR_DEVICE_ATTR here. DEVICE_ATTR is sufficient.

Another option would be to store temperature and humidity in an array
and use the last parameter of SENSOR_DEVICE_ATTR to index the array.
This way you would only need a single show function. I'll leave
that up to you.

> +
> +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,
> +};

Please use ATTRIBUTE_GROUPS().

> +
> +static int shtc1_probe(struct i2c_client *client,
> +				const struct i2c_device_id *id)
> +{
> +	struct shtc1_data *data;

A local variable
	struct device *dev = &client->dev;
would save you a number of dereference operations.

> +	int err;
> +	struct i2c_adapter *adap = client->adapter;
> +	char id_reg[2];
> +
> +	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
> +		dev_err(&client->dev,
> +			"adapter does not support plain i2c transactions\n");
> +		return -ENODEV;
> +	}
> +
> +	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
> +
Please no empty lines before error checks.

> +	if (err < 0) {

Also err != SHTC1_CMD_LENGTH.

> +		dev_err(&client->dev, "could not send read command: %d\n", err);
> +		return -ENODEV;
> +	}
> +	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
> +	if (err != sizeof(id_reg)) {
> +		dev_err(&client->dev, "could not read ID register: %d\n", err);
> +		return -ENODEV;
> +	}
> +	if ((id_reg[1] & shtc1_id_reg_mask) != shtc1_id_reg_content) {
> +		dev_err(&client->dev, "ID register doesn't match\n");
> +		return -ENODEV;
> +	}
> +
> +	data = devm_kzalloc(&client->dev, sizeof(struct shtc1_data),

	sizeof(*data) is preferred.

> +				GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	/* defaults: blocking, high precision mode */
> +	data->setup.blocking_io = 1;
> +	data->setup.high_precision = 1;
> +
		= true;
for both.

> +	if (client->dev.platform_data)
> +		data->setup = *(struct shtc1_platform_data *)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");
> +		goto fail_free;
> +		return err;

goto or return, but not both (doesn't this create a warning about unreachable code ?).
goto is unnecessary, actually. return err is just fine.

> +	}
> +	data->hwmon_dev = hwmon_device_register(&client->dev);

Please use devm_hwmon_device_register_with_groups().

	struct device *hwmon_dev;
	...
	hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev, client->name,
							data, sht1c_groups);
	return PTR_ERR_OR_ZERO(hwmon_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;
> +	}
> +
> +
No more than one empty line, please.

> +	dev_info(&client->dev, "initialized\n");

Unnecessary noise.

> +
> +	return 0;
> +
> +fail_remove_sysfs:
> +	sysfs_remove_group(&client->dev.kobj, &shtc1_attr_group);
> +fail_free:
> +	kfree(data);

Unnecessary kfree.

> +
> +	return err;
> +}
> +
> +/**
> + * shtc1_remove() - remove device
> + * @client: I2C client device
> + */
> +static int 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;
> +}

You can drop this entire function with the new hwmon API.

> +
> +/* device ID table */
> +static const struct i2c_device_id shtc1_id[] = {
> +	{ "shtc1", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, shtc1_id);
> +
> +static struct i2c_driver shtc1_i2c_driver = {
> +	.driver.name = "shtc1",
> +	.probe	= shtc1_probe,
> +	.remove      = shtc1_remove,
> +	.id_table    = shtc1_id,
> +};
> +
> +/**
> + * shtc1_init() - initialize driver
> + *
> + * Called when kernel is booted or module is inserted.
> + * Returns 0 on success.
> + */
> +static int __init shtc1_init(void)
> +{
> +	return i2c_add_driver(&shtc1_i2c_driver);
> +}
> +module_init(shtc1_init);
> +
> +/*
> + * shtc1_exit() - clean up driver
> + *
> + * Called when module is removed.
> + */
> +static void __exit shtc1_exit(void)
> +{
> +	i2c_del_driver(&shtc1_i2c_driver);
> +}
> +
> +module_exit(shtc1_exit);

Please use module_i2c_driver().

> +
> +
> +MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.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..4629364
> --- /dev/null
> +++ b/include/linux/platform_data/shtc1.h
> @@ -0,0 +1,24 @@
> +/*
> + * Copyright (C) 2012 Sensirion AG, Switzerland

2014 ?

> + * 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;
> +};
> +

Please no empty line at the end.

Wondering ... do you plan to implement devicetree support (or have customers who need it) ?

I could imagine that a chip like this will be used, for example, on beagleboard, which would
require devicetree support.

Thanks,
Guenter


_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

Re: [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Tomas Pop]

Hi Guenter, thanks for comments! I will include them in third version,
but I have still few questions...

On Don, 2014-05-01 at 19:06 -0700, Guenter Roeck wrote:
> On 05/01/2014 04:05 PM, Tomas Pop wrote:
> > One more time this patch sent with correct settings of my email client
> > - I'm sorry for this.
> >
> > This is a second version of the driver for Sensirion SHTC1 humidity and
> > temperature sensor. Initial version was submitted in July 2012.
> > http://www.gossamer-threads.com/lists/linux/kernel/1569130#1569130
> >
> > We included suggested corrections formerly discussed in this list after
> > initial submission, but since it is quite a while, we are re-submitting
> > it again as a request for comments. Here is a list of important changes
> > to the initial version:
> >
> > * returning real error codes instead of -1 or -ENODEV
> > * using boolean variables instead of bitmaps where possible
> > * macros be16_to_cpup used for conversion of indianneess
> > * corrected formula for decoding of humidity and temperature values
> > * documentation update
> >
> > Patch was generated against kernel v3.15-rc3
> >
> > Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
> > ---
> >   Documentation/hwmon/shtc1           |  38 +++++
> >   drivers/hwmon/Kconfig               |  10 ++
> >   drivers/hwmon/Makefile              |   1 +
> >   drivers/hwmon/shtc1.c               | 323 ++++++++++++++++++++++++++++++++++++
> >   include/linux/platform_data/shtc1.h |  24 +++
> >   5 files changed, 396 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..6a72ae2d
> > --- /dev/null
> > +++ b/Documentation/hwmon/shtc1
> > @@ -0,0 +1,38 @@
> > +Kernel driver shtc1
> > +===================
> > +
> > +Supported chips:
> > +  * Sensirion SHTC1
> > +    Prefix: 'shtc1'
> > +    Addresses scanned: none
> > +    Datasheet: Publicly available at the Sensirion website
> > +    http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_SHTC1_Datasheet.pdf
> 
> Ok to add SHTW1 here if it is known to work.
> Just say:
> 	Datasheet: Not publicly available

Actually, there is no way to find out, if you are speaking 
to SHTC1 or SHTW1. (i.e., the id is the same for both).
So I will add it here and we will provide link to data-sheet 
later in a separate patch.

> > +
> > +Author:
> > +  Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> > +
> > +Description
> > +-----------
> > +
> > +This driver implements support for the Sensirion  SHTC1 chip, a humidity and
> 
> Two spaces
> 
> > +temperature sensor. Temperature is measured in degrees celsius, relative
> > +humidity is expressed as a percentage. Driver can be used as well for SHTW1
> > +chip, that has the same electrical interface, but datasheet has not been
> 
> ... for SHTW1, which has the same electrical interface.
> 
> > +yet published.
> > +
> 
> Either add support for the second now, or don't mention it at all
> (especially if the chip has a different ID and you don't want to add
> that ID at this point for some reason).
> 
> > +The device communicates with the I2C protocol. All sensors are set to the same
> 
> ... are set to I2C address 0x70.
> 
> > +I2C address 0x70, so an entry with I2C_BOARD_INFO("shtc1", 0x70) can be used
> > +in the board setup code. See Documentation/i2c/instantiating-devices for
> > +other methods to instantiate the device.
> > +
> I would suggest to just refer to the instantiating-devices document and drop
> the I2C_BOARD_INFO example.
> 
> > +Furthermore, there are two configuration options by means of platform_data:
> 
> options configurable by means ...
> 
> > +1. blocking (pull the I2C clock line down while performing the measurement) or
> > +   non-blocking, mode. Blocking mode will guarantee the fastest result, but
> 
> non-blocking mode (no comma)
> 
> > +   the I2C bus will be busy during that time
> 
> 					that time.
> 
> > +2. high or low accuracy. Using high accuracy is always recommended.
> > +
> > +sysfs-Interface
> > +---------------
> > +
> > +temp1_input - temperature input
> > +humidity1_input - humidity input
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index bc196f4..4d58149 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -1114,6 +1114,16 @@ 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 humidity
> 
> and SHTW1 ?

I will add SHTW1 here as well

> 
> > +	  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 c48f987..1cc5273 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -125,6 +125,7 @@ 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..96d398b
> > --- /dev/null
> > +++ b/drivers/hwmon/shtc1.c
> > @@ -0,0 +1,323 @@
> > +/* Sensirion SHTC1 humidity and temperature sensor driver
> > + *
> > + * Copyright (C) 2012 Sensirion AG, Switzerland
> 
> 2014 ?
> 
> > + * Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> > + *
> Is Johannes still involved ?

Yes, Johannes is aware of this re-submission, but I will try to take
care about the process this time. I will add him in CC.

> 
> > + * 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.
> > + *
> > + * Data sheet available soon
> > + *  TODO: add link
> 
> Datasheet is referenced in documentation, so you don't need the link here.
> Better to keep it in one please, then there is only one place to change
> if it needs to be updated.
> > + */
> > +
> > +#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 and constants for reading the ID register */
> > +static const unsigned char shtc1_cmd_read_id_reg[]	     = { 0xef, 0xc8 };
> > +static const unsigned char shtc1_id_reg_content = 0x07;
> > +static const unsigned char shtc1_id_reg_mask    = 0x1f;
> > +
> Please use defines here. There is no benefit to have one-byte constants.
> If the W1 chip has a different ID, you might as well add it in now and detect it.
> 
> > +/* delays for non-blocking i2c commands */
> > +#define SHTC1_NONBLOCKING_WAIT_TIME_HPM  10
> > +#define SHTC1_NONBLOCKING_WAIT_TIME_LPM   1
> 
> 	delay in what ? ms ? us ? seconds ?
> 	Please specify.
> 

The delays are in miliseconds. You mean to use it in names - e.g.,
SHTC1_NONBLOCKING_WAIT_TIME_LPM_MS? Or comment is enough?

May be I should then rename 
also data->nonblocking_wait_time to data->nonblocking_wait_time_ms...

> > +
> > +#define SHTC1_CMD_LENGTH      2
> > +#define SHTC1_RESPONSE_LENGTH 6
> > +
> > +struct shtc1_data {
> > +	struct device *hwmon_dev;
> > +	struct mutex update_lock;
> > +	bool valid;
> > +	unsigned long last_updated; /* In jiffies */
> > +
> > +	const unsigned char *command;
> > +	unsigned int nonblocking_wait_time;
> > +
> > +	struct shtc1_platform_data 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;
> > +	}
> > +}
> > +
> Please move this function down, just before the probe function.
> 
> > +static int shtc1_update_values(struct i2c_client *client,
> > +				struct shtc1_data *data,
> > +				char *buf,
> > +				int bufsize)
> 
> Please align continuation lines with (, and limit the number of continuation lines
> where possible (eg, buf and bufsize fit into one line).
> 
> > +{
> > +	int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
> > +	if (ret < 0) {
> > +		dev_err(&client->dev, "failed to send command: %d", ret);
> 
> Newline missing.
> 
> > +		return ret;
> > +	}
> 
> There is another error condition: the function returns the number of bytes written,
> which can be smaller than SHTC1_CMD_LENGTH.
> 
> > +
> > +	/*
> > +	* 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().
> > +	*
> > +	* TODO: consider usleep_range
> 
> Please do ... and fix all the other TODOs in case I missed any.

Sure. I checked the documentation and if I understand it correctly, we  should really use in this case something like:
	if (!data->setup.blocking_io)
		usleep_range(data->nonblocking_wait_time_min_us,
			     data->nonblocking_wait_time_max_us);

where max_time will be min_time plus some fixed margin, e.g, 2000us

sounds this reasonable to you?

> 
> > +	*/
> > +	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);
> 
> Newline.
> 
> The return value can be >= 0, meaning the calling code can get confused.
> Please make sure that the function always returns a valid error code.

Ok, so return -EIO or better -ENODEV?

> 
> > +		return ret;
> > +	}
> > +
> > +	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);
> > +
> > +	unsigned 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;
> 
> So ret gets pre-initialized with 1 if valid == 0. Doesn't really make sense.
> Just initialize it with 0 above.
> 
> 	int ret = 0;

Sure, thanks.

> 
> > +
> > +	if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
> > +		ret = shtc1_update_values(client, data, buf, sizeof(buf));
> > +
> Unnecessary empty line.
> 
> > +		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));
> 
> 	Spaces before and after '+'
> 
> Just wondering .. what is in buf[2] and buf[5] ?

There are two CRC-8 checksums: 
buf[2] for humidity, buf[5] for temperature value. We would prefer
not to check CRC it in this version of the driver...

> 
> > +		data->humidity = ((12500 * val) >> 13);
> > +
> > +		data->last_updated = jiffies;
> > +		data->valid = 1;
> 
> 			= true;
> 
> > +	}
> > +
> > +out:
> > +	mutex_unlock(&data->update_lock);
> > +
> > +	return ret == 0 ? data : ERR_PTR(ret);
> > +}
> > +
> > +static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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 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);
> 
> You don't need SENSOR_DEVICE_ATTR here. DEVICE_ATTR is sufficient.
> 
> Another option would be to store temperature and humidity in an array
> and use the last parameter of SENSOR_DEVICE_ATTR to index the array.
> This way you would only need a single show function. I'll leave
> that up to you.

Ok, then we will use DEVICE_ATTR...
> 
> > +
> > +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,
> > +};
> 
> Please use ATTRIBUTE_GROUPS().
> 
> > +
> > +static int shtc1_probe(struct i2c_client *client,
> > +				const struct i2c_device_id *id)
> > +{
> > +	struct shtc1_data *data;
> 
> A local variable
> 	struct device *dev = &client->dev;
> would save you a number of dereference operations.
> 
> > +	int err;
> > +	struct i2c_adapter *adap = client->adapter;
> > +	char id_reg[2];
> > +
> > +	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
> > +		dev_err(&client->dev,
> > +			"adapter does not support plain i2c transactions\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
> > +
> Please no empty lines before error checks.
> 
> > +	if (err < 0) {
> 
> Also err != SHTC1_CMD_LENGTH.

This is similar to my question above, do you think it is better in that
case return -EIO or -ENODEV?

> 
> > +		dev_err(&client->dev, "could not send read command: %d\n", err);
> > +		return -ENODEV;
> > +	}
> > +	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
> > +	if (err != sizeof(id_reg)) {
> > +		dev_err(&client->dev, "could not read ID register: %d\n", err);
> > +		return -ENODEV;
> > +	}
> > +	if ((id_reg[1] & shtc1_id_reg_mask) != shtc1_id_reg_content) {
> > +		dev_err(&client->dev, "ID register doesn't match\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	data = devm_kzalloc(&client->dev, sizeof(struct shtc1_data),
> 
> 	sizeof(*data) is preferred.
> 
> > +				GFP_KERNEL);
> > +	if (!data)
> > +		return -ENOMEM;
> > +
> > +	/* defaults: blocking, high precision mode */
> > +	data->setup.blocking_io = 1;
> > +	data->setup.high_precision = 1;
> > +
> 		= true;
> for both.
> 
> > +	if (client->dev.platform_data)
> > +		data->setup = *(struct shtc1_platform_data *)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");
> > +		goto fail_free;
> > +		return err;
> 
> goto or return, but not both (doesn't this create a warning about unreachable code ?).
> goto is unnecessary, actually. return err is just fine.

I think, there were no warnings, but of course you are right...

> 
> > +	}
> > +	data->hwmon_dev = hwmon_device_register(&client->dev);
> 
> Please use devm_hwmon_device_register_with_groups().
> 
> 	struct device *hwmon_dev;
> 	...
> 	hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev, client->name,
> 							data, sht1c_groups);
> 	return PTR_ERR_OR_ZERO(hwmon_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;
> > +	}
> > +
> > +
> No more than one empty line, please.
> 
> > +	dev_info(&client->dev, "initialized\n");
> 
> Unnecessary noise.
> 
> > +
> > +	return 0;
> > +
> > +fail_remove_sysfs:
> > +	sysfs_remove_group(&client->dev.kobj, &shtc1_attr_group);
> > +fail_free:
> > +	kfree(data);
> 
> Unnecessary kfree.

I will remove these two lines at all.

> 
> > +
> > +	return err;
> > +}
> > +
> > +/**
> > + * shtc1_remove() - remove device
> > + * @client: I2C client device
> > + */
> > +static int 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;
> > +}
> 
> You can drop this entire function with the new hwmon API.
> 
> > +
> > +/* device ID table */
> > +static const struct i2c_device_id shtc1_id[] = {
> > +	{ "shtc1", 0 },
> > +	{ }
> > +};
> > +MODULE_DEVICE_TABLE(i2c, shtc1_id);
> > +
> > +static struct i2c_driver shtc1_i2c_driver = {
> > +	.driver.name = "shtc1",
> > +	.probe	= shtc1_probe,
> > +	.remove      = shtc1_remove,
> > +	.id_table    = shtc1_id,
> > +};
> > +
> > +/**
> > + * shtc1_init() - initialize driver
> > + *
> > + * Called when kernel is booted or module is inserted.
> > + * Returns 0 on success.
> > + */
> > +static int __init shtc1_init(void)
> > +{
> > +	return i2c_add_driver(&shtc1_i2c_driver);
> > +}
> > +module_init(shtc1_init);
> > +
> > +/*
> > + * shtc1_exit() - clean up driver
> > + *
> > + * Called when module is removed.
> > + */
> > +static void __exit shtc1_exit(void)
> > +{
> > +	i2c_del_driver(&shtc1_i2c_driver);
> > +}
> > +
> > +module_exit(shtc1_exit);
> 
> Please use module_i2c_driver().
> 
> > +
> > +
> > +MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.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..4629364
> > --- /dev/null
> > +++ b/include/linux/platform_data/shtc1.h
> > @@ -0,0 +1,24 @@
> > +/*
> > + * Copyright (C) 2012 Sensirion AG, Switzerland
> 
> 2014 ?
> 
> > + * 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;
> > +};
> > +
> 
> Please no empty line at the end.
> 
> Wondering ... do you plan to implement devicetree support (or have customers who need it) ?
> 
> I could imagine that a chip like this will be used, for example, on beagleboard, which would
> require devicetree support.
> 

Right now, I'm not aware of any particular time plan to implement device
tree support, but this may change, if somebody will request it...

> Thanks,
> Guenter
> 

Thanks, 
Tomas

Re: [lm-sensors] [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Tomas Pop]

Hi Guenter, thanks for comments! I will include them in third version,
but I have still few questions...

On Don, 2014-05-01 at 19:06 -0700, Guenter Roeck wrote:
> On 05/01/2014 04:05 PM, Tomas Pop wrote:
> > One more time this patch sent with correct settings of my email client
> > - I'm sorry for this.
> >
> > This is a second version of the driver for Sensirion SHTC1 humidity and
> > temperature sensor. Initial version was submitted in July 2012.
> > http://www.gossamer-threads.com/lists/linux/kernel/1569130#1569130
> >
> > We included suggested corrections formerly discussed in this list after
> > initial submission, but since it is quite a while, we are re-submitting
> > it again as a request for comments. Here is a list of important changes
> > to the initial version:
> >
> > * returning real error codes instead of -1 or -ENODEV
> > * using boolean variables instead of bitmaps where possible
> > * macros be16_to_cpup used for conversion of indianneess
> > * corrected formula for decoding of humidity and temperature values
> > * documentation update
> >
> > Patch was generated against kernel v3.15-rc3
> >
> > Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
> > ---
> >   Documentation/hwmon/shtc1           |  38 +++++
> >   drivers/hwmon/Kconfig               |  10 ++
> >   drivers/hwmon/Makefile              |   1 +
> >   drivers/hwmon/shtc1.c               | 323 ++++++++++++++++++++++++++++++++++++
> >   include/linux/platform_data/shtc1.h |  24 +++
> >   5 files changed, 396 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..6a72ae2d
> > --- /dev/null
> > +++ b/Documentation/hwmon/shtc1
> > @@ -0,0 +1,38 @@
> > +Kernel driver shtc1
> > +=========> > +
> > +Supported chips:
> > +  * Sensirion SHTC1
> > +    Prefix: 'shtc1'
> > +    Addresses scanned: none
> > +    Datasheet: Publicly available at the Sensirion website
> > +    http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_SHTC1_Datasheet.pdf
> 
> Ok to add SHTW1 here if it is known to work.
> Just say:
> 	Datasheet: Not publicly available

Actually, there is no way to find out, if you are speaking 
to SHTC1 or SHTW1. (i.e., the id is the same for both).
So I will add it here and we will provide link to data-sheet 
later in a separate patch.

> > +
> > +Author:
> > +  Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> > +
> > +Description
> > +-----------
> > +
> > +This driver implements support for the Sensirion  SHTC1 chip, a humidity and
> 
> Two spaces
> 
> > +temperature sensor. Temperature is measured in degrees celsius, relative
> > +humidity is expressed as a percentage. Driver can be used as well for SHTW1
> > +chip, that has the same electrical interface, but datasheet has not been
> 
> ... for SHTW1, which has the same electrical interface.
> 
> > +yet published.
> > +
> 
> Either add support for the second now, or don't mention it at all
> (especially if the chip has a different ID and you don't want to add
> that ID at this point for some reason).
> 
> > +The device communicates with the I2C protocol. All sensors are set to the same
> 
> ... are set to I2C address 0x70.
> 
> > +I2C address 0x70, so an entry with I2C_BOARD_INFO("shtc1", 0x70) can be used
> > +in the board setup code. See Documentation/i2c/instantiating-devices for
> > +other methods to instantiate the device.
> > +
> I would suggest to just refer to the instantiating-devices document and drop
> the I2C_BOARD_INFO example.
> 
> > +Furthermore, there are two configuration options by means of platform_data:
> 
> options configurable by means ...
> 
> > +1. blocking (pull the I2C clock line down while performing the measurement) or
> > +   non-blocking, mode. Blocking mode will guarantee the fastest result, but
> 
> non-blocking mode (no comma)
> 
> > +   the I2C bus will be busy during that time
> 
> 					that time.
> 
> > +2. high or low accuracy. Using high accuracy is always recommended.
> > +
> > +sysfs-Interface
> > +---------------
> > +
> > +temp1_input - temperature input
> > +humidity1_input - humidity input
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index bc196f4..4d58149 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -1114,6 +1114,16 @@ 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 humidity
> 
> and SHTW1 ?

I will add SHTW1 here as well

> 
> > +	  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 c48f987..1cc5273 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -125,6 +125,7 @@ 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..96d398b
> > --- /dev/null
> > +++ b/drivers/hwmon/shtc1.c
> > @@ -0,0 +1,323 @@
> > +/* Sensirion SHTC1 humidity and temperature sensor driver
> > + *
> > + * Copyright (C) 2012 Sensirion AG, Switzerland
> 
> 2014 ?
> 
> > + * Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> > + *
> Is Johannes still involved ?

Yes, Johannes is aware of this re-submission, but I will try to take
care about the process this time. I will add him in CC.

> 
> > + * 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.
> > + *
> > + * Data sheet available soon
> > + *  TODO: add link
> 
> Datasheet is referenced in documentation, so you don't need the link here.
> Better to keep it in one please, then there is only one place to change
> if it needs to be updated.
> > + */
> > +
> > +#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 and constants for reading the ID register */
> > +static const unsigned char shtc1_cmd_read_id_reg[]	     = { 0xef, 0xc8 };
> > +static const unsigned char shtc1_id_reg_content = 0x07;
> > +static const unsigned char shtc1_id_reg_mask    = 0x1f;
> > +
> Please use defines here. There is no benefit to have one-byte constants.
> If the W1 chip has a different ID, you might as well add it in now and detect it.
> 
> > +/* delays for non-blocking i2c commands */
> > +#define SHTC1_NONBLOCKING_WAIT_TIME_HPM  10
> > +#define SHTC1_NONBLOCKING_WAIT_TIME_LPM   1
> 
> 	delay in what ? ms ? us ? seconds ?
> 	Please specify.
> 

The delays are in miliseconds. You mean to use it in names - e.g.,
SHTC1_NONBLOCKING_WAIT_TIME_LPM_MS? Or comment is enough?

May be I should then rename 
also data->nonblocking_wait_time to data->nonblocking_wait_time_ms...

> > +
> > +#define SHTC1_CMD_LENGTH      2
> > +#define SHTC1_RESPONSE_LENGTH 6
> > +
> > +struct shtc1_data {
> > +	struct device *hwmon_dev;
> > +	struct mutex update_lock;
> > +	bool valid;
> > +	unsigned long last_updated; /* In jiffies */
> > +
> > +	const unsigned char *command;
> > +	unsigned int nonblocking_wait_time;
> > +
> > +	struct shtc1_platform_data 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;
> > +	}
> > +}
> > +
> Please move this function down, just before the probe function.
> 
> > +static int shtc1_update_values(struct i2c_client *client,
> > +				struct shtc1_data *data,
> > +				char *buf,
> > +				int bufsize)
> 
> Please align continuation lines with (, and limit the number of continuation lines
> where possible (eg, buf and bufsize fit into one line).
> 
> > +{
> > +	int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
> > +	if (ret < 0) {
> > +		dev_err(&client->dev, "failed to send command: %d", ret);
> 
> Newline missing.
> 
> > +		return ret;
> > +	}
> 
> There is another error condition: the function returns the number of bytes written,
> which can be smaller than SHTC1_CMD_LENGTH.
> 
> > +
> > +	/*
> > +	* 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().
> > +	*
> > +	* TODO: consider usleep_range
> 
> Please do ... and fix all the other TODOs in case I missed any.

Sure. I checked the documentation and if I understand it correctly, we  should really use in this case something like:
	if (!data->setup.blocking_io)
		usleep_range(data->nonblocking_wait_time_min_us,
			     data->nonblocking_wait_time_max_us);

where max_time will be min_time plus some fixed margin, e.g, 2000us

sounds this reasonable to you?

> 
> > +	*/
> > +	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);
> 
> Newline.
> 
> The return value can be >= 0, meaning the calling code can get confused.
> Please make sure that the function always returns a valid error code.

Ok, so return -EIO or better -ENODEV?

> 
> > +		return ret;
> > +	}
> > +
> > +	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);
> > +
> > +	unsigned 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;
> 
> So ret gets pre-initialized with 1 if valid = 0. Doesn't really make sense.
> Just initialize it with 0 above.
> 
> 	int ret = 0;

Sure, thanks.

> 
> > +
> > +	if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
> > +		ret = shtc1_update_values(client, data, buf, sizeof(buf));
> > +
> Unnecessary empty line.
> 
> > +		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));
> 
> 	Spaces before and after '+'
> 
> Just wondering .. what is in buf[2] and buf[5] ?

There are two CRC-8 checksums: 
buf[2] for humidity, buf[5] for temperature value. We would prefer
not to check CRC it in this version of the driver...

> 
> > +		data->humidity = ((12500 * val) >> 13);
> > +
> > +		data->last_updated = jiffies;
> > +		data->valid = 1;
> 
> 			= true;
> 
> > +	}
> > +
> > +out:
> > +	mutex_unlock(&data->update_lock);
> > +
> > +	return ret = 0 ? data : ERR_PTR(ret);
> > +}
> > +
> > +static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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 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);
> 
> You don't need SENSOR_DEVICE_ATTR here. DEVICE_ATTR is sufficient.
> 
> Another option would be to store temperature and humidity in an array
> and use the last parameter of SENSOR_DEVICE_ATTR to index the array.
> This way you would only need a single show function. I'll leave
> that up to you.

Ok, then we will use DEVICE_ATTR...
> 
> > +
> > +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,
> > +};
> 
> Please use ATTRIBUTE_GROUPS().
> 
> > +
> > +static int shtc1_probe(struct i2c_client *client,
> > +				const struct i2c_device_id *id)
> > +{
> > +	struct shtc1_data *data;
> 
> A local variable
> 	struct device *dev = &client->dev;
> would save you a number of dereference operations.
> 
> > +	int err;
> > +	struct i2c_adapter *adap = client->adapter;
> > +	char id_reg[2];
> > +
> > +	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
> > +		dev_err(&client->dev,
> > +			"adapter does not support plain i2c transactions\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
> > +
> Please no empty lines before error checks.
> 
> > +	if (err < 0) {
> 
> Also err != SHTC1_CMD_LENGTH.

This is similar to my question above, do you think it is better in that
case return -EIO or -ENODEV?

> 
> > +		dev_err(&client->dev, "could not send read command: %d\n", err);
> > +		return -ENODEV;
> > +	}
> > +	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
> > +	if (err != sizeof(id_reg)) {
> > +		dev_err(&client->dev, "could not read ID register: %d\n", err);
> > +		return -ENODEV;
> > +	}
> > +	if ((id_reg[1] & shtc1_id_reg_mask) != shtc1_id_reg_content) {
> > +		dev_err(&client->dev, "ID register doesn't match\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	data = devm_kzalloc(&client->dev, sizeof(struct shtc1_data),
> 
> 	sizeof(*data) is preferred.
> 
> > +				GFP_KERNEL);
> > +	if (!data)
> > +		return -ENOMEM;
> > +
> > +	/* defaults: blocking, high precision mode */
> > +	data->setup.blocking_io = 1;
> > +	data->setup.high_precision = 1;
> > +
> 		= true;
> for both.
> 
> > +	if (client->dev.platform_data)
> > +		data->setup = *(struct shtc1_platform_data *)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");
> > +		goto fail_free;
> > +		return err;
> 
> goto or return, but not both (doesn't this create a warning about unreachable code ?).
> goto is unnecessary, actually. return err is just fine.

I think, there were no warnings, but of course you are right...

> 
> > +	}
> > +	data->hwmon_dev = hwmon_device_register(&client->dev);
> 
> Please use devm_hwmon_device_register_with_groups().
> 
> 	struct device *hwmon_dev;
> 	...
> 	hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev, client->name,
> 							data, sht1c_groups);
> 	return PTR_ERR_OR_ZERO(hwmon_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;
> > +	}
> > +
> > +
> No more than one empty line, please.
> 
> > +	dev_info(&client->dev, "initialized\n");
> 
> Unnecessary noise.
> 
> > +
> > +	return 0;
> > +
> > +fail_remove_sysfs:
> > +	sysfs_remove_group(&client->dev.kobj, &shtc1_attr_group);
> > +fail_free:
> > +	kfree(data);
> 
> Unnecessary kfree.

I will remove these two lines at all.

> 
> > +
> > +	return err;
> > +}
> > +
> > +/**
> > + * shtc1_remove() - remove device
> > + * @client: I2C client device
> > + */
> > +static int 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;
> > +}
> 
> You can drop this entire function with the new hwmon API.
> 
> > +
> > +/* device ID table */
> > +static const struct i2c_device_id shtc1_id[] = {
> > +	{ "shtc1", 0 },
> > +	{ }
> > +};
> > +MODULE_DEVICE_TABLE(i2c, shtc1_id);
> > +
> > +static struct i2c_driver shtc1_i2c_driver = {
> > +	.driver.name = "shtc1",
> > +	.probe	= shtc1_probe,
> > +	.remove      = shtc1_remove,
> > +	.id_table    = shtc1_id,
> > +};
> > +
> > +/**
> > + * shtc1_init() - initialize driver
> > + *
> > + * Called when kernel is booted or module is inserted.
> > + * Returns 0 on success.
> > + */
> > +static int __init shtc1_init(void)
> > +{
> > +	return i2c_add_driver(&shtc1_i2c_driver);
> > +}
> > +module_init(shtc1_init);
> > +
> > +/*
> > + * shtc1_exit() - clean up driver
> > + *
> > + * Called when module is removed.
> > + */
> > +static void __exit shtc1_exit(void)
> > +{
> > +	i2c_del_driver(&shtc1_i2c_driver);
> > +}
> > +
> > +module_exit(shtc1_exit);
> 
> Please use module_i2c_driver().
> 
> > +
> > +
> > +MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.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..4629364
> > --- /dev/null
> > +++ b/include/linux/platform_data/shtc1.h
> > @@ -0,0 +1,24 @@
> > +/*
> > + * Copyright (C) 2012 Sensirion AG, Switzerland
> 
> 2014 ?
> 
> > + * 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;
> > +};
> > +
> 
> Please no empty line at the end.
> 
> Wondering ... do you plan to implement devicetree support (or have customers who need it) ?
> 
> I could imagine that a chip like this will be used, for example, on beagleboard, which would
> require devicetree support.
> 

Right now, I'm not aware of any particular time plan to implement device
tree support, but this may change, if somebody will request it...

> Thanks,
> Guenter
> 

Thanks, 
Tomas


_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

Re: [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Guenter Roeck]

On Fri, May 02, 2014 at 01:59:29PM -0700, Tomas Pop wrote:
> Hi Guenter, thanks for comments! I will include them in third version,
> but I have still few questions...
> 
> On Don, 2014-05-01 at 19:06 -0700, Guenter Roeck wrote:
> > On 05/01/2014 04:05 PM, Tomas Pop wrote:
> > > One more time this patch sent with correct settings of my email client
> > > - I'm sorry for this.
> > >
> > > This is a second version of the driver for Sensirion SHTC1 humidity and
> > > temperature sensor. Initial version was submitted in July 2012.
> > > http://www.gossamer-threads.com/lists/linux/kernel/1569130#1569130
> > >
> > > We included suggested corrections formerly discussed in this list after
> > > initial submission, but since it is quite a while, we are re-submitting
> > > it again as a request for comments. Here is a list of important changes
> > > to the initial version:
> > >
> > > * returning real error codes instead of -1 or -ENODEV
> > > * using boolean variables instead of bitmaps where possible
> > > * macros be16_to_cpup used for conversion of indianneess
> > > * corrected formula for decoding of humidity and temperature values
> > > * documentation update
> > >
> > > Patch was generated against kernel v3.15-rc3
> > >
> > > Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
> > > ---
> > >   Documentation/hwmon/shtc1           |  38 +++++
> > >   drivers/hwmon/Kconfig               |  10 ++
> > >   drivers/hwmon/Makefile              |   1 +
> > >   drivers/hwmon/shtc1.c               | 323 ++++++++++++++++++++++++++++++++++++
> > >   include/linux/platform_data/shtc1.h |  24 +++
> > >   5 files changed, 396 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..6a72ae2d
> > > --- /dev/null
> > > +++ b/Documentation/hwmon/shtc1
> > > @@ -0,0 +1,38 @@
> > > +Kernel driver shtc1
> > > +===================
> > > +
> > > +Supported chips:
> > > +  * Sensirion SHTC1
> > > +    Prefix: 'shtc1'
> > > +    Addresses scanned: none
> > > +    Datasheet: Publicly available at the Sensirion website
> > > +    http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_SHTC1_Datasheet.pdf
> > 
> > Ok to add SHTW1 here if it is known to work.
> > Just say:
> > 	Datasheet: Not publicly available
> 
> Actually, there is no way to find out, if you are speaking 
> to SHTC1 or SHTW1. (i.e., the id is the same for both).
> So I will add it here and we will provide link to data-sheet 
> later in a separate patch.
> 
Ok.

> > > +
> > > +Author:
> > > +  Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> > > +
> > > +Description
> > > +-----------
> > > +
> > > +This driver implements support for the Sensirion  SHTC1 chip, a humidity and
> > 
> > Two spaces
> > 
> > > +temperature sensor. Temperature is measured in degrees celsius, relative
> > > +humidity is expressed as a percentage. Driver can be used as well for SHTW1
> > > +chip, that has the same electrical interface, but datasheet has not been
> > 
> > ... for SHTW1, which has the same electrical interface.
> > 
> > > +yet published.
> > > +
> > 
> > Either add support for the second now, or don't mention it at all
> > (especially if the chip has a different ID and you don't want to add
> > that ID at this point for some reason).
> > 
> > > +The device communicates with the I2C protocol. All sensors are set to the same
> > 
> > ... are set to I2C address 0x70.
> > 
> > > +I2C address 0x70, so an entry with I2C_BOARD_INFO("shtc1", 0x70) can be used
> > > +in the board setup code. See Documentation/i2c/instantiating-devices for
> > > +other methods to instantiate the device.
> > > +
> > I would suggest to just refer to the instantiating-devices document and drop
> > the I2C_BOARD_INFO example.
> > 
> > > +Furthermore, there are two configuration options by means of platform_data:
> > 
> > options configurable by means ...
> > 
> > > +1. blocking (pull the I2C clock line down while performing the measurement) or
> > > +   non-blocking, mode. Blocking mode will guarantee the fastest result, but
> > 
> > non-blocking mode (no comma)
> > 
> > > +   the I2C bus will be busy during that time
> > 
> > 					that time.
> > 
> > > +2. high or low accuracy. Using high accuracy is always recommended.
> > > +
> > > +sysfs-Interface
> > > +---------------
> > > +
> > > +temp1_input - temperature input
> > > +humidity1_input - humidity input
> > > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > > index bc196f4..4d58149 100644
> > > --- a/drivers/hwmon/Kconfig
> > > +++ b/drivers/hwmon/Kconfig
> > > @@ -1114,6 +1114,16 @@ 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 humidity
> > 
> > and SHTW1 ?
> 
> I will add SHTW1 here as well
> 
> > 
> > > +	  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 c48f987..1cc5273 100644
> > > --- a/drivers/hwmon/Makefile
> > > +++ b/drivers/hwmon/Makefile
> > > @@ -125,6 +125,7 @@ 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..96d398b
> > > --- /dev/null
> > > +++ b/drivers/hwmon/shtc1.c
> > > @@ -0,0 +1,323 @@
> > > +/* Sensirion SHTC1 humidity and temperature sensor driver
> > > + *
> > > + * Copyright (C) 2012 Sensirion AG, Switzerland
> > 
> > 2014 ?
> > 
> > > + * Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> > > + *
> > Is Johannes still involved ?
> 
> Yes, Johannes is aware of this re-submission, but I will try to take
> care about the process this time. I will add him in CC.
> 
> > 
> > > + * 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.
> > > + *
> > > + * Data sheet available soon
> > > + *  TODO: add link
> > 
> > Datasheet is referenced in documentation, so you don't need the link here.
> > Better to keep it in one please, then there is only one place to change
> > if it needs to be updated.
> > > + */
> > > +
> > > +#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 and constants for reading the ID register */
> > > +static const unsigned char shtc1_cmd_read_id_reg[]	     = { 0xef, 0xc8 };
> > > +static const unsigned char shtc1_id_reg_content = 0x07;
> > > +static const unsigned char shtc1_id_reg_mask    = 0x1f;
> > > +
> > Please use defines here. There is no benefit to have one-byte constants.
> > If the W1 chip has a different ID, you might as well add it in now and detect it.
> > 
> > > +/* delays for non-blocking i2c commands */
> > > +#define SHTC1_NONBLOCKING_WAIT_TIME_HPM  10
> > > +#define SHTC1_NONBLOCKING_WAIT_TIME_LPM   1

Just noticed. Please use tabs between definition and the number.

> > 
> > 	delay in what ? ms ? us ? seconds ?
> > 	Please specify.
> > 
> 
> The delays are in miliseconds. You mean to use it in names - e.g.,
> SHTC1_NONBLOCKING_WAIT_TIME_LPM_MS? Or comment is enough?
> 

Just a comment is enough. No name change, please; that would be overkill.

#define SHTC1_NONBLOCKING_WAIT_TIME_HPM	10	/* in ms */

> May be I should then rename 
> also data->nonblocking_wait_time to data->nonblocking_wait_time_ms...
> 
No. 

> > > +
> > > +#define SHTC1_CMD_LENGTH      2
> > > +#define SHTC1_RESPONSE_LENGTH 6
> > > +
> > > +struct shtc1_data {
> > > +	struct device *hwmon_dev;
> > > +	struct mutex update_lock;
> > > +	bool valid;
> > > +	unsigned long last_updated; /* In jiffies */
> > > +
> > > +	const unsigned char *command;
> > > +	unsigned int nonblocking_wait_time;
> > > +
> > > +	struct shtc1_platform_data 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;
> > > +	}
> > > +}
> > > +
> > Please move this function down, just before the probe function.
> > 
> > > +static int shtc1_update_values(struct i2c_client *client,
> > > +				struct shtc1_data *data,
> > > +				char *buf,
> > > +				int bufsize)
> > 
> > Please align continuation lines with (, and limit the number of continuation lines
> > where possible (eg, buf and bufsize fit into one line).
> > 
> > > +{
> > > +	int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
> > > +	if (ret < 0) {
> > > +		dev_err(&client->dev, "failed to send command: %d", ret);
> > 
> > Newline missing.
> > 
> > > +		return ret;
> > > +	}
> > 
> > There is another error condition: the function returns the number of bytes written,
> > which can be smaller than SHTC1_CMD_LENGTH.
> > 
> > > +
> > > +	/*
> > > +	* 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().
> > > +	*
> > > +	* TODO: consider usleep_range
> > 
> > Please do ... and fix all the other TODOs in case I missed any.
> 
> Sure. I checked the documentation and if I understand it correctly, we  should really use in this case something like:
> 	if (!data->setup.blocking_io)
> 		usleep_range(data->nonblocking_wait_time_min_us,
> 			     data->nonblocking_wait_time_max_us);
> 
> where max_time will be min_time plus some fixed margin, e.g, 2000us
> 
> sounds this reasonable to you?
> 
Yes, but you don't need the second variable. Just add the fixed offset,

		usleep_range(data->nonblocking_wait_time,
			     data->nonblocking_wait_time + 2000);

[ and of course specify the timeout in uS, not mS ].

> > 
> > > +	*/
> > > +	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);
> > 
> > Newline.
> > 
> > The return value can be >= 0, meaning the calling code can get confused.
> > Please make sure that the function always returns a valid error code.
> 
> Ok, so return -EIO or better -ENODEV?
> 
-EIO seems common. -ENODEV would be wrong.

> > 
> > > +		return ret;
> > > +	}
> > > +
> > > +	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);
> > > +
> > > +	unsigned 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;
> > 
> > So ret gets pre-initialized with 1 if valid == 0. Doesn't really make sense.
> > Just initialize it with 0 above.
> > 
> > 	int ret = 0;
> 
> Sure, thanks.
> 
> > 
> > > +
> > > +	if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
> > > +		ret = shtc1_update_values(client, data, buf, sizeof(buf));
> > > +
> > Unnecessary empty line.
> > 
> > > +		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));
> > 
> > 	Spaces before and after '+'
> > 
> > Just wondering .. what is in buf[2] and buf[5] ?
> 
> There are two CRC-8 checksums: 
> buf[2] for humidity, buf[5] for temperature value. We would prefer
> not to check CRC it in this version of the driver...
> 
Fine with me - your chip, your call - just asking.

> > 
> > > +		data->humidity = ((12500 * val) >> 13);
> > > +
> > > +		data->last_updated = jiffies;
> > > +		data->valid = 1;
> > 
> > 			= true;
> > 
> > > +	}
> > > +
> > > +out:
> > > +	mutex_unlock(&data->update_lock);
> > > +
> > > +	return ret == 0 ? data : ERR_PTR(ret);
> > > +}
> > > +
> > > +static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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 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);
> > 
> > You don't need SENSOR_DEVICE_ATTR here. DEVICE_ATTR is sufficient.
> > 
> > Another option would be to store temperature and humidity in an array
> > and use the last parameter of SENSOR_DEVICE_ATTR to index the array.
> > This way you would only need a single show function. I'll leave
> > that up to you.
> 
> Ok, then we will use DEVICE_ATTR...
> > 
> > > +
> > > +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,
> > > +};
> > 
> > Please use ATTRIBUTE_GROUPS().
> > 
> > > +
> > > +static int shtc1_probe(struct i2c_client *client,
> > > +				const struct i2c_device_id *id)
> > > +{
> > > +	struct shtc1_data *data;
> > 
> > A local variable
> > 	struct device *dev = &client->dev;
> > would save you a number of dereference operations.
> > 
> > > +	int err;
> > > +	struct i2c_adapter *adap = client->adapter;
> > > +	char id_reg[2];
> > > +
> > > +	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
> > > +		dev_err(&client->dev,
> > > +			"adapter does not support plain i2c transactions\n");
> > > +		return -ENODEV;
> > > +	}
> > > +
> > > +	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
> > > +
> > Please no empty lines before error checks.
> > 
> > > +	if (err < 0) {
> > 
> > Also err != SHTC1_CMD_LENGTH.
> 
> This is similar to my question above, do you think it is better in that
> case return -EIO or -ENODEV?
> 

This is the probe function, so here you return -ENODEV.

> > 
> > > +		dev_err(&client->dev, "could not send read command: %d\n", err);
> > > +		return -ENODEV;
> > > +	}
> > > +	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
> > > +	if (err != sizeof(id_reg)) {
> > > +		dev_err(&client->dev, "could not read ID register: %d\n", err);
> > > +		return -ENODEV;
> > > +	}
> > > +	if ((id_reg[1] & shtc1_id_reg_mask) != shtc1_id_reg_content) {
> > > +		dev_err(&client->dev, "ID register doesn't match\n");
> > > +		return -ENODEV;
> > > +	}
> > > +
> > > +	data = devm_kzalloc(&client->dev, sizeof(struct shtc1_data),
> > 
> > 	sizeof(*data) is preferred.
> > 
> > > +				GFP_KERNEL);
> > > +	if (!data)
> > > +		return -ENOMEM;
> > > +
> > > +	/* defaults: blocking, high precision mode */
> > > +	data->setup.blocking_io = 1;
> > > +	data->setup.high_precision = 1;
> > > +
> > 		= true;
> > for both.
> > 
> > > +	if (client->dev.platform_data)
> > > +		data->setup = *(struct shtc1_platform_data *)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");
> > > +		goto fail_free;
> > > +		return err;
> > 
> > goto or return, but not both (doesn't this create a warning about unreachable code ?).
> > goto is unnecessary, actually. return err is just fine.
> 
> I think, there were no warnings, but of course you are right...
> 
You might get the warning if you compile with C=1. Might be useful ...
I'll do it when I merge the driver, so it will save me and you some time
if you make sure that it is clean.

> > 
> > > +	}
> > > +	data->hwmon_dev = hwmon_device_register(&client->dev);
> > 
> > Please use devm_hwmon_device_register_with_groups().
> > 
> > 	struct device *hwmon_dev;
> > 	...
> > 	hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev, client->name,
> > 							data, sht1c_groups);
> > 	return PTR_ERR_OR_ZERO(hwmon_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;
> > > +	}
> > > +
> > > +
> > No more than one empty line, please.
> > 
> > > +	dev_info(&client->dev, "initialized\n");
> > 
> > Unnecessary noise.
> > 
> > > +
> > > +	return 0;
> > > +
> > > +fail_remove_sysfs:
> > > +	sysfs_remove_group(&client->dev.kobj, &shtc1_attr_group);
> > > +fail_free:
> > > +	kfree(data);
> > 
> > Unnecessary kfree.
> 
> I will remove these two lines at all.
> 
> > 
> > > +
> > > +	return err;
> > > +}
> > > +
> > > +/**
> > > + * shtc1_remove() - remove device
> > > + * @client: I2C client device
> > > + */
> > > +static int 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;
> > > +}
> > 
> > You can drop this entire function with the new hwmon API.
> > 
> > > +
> > > +/* device ID table */
> > > +static const struct i2c_device_id shtc1_id[] = {
> > > +	{ "shtc1", 0 },
> > > +	{ }
> > > +};
> > > +MODULE_DEVICE_TABLE(i2c, shtc1_id);
> > > +
> > > +static struct i2c_driver shtc1_i2c_driver = {
> > > +	.driver.name = "shtc1",
> > > +	.probe	= shtc1_probe,
> > > +	.remove      = shtc1_remove,
> > > +	.id_table    = shtc1_id,
> > > +};
> > > +
> > > +/**
> > > + * shtc1_init() - initialize driver
> > > + *
> > > + * Called when kernel is booted or module is inserted.
> > > + * Returns 0 on success.
> > > + */
> > > +static int __init shtc1_init(void)
> > > +{
> > > +	return i2c_add_driver(&shtc1_i2c_driver);
> > > +}
> > > +module_init(shtc1_init);
> > > +
> > > +/*
> > > + * shtc1_exit() - clean up driver
> > > + *
> > > + * Called when module is removed.
> > > + */
> > > +static void __exit shtc1_exit(void)
> > > +{
> > > +	i2c_del_driver(&shtc1_i2c_driver);
> > > +}
> > > +
> > > +module_exit(shtc1_exit);
> > 
> > Please use module_i2c_driver().
> > 
> > > +
> > > +
> > > +MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.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..4629364
> > > --- /dev/null
> > > +++ b/include/linux/platform_data/shtc1.h
> > > @@ -0,0 +1,24 @@
> > > +/*
> > > + * Copyright (C) 2012 Sensirion AG, Switzerland
> > 
> > 2014 ?
> > 
> > > + * 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;
> > > +};
> > > +
> > 
> > Please no empty line at the end.
> > 
> > Wondering ... do you plan to implement devicetree support (or have customers who need it) ?
> > 
> > I could imagine that a chip like this will be used, for example, on beagleboard, which would
> > require devicetree support.
> > 
> 
> Right now, I'm not aware of any particular time plan to implement device
> tree support, but this may change, if somebody will request it...
> 
Fine with me, just asking.

Thanks,
Guenter

Re: [lm-sensors] [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Guenter Roeck]

On Fri, May 02, 2014 at 01:59:29PM -0700, Tomas Pop wrote:
> Hi Guenter, thanks for comments! I will include them in third version,
> but I have still few questions...
> 
> On Don, 2014-05-01 at 19:06 -0700, Guenter Roeck wrote:
> > On 05/01/2014 04:05 PM, Tomas Pop wrote:
> > > One more time this patch sent with correct settings of my email client
> > > - I'm sorry for this.
> > >
> > > This is a second version of the driver for Sensirion SHTC1 humidity and
> > > temperature sensor. Initial version was submitted in July 2012.
> > > http://www.gossamer-threads.com/lists/linux/kernel/1569130#1569130
> > >
> > > We included suggested corrections formerly discussed in this list after
> > > initial submission, but since it is quite a while, we are re-submitting
> > > it again as a request for comments. Here is a list of important changes
> > > to the initial version:
> > >
> > > * returning real error codes instead of -1 or -ENODEV
> > > * using boolean variables instead of bitmaps where possible
> > > * macros be16_to_cpup used for conversion of indianneess
> > > * corrected formula for decoding of humidity and temperature values
> > > * documentation update
> > >
> > > Patch was generated against kernel v3.15-rc3
> > >
> > > Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
> > > ---
> > >   Documentation/hwmon/shtc1           |  38 +++++
> > >   drivers/hwmon/Kconfig               |  10 ++
> > >   drivers/hwmon/Makefile              |   1 +
> > >   drivers/hwmon/shtc1.c               | 323 ++++++++++++++++++++++++++++++++++++
> > >   include/linux/platform_data/shtc1.h |  24 +++
> > >   5 files changed, 396 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..6a72ae2d
> > > --- /dev/null
> > > +++ b/Documentation/hwmon/shtc1
> > > @@ -0,0 +1,38 @@
> > > +Kernel driver shtc1
> > > +=========> > > +
> > > +Supported chips:
> > > +  * Sensirion SHTC1
> > > +    Prefix: 'shtc1'
> > > +    Addresses scanned: none
> > > +    Datasheet: Publicly available at the Sensirion website
> > > +    http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_SHTC1_Datasheet.pdf
> > 
> > Ok to add SHTW1 here if it is known to work.
> > Just say:
> > 	Datasheet: Not publicly available
> 
> Actually, there is no way to find out, if you are speaking 
> to SHTC1 or SHTW1. (i.e., the id is the same for both).
> So I will add it here and we will provide link to data-sheet 
> later in a separate patch.
> 
Ok.

> > > +
> > > +Author:
> > > +  Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> > > +
> > > +Description
> > > +-----------
> > > +
> > > +This driver implements support for the Sensirion  SHTC1 chip, a humidity and
> > 
> > Two spaces
> > 
> > > +temperature sensor. Temperature is measured in degrees celsius, relative
> > > +humidity is expressed as a percentage. Driver can be used as well for SHTW1
> > > +chip, that has the same electrical interface, but datasheet has not been
> > 
> > ... for SHTW1, which has the same electrical interface.
> > 
> > > +yet published.
> > > +
> > 
> > Either add support for the second now, or don't mention it at all
> > (especially if the chip has a different ID and you don't want to add
> > that ID at this point for some reason).
> > 
> > > +The device communicates with the I2C protocol. All sensors are set to the same
> > 
> > ... are set to I2C address 0x70.
> > 
> > > +I2C address 0x70, so an entry with I2C_BOARD_INFO("shtc1", 0x70) can be used
> > > +in the board setup code. See Documentation/i2c/instantiating-devices for
> > > +other methods to instantiate the device.
> > > +
> > I would suggest to just refer to the instantiating-devices document and drop
> > the I2C_BOARD_INFO example.
> > 
> > > +Furthermore, there are two configuration options by means of platform_data:
> > 
> > options configurable by means ...
> > 
> > > +1. blocking (pull the I2C clock line down while performing the measurement) or
> > > +   non-blocking, mode. Blocking mode will guarantee the fastest result, but
> > 
> > non-blocking mode (no comma)
> > 
> > > +   the I2C bus will be busy during that time
> > 
> > 					that time.
> > 
> > > +2. high or low accuracy. Using high accuracy is always recommended.
> > > +
> > > +sysfs-Interface
> > > +---------------
> > > +
> > > +temp1_input - temperature input
> > > +humidity1_input - humidity input
> > > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > > index bc196f4..4d58149 100644
> > > --- a/drivers/hwmon/Kconfig
> > > +++ b/drivers/hwmon/Kconfig
> > > @@ -1114,6 +1114,16 @@ 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 humidity
> > 
> > and SHTW1 ?
> 
> I will add SHTW1 here as well
> 
> > 
> > > +	  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 c48f987..1cc5273 100644
> > > --- a/drivers/hwmon/Makefile
> > > +++ b/drivers/hwmon/Makefile
> > > @@ -125,6 +125,7 @@ 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..96d398b
> > > --- /dev/null
> > > +++ b/drivers/hwmon/shtc1.c
> > > @@ -0,0 +1,323 @@
> > > +/* Sensirion SHTC1 humidity and temperature sensor driver
> > > + *
> > > + * Copyright (C) 2012 Sensirion AG, Switzerland
> > 
> > 2014 ?
> > 
> > > + * Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> > > + *
> > Is Johannes still involved ?
> 
> Yes, Johannes is aware of this re-submission, but I will try to take
> care about the process this time. I will add him in CC.
> 
> > 
> > > + * 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.
> > > + *
> > > + * Data sheet available soon
> > > + *  TODO: add link
> > 
> > Datasheet is referenced in documentation, so you don't need the link here.
> > Better to keep it in one please, then there is only one place to change
> > if it needs to be updated.
> > > + */
> > > +
> > > +#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 and constants for reading the ID register */
> > > +static const unsigned char shtc1_cmd_read_id_reg[]	     = { 0xef, 0xc8 };
> > > +static const unsigned char shtc1_id_reg_content = 0x07;
> > > +static const unsigned char shtc1_id_reg_mask    = 0x1f;
> > > +
> > Please use defines here. There is no benefit to have one-byte constants.
> > If the W1 chip has a different ID, you might as well add it in now and detect it.
> > 
> > > +/* delays for non-blocking i2c commands */
> > > +#define SHTC1_NONBLOCKING_WAIT_TIME_HPM  10
> > > +#define SHTC1_NONBLOCKING_WAIT_TIME_LPM   1

Just noticed. Please use tabs between definition and the number.

> > 
> > 	delay in what ? ms ? us ? seconds ?
> > 	Please specify.
> > 
> 
> The delays are in miliseconds. You mean to use it in names - e.g.,
> SHTC1_NONBLOCKING_WAIT_TIME_LPM_MS? Or comment is enough?
> 

Just a comment is enough. No name change, please; that would be overkill.

#define SHTC1_NONBLOCKING_WAIT_TIME_HPM	10	/* in ms */

> May be I should then rename 
> also data->nonblocking_wait_time to data->nonblocking_wait_time_ms...
> 
No. 

> > > +
> > > +#define SHTC1_CMD_LENGTH      2
> > > +#define SHTC1_RESPONSE_LENGTH 6
> > > +
> > > +struct shtc1_data {
> > > +	struct device *hwmon_dev;
> > > +	struct mutex update_lock;
> > > +	bool valid;
> > > +	unsigned long last_updated; /* In jiffies */
> > > +
> > > +	const unsigned char *command;
> > > +	unsigned int nonblocking_wait_time;
> > > +
> > > +	struct shtc1_platform_data 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;
> > > +	}
> > > +}
> > > +
> > Please move this function down, just before the probe function.
> > 
> > > +static int shtc1_update_values(struct i2c_client *client,
> > > +				struct shtc1_data *data,
> > > +				char *buf,
> > > +				int bufsize)
> > 
> > Please align continuation lines with (, and limit the number of continuation lines
> > where possible (eg, buf and bufsize fit into one line).
> > 
> > > +{
> > > +	int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
> > > +	if (ret < 0) {
> > > +		dev_err(&client->dev, "failed to send command: %d", ret);
> > 
> > Newline missing.
> > 
> > > +		return ret;
> > > +	}
> > 
> > There is another error condition: the function returns the number of bytes written,
> > which can be smaller than SHTC1_CMD_LENGTH.
> > 
> > > +
> > > +	/*
> > > +	* 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().
> > > +	*
> > > +	* TODO: consider usleep_range
> > 
> > Please do ... and fix all the other TODOs in case I missed any.
> 
> Sure. I checked the documentation and if I understand it correctly, we  should really use in this case something like:
> 	if (!data->setup.blocking_io)
> 		usleep_range(data->nonblocking_wait_time_min_us,
> 			     data->nonblocking_wait_time_max_us);
> 
> where max_time will be min_time plus some fixed margin, e.g, 2000us
> 
> sounds this reasonable to you?
> 
Yes, but you don't need the second variable. Just add the fixed offset,

		usleep_range(data->nonblocking_wait_time,
			     data->nonblocking_wait_time + 2000);

[ and of course specify the timeout in uS, not mS ].

> > 
> > > +	*/
> > > +	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);
> > 
> > Newline.
> > 
> > The return value can be >= 0, meaning the calling code can get confused.
> > Please make sure that the function always returns a valid error code.
> 
> Ok, so return -EIO or better -ENODEV?
> 
-EIO seems common. -ENODEV would be wrong.

> > 
> > > +		return ret;
> > > +	}
> > > +
> > > +	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);
> > > +
> > > +	unsigned 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;
> > 
> > So ret gets pre-initialized with 1 if valid = 0. Doesn't really make sense.
> > Just initialize it with 0 above.
> > 
> > 	int ret = 0;
> 
> Sure, thanks.
> 
> > 
> > > +
> > > +	if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
> > > +		ret = shtc1_update_values(client, data, buf, sizeof(buf));
> > > +
> > Unnecessary empty line.
> > 
> > > +		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));
> > 
> > 	Spaces before and after '+'
> > 
> > Just wondering .. what is in buf[2] and buf[5] ?
> 
> There are two CRC-8 checksums: 
> buf[2] for humidity, buf[5] for temperature value. We would prefer
> not to check CRC it in this version of the driver...
> 
Fine with me - your chip, your call - just asking.

> > 
> > > +		data->humidity = ((12500 * val) >> 13);
> > > +
> > > +		data->last_updated = jiffies;
> > > +		data->valid = 1;
> > 
> > 			= true;
> > 
> > > +	}
> > > +
> > > +out:
> > > +	mutex_unlock(&data->update_lock);
> > > +
> > > +	return ret = 0 ? data : ERR_PTR(ret);
> > > +}
> > > +
> > > +static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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 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);
> > 
> > You don't need SENSOR_DEVICE_ATTR here. DEVICE_ATTR is sufficient.
> > 
> > Another option would be to store temperature and humidity in an array
> > and use the last parameter of SENSOR_DEVICE_ATTR to index the array.
> > This way you would only need a single show function. I'll leave
> > that up to you.
> 
> Ok, then we will use DEVICE_ATTR...
> > 
> > > +
> > > +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,
> > > +};
> > 
> > Please use ATTRIBUTE_GROUPS().
> > 
> > > +
> > > +static int shtc1_probe(struct i2c_client *client,
> > > +				const struct i2c_device_id *id)
> > > +{
> > > +	struct shtc1_data *data;
> > 
> > A local variable
> > 	struct device *dev = &client->dev;
> > would save you a number of dereference operations.
> > 
> > > +	int err;
> > > +	struct i2c_adapter *adap = client->adapter;
> > > +	char id_reg[2];
> > > +
> > > +	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
> > > +		dev_err(&client->dev,
> > > +			"adapter does not support plain i2c transactions\n");
> > > +		return -ENODEV;
> > > +	}
> > > +
> > > +	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
> > > +
> > Please no empty lines before error checks.
> > 
> > > +	if (err < 0) {
> > 
> > Also err != SHTC1_CMD_LENGTH.
> 
> This is similar to my question above, do you think it is better in that
> case return -EIO or -ENODEV?
> 

This is the probe function, so here you return -ENODEV.

> > 
> > > +		dev_err(&client->dev, "could not send read command: %d\n", err);
> > > +		return -ENODEV;
> > > +	}
> > > +	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
> > > +	if (err != sizeof(id_reg)) {
> > > +		dev_err(&client->dev, "could not read ID register: %d\n", err);
> > > +		return -ENODEV;
> > > +	}
> > > +	if ((id_reg[1] & shtc1_id_reg_mask) != shtc1_id_reg_content) {
> > > +		dev_err(&client->dev, "ID register doesn't match\n");
> > > +		return -ENODEV;
> > > +	}
> > > +
> > > +	data = devm_kzalloc(&client->dev, sizeof(struct shtc1_data),
> > 
> > 	sizeof(*data) is preferred.
> > 
> > > +				GFP_KERNEL);
> > > +	if (!data)
> > > +		return -ENOMEM;
> > > +
> > > +	/* defaults: blocking, high precision mode */
> > > +	data->setup.blocking_io = 1;
> > > +	data->setup.high_precision = 1;
> > > +
> > 		= true;
> > for both.
> > 
> > > +	if (client->dev.platform_data)
> > > +		data->setup = *(struct shtc1_platform_data *)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");
> > > +		goto fail_free;
> > > +		return err;
> > 
> > goto or return, but not both (doesn't this create a warning about unreachable code ?).
> > goto is unnecessary, actually. return err is just fine.
> 
> I think, there were no warnings, but of course you are right...
> 
You might get the warning if you compile with C=1. Might be useful ...
I'll do it when I merge the driver, so it will save me and you some time
if you make sure that it is clean.

> > 
> > > +	}
> > > +	data->hwmon_dev = hwmon_device_register(&client->dev);
> > 
> > Please use devm_hwmon_device_register_with_groups().
> > 
> > 	struct device *hwmon_dev;
> > 	...
> > 	hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev, client->name,
> > 							data, sht1c_groups);
> > 	return PTR_ERR_OR_ZERO(hwmon_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;
> > > +	}
> > > +
> > > +
> > No more than one empty line, please.
> > 
> > > +	dev_info(&client->dev, "initialized\n");
> > 
> > Unnecessary noise.
> > 
> > > +
> > > +	return 0;
> > > +
> > > +fail_remove_sysfs:
> > > +	sysfs_remove_group(&client->dev.kobj, &shtc1_attr_group);
> > > +fail_free:
> > > +	kfree(data);
> > 
> > Unnecessary kfree.
> 
> I will remove these two lines at all.
> 
> > 
> > > +
> > > +	return err;
> > > +}
> > > +
> > > +/**
> > > + * shtc1_remove() - remove device
> > > + * @client: I2C client device
> > > + */
> > > +static int 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;
> > > +}
> > 
> > You can drop this entire function with the new hwmon API.
> > 
> > > +
> > > +/* device ID table */
> > > +static const struct i2c_device_id shtc1_id[] = {
> > > +	{ "shtc1", 0 },
> > > +	{ }
> > > +};
> > > +MODULE_DEVICE_TABLE(i2c, shtc1_id);
> > > +
> > > +static struct i2c_driver shtc1_i2c_driver = {
> > > +	.driver.name = "shtc1",
> > > +	.probe	= shtc1_probe,
> > > +	.remove      = shtc1_remove,
> > > +	.id_table    = shtc1_id,
> > > +};
> > > +
> > > +/**
> > > + * shtc1_init() - initialize driver
> > > + *
> > > + * Called when kernel is booted or module is inserted.
> > > + * Returns 0 on success.
> > > + */
> > > +static int __init shtc1_init(void)
> > > +{
> > > +	return i2c_add_driver(&shtc1_i2c_driver);
> > > +}
> > > +module_init(shtc1_init);
> > > +
> > > +/*
> > > + * shtc1_exit() - clean up driver
> > > + *
> > > + * Called when module is removed.
> > > + */
> > > +static void __exit shtc1_exit(void)
> > > +{
> > > +	i2c_del_driver(&shtc1_i2c_driver);
> > > +}
> > > +
> > > +module_exit(shtc1_exit);
> > 
> > Please use module_i2c_driver().
> > 
> > > +
> > > +
> > > +MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.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..4629364
> > > --- /dev/null
> > > +++ b/include/linux/platform_data/shtc1.h
> > > @@ -0,0 +1,24 @@
> > > +/*
> > > + * Copyright (C) 2012 Sensirion AG, Switzerland
> > 
> > 2014 ?
> > 
> > > + * 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;
> > > +};
> > > +
> > 
> > Please no empty line at the end.
> > 
> > Wondering ... do you plan to implement devicetree support (or have customers who need it) ?
> > 
> > I could imagine that a chip like this will be used, for example, on beagleboard, which would
> > require devicetree support.
> > 
> 
> Right now, I'm not aware of any particular time plan to implement device
> tree support, but this may change, if somebody will request it...
> 
Fine with me, just asking.

Thanks,
Guenter

_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

Re: [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Tomas Pop]

Hi Guenter, 

Here is a corrected version, I tried to address your comments and I'm sending it
again with a kind request for comments - we will do some more extensive testing
before the final submission, but I would like to make the code as complete as
as possible before. Here is a list of changes to the previous version:

* positive, but incorrect return codes/lengths from i2c_mater_* are checked
* usleep_range used instead of msleep
* DEVICE_ATTR used instead of SENSOR_DEVICE_ATTR, ATTRIBITE_GROUPS used
* devm_hwmon_device_register_with_groups instead of devm_hwmon_device_register
* direct calls to sysfs_create_group and sysfs_create_group dropped
* shtc1_remove function dropped
* SHTW1 added to documentation and Kconfig
* documentation and formating updates/corrections

I did re-compile with C=1 as suggested and it is clear.

Patch was generated against kernel v3.15-rc3

Thanks,
Tomas

Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
---
 Documentation/hwmon/shtc1           |  41 ++++++
 drivers/hwmon/Kconfig               |  10 ++
 drivers/hwmon/Makefile              |   1 +
 drivers/hwmon/shtc1.c               | 266 ++++++++++++++++++++++++++++++++++++
 include/linux/platform_data/shtc1.h |  24 ++++
 5 files changed, 342 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..47c9ed1
--- /dev/null
+++ b/Documentation/hwmon/shtc1
@@ -0,0 +1,41 @@
+Kernel driver shtc1
+===================
+
+Supported chips:
+  * Sensirion SHTC1
+    Prefix: 'shtc1'
+    Addresses scanned: none
+    Datasheet: Publicly available at the Sensirion website
+    http://www.sensirion.com/file/datasheet_shtc1
+
+  * Sensirion SHTW1
+    Prefix: 'shtc1'
+    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.
+2. high or low accuracy. Using high accuracy is strongly recommended.
+
+sysfs-Interface
+---------------
+
+temp1_input - temperature input
+humidity1_input - humidity input
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index bc196f4..f95ba5b 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1114,6 +1114,16 @@ 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 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 c48f987..1cc5273 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -125,6 +125,7 @@ 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..c94f670
--- /dev/null
+++ b/drivers/hwmon/shtc1.c
@@ -0,0 +1,266 @@
+/* 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_REG_CONTENT 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 device *hwmon_dev;
+	struct mutex update_lock;
+	bool valid;
+	unsigned long last_updated; /* In jiffies */
+
+	const unsigned char *command;
+	unsigned int nonblocking_wait_time;
+
+	struct shtc1_platform_data setup;
+
+	int temperature;
+	int humidity;
+};
+
+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: %d\n", ret);
+		return ret;
+	}
+	if (ret != SHTC1_CMD_LENGTH) {
+		dev_err(&client->dev, "wrong nr bytes written: %d\n", ret);
+		return -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 + 2000);
+
+	ret = i2c_master_recv(client, buf, bufsize);
+	if (ret != bufsize) {
+		dev_err(&client->dev, "failed to read values: %d\n", ret);
+		if (ret < 0)
+			return ret;
+		return -EIO;
+	}
+
+	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);
+
+	unsigned 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 = 0;
+
+	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 = 1;
+	}
+
+out:
+	mutex_unlock(&data->update_lock);
+
+	return ret == 0 ? data : ERR_PTR(ret);
+}
+
+static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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(temp1_input, S_IRUGO, shtc1_show_temperature, NULL);
+static DEVICE_ATTR(humidity1_input, S_IRUGO, shtc1_show_humidity, NULL);
+
+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)
+{
+	struct shtc1_data *data;
+	int err;
+	struct i2c_adapter *adap = client->adapter;
+	char id_reg[2];
+
+	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
+		dev_err(&client->dev,
+			"adapter does not support plain i2c transactions\n");
+		return -ENODEV;
+	}
+
+	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
+	if (err < 0) {
+		dev_err(&client->dev, "could not send read command: %d\n", err);
+		return -ENODEV;
+	}
+	if (err != SHTC1_CMD_LENGTH) {
+		dev_err(&client->dev, "num bytes send is wrong: %d\n", err);
+		return -ENODEV;
+	}
+	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
+	if (err != sizeof(id_reg)) {
+		dev_err(&client->dev, "could not read ID register: %d\n", err);
+		return -ENODEV;
+	}
+	if ((id_reg[1] & SHTC1_ID_REG_MASK) != SHTC1_ID_REG_CONTENT) {
+		dev_err(&client->dev, "ID register doesn't match\n");
+		return -ENODEV;
+	}
+
+	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	/* defaults: blocking, high precision mode */
+	data->setup.blocking_io = true;
+	data->setup.high_precision = true;
+
+	if (client->dev.platform_data)
+		data->setup = *(struct shtc1_platform_data *)client->dev.platform_data;
+	shtc1_select_command(data);
+	i2c_set_clientdata(client, data);
+	mutex_init(&data->update_lock);
+
+	data->hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev,
+								 client->name,
+								 data,
+								 shtc1_groups);
+	if (IS_ERR(data->hwmon_dev))
+		dev_dbg(&client->dev, "unable to register hwmon device\n");
+
+	return PTR_ERR_OR_ZERO(data->hwmon_dev);
+}
+
+/* device ID table */
+static const struct i2c_device_id shtc1_id[] = {
+	{ "shtc1", 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");
diff --git a/include/linux/platform_data/shtc1.h b/include/linux/platform_data/shtc1.h
new file mode 100644
index 0000000..b06e3db
--- /dev/null
+++ b/include/linux/platform_data/shtc1.h
@@ -0,0 +1,24 @@
+/*
+ * 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_ */
-- 
1.8.3.2


On Fre, 2014-05-02 at 16:15 -0700, Guenter Roeck wrote:
> On Fri, May 02, 2014 at 01:59:29PM -0700, Tomas Pop wrote:
> > Hi Guenter, thanks for comments! I will include them in third version,
> > but I have still few questions...
> > 
> > On Don, 2014-05-01 at 19:06 -0700, Guenter Roeck wrote:
> > > On 05/01/2014 04:05 PM, Tomas Pop wrote:
> > > > One more time this patch sent with correct settings of my email client
> > > > - I'm sorry for this.
> > > >
> > > > This is a second version of the driver for Sensirion SHTC1 humidity and
> > > > temperature sensor. Initial version was submitted in July 2012.
> > > > http://www.gossamer-threads.com/lists/linux/kernel/1569130#1569130
> > > >
> > > > We included suggested corrections formerly discussed in this list after
> > > > initial submission, but since it is quite a while, we are re-submitting
> > > > it again as a request for comments. Here is a list of important changes
> > > > to the initial version:
> > > >
> > > > * returning real error codes instead of -1 or -ENODEV
> > > > * using boolean variables instead of bitmaps where possible
> > > > * macros be16_to_cpup used for conversion of indianneess
> > > > * corrected formula for decoding of humidity and temperature values
> > > > * documentation update
> > > >
> > > > Patch was generated against kernel v3.15-rc3
> > > >
> > > > Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
> > > > ---
> > > >   Documentation/hwmon/shtc1           |  38 +++++
> > > >   drivers/hwmon/Kconfig               |  10 ++
> > > >   drivers/hwmon/Makefile              |   1 +
> > > >   drivers/hwmon/shtc1.c               | 323 ++++++++++++++++++++++++++++++++++++
> > > >   include/linux/platform_data/shtc1.h |  24 +++
> > > >   5 files changed, 396 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..6a72ae2d
> > > > --- /dev/null
> > > > +++ b/Documentation/hwmon/shtc1
> > > > @@ -0,0 +1,38 @@
> > > > +Kernel driver shtc1
> > > > +===================
> > > > +
> > > > +Supported chips:
> > > > +  * Sensirion SHTC1
> > > > +    Prefix: 'shtc1'
> > > > +    Addresses scanned: none
> > > > +    Datasheet: Publicly available at the Sensirion website
> > > > +    http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_SHTC1_Datasheet.pdf
> > > 
> > > Ok to add SHTW1 here if it is known to work.
> > > Just say:
> > > 	Datasheet: Not publicly available
> > 
> > Actually, there is no way to find out, if you are speaking 
> > to SHTC1 or SHTW1. (i.e., the id is the same for both).
> > So I will add it here and we will provide link to data-sheet 
> > later in a separate patch.
> > 
> Ok.
> 
> > > > +
> > > > +Author:
> > > > +  Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> > > > +
> > > > +Description
> > > > +-----------
> > > > +
> > > > +This driver implements support for the Sensirion  SHTC1 chip, a humidity and
> > > 
> > > Two spaces
> > > 
> > > > +temperature sensor. Temperature is measured in degrees celsius, relative
> > > > +humidity is expressed as a percentage. Driver can be used as well for SHTW1
> > > > +chip, that has the same electrical interface, but datasheet has not been
> > > 
> > > ... for SHTW1, which has the same electrical interface.
> > > 
> > > > +yet published.
> > > > +
> > > 
> > > Either add support for the second now, or don't mention it at all
> > > (especially if the chip has a different ID and you don't want to add
> > > that ID at this point for some reason).
> > > 
> > > > +The device communicates with the I2C protocol. All sensors are set to the same
> > > 
> > > ... are set to I2C address 0x70.
> > > 
> > > > +I2C address 0x70, so an entry with I2C_BOARD_INFO("shtc1", 0x70) can be used
> > > > +in the board setup code. See Documentation/i2c/instantiating-devices for
> > > > +other methods to instantiate the device.
> > > > +
> > > I would suggest to just refer to the instantiating-devices document and drop
> > > the I2C_BOARD_INFO example.
> > > 
> > > > +Furthermore, there are two configuration options by means of platform_data:
> > > 
> > > options configurable by means ...
> > > 
> > > > +1. blocking (pull the I2C clock line down while performing the measurement) or
> > > > +   non-blocking, mode. Blocking mode will guarantee the fastest result, but
> > > 
> > > non-blocking mode (no comma)
> > > 
> > > > +   the I2C bus will be busy during that time
> > > 
> > > 					that time.
> > > 
> > > > +2. high or low accuracy. Using high accuracy is always recommended.
> > > > +
> > > > +sysfs-Interface
> > > > +---------------
> > > > +
> > > > +temp1_input - temperature input
> > > > +humidity1_input - humidity input
> > > > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > > > index bc196f4..4d58149 100644
> > > > --- a/drivers/hwmon/Kconfig
> > > > +++ b/drivers/hwmon/Kconfig
> > > > @@ -1114,6 +1114,16 @@ 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 humidity
> > > 
> > > and SHTW1 ?
> > 
> > I will add SHTW1 here as well
> > 
> > > 
> > > > +	  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 c48f987..1cc5273 100644
> > > > --- a/drivers/hwmon/Makefile
> > > > +++ b/drivers/hwmon/Makefile
> > > > @@ -125,6 +125,7 @@ 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..96d398b
> > > > --- /dev/null
> > > > +++ b/drivers/hwmon/shtc1.c
> > > > @@ -0,0 +1,323 @@
> > > > +/* Sensirion SHTC1 humidity and temperature sensor driver
> > > > + *
> > > > + * Copyright (C) 2012 Sensirion AG, Switzerland
> > > 
> > > 2014 ?
> > > 
> > > > + * Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> > > > + *
> > > Is Johannes still involved ?
> > 
> > Yes, Johannes is aware of this re-submission, but I will try to take
> > care about the process this time. I will add him in CC.
> > 
> > > 
> > > > + * 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.
> > > > + *
> > > > + * Data sheet available soon
> > > > + *  TODO: add link
> > > 
> > > Datasheet is referenced in documentation, so you don't need the link here.
> > > Better to keep it in one please, then there is only one place to change
> > > if it needs to be updated.
> > > > + */
> > > > +
> > > > +#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 and constants for reading the ID register */
> > > > +static const unsigned char shtc1_cmd_read_id_reg[]	     = { 0xef, 0xc8 };
> > > > +static const unsigned char shtc1_id_reg_content = 0x07;
> > > > +static const unsigned char shtc1_id_reg_mask    = 0x1f;
> > > > +
> > > Please use defines here. There is no benefit to have one-byte constants.
> > > If the W1 chip has a different ID, you might as well add it in now and detect it.
> > > 
> > > > +/* delays for non-blocking i2c commands */
> > > > +#define SHTC1_NONBLOCKING_WAIT_TIME_HPM  10
> > > > +#define SHTC1_NONBLOCKING_WAIT_TIME_LPM   1
> 
> Just noticed. Please use tabs between definition and the number.
> 
> > > 
> > > 	delay in what ? ms ? us ? seconds ?
> > > 	Please specify.
> > > 
> > 
> > The delays are in miliseconds. You mean to use it in names - e.g.,
> > SHTC1_NONBLOCKING_WAIT_TIME_LPM_MS? Or comment is enough?
> > 
> 
> Just a comment is enough. No name change, please; that would be overkill.
> 
> #define SHTC1_NONBLOCKING_WAIT_TIME_HPM	10	/* in ms */
> 
> > May be I should then rename 
> > also data->nonblocking_wait_time to data->nonblocking_wait_time_ms...
> > 
> No. 
> 
> > > > +
> > > > +#define SHTC1_CMD_LENGTH      2
> > > > +#define SHTC1_RESPONSE_LENGTH 6
> > > > +
> > > > +struct shtc1_data {
> > > > +	struct device *hwmon_dev;
> > > > +	struct mutex update_lock;
> > > > +	bool valid;
> > > > +	unsigned long last_updated; /* In jiffies */
> > > > +
> > > > +	const unsigned char *command;
> > > > +	unsigned int nonblocking_wait_time;
> > > > +
> > > > +	struct shtc1_platform_data 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;
> > > > +	}
> > > > +}
> > > > +
> > > Please move this function down, just before the probe function.
> > > 
> > > > +static int shtc1_update_values(struct i2c_client *client,
> > > > +				struct shtc1_data *data,
> > > > +				char *buf,
> > > > +				int bufsize)
> > > 
> > > Please align continuation lines with (, and limit the number of continuation lines
> > > where possible (eg, buf and bufsize fit into one line).
> > > 
> > > > +{
> > > > +	int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
> > > > +	if (ret < 0) {
> > > > +		dev_err(&client->dev, "failed to send command: %d", ret);
> > > 
> > > Newline missing.
> > > 
> > > > +		return ret;
> > > > +	}
> > > 
> > > There is another error condition: the function returns the number of bytes written,
> > > which can be smaller than SHTC1_CMD_LENGTH.
> > > 
> > > > +
> > > > +	/*
> > > > +	* 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().
> > > > +	*
> > > > +	* TODO: consider usleep_range
> > > 
> > > Please do ... and fix all the other TODOs in case I missed any.
> > 
> > Sure. I checked the documentation and if I understand it correctly, we  should really use in this case something like:
> > 	if (!data->setup.blocking_io)
> > 		usleep_range(data->nonblocking_wait_time_min_us,
> > 			     data->nonblocking_wait_time_max_us);
> > 
> > where max_time will be min_time plus some fixed margin, e.g, 2000us
> > 
> > sounds this reasonable to you?
> > 
> Yes, but you don't need the second variable. Just add the fixed offset,
> 
> 		usleep_range(data->nonblocking_wait_time,
> 			     data->nonblocking_wait_time + 2000);
> 
> [ and of course specify the timeout in uS, not mS ].
> 
> > > 
> > > > +	*/
> > > > +	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);
> > > 
> > > Newline.
> > > 
> > > The return value can be >= 0, meaning the calling code can get confused.
> > > Please make sure that the function always returns a valid error code.
> > 
> > Ok, so return -EIO or better -ENODEV?
> > 
> -EIO seems common. -ENODEV would be wrong.
> 
> > > 
> > > > +		return ret;
> > > > +	}
> > > > +
> > > > +	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);
> > > > +
> > > > +	unsigned 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;
> > > 
> > > So ret gets pre-initialized with 1 if valid == 0. Doesn't really make sense.
> > > Just initialize it with 0 above.
> > > 
> > > 	int ret = 0;
> > 
> > Sure, thanks.
> > 
> > > 
> > > > +
> > > > +	if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
> > > > +		ret = shtc1_update_values(client, data, buf, sizeof(buf));
> > > > +
> > > Unnecessary empty line.
> > > 
> > > > +		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));
> > > 
> > > 	Spaces before and after '+'
> > > 
> > > Just wondering .. what is in buf[2] and buf[5] ?
> > 
> > There are two CRC-8 checksums: 
> > buf[2] for humidity, buf[5] for temperature value. We would prefer
> > not to check CRC it in this version of the driver...
> > 
> Fine with me - your chip, your call - just asking.
> 
> > > 
> > > > +		data->humidity = ((12500 * val) >> 13);
> > > > +
> > > > +		data->last_updated = jiffies;
> > > > +		data->valid = 1;
> > > 
> > > 			= true;
> > > 
> > > > +	}
> > > > +
> > > > +out:
> > > > +	mutex_unlock(&data->update_lock);
> > > > +
> > > > +	return ret == 0 ? data : ERR_PTR(ret);
> > > > +}
> > > > +
> > > > +static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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 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);
> > > 
> > > You don't need SENSOR_DEVICE_ATTR here. DEVICE_ATTR is sufficient.
> > > 
> > > Another option would be to store temperature and humidity in an array
> > > and use the last parameter of SENSOR_DEVICE_ATTR to index the array.
> > > This way you would only need a single show function. I'll leave
> > > that up to you.
> > 
> > Ok, then we will use DEVICE_ATTR...
> > > 
> > > > +
> > > > +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,
> > > > +};
> > > 
> > > Please use ATTRIBUTE_GROUPS().
> > > 
> > > > +
> > > > +static int shtc1_probe(struct i2c_client *client,
> > > > +				const struct i2c_device_id *id)
> > > > +{
> > > > +	struct shtc1_data *data;
> > > 
> > > A local variable
> > > 	struct device *dev = &client->dev;
> > > would save you a number of dereference operations.
> > > 
> > > > +	int err;
> > > > +	struct i2c_adapter *adap = client->adapter;
> > > > +	char id_reg[2];
> > > > +
> > > > +	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
> > > > +		dev_err(&client->dev,
> > > > +			"adapter does not support plain i2c transactions\n");
> > > > +		return -ENODEV;
> > > > +	}
> > > > +
> > > > +	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
> > > > +
> > > Please no empty lines before error checks.
> > > 
> > > > +	if (err < 0) {
> > > 
> > > Also err != SHTC1_CMD_LENGTH.
> > 
> > This is similar to my question above, do you think it is better in that
> > case return -EIO or -ENODEV?
> > 
> 
> This is the probe function, so here you return -ENODEV.
> 
> > > 
> > > > +		dev_err(&client->dev, "could not send read command: %d\n", err);
> > > > +		return -ENODEV;
> > > > +	}
> > > > +	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
> > > > +	if (err != sizeof(id_reg)) {
> > > > +		dev_err(&client->dev, "could not read ID register: %d\n", err);
> > > > +		return -ENODEV;
> > > > +	}
> > > > +	if ((id_reg[1] & shtc1_id_reg_mask) != shtc1_id_reg_content) {
> > > > +		dev_err(&client->dev, "ID register doesn't match\n");
> > > > +		return -ENODEV;
> > > > +	}
> > > > +
> > > > +	data = devm_kzalloc(&client->dev, sizeof(struct shtc1_data),
> > > 
> > > 	sizeof(*data) is preferred.
> > > 
> > > > +				GFP_KERNEL);
> > > > +	if (!data)
> > > > +		return -ENOMEM;
> > > > +
> > > > +	/* defaults: blocking, high precision mode */
> > > > +	data->setup.blocking_io = 1;
> > > > +	data->setup.high_precision = 1;
> > > > +
> > > 		= true;
> > > for both.
> > > 
> > > > +	if (client->dev.platform_data)
> > > > +		data->setup = *(struct shtc1_platform_data *)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");
> > > > +		goto fail_free;
> > > > +		return err;
> > > 
> > > goto or return, but not both (doesn't this create a warning about unreachable code ?).
> > > goto is unnecessary, actually. return err is just fine.
> > 
> > I think, there were no warnings, but of course you are right...
> > 
> You might get the warning if you compile with C=1. Might be useful ...
> I'll do it when I merge the driver, so it will save me and you some time
> if you make sure that it is clean.
> 
> > > 
> > > > +	}
> > > > +	data->hwmon_dev = hwmon_device_register(&client->dev);
> > > 
> > > Please use devm_hwmon_device_register_with_groups().
> > > 
> > > 	struct device *hwmon_dev;
> > > 	...
> > > 	hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev, client->name,
> > > 							data, sht1c_groups);
> > > 	return PTR_ERR_OR_ZERO(hwmon_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;
> > > > +	}
> > > > +
> > > > +
> > > No more than one empty line, please.
> > > 
> > > > +	dev_info(&client->dev, "initialized\n");
> > > 
> > > Unnecessary noise.
> > > 
> > > > +
> > > > +	return 0;
> > > > +
> > > > +fail_remove_sysfs:
> > > > +	sysfs_remove_group(&client->dev.kobj, &shtc1_attr_group);
> > > > +fail_free:
> > > > +	kfree(data);
> > > 
> > > Unnecessary kfree.
> > 
> > I will remove these two lines at all.
> > 
> > > 
> > > > +
> > > > +	return err;
> > > > +}
> > > > +
> > > > +/**
> > > > + * shtc1_remove() - remove device
> > > > + * @client: I2C client device
> > > > + */
> > > > +static int 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;
> > > > +}
> > > 
> > > You can drop this entire function with the new hwmon API.
> > > 
> > > > +
> > > > +/* device ID table */
> > > > +static const struct i2c_device_id shtc1_id[] = {
> > > > +	{ "shtc1", 0 },
> > > > +	{ }
> > > > +};
> > > > +MODULE_DEVICE_TABLE(i2c, shtc1_id);
> > > > +
> > > > +static struct i2c_driver shtc1_i2c_driver = {
> > > > +	.driver.name = "shtc1",
> > > > +	.probe	= shtc1_probe,
> > > > +	.remove      = shtc1_remove,
> > > > +	.id_table    = shtc1_id,
> > > > +};
> > > > +
> > > > +/**
> > > > + * shtc1_init() - initialize driver
> > > > + *
> > > > + * Called when kernel is booted or module is inserted.
> > > > + * Returns 0 on success.
> > > > + */
> > > > +static int __init shtc1_init(void)
> > > > +{
> > > > +	return i2c_add_driver(&shtc1_i2c_driver);
> > > > +}
> > > > +module_init(shtc1_init);
> > > > +
> > > > +/*
> > > > + * shtc1_exit() - clean up driver
> > > > + *
> > > > + * Called when module is removed.
> > > > + */
> > > > +static void __exit shtc1_exit(void)
> > > > +{
> > > > +	i2c_del_driver(&shtc1_i2c_driver);
> > > > +}
> > > > +
> > > > +module_exit(shtc1_exit);
> > > 
> > > Please use module_i2c_driver().
> > > 
> > > > +
> > > > +
> > > > +MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.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..4629364
> > > > --- /dev/null
> > > > +++ b/include/linux/platform_data/shtc1.h
> > > > @@ -0,0 +1,24 @@
> > > > +/*
> > > > + * Copyright (C) 2012 Sensirion AG, Switzerland
> > > 
> > > 2014 ?
> > > 
> > > > + * 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;
> > > > +};
> > > > +
> > > 
> > > Please no empty line at the end.
> > > 
> > > Wondering ... do you plan to implement devicetree support (or have customers who need it) ?
> > > 
> > > I could imagine that a chip like this will be used, for example, on beagleboard, which would
> > > require devicetree support.
> > > 
> > 
> > Right now, I'm not aware of any particular time plan to implement device
> > tree support, but this may change, if somebody will request it...
> > 
> Fine with me, just asking.
> 
> Thanks,
> Guenter

Re: [lm-sensors] [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Tomas Pop]

Hi Guenter, 

Here is a corrected version, I tried to address your comments and I'm sending it
again with a kind request for comments - we will do some more extensive testing
before the final submission, but I would like to make the code as complete as
as possible before. Here is a list of changes to the previous version:

* positive, but incorrect return codes/lengths from i2c_mater_* are checked
* usleep_range used instead of msleep
* DEVICE_ATTR used instead of SENSOR_DEVICE_ATTR, ATTRIBITE_GROUPS used
* devm_hwmon_device_register_with_groups instead of devm_hwmon_device_register
* direct calls to sysfs_create_group and sysfs_create_group dropped
* shtc1_remove function dropped
* SHTW1 added to documentation and Kconfig
* documentation and formating updates/corrections

I did re-compile with C=1 as suggested and it is clear.

Patch was generated against kernel v3.15-rc3

Thanks,
Tomas

Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
---
 Documentation/hwmon/shtc1           |  41 ++++++
 drivers/hwmon/Kconfig               |  10 ++
 drivers/hwmon/Makefile              |   1 +
 drivers/hwmon/shtc1.c               | 266 ++++++++++++++++++++++++++++++++++++
 include/linux/platform_data/shtc1.h |  24 ++++
 5 files changed, 342 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..47c9ed1
--- /dev/null
+++ b/Documentation/hwmon/shtc1
@@ -0,0 +1,41 @@
+Kernel driver shtc1
+=========+
+Supported chips:
+  * Sensirion SHTC1
+    Prefix: 'shtc1'
+    Addresses scanned: none
+    Datasheet: Publicly available at the Sensirion website
+    http://www.sensirion.com/file/datasheet_shtc1
+
+  * Sensirion SHTW1
+    Prefix: 'shtc1'
+    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.
+2. high or low accuracy. Using high accuracy is strongly recommended.
+
+sysfs-Interface
+---------------
+
+temp1_input - temperature input
+humidity1_input - humidity input
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index bc196f4..f95ba5b 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1114,6 +1114,16 @@ 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 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 c48f987..1cc5273 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -125,6 +125,7 @@ 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..c94f670
--- /dev/null
+++ b/drivers/hwmon/shtc1.c
@@ -0,0 +1,266 @@
+/* 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_REG_CONTENT 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 device *hwmon_dev;
+	struct mutex update_lock;
+	bool valid;
+	unsigned long last_updated; /* In jiffies */
+
+	const unsigned char *command;
+	unsigned int nonblocking_wait_time;
+
+	struct shtc1_platform_data setup;
+
+	int temperature;
+	int humidity;
+};
+
+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: %d\n", ret);
+		return ret;
+	}
+	if (ret != SHTC1_CMD_LENGTH) {
+		dev_err(&client->dev, "wrong nr bytes written: %d\n", ret);
+		return -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 + 2000);
+
+	ret = i2c_master_recv(client, buf, bufsize);
+	if (ret != bufsize) {
+		dev_err(&client->dev, "failed to read values: %d\n", ret);
+		if (ret < 0)
+			return ret;
+		return -EIO;
+	}
+
+	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);
+
+	unsigned 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 = 0;
+
+	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 = 1;
+	}
+
+out:
+	mutex_unlock(&data->update_lock);
+
+	return ret = 0 ? data : ERR_PTR(ret);
+}
+
+static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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(temp1_input, S_IRUGO, shtc1_show_temperature, NULL);
+static DEVICE_ATTR(humidity1_input, S_IRUGO, shtc1_show_humidity, NULL);
+
+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)
+{
+	struct shtc1_data *data;
+	int err;
+	struct i2c_adapter *adap = client->adapter;
+	char id_reg[2];
+
+	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
+		dev_err(&client->dev,
+			"adapter does not support plain i2c transactions\n");
+		return -ENODEV;
+	}
+
+	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
+	if (err < 0) {
+		dev_err(&client->dev, "could not send read command: %d\n", err);
+		return -ENODEV;
+	}
+	if (err != SHTC1_CMD_LENGTH) {
+		dev_err(&client->dev, "num bytes send is wrong: %d\n", err);
+		return -ENODEV;
+	}
+	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
+	if (err != sizeof(id_reg)) {
+		dev_err(&client->dev, "could not read ID register: %d\n", err);
+		return -ENODEV;
+	}
+	if ((id_reg[1] & SHTC1_ID_REG_MASK) != SHTC1_ID_REG_CONTENT) {
+		dev_err(&client->dev, "ID register doesn't match\n");
+		return -ENODEV;
+	}
+
+	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	/* defaults: blocking, high precision mode */
+	data->setup.blocking_io = true;
+	data->setup.high_precision = true;
+
+	if (client->dev.platform_data)
+		data->setup = *(struct shtc1_platform_data *)client->dev.platform_data;
+	shtc1_select_command(data);
+	i2c_set_clientdata(client, data);
+	mutex_init(&data->update_lock);
+
+	data->hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev,
+								 client->name,
+								 data,
+								 shtc1_groups);
+	if (IS_ERR(data->hwmon_dev))
+		dev_dbg(&client->dev, "unable to register hwmon device\n");
+
+	return PTR_ERR_OR_ZERO(data->hwmon_dev);
+}
+
+/* device ID table */
+static const struct i2c_device_id shtc1_id[] = {
+	{ "shtc1", 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");
diff --git a/include/linux/platform_data/shtc1.h b/include/linux/platform_data/shtc1.h
new file mode 100644
index 0000000..b06e3db
--- /dev/null
+++ b/include/linux/platform_data/shtc1.h
@@ -0,0 +1,24 @@
+/*
+ * 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_ */
-- 
1.8.3.2


On Fre, 2014-05-02 at 16:15 -0700, Guenter Roeck wrote:
> On Fri, May 02, 2014 at 01:59:29PM -0700, Tomas Pop wrote:
> > Hi Guenter, thanks for comments! I will include them in third version,
> > but I have still few questions...
> > 
> > On Don, 2014-05-01 at 19:06 -0700, Guenter Roeck wrote:
> > > On 05/01/2014 04:05 PM, Tomas Pop wrote:
> > > > One more time this patch sent with correct settings of my email client
> > > > - I'm sorry for this.
> > > >
> > > > This is a second version of the driver for Sensirion SHTC1 humidity and
> > > > temperature sensor. Initial version was submitted in July 2012.
> > > > http://www.gossamer-threads.com/lists/linux/kernel/1569130#1569130
> > > >
> > > > We included suggested corrections formerly discussed in this list after
> > > > initial submission, but since it is quite a while, we are re-submitting
> > > > it again as a request for comments. Here is a list of important changes
> > > > to the initial version:
> > > >
> > > > * returning real error codes instead of -1 or -ENODEV
> > > > * using boolean variables instead of bitmaps where possible
> > > > * macros be16_to_cpup used for conversion of indianneess
> > > > * corrected formula for decoding of humidity and temperature values
> > > > * documentation update
> > > >
> > > > Patch was generated against kernel v3.15-rc3
> > > >
> > > > Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
> > > > ---
> > > >   Documentation/hwmon/shtc1           |  38 +++++
> > > >   drivers/hwmon/Kconfig               |  10 ++
> > > >   drivers/hwmon/Makefile              |   1 +
> > > >   drivers/hwmon/shtc1.c               | 323 ++++++++++++++++++++++++++++++++++++
> > > >   include/linux/platform_data/shtc1.h |  24 +++
> > > >   5 files changed, 396 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..6a72ae2d
> > > > --- /dev/null
> > > > +++ b/Documentation/hwmon/shtc1
> > > > @@ -0,0 +1,38 @@
> > > > +Kernel driver shtc1
> > > > +=========> > > > +
> > > > +Supported chips:
> > > > +  * Sensirion SHTC1
> > > > +    Prefix: 'shtc1'
> > > > +    Addresses scanned: none
> > > > +    Datasheet: Publicly available at the Sensirion website
> > > > +    http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_SHTC1_Datasheet.pdf
> > > 
> > > Ok to add SHTW1 here if it is known to work.
> > > Just say:
> > > 	Datasheet: Not publicly available
> > 
> > Actually, there is no way to find out, if you are speaking 
> > to SHTC1 or SHTW1. (i.e., the id is the same for both).
> > So I will add it here and we will provide link to data-sheet 
> > later in a separate patch.
> > 
> Ok.
> 
> > > > +
> > > > +Author:
> > > > +  Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> > > > +
> > > > +Description
> > > > +-----------
> > > > +
> > > > +This driver implements support for the Sensirion  SHTC1 chip, a humidity and
> > > 
> > > Two spaces
> > > 
> > > > +temperature sensor. Temperature is measured in degrees celsius, relative
> > > > +humidity is expressed as a percentage. Driver can be used as well for SHTW1
> > > > +chip, that has the same electrical interface, but datasheet has not been
> > > 
> > > ... for SHTW1, which has the same electrical interface.
> > > 
> > > > +yet published.
> > > > +
> > > 
> > > Either add support for the second now, or don't mention it at all
> > > (especially if the chip has a different ID and you don't want to add
> > > that ID at this point for some reason).
> > > 
> > > > +The device communicates with the I2C protocol. All sensors are set to the same
> > > 
> > > ... are set to I2C address 0x70.
> > > 
> > > > +I2C address 0x70, so an entry with I2C_BOARD_INFO("shtc1", 0x70) can be used
> > > > +in the board setup code. See Documentation/i2c/instantiating-devices for
> > > > +other methods to instantiate the device.
> > > > +
> > > I would suggest to just refer to the instantiating-devices document and drop
> > > the I2C_BOARD_INFO example.
> > > 
> > > > +Furthermore, there are two configuration options by means of platform_data:
> > > 
> > > options configurable by means ...
> > > 
> > > > +1. blocking (pull the I2C clock line down while performing the measurement) or
> > > > +   non-blocking, mode. Blocking mode will guarantee the fastest result, but
> > > 
> > > non-blocking mode (no comma)
> > > 
> > > > +   the I2C bus will be busy during that time
> > > 
> > > 					that time.
> > > 
> > > > +2. high or low accuracy. Using high accuracy is always recommended.
> > > > +
> > > > +sysfs-Interface
> > > > +---------------
> > > > +
> > > > +temp1_input - temperature input
> > > > +humidity1_input - humidity input
> > > > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > > > index bc196f4..4d58149 100644
> > > > --- a/drivers/hwmon/Kconfig
> > > > +++ b/drivers/hwmon/Kconfig
> > > > @@ -1114,6 +1114,16 @@ 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 humidity
> > > 
> > > and SHTW1 ?
> > 
> > I will add SHTW1 here as well
> > 
> > > 
> > > > +	  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 c48f987..1cc5273 100644
> > > > --- a/drivers/hwmon/Makefile
> > > > +++ b/drivers/hwmon/Makefile
> > > > @@ -125,6 +125,7 @@ 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..96d398b
> > > > --- /dev/null
> > > > +++ b/drivers/hwmon/shtc1.c
> > > > @@ -0,0 +1,323 @@
> > > > +/* Sensirion SHTC1 humidity and temperature sensor driver
> > > > + *
> > > > + * Copyright (C) 2012 Sensirion AG, Switzerland
> > > 
> > > 2014 ?
> > > 
> > > > + * Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
> > > > + *
> > > Is Johannes still involved ?
> > 
> > Yes, Johannes is aware of this re-submission, but I will try to take
> > care about the process this time. I will add him in CC.
> > 
> > > 
> > > > + * 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.
> > > > + *
> > > > + * Data sheet available soon
> > > > + *  TODO: add link
> > > 
> > > Datasheet is referenced in documentation, so you don't need the link here.
> > > Better to keep it in one please, then there is only one place to change
> > > if it needs to be updated.
> > > > + */
> > > > +
> > > > +#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 and constants for reading the ID register */
> > > > +static const unsigned char shtc1_cmd_read_id_reg[]	     = { 0xef, 0xc8 };
> > > > +static const unsigned char shtc1_id_reg_content = 0x07;
> > > > +static const unsigned char shtc1_id_reg_mask    = 0x1f;
> > > > +
> > > Please use defines here. There is no benefit to have one-byte constants.
> > > If the W1 chip has a different ID, you might as well add it in now and detect it.
> > > 
> > > > +/* delays for non-blocking i2c commands */
> > > > +#define SHTC1_NONBLOCKING_WAIT_TIME_HPM  10
> > > > +#define SHTC1_NONBLOCKING_WAIT_TIME_LPM   1
> 
> Just noticed. Please use tabs between definition and the number.
> 
> > > 
> > > 	delay in what ? ms ? us ? seconds ?
> > > 	Please specify.
> > > 
> > 
> > The delays are in miliseconds. You mean to use it in names - e.g.,
> > SHTC1_NONBLOCKING_WAIT_TIME_LPM_MS? Or comment is enough?
> > 
> 
> Just a comment is enough. No name change, please; that would be overkill.
> 
> #define SHTC1_NONBLOCKING_WAIT_TIME_HPM	10	/* in ms */
> 
> > May be I should then rename 
> > also data->nonblocking_wait_time to data->nonblocking_wait_time_ms...
> > 
> No. 
> 
> > > > +
> > > > +#define SHTC1_CMD_LENGTH      2
> > > > +#define SHTC1_RESPONSE_LENGTH 6
> > > > +
> > > > +struct shtc1_data {
> > > > +	struct device *hwmon_dev;
> > > > +	struct mutex update_lock;
> > > > +	bool valid;
> > > > +	unsigned long last_updated; /* In jiffies */
> > > > +
> > > > +	const unsigned char *command;
> > > > +	unsigned int nonblocking_wait_time;
> > > > +
> > > > +	struct shtc1_platform_data 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;
> > > > +	}
> > > > +}
> > > > +
> > > Please move this function down, just before the probe function.
> > > 
> > > > +static int shtc1_update_values(struct i2c_client *client,
> > > > +				struct shtc1_data *data,
> > > > +				char *buf,
> > > > +				int bufsize)
> > > 
> > > Please align continuation lines with (, and limit the number of continuation lines
> > > where possible (eg, buf and bufsize fit into one line).
> > > 
> > > > +{
> > > > +	int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
> > > > +	if (ret < 0) {
> > > > +		dev_err(&client->dev, "failed to send command: %d", ret);
> > > 
> > > Newline missing.
> > > 
> > > > +		return ret;
> > > > +	}
> > > 
> > > There is another error condition: the function returns the number of bytes written,
> > > which can be smaller than SHTC1_CMD_LENGTH.
> > > 
> > > > +
> > > > +	/*
> > > > +	* 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().
> > > > +	*
> > > > +	* TODO: consider usleep_range
> > > 
> > > Please do ... and fix all the other TODOs in case I missed any.
> > 
> > Sure. I checked the documentation and if I understand it correctly, we  should really use in this case something like:
> > 	if (!data->setup.blocking_io)
> > 		usleep_range(data->nonblocking_wait_time_min_us,
> > 			     data->nonblocking_wait_time_max_us);
> > 
> > where max_time will be min_time plus some fixed margin, e.g, 2000us
> > 
> > sounds this reasonable to you?
> > 
> Yes, but you don't need the second variable. Just add the fixed offset,
> 
> 		usleep_range(data->nonblocking_wait_time,
> 			     data->nonblocking_wait_time + 2000);
> 
> [ and of course specify the timeout in uS, not mS ].
> 
> > > 
> > > > +	*/
> > > > +	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);
> > > 
> > > Newline.
> > > 
> > > The return value can be >= 0, meaning the calling code can get confused.
> > > Please make sure that the function always returns a valid error code.
> > 
> > Ok, so return -EIO or better -ENODEV?
> > 
> -EIO seems common. -ENODEV would be wrong.
> 
> > > 
> > > > +		return ret;
> > > > +	}
> > > > +
> > > > +	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);
> > > > +
> > > > +	unsigned 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;
> > > 
> > > So ret gets pre-initialized with 1 if valid = 0. Doesn't really make sense.
> > > Just initialize it with 0 above.
> > > 
> > > 	int ret = 0;
> > 
> > Sure, thanks.
> > 
> > > 
> > > > +
> > > > +	if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
> > > > +		ret = shtc1_update_values(client, data, buf, sizeof(buf));
> > > > +
> > > Unnecessary empty line.
> > > 
> > > > +		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));
> > > 
> > > 	Spaces before and after '+'
> > > 
> > > Just wondering .. what is in buf[2] and buf[5] ?
> > 
> > There are two CRC-8 checksums: 
> > buf[2] for humidity, buf[5] for temperature value. We would prefer
> > not to check CRC it in this version of the driver...
> > 
> Fine with me - your chip, your call - just asking.
> 
> > > 
> > > > +		data->humidity = ((12500 * val) >> 13);
> > > > +
> > > > +		data->last_updated = jiffies;
> > > > +		data->valid = 1;
> > > 
> > > 			= true;
> > > 
> > > > +	}
> > > > +
> > > > +out:
> > > > +	mutex_unlock(&data->update_lock);
> > > > +
> > > > +	return ret = 0 ? data : ERR_PTR(ret);
> > > > +}
> > > > +
> > > > +static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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 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);
> > > 
> > > You don't need SENSOR_DEVICE_ATTR here. DEVICE_ATTR is sufficient.
> > > 
> > > Another option would be to store temperature and humidity in an array
> > > and use the last parameter of SENSOR_DEVICE_ATTR to index the array.
> > > This way you would only need a single show function. I'll leave
> > > that up to you.
> > 
> > Ok, then we will use DEVICE_ATTR...
> > > 
> > > > +
> > > > +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,
> > > > +};
> > > 
> > > Please use ATTRIBUTE_GROUPS().
> > > 
> > > > +
> > > > +static int shtc1_probe(struct i2c_client *client,
> > > > +				const struct i2c_device_id *id)
> > > > +{
> > > > +	struct shtc1_data *data;
> > > 
> > > A local variable
> > > 	struct device *dev = &client->dev;
> > > would save you a number of dereference operations.
> > > 
> > > > +	int err;
> > > > +	struct i2c_adapter *adap = client->adapter;
> > > > +	char id_reg[2];
> > > > +
> > > > +	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
> > > > +		dev_err(&client->dev,
> > > > +			"adapter does not support plain i2c transactions\n");
> > > > +		return -ENODEV;
> > > > +	}
> > > > +
> > > > +	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
> > > > +
> > > Please no empty lines before error checks.
> > > 
> > > > +	if (err < 0) {
> > > 
> > > Also err != SHTC1_CMD_LENGTH.
> > 
> > This is similar to my question above, do you think it is better in that
> > case return -EIO or -ENODEV?
> > 
> 
> This is the probe function, so here you return -ENODEV.
> 
> > > 
> > > > +		dev_err(&client->dev, "could not send read command: %d\n", err);
> > > > +		return -ENODEV;
> > > > +	}
> > > > +	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
> > > > +	if (err != sizeof(id_reg)) {
> > > > +		dev_err(&client->dev, "could not read ID register: %d\n", err);
> > > > +		return -ENODEV;
> > > > +	}
> > > > +	if ((id_reg[1] & shtc1_id_reg_mask) != shtc1_id_reg_content) {
> > > > +		dev_err(&client->dev, "ID register doesn't match\n");
> > > > +		return -ENODEV;
> > > > +	}
> > > > +
> > > > +	data = devm_kzalloc(&client->dev, sizeof(struct shtc1_data),
> > > 
> > > 	sizeof(*data) is preferred.
> > > 
> > > > +				GFP_KERNEL);
> > > > +	if (!data)
> > > > +		return -ENOMEM;
> > > > +
> > > > +	/* defaults: blocking, high precision mode */
> > > > +	data->setup.blocking_io = 1;
> > > > +	data->setup.high_precision = 1;
> > > > +
> > > 		= true;
> > > for both.
> > > 
> > > > +	if (client->dev.platform_data)
> > > > +		data->setup = *(struct shtc1_platform_data *)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");
> > > > +		goto fail_free;
> > > > +		return err;
> > > 
> > > goto or return, but not both (doesn't this create a warning about unreachable code ?).
> > > goto is unnecessary, actually. return err is just fine.
> > 
> > I think, there were no warnings, but of course you are right...
> > 
> You might get the warning if you compile with C=1. Might be useful ...
> I'll do it when I merge the driver, so it will save me and you some time
> if you make sure that it is clean.
> 
> > > 
> > > > +	}
> > > > +	data->hwmon_dev = hwmon_device_register(&client->dev);
> > > 
> > > Please use devm_hwmon_device_register_with_groups().
> > > 
> > > 	struct device *hwmon_dev;
> > > 	...
> > > 	hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev, client->name,
> > > 							data, sht1c_groups);
> > > 	return PTR_ERR_OR_ZERO(hwmon_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;
> > > > +	}
> > > > +
> > > > +
> > > No more than one empty line, please.
> > > 
> > > > +	dev_info(&client->dev, "initialized\n");
> > > 
> > > Unnecessary noise.
> > > 
> > > > +
> > > > +	return 0;
> > > > +
> > > > +fail_remove_sysfs:
> > > > +	sysfs_remove_group(&client->dev.kobj, &shtc1_attr_group);
> > > > +fail_free:
> > > > +	kfree(data);
> > > 
> > > Unnecessary kfree.
> > 
> > I will remove these two lines at all.
> > 
> > > 
> > > > +
> > > > +	return err;
> > > > +}
> > > > +
> > > > +/**
> > > > + * shtc1_remove() - remove device
> > > > + * @client: I2C client device
> > > > + */
> > > > +static int 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;
> > > > +}
> > > 
> > > You can drop this entire function with the new hwmon API.
> > > 
> > > > +
> > > > +/* device ID table */
> > > > +static const struct i2c_device_id shtc1_id[] = {
> > > > +	{ "shtc1", 0 },
> > > > +	{ }
> > > > +};
> > > > +MODULE_DEVICE_TABLE(i2c, shtc1_id);
> > > > +
> > > > +static struct i2c_driver shtc1_i2c_driver = {
> > > > +	.driver.name = "shtc1",
> > > > +	.probe	= shtc1_probe,
> > > > +	.remove      = shtc1_remove,
> > > > +	.id_table    = shtc1_id,
> > > > +};
> > > > +
> > > > +/**
> > > > + * shtc1_init() - initialize driver
> > > > + *
> > > > + * Called when kernel is booted or module is inserted.
> > > > + * Returns 0 on success.
> > > > + */
> > > > +static int __init shtc1_init(void)
> > > > +{
> > > > +	return i2c_add_driver(&shtc1_i2c_driver);
> > > > +}
> > > > +module_init(shtc1_init);
> > > > +
> > > > +/*
> > > > + * shtc1_exit() - clean up driver
> > > > + *
> > > > + * Called when module is removed.
> > > > + */
> > > > +static void __exit shtc1_exit(void)
> > > > +{
> > > > +	i2c_del_driver(&shtc1_i2c_driver);
> > > > +}
> > > > +
> > > > +module_exit(shtc1_exit);
> > > 
> > > Please use module_i2c_driver().
> > > 
> > > > +
> > > > +
> > > > +MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.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..4629364
> > > > --- /dev/null
> > > > +++ b/include/linux/platform_data/shtc1.h
> > > > @@ -0,0 +1,24 @@
> > > > +/*
> > > > + * Copyright (C) 2012 Sensirion AG, Switzerland
> > > 
> > > 2014 ?
> > > 
> > > > + * 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;
> > > > +};
> > > > +
> > > 
> > > Please no empty line at the end.
> > > 
> > > Wondering ... do you plan to implement devicetree support (or have customers who need it) ?
> > > 
> > > I could imagine that a chip like this will be used, for example, on beagleboard, which would
> > > require devicetree support.
> > > 
> > 
> > Right now, I'm not aware of any particular time plan to implement device
> > tree support, but this may change, if somebody will request it...
> > 
> Fine with me, just asking.
> 
> Thanks,
> Guenter



_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

Re: [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Guenter Roeck]

Hi Tomas,

On 05/05/2014 06:03 PM, Tomas Pop wrote:
> Hi Guenter,
>
> Here is a corrected version, I tried to address your comments and I'm sending it
> again with a kind request for comments - we will do some more extensive testing
> before the final submission, but I would like to make the code as complete as
> as possible before. Here is a list of changes to the previous version:
>
Comments below. But I don't think you tested this with real HW, did you ? :-)

> * positive, but incorrect return codes/lengths from i2c_mater_* are checked
> * usleep_range used instead of msleep
> * DEVICE_ATTR used instead of SENSOR_DEVICE_ATTR, ATTRIBITE_GROUPS used
> * devm_hwmon_device_register_with_groups instead of devm_hwmon_device_register
> * direct calls to sysfs_create_group and sysfs_create_group dropped
> * shtc1_remove function dropped
> * SHTW1 added to documentation and Kconfig
> * documentation and formating updates/corrections
>
> I did re-compile with C=1 as suggested and it is clear.
>
> Patch was generated against kernel v3.15-rc3
>
> Thanks,
> Tomas
>
> Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
> ---
>   Documentation/hwmon/shtc1           |  41 ++++++
>   drivers/hwmon/Kconfig               |  10 ++
>   drivers/hwmon/Makefile              |   1 +
>   drivers/hwmon/shtc1.c               | 266 ++++++++++++++++++++++++++++++++++++
>   include/linux/platform_data/shtc1.h |  24 ++++
>   5 files changed, 342 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..47c9ed1
> --- /dev/null
> +++ b/Documentation/hwmon/shtc1
> @@ -0,0 +1,41 @@
> +Kernel driver shtc1
> +===================
> +
> +Supported chips:
> +  * Sensirion SHTC1
> +    Prefix: 'shtc1'
> +    Addresses scanned: none
> +    Datasheet: Publicly available at the Sensirion website
> +    http://www.sensirion.com/file/datasheet_shtc1
> +
> +  * Sensirion SHTW1
> +    Prefix: 'shtc1'
> +    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.
> +2. high or low accuracy. Using high accuracy is strongly recommended.
> +
> +sysfs-Interface
> +---------------
> +
> +temp1_input - temperature input
> +humidity1_input - humidity input
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index bc196f4..f95ba5b 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1114,6 +1114,16 @@ 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 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 c48f987..1cc5273 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -125,6 +125,7 @@ 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..c94f670
> --- /dev/null
> +++ b/drivers/hwmon/shtc1.c
> @@ -0,0 +1,266 @@
> +/* 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_REG_CONTENT 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 device *hwmon_dev;

Not needed. But you need the i2c client here.

> +	struct mutex update_lock;
> +	bool valid;
> +	unsigned long last_updated; /* In jiffies */
> +
> +	const unsigned char *command;
> +	unsigned int nonblocking_wait_time;
> +
> +	struct shtc1_platform_data setup;
> +
> +	int temperature;
> +	int humidity;
> +};
> +
> +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: %d\n", ret);
> +		return ret;
> +	}
> +	if (ret != SHTC1_CMD_LENGTH) {
> +		dev_err(&client->dev, "wrong nr bytes written: %d\n", ret);
> +		return -EIO;
> +	}

Can you merge those into one ? Something like

	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

	s/for/For/

> +	* have to wait ourselves.
> +	*/
> +	if (!data->setup.blocking_io)
> +		usleep_range(data->nonblocking_wait_time,
> +			     data->nonblocking_wait_time + 2000);
> +
In the low precision case, this results in a wait time of 1 to 3 ms.
How about giving it a 1 ms range ? Seems to me that should be enough
and an acceptable trade-off.

> +	ret = i2c_master_recv(client, buf, bufsize);
> +	if (ret != bufsize) {
> +		dev_err(&client->dev, "failed to read values: %d\n", ret);
> +		if (ret < 0)
> +			return ret;
> +		return -EIO;

or simpler
		return ret < 0 ? ret : -EIO;

> +	}
> +
> +	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);
> +

That won't work with the new ABI (please test ;-).
You need something like
	struct shtc1_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->client;

This is because the attributes are now attached to the hwmon device,
no longer to the i2c device. The ABI saves the pointer to 'data'
in drvdata for the hwmon device, so you can get it with dev_get_drvdata().

> +	unsigned 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 = 0;

A bit excessive. We all know C, or should. Just make it
	int ret = 0;
above; you don't need any comments here.

> +
> +	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 = 1;
> +	}
> +
> +out:
> +	mutex_unlock(&data->update_lock);
> +
> +	return ret == 0 ? data : ERR_PTR(ret);
> +}
> +
> +static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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(temp1_input, S_IRUGO, shtc1_show_temperature, NULL);
> +static DEVICE_ATTR(humidity1_input, S_IRUGO, shtc1_show_humidity, NULL);
> +
> +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)
> +{
> +	struct shtc1_data *data;
> +	int err;
> +	struct i2c_adapter *adap = client->adapter;
> +	char id_reg[2];
> +
I would suggest a local variable dev here
	struct device *dev = &client->dev;
to save all the client->dev dereferences below.

> +	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
> +		dev_err(&client->dev,
> +			"adapter does not support plain i2c transactions\n");
> +		return -ENODEV;
> +	}
> +
> +	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
> +	if (err < 0) {
> +		dev_err(&client->dev, "could not send read command: %d\n", err);

read id command

> +		return -ENODEV;
> +	}
> +	if (err != SHTC1_CMD_LENGTH) {
> +		dev_err(&client->dev, "num bytes send is wrong: %d\n", err);

sent

Also, I would prefer a single if statement.

> +		return -ENODEV;
> +	}
> +	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
> +	if (err != sizeof(id_reg)) {
> +		dev_err(&client->dev, "could not read ID register: %d\n", err);
> +		return -ENODEV;
> +	}
> +	if ((id_reg[1] & SHTC1_ID_REG_MASK) != SHTC1_ID_REG_CONTENT) {
> +		dev_err(&client->dev, "ID register doesn't match\n");
> +		return -ENODEV;
> +	}
> +
> +	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	/* defaults: blocking, high precision mode */
> +	data->setup.blocking_io = true;
> +	data->setup.high_precision = true;
> +
> +	if (client->dev.platform_data)
> +		data->setup = *(struct shtc1_platform_data *)client->dev.platform_data;

Line too long here. One way to solve it would be to use a local dev variable
as sugested above.

> +	shtc1_select_command(data);
> +	i2c_set_clientdata(client, data);

Not needed. But you need to save client for the update function.
	data->client = client;

> +	mutex_init(&data->update_lock);
> +
> +	data->hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev,

You don't need to keep hwmon_dev in the data structure. Just use a local variable.

> +								 client->name,
> +								 data,
> +								 shtc1_groups);
> +	if (IS_ERR(data->hwmon_dev))
> +		dev_dbg(&client->dev, "unable to register hwmon device\n");
> +
> +	return PTR_ERR_OR_ZERO(data->hwmon_dev);
> +}
> +
> +/* device ID table */
> +static const struct i2c_device_id shtc1_id[] = {
> +	{ "shtc1", 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");
> diff --git a/include/linux/platform_data/shtc1.h b/include/linux/platform_data/shtc1.h
> new file mode 100644
> index 0000000..b06e3db
> --- /dev/null
> +++ b/include/linux/platform_data/shtc1.h
> @@ -0,0 +1,24 @@
> +/*
> + * 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_ */
>

Re: [lm-sensors] [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Guenter Roeck]

Hi Tomas,

On 05/05/2014 06:03 PM, Tomas Pop wrote:
> Hi Guenter,
>
> Here is a corrected version, I tried to address your comments and I'm sending it
> again with a kind request for comments - we will do some more extensive testing
> before the final submission, but I would like to make the code as complete as
> as possible before. Here is a list of changes to the previous version:
>
Comments below. But I don't think you tested this with real HW, did you ? :-)

> * positive, but incorrect return codes/lengths from i2c_mater_* are checked
> * usleep_range used instead of msleep
> * DEVICE_ATTR used instead of SENSOR_DEVICE_ATTR, ATTRIBITE_GROUPS used
> * devm_hwmon_device_register_with_groups instead of devm_hwmon_device_register
> * direct calls to sysfs_create_group and sysfs_create_group dropped
> * shtc1_remove function dropped
> * SHTW1 added to documentation and Kconfig
> * documentation and formating updates/corrections
>
> I did re-compile with C=1 as suggested and it is clear.
>
> Patch was generated against kernel v3.15-rc3
>
> Thanks,
> Tomas
>
> Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
> ---
>   Documentation/hwmon/shtc1           |  41 ++++++
>   drivers/hwmon/Kconfig               |  10 ++
>   drivers/hwmon/Makefile              |   1 +
>   drivers/hwmon/shtc1.c               | 266 ++++++++++++++++++++++++++++++++++++
>   include/linux/platform_data/shtc1.h |  24 ++++
>   5 files changed, 342 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..47c9ed1
> --- /dev/null
> +++ b/Documentation/hwmon/shtc1
> @@ -0,0 +1,41 @@
> +Kernel driver shtc1
> +=========> +
> +Supported chips:
> +  * Sensirion SHTC1
> +    Prefix: 'shtc1'
> +    Addresses scanned: none
> +    Datasheet: Publicly available at the Sensirion website
> +    http://www.sensirion.com/file/datasheet_shtc1
> +
> +  * Sensirion SHTW1
> +    Prefix: 'shtc1'
> +    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.
> +2. high or low accuracy. Using high accuracy is strongly recommended.
> +
> +sysfs-Interface
> +---------------
> +
> +temp1_input - temperature input
> +humidity1_input - humidity input
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index bc196f4..f95ba5b 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1114,6 +1114,16 @@ 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 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 c48f987..1cc5273 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -125,6 +125,7 @@ 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..c94f670
> --- /dev/null
> +++ b/drivers/hwmon/shtc1.c
> @@ -0,0 +1,266 @@
> +/* 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_REG_CONTENT 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 device *hwmon_dev;

Not needed. But you need the i2c client here.

> +	struct mutex update_lock;
> +	bool valid;
> +	unsigned long last_updated; /* In jiffies */
> +
> +	const unsigned char *command;
> +	unsigned int nonblocking_wait_time;
> +
> +	struct shtc1_platform_data setup;
> +
> +	int temperature;
> +	int humidity;
> +};
> +
> +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: %d\n", ret);
> +		return ret;
> +	}
> +	if (ret != SHTC1_CMD_LENGTH) {
> +		dev_err(&client->dev, "wrong nr bytes written: %d\n", ret);
> +		return -EIO;
> +	}

Can you merge those into one ? Something like

	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

	s/for/For/

> +	* have to wait ourselves.
> +	*/
> +	if (!data->setup.blocking_io)
> +		usleep_range(data->nonblocking_wait_time,
> +			     data->nonblocking_wait_time + 2000);
> +
In the low precision case, this results in a wait time of 1 to 3 ms.
How about giving it a 1 ms range ? Seems to me that should be enough
and an acceptable trade-off.

> +	ret = i2c_master_recv(client, buf, bufsize);
> +	if (ret != bufsize) {
> +		dev_err(&client->dev, "failed to read values: %d\n", ret);
> +		if (ret < 0)
> +			return ret;
> +		return -EIO;

or simpler
		return ret < 0 ? ret : -EIO;

> +	}
> +
> +	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);
> +

That won't work with the new ABI (please test ;-).
You need something like
	struct shtc1_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->client;

This is because the attributes are now attached to the hwmon device,
no longer to the i2c device. The ABI saves the pointer to 'data'
in drvdata for the hwmon device, so you can get it with dev_get_drvdata().

> +	unsigned 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 = 0;

A bit excessive. We all know C, or should. Just make it
	int ret = 0;
above; you don't need any comments here.

> +
> +	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 = 1;
> +	}
> +
> +out:
> +	mutex_unlock(&data->update_lock);
> +
> +	return ret = 0 ? data : ERR_PTR(ret);
> +}
> +
> +static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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(temp1_input, S_IRUGO, shtc1_show_temperature, NULL);
> +static DEVICE_ATTR(humidity1_input, S_IRUGO, shtc1_show_humidity, NULL);
> +
> +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)
> +{
> +	struct shtc1_data *data;
> +	int err;
> +	struct i2c_adapter *adap = client->adapter;
> +	char id_reg[2];
> +
I would suggest a local variable dev here
	struct device *dev = &client->dev;
to save all the client->dev dereferences below.

> +	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
> +		dev_err(&client->dev,
> +			"adapter does not support plain i2c transactions\n");
> +		return -ENODEV;
> +	}
> +
> +	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
> +	if (err < 0) {
> +		dev_err(&client->dev, "could not send read command: %d\n", err);

read id command

> +		return -ENODEV;
> +	}
> +	if (err != SHTC1_CMD_LENGTH) {
> +		dev_err(&client->dev, "num bytes send is wrong: %d\n", err);

sent

Also, I would prefer a single if statement.

> +		return -ENODEV;
> +	}
> +	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
> +	if (err != sizeof(id_reg)) {
> +		dev_err(&client->dev, "could not read ID register: %d\n", err);
> +		return -ENODEV;
> +	}
> +	if ((id_reg[1] & SHTC1_ID_REG_MASK) != SHTC1_ID_REG_CONTENT) {
> +		dev_err(&client->dev, "ID register doesn't match\n");
> +		return -ENODEV;
> +	}
> +
> +	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	/* defaults: blocking, high precision mode */
> +	data->setup.blocking_io = true;
> +	data->setup.high_precision = true;
> +
> +	if (client->dev.platform_data)
> +		data->setup = *(struct shtc1_platform_data *)client->dev.platform_data;

Line too long here. One way to solve it would be to use a local dev variable
as sugested above.

> +	shtc1_select_command(data);
> +	i2c_set_clientdata(client, data);

Not needed. But you need to save client for the update function.
	data->client = client;

> +	mutex_init(&data->update_lock);
> +
> +	data->hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev,

You don't need to keep hwmon_dev in the data structure. Just use a local variable.

> +								 client->name,
> +								 data,
> +								 shtc1_groups);
> +	if (IS_ERR(data->hwmon_dev))
> +		dev_dbg(&client->dev, "unable to register hwmon device\n");
> +
> +	return PTR_ERR_OR_ZERO(data->hwmon_dev);
> +}
> +
> +/* device ID table */
> +static const struct i2c_device_id shtc1_id[] = {
> +	{ "shtc1", 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");
> diff --git a/include/linux/platform_data/shtc1.h b/include/linux/platform_data/shtc1.h
> new file mode 100644
> index 0000000..b06e3db
> --- /dev/null
> +++ b/include/linux/platform_data/shtc1.h
> @@ -0,0 +1,24 @@
> +/*
> + * 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_ */
>


_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

Re: [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Tomas Pop]

Hi Guenter, 

Thanks a lot for comments and patience - with the testing you are right,
I'm still waiting for board, where I will be able to run latest kernel
and have the chip wired in - sorry for this...

Thanks, Tomas

On Mon, 2014-05-05 at 18:39 -0700, Guenter Roeck wrote:
> Hi Tomas,
> 
> On 05/05/2014 06:03 PM, Tomas Pop wrote:
> > Hi Guenter,
> >
> > Here is a corrected version, I tried to address your comments and I'm sending it
> > again with a kind request for comments - we will do some more extensive testing
> > before the final submission, but I would like to make the code as complete as
> > as possible before. Here is a list of changes to the previous version:
> >
> Comments below. But I don't think you tested this with real HW, did you ? :-)
> 
> > * positive, but incorrect return codes/lengths from i2c_mater_* are checked
> > * usleep_range used instead of msleep
> > * DEVICE_ATTR used instead of SENSOR_DEVICE_ATTR, ATTRIBITE_GROUPS used
> > * devm_hwmon_device_register_with_groups instead of devm_hwmon_device_register
> > * direct calls to sysfs_create_group and sysfs_create_group dropped
> > * shtc1_remove function dropped
> > * SHTW1 added to documentation and Kconfig
> > * documentation and formating updates/corrections
> >
> > I did re-compile with C=1 as suggested and it is clear.
> >
> > Patch was generated against kernel v3.15-rc3
> >
> > Thanks,
> > Tomas
> >
> > Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
> > ---
> >   Documentation/hwmon/shtc1           |  41 ++++++
> >   drivers/hwmon/Kconfig               |  10 ++
> >   drivers/hwmon/Makefile              |   1 +
> >   drivers/hwmon/shtc1.c               | 266 ++++++++++++++++++++++++++++++++++++
> >   include/linux/platform_data/shtc1.h |  24 ++++
> >   5 files changed, 342 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..47c9ed1
> > --- /dev/null
> > +++ b/Documentation/hwmon/shtc1
> > @@ -0,0 +1,41 @@
> > +Kernel driver shtc1
> > +===================
> > +
> > +Supported chips:
> > +  * Sensirion SHTC1
> > +    Prefix: 'shtc1'
> > +    Addresses scanned: none
> > +    Datasheet: Publicly available at the Sensirion website
> > +    http://www.sensirion.com/file/datasheet_shtc1
> > +
> > +  * Sensirion SHTW1
> > +    Prefix: 'shtc1'
> > +    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.
> > +2. high or low accuracy. Using high accuracy is strongly recommended.
> > +
> > +sysfs-Interface
> > +---------------
> > +
> > +temp1_input - temperature input
> > +humidity1_input - humidity input
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index bc196f4..f95ba5b 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -1114,6 +1114,16 @@ 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 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 c48f987..1cc5273 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -125,6 +125,7 @@ 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..c94f670
> > --- /dev/null
> > +++ b/drivers/hwmon/shtc1.c
> > @@ -0,0 +1,266 @@
> > +/* 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_REG_CONTENT 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 device *hwmon_dev;
> 
> Not needed. But you need the i2c client here.
> 
> > +	struct mutex update_lock;
> > +	bool valid;
> > +	unsigned long last_updated; /* In jiffies */
> > +
> > +	const unsigned char *command;
> > +	unsigned int nonblocking_wait_time;
> > +
> > +	struct shtc1_platform_data setup;
> > +
> > +	int temperature;
> > +	int humidity;
> > +};
> > +
> > +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: %d\n", ret);
> > +		return ret;
> > +	}
> > +	if (ret != SHTC1_CMD_LENGTH) {
> > +		dev_err(&client->dev, "wrong nr bytes written: %d\n", ret);
> > +		return -EIO;
> > +	}
> 
> Can you merge those into one ? Something like
> 
> 	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
> 
> 	s/for/For/
> 
> > +	* have to wait ourselves.
> > +	*/
> > +	if (!data->setup.blocking_io)
> > +		usleep_range(data->nonblocking_wait_time,
> > +			     data->nonblocking_wait_time + 2000);
> > +
> In the low precision case, this results in a wait time of 1 to 3 ms.
> How about giving it a 1 ms range ? Seems to me that should be enough
> and an acceptable trade-off.
> 
> > +	ret = i2c_master_recv(client, buf, bufsize);
> > +	if (ret != bufsize) {
> > +		dev_err(&client->dev, "failed to read values: %d\n", ret);
> > +		if (ret < 0)
> > +			return ret;
> > +		return -EIO;
> 
> or simpler
> 		return ret < 0 ? ret : -EIO;
> 
> > +	}
> > +
> > +	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);
> > +
> 
> That won't work with the new ABI (please test ;-).
> You need something like
> 	struct shtc1_data *data = dev_get_drvdata(dev);
> 	struct i2c_client *client = data->client;
> 
> This is because the attributes are now attached to the hwmon device,
> no longer to the i2c device. The ABI saves the pointer to 'data'
> in drvdata for the hwmon device, so you can get it with dev_get_drvdata().
> 
> > +	unsigned 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 = 0;
> 
> A bit excessive. We all know C, or should. Just make it
> 	int ret = 0;
> above; you don't need any comments here.
> 
> > +
> > +	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 = 1;
> > +	}
> > +
> > +out:
> > +	mutex_unlock(&data->update_lock);
> > +
> > +	return ret == 0 ? data : ERR_PTR(ret);
> > +}
> > +
> > +static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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(temp1_input, S_IRUGO, shtc1_show_temperature, NULL);
> > +static DEVICE_ATTR(humidity1_input, S_IRUGO, shtc1_show_humidity, NULL);
> > +
> > +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)
> > +{
> > +	struct shtc1_data *data;
> > +	int err;
> > +	struct i2c_adapter *adap = client->adapter;
> > +	char id_reg[2];
> > +
> I would suggest a local variable dev here
> 	struct device *dev = &client->dev;
> to save all the client->dev dereferences below.
> 
> > +	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
> > +		dev_err(&client->dev,
> > +			"adapter does not support plain i2c transactions\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
> > +	if (err < 0) {
> > +		dev_err(&client->dev, "could not send read command: %d\n", err);
> 
> read id command
> 
> > +		return -ENODEV;
> > +	}
> > +	if (err != SHTC1_CMD_LENGTH) {
> > +		dev_err(&client->dev, "num bytes send is wrong: %d\n", err);
> 
> sent
> 
> Also, I would prefer a single if statement.
> 
> > +		return -ENODEV;
> > +	}
> > +	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
> > +	if (err != sizeof(id_reg)) {
> > +		dev_err(&client->dev, "could not read ID register: %d\n", err);
> > +		return -ENODEV;
> > +	}
> > +	if ((id_reg[1] & SHTC1_ID_REG_MASK) != SHTC1_ID_REG_CONTENT) {
> > +		dev_err(&client->dev, "ID register doesn't match\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
> > +	if (!data)
> > +		return -ENOMEM;
> > +
> > +	/* defaults: blocking, high precision mode */
> > +	data->setup.blocking_io = true;
> > +	data->setup.high_precision = true;
> > +
> > +	if (client->dev.platform_data)
> > +		data->setup = *(struct shtc1_platform_data *)client->dev.platform_data;
> 
> Line too long here. One way to solve it would be to use a local dev variable
> as sugested above.
> 
> > +	shtc1_select_command(data);
> > +	i2c_set_clientdata(client, data);
> 
> Not needed. But you need to save client for the update function.
> 	data->client = client;
> 
> > +	mutex_init(&data->update_lock);
> > +
> > +	data->hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev,
> 
> You don't need to keep hwmon_dev in the data structure. Just use a local variable.
> 
> > +								 client->name,
> > +								 data,
> > +								 shtc1_groups);
> > +	if (IS_ERR(data->hwmon_dev))
> > +		dev_dbg(&client->dev, "unable to register hwmon device\n");
> > +
> > +	return PTR_ERR_OR_ZERO(data->hwmon_dev);
> > +}
> > +
> > +/* device ID table */
> > +static const struct i2c_device_id shtc1_id[] = {
> > +	{ "shtc1", 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");
> > diff --git a/include/linux/platform_data/shtc1.h b/include/linux/platform_data/shtc1.h
> > new file mode 100644
> > index 0000000..b06e3db
> > --- /dev/null
> > +++ b/include/linux/platform_data/shtc1.h
> > @@ -0,0 +1,24 @@
> > +/*
> > + * 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_ */
> >
> 

Re: [lm-sensors] [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Tomas Pop]

Hi Guenter, 

Thanks a lot for comments and patience - with the testing you are right,
I'm still waiting for board, where I will be able to run latest kernel
and have the chip wired in - sorry for this...

Thanks, Tomas

On Mon, 2014-05-05 at 18:39 -0700, Guenter Roeck wrote:
> Hi Tomas,
> 
> On 05/05/2014 06:03 PM, Tomas Pop wrote:
> > Hi Guenter,
> >
> > Here is a corrected version, I tried to address your comments and I'm sending it
> > again with a kind request for comments - we will do some more extensive testing
> > before the final submission, but I would like to make the code as complete as
> > as possible before. Here is a list of changes to the previous version:
> >
> Comments below. But I don't think you tested this with real HW, did you ? :-)
> 
> > * positive, but incorrect return codes/lengths from i2c_mater_* are checked
> > * usleep_range used instead of msleep
> > * DEVICE_ATTR used instead of SENSOR_DEVICE_ATTR, ATTRIBITE_GROUPS used
> > * devm_hwmon_device_register_with_groups instead of devm_hwmon_device_register
> > * direct calls to sysfs_create_group and sysfs_create_group dropped
> > * shtc1_remove function dropped
> > * SHTW1 added to documentation and Kconfig
> > * documentation and formating updates/corrections
> >
> > I did re-compile with C=1 as suggested and it is clear.
> >
> > Patch was generated against kernel v3.15-rc3
> >
> > Thanks,
> > Tomas
> >
> > Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
> > ---
> >   Documentation/hwmon/shtc1           |  41 ++++++
> >   drivers/hwmon/Kconfig               |  10 ++
> >   drivers/hwmon/Makefile              |   1 +
> >   drivers/hwmon/shtc1.c               | 266 ++++++++++++++++++++++++++++++++++++
> >   include/linux/platform_data/shtc1.h |  24 ++++
> >   5 files changed, 342 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..47c9ed1
> > --- /dev/null
> > +++ b/Documentation/hwmon/shtc1
> > @@ -0,0 +1,41 @@
> > +Kernel driver shtc1
> > +=========> > +
> > +Supported chips:
> > +  * Sensirion SHTC1
> > +    Prefix: 'shtc1'
> > +    Addresses scanned: none
> > +    Datasheet: Publicly available at the Sensirion website
> > +    http://www.sensirion.com/file/datasheet_shtc1
> > +
> > +  * Sensirion SHTW1
> > +    Prefix: 'shtc1'
> > +    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.
> > +2. high or low accuracy. Using high accuracy is strongly recommended.
> > +
> > +sysfs-Interface
> > +---------------
> > +
> > +temp1_input - temperature input
> > +humidity1_input - humidity input
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index bc196f4..f95ba5b 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -1114,6 +1114,16 @@ 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 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 c48f987..1cc5273 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -125,6 +125,7 @@ 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..c94f670
> > --- /dev/null
> > +++ b/drivers/hwmon/shtc1.c
> > @@ -0,0 +1,266 @@
> > +/* 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_REG_CONTENT 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 device *hwmon_dev;
> 
> Not needed. But you need the i2c client here.
> 
> > +	struct mutex update_lock;
> > +	bool valid;
> > +	unsigned long last_updated; /* In jiffies */
> > +
> > +	const unsigned char *command;
> > +	unsigned int nonblocking_wait_time;
> > +
> > +	struct shtc1_platform_data setup;
> > +
> > +	int temperature;
> > +	int humidity;
> > +};
> > +
> > +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: %d\n", ret);
> > +		return ret;
> > +	}
> > +	if (ret != SHTC1_CMD_LENGTH) {
> > +		dev_err(&client->dev, "wrong nr bytes written: %d\n", ret);
> > +		return -EIO;
> > +	}
> 
> Can you merge those into one ? Something like
> 
> 	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
> 
> 	s/for/For/
> 
> > +	* have to wait ourselves.
> > +	*/
> > +	if (!data->setup.blocking_io)
> > +		usleep_range(data->nonblocking_wait_time,
> > +			     data->nonblocking_wait_time + 2000);
> > +
> In the low precision case, this results in a wait time of 1 to 3 ms.
> How about giving it a 1 ms range ? Seems to me that should be enough
> and an acceptable trade-off.
> 
> > +	ret = i2c_master_recv(client, buf, bufsize);
> > +	if (ret != bufsize) {
> > +		dev_err(&client->dev, "failed to read values: %d\n", ret);
> > +		if (ret < 0)
> > +			return ret;
> > +		return -EIO;
> 
> or simpler
> 		return ret < 0 ? ret : -EIO;
> 
> > +	}
> > +
> > +	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);
> > +
> 
> That won't work with the new ABI (please test ;-).
> You need something like
> 	struct shtc1_data *data = dev_get_drvdata(dev);
> 	struct i2c_client *client = data->client;
> 
> This is because the attributes are now attached to the hwmon device,
> no longer to the i2c device. The ABI saves the pointer to 'data'
> in drvdata for the hwmon device, so you can get it with dev_get_drvdata().
> 
> > +	unsigned 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 = 0;
> 
> A bit excessive. We all know C, or should. Just make it
> 	int ret = 0;
> above; you don't need any comments here.
> 
> > +
> > +	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 = 1;
> > +	}
> > +
> > +out:
> > +	mutex_unlock(&data->update_lock);
> > +
> > +	return ret = 0 ? data : ERR_PTR(ret);
> > +}
> > +
> > +static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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(temp1_input, S_IRUGO, shtc1_show_temperature, NULL);
> > +static DEVICE_ATTR(humidity1_input, S_IRUGO, shtc1_show_humidity, NULL);
> > +
> > +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)
> > +{
> > +	struct shtc1_data *data;
> > +	int err;
> > +	struct i2c_adapter *adap = client->adapter;
> > +	char id_reg[2];
> > +
> I would suggest a local variable dev here
> 	struct device *dev = &client->dev;
> to save all the client->dev dereferences below.
> 
> > +	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
> > +		dev_err(&client->dev,
> > +			"adapter does not support plain i2c transactions\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	err = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
> > +	if (err < 0) {
> > +		dev_err(&client->dev, "could not send read command: %d\n", err);
> 
> read id command
> 
> > +		return -ENODEV;
> > +	}
> > +	if (err != SHTC1_CMD_LENGTH) {
> > +		dev_err(&client->dev, "num bytes send is wrong: %d\n", err);
> 
> sent
> 
> Also, I would prefer a single if statement.
> 
> > +		return -ENODEV;
> > +	}
> > +	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
> > +	if (err != sizeof(id_reg)) {
> > +		dev_err(&client->dev, "could not read ID register: %d\n", err);
> > +		return -ENODEV;
> > +	}
> > +	if ((id_reg[1] & SHTC1_ID_REG_MASK) != SHTC1_ID_REG_CONTENT) {
> > +		dev_err(&client->dev, "ID register doesn't match\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
> > +	if (!data)
> > +		return -ENOMEM;
> > +
> > +	/* defaults: blocking, high precision mode */
> > +	data->setup.blocking_io = true;
> > +	data->setup.high_precision = true;
> > +
> > +	if (client->dev.platform_data)
> > +		data->setup = *(struct shtc1_platform_data *)client->dev.platform_data;
> 
> Line too long here. One way to solve it would be to use a local dev variable
> as sugested above.
> 
> > +	shtc1_select_command(data);
> > +	i2c_set_clientdata(client, data);
> 
> Not needed. But you need to save client for the update function.
> 	data->client = client;
> 
> > +	mutex_init(&data->update_lock);
> > +
> > +	data->hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev,
> 
> You don't need to keep hwmon_dev in the data structure. Just use a local variable.
> 
> > +								 client->name,
> > +								 data,
> > +								 shtc1_groups);
> > +	if (IS_ERR(data->hwmon_dev))
> > +		dev_dbg(&client->dev, "unable to register hwmon device\n");
> > +
> > +	return PTR_ERR_OR_ZERO(data->hwmon_dev);
> > +}
> > +
> > +/* device ID table */
> > +static const struct i2c_device_id shtc1_id[] = {
> > +	{ "shtc1", 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");
> > diff --git a/include/linux/platform_data/shtc1.h b/include/linux/platform_data/shtc1.h
> > new file mode 100644
> > index 0000000..b06e3db
> > --- /dev/null
> > +++ b/include/linux/platform_data/shtc1.h
> > @@ -0,0 +1,24 @@
> > +/*
> > + * 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_ */
> >
> 



_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

Re: [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Guenter Roeck]

On 05/05/2014 07:01 PM, Tomas Pop wrote:
> Hi Guenter,
>
> Thanks a lot for comments and patience - with the testing you are right,
> I'm still waiting for board, where I will be able to run latest kernel
> and have the chip wired in - sorry for this...
>

No problem. Please make sure that the driver has been tested with the real
chip before the final submission.

Just wondering - don't you have a little test board to make the i2c pins
more readily available ? Such a board could be connected to any i2c adapter
and/or to a mainboard which exposes i2c pins. That is usually how I test
the various sensors I am working with. You could even sell that to the
hobbyists :-).

Thanks,
Guenter

Re: [lm-sensors] [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Guenter Roeck]

On 05/05/2014 07:01 PM, Tomas Pop wrote:
> Hi Guenter,
>
> Thanks a lot for comments and patience - with the testing you are right,
> I'm still waiting for board, where I will be able to run latest kernel
> and have the chip wired in - sorry for this...
>

No problem. Please make sure that the driver has been tested with the real
chip before the final submission.

Just wondering - don't you have a little test board to make the i2c pins
more readily available ? Such a board could be connected to any i2c adapter
and/or to a mainboard which exposes i2c pins. That is usually how I test
the various sensors I am working with. You could even sell that to the
hobbyists :-).

Thanks,
Guenter


_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

Re: [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Tomas Pop]

Hi Gunter,

Yes, that's exactly the idea - we would like to provide basic support
for a few low-cost boards as a starting point for anybody who is
interested in the sensor. Previously I was testing mostly on some
Android devices (kernel 3.4), and it seems, that a lot of thinks changed
in since version 3.4 :-)

I will send in few days a tested version..

Thanks,
Tomas

 

On Mon, 2014-05-05 at 20:15 -0700, Guenter Roeck wrote:
> On 05/05/2014 07:01 PM, Tomas Pop wrote:
> > Hi Guenter,
> >
> > Thanks a lot for comments and patience - with the testing you are right,
> > I'm still waiting for board, where I will be able to run latest kernel
> > and have the chip wired in - sorry for this...
> >
> 
> No problem. Please make sure that the driver has been tested with the real
> chip before the final submission.
> 
> Just wondering - don't you have a little test board to make the i2c pins
> more readily available ? Such a board could be connected to any i2c adapter
> and/or to a mainboard which exposes i2c pins. That is usually how I test
> the various sensors I am working with. You could even sell that to the
> hobbyists :-).
> 
> Thanks,
> Guenter
> 

Re: [lm-sensors] [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Tomas Pop]

Hi Gunter,

Yes, that's exactly the idea - we would like to provide basic support
for a few low-cost boards as a starting point for anybody who is
interested in the sensor. Previously I was testing mostly on some
Android devices (kernel 3.4), and it seems, that a lot of thinks changed
in since version 3.4 :-)

I will send in few days a tested version..

Thanks,
Tomas

 

On Mon, 2014-05-05 at 20:15 -0700, Guenter Roeck wrote:
> On 05/05/2014 07:01 PM, Tomas Pop wrote:
> > Hi Guenter,
> >
> > Thanks a lot for comments and patience - with the testing you are right,
> > I'm still waiting for board, where I will be able to run latest kernel
> > and have the chip wired in - sorry for this...
> >
> 
> No problem. Please make sure that the driver has been tested with the real
> chip before the final submission.
> 
> Just wondering - don't you have a little test board to make the i2c pins
> more readily available ? Such a board could be connected to any i2c adapter
> and/or to a mainboard which exposes i2c pins. That is usually how I test
> the various sensors I am working with. You could even sell that to the
> hobbyists :-).
> 
> Thanks,
> Guenter
> 



_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

Re: [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Guenter Roeck]

On 05/06/2014 09:03 AM, Tomas Pop wrote:
> Hi Gunter,
>
> Yes, that's exactly the idea - we would like to provide basic support
> for a few low-cost boards as a starting point for anybody who is
> interested in the sensor. Previously I was testing mostly on some
> Android devices (kernel 3.4), and it seems, that a lot of thinks changed
> in since version 3.4 :-)
>
> I will send in few days a tested version..
>
Great. Unfortunately those chips are so small that they don't fit on
my test boards, or I would have ordered some myself. I am looking forward
to see those boards available for order somewhere ... hopefully at a lower
price point than your evaluation boards ;-).

Thanks,
Guenter

Re: [lm-sensors] [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Guenter Roeck]

On 05/06/2014 09:03 AM, Tomas Pop wrote:
> Hi Gunter,
>
> Yes, that's exactly the idea - we would like to provide basic support
> for a few low-cost boards as a starting point for anybody who is
> interested in the sensor. Previously I was testing mostly on some
> Android devices (kernel 3.4), and it seems, that a lot of thinks changed
> in since version 3.4 :-)
>
> I will send in few days a tested version..
>
Great. Unfortunately those chips are so small that they don't fit on
my test boards, or I would have ordered some myself. I am looking forward
to see those boards available for order somewhere ... hopefully at a lower
price point than your evaluation boards ;-).

Thanks,
Guenter


_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

Re: [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Tomas Pop]

On Die, 2014-05-06 at 19:47 -0700, Guenter Roeck wrote:
> Great. Unfortunately those chips are so small that they don't fit on
> my test boards, or I would have ordered some myself. I am looking forward
> to see those boards available for order somewhere ... hopefully at a lower
> price point than your evaluation boards ;-).
> 
> Thanks,
> Guenter
> 

Hi Guenter, 
I think, it would be great if somebody independent like you can play 
a bit with the sensor, before the patch will be merged. I will try to
find out, what I could do about this ;-)

Thanks!
Tomas

Re: [lm-sensors] [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Tomas Pop]

On Die, 2014-05-06 at 19:47 -0700, Guenter Roeck wrote:
> Great. Unfortunately those chips are so small that they don't fit on
> my test boards, or I would have ordered some myself. I am looking forward
> to see those boards available for order somewhere ... hopefully at a lower
> price point than your evaluation boards ;-).
> 
> Thanks,
> Guenter
> 

Hi Guenter, 
I think, it would be great if somebody independent like you can play 
a bit with the sensor, before the patch will be merged. I will try to
find out, what I could do about this ;-)

Thanks!
Tomas


_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

Re: [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Guenter Roeck]

On Wed, May 07, 2014 at 09:58:06AM -0700, Tomas Pop wrote:
> On Die, 2014-05-06 at 19:47 -0700, Guenter Roeck wrote:
> > Great. Unfortunately those chips are so small that they don't fit on
> > my test boards, or I would have ordered some myself. I am looking forward
> > to see those boards available for order somewhere ... hopefully at a lower
> > price point than your evaluation boards ;-).
> > 
> > Thanks,
> > Guenter
> > 
> 
> Hi Guenter, 
> I think, it would be great if somebody independent like you can play 
> a bit with the sensor, before the patch will be merged. I will try to
> find out, what I could do about this ;-)
> 
I for sure wouldn't mind if an evaluation / test board finds its way to me.
Note that all I would need is a little board with power and i2c connectors
similar to [1] or [2].

Guenter

[1] https://www.sparkfun.com/products/11931
[2] https://www.sparkfun.com/products/8257

Re: [lm-sensors] [RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Guenter Roeck]

On Wed, May 07, 2014 at 09:58:06AM -0700, Tomas Pop wrote:
> On Die, 2014-05-06 at 19:47 -0700, Guenter Roeck wrote:
> > Great. Unfortunately those chips are so small that they don't fit on
> > my test boards, or I would have ordered some myself. I am looking forward
> > to see those boards available for order somewhere ... hopefully at a lower
> > price point than your evaluation boards ;-).
> > 
> > Thanks,
> > Guenter
> > 
> 
> Hi Guenter, 
> I think, it would be great if somebody independent like you can play 
> a bit with the sensor, before the patch will be merged. I will try to
> find out, what I could do about this ;-)
> 
I for sure wouldn't mind if an evaluation / test board finds its way to me.
Note that all I would need is a little board with power and i2c connectors
similar to [1] or [2].

Guenter

[1] https://www.sparkfun.com/products/11931
[2] https://www.sparkfun.com/products/8257

_______________________________________________
lm-sensors mailing list
lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors

[RFC][PATCH v2] hwmon: add support for Sensirion SHTC1 sensor

[Tomas Pop]

This is a second version of the driver for Sensirion SHTC1 humidity and
temperature sensor. Initial version was submitted in July 2012.
http://www.gossamer-threads.com/lists/linux/kernel/1569130#1569130

We included suggested corrections formerly discussed in this list after
initial submission, but since it is quite a while, we are re-submitting
it again as a request for comments. Here is a list of important changes
to the initial version:

* returning real error codes instead of -1 or -ENODEV
* using boolean variables instead of bitmaps where possible
* macros be16_to_cpup used for conversion of indianneess
* corrected formula for decoding of humidity and temperature values
* documentation update

Patch was generated against kernel v3.15-rc3

Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
---
 Documentation/hwmon/shtc1           |  38 +++++
 drivers/hwmon/Kconfig               |  10 ++
 drivers/hwmon/Makefile              |   1 +
 drivers/hwmon/shtc1.c               | 323
++++++++++++++++++++++++++++++++++++
 include/linux/platform_data/shtc1.h |  24 +++
 5 files changed, 396 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..6a72ae2d
--- /dev/null
+++ b/Documentation/hwmon/shtc1
@@ -0,0 +1,38 @@
+Kernel driver shtc1
+===================
+
+Supported chips:
+  * Sensirion SHTC1
+    Prefix: 'shtc1'
+    Addresses scanned: none
+    Datasheet: Publicly available at the Sensirion website
+
http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_SHTC1_Datasheet.pdf
+
+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, that has the same electrical interface, but datasheet has not
been
+yet published.
+
+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. See Documentation/i2c/instantiating-devices
for
+other methods to instantiate the device.
+
+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
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index bc196f4..4d58149 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1114,6 +1114,16 @@ 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 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 c48f987..1cc5273 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -125,6 +125,7 @@ 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..96d398b
--- /dev/null
+++ b/drivers/hwmon/shtc1.c
@@ -0,0 +1,323 @@
+/* Sensirion SHTC1 humidity and temperature sensor driver
+ *
+ * Copyright (C) 2012 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.
+ *
+ * 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 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 and constants for reading the ID register */
+static const unsigned char shtc1_cmd_read_id_reg[]	     = { 0xef,
0xc8 };
+static const unsigned char shtc1_id_reg_content = 0x07;
+static const unsigned char shtc1_id_reg_mask    = 0x1f;
+
+/* delays for non-blocking i2c commands */
+/* TODO: use max timings */
+#define SHTC1_NONBLOCKING_WAIT_TIME_HPM  10
+#define 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;
+	bool valid;
+	unsigned long last_updated; /* In jiffies */
+
+	const unsigned char *command;
+	unsigned int nonblocking_wait_time;
+
+	struct shtc1_platform_data 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: %d", ret);
+		return ret;
+	}
+
+	/*
+	* 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().
+	*
+	* TODO: consider usleep_range
+	*/
+	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 ret;
+	}
+
+	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);
+
+	unsigned 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 = 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 = 1;
+	}
+
+out:
+	mutex_unlock(&data->update_lock);
+
+	return ret == 0 ? data : ERR_PTR(ret);
+}
+
+static ssize_t shtc1_show_temperature(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 shtc1_show_humidity(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 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 shtc1_probe(struct i2c_client *client,
+				const struct i2c_device_id *id)
+{
+	struct shtc1_data *data;
+	int err;
+	struct i2c_adapter *adap = client->adapter;
+	char id_reg[2];
+
+	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
+		dev_err(&client->dev,
+			"adapter does not support plain i2c transactions\n");
+		return -ENODEV;
+	}
+
+	err = i2c_master_send(client, shtc1_cmd_read_id_reg,
SHTC1_CMD_LENGTH);
+
+	if (err < 0) {
+		dev_err(&client->dev, "could not send read command: %d\n", err);
+		return -ENODEV;
+	}
+	err = i2c_master_recv(client, id_reg, sizeof(id_reg));
+	if (err != sizeof(id_reg)) {
+		dev_err(&client->dev, "could not read ID register: %d\n", err);
+		return -ENODEV;
+	}
+	if ((id_reg[1] & shtc1_id_reg_mask) != shtc1_id_reg_content) {
+		dev_err(&client->dev, "ID register doesn't match\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_platform_data
*)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");
+		goto fail_free;
+		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);
+fail_free:
+	kfree(data);
+
+	return err;
+}
+
+/**
+ * shtc1_remove() - remove device
+ * @client: I2C client device
+ */
+static int 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, shtc1_id);
+
+static struct i2c_driver shtc1_i2c_driver = {
+	.driver.name = "shtc1",
+	.probe	= shtc1_probe,
+	.remove      = shtc1_remove,
+	.id_table    = shtc1_id,
+};
+
+/**
+ * shtc1_init() - initialize driver
+ *
+ * Called when kernel is booted or module is inserted.
+ * Returns 0 on success.
+ */
+static int __init shtc1_init(void)
+{
+	return i2c_add_driver(&shtc1_i2c_driver);
+}
+module_init(shtc1_init);
+
+/*
+ * shtc1_exit() - clean up driver
+ *
+ * Called when module is removed.
+ */
+static void __exit shtc1_exit(void)
+{
+	i2c_del_driver(&shtc1_i2c_driver);
+}
+
+module_exit(shtc1_exit);
+
+
+MODULE_AUTHOR("Johannes Winkelmann
<johannes.winkelmann@sensirion.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..4629364
--- /dev/null
+++ b/include/linux/platform_data/shtc1.h
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2012 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
-- 
1.8.3.2