hwmon: add support for Sensirion SHT3x sensors
This driver implements support for the Sensirion SHT3x-DIS chip,
a humidity and temperature sensor. Temperature is measured
in degrees celsius, relative humidity is expressed as a percentage.
In the sysfs interface, all values are scaled by 1000,
i.e. the value for 31.5 degrees celsius is 31500.
Signed-off-by: Pascal Sachs <pascal.sachs@sensirion.com>
[groeck: Fixed 'Variable length array is used' gcc warning]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
diff --git a/Documentation/hwmon/sht3x b/Documentation/hwmon/sht3x
new file mode 100644
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+Kernel driver sht3x
+===================
+
+Supported chips:
+ * Sensirion SHT3x-DIS
+ Prefix: 'sht3x'
+ Addresses scanned: none
+ Datasheet: http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_Datasheet_SHT3x_DIS.pdf
+
+Author:
+ David Frey <david.frey@sensirion.com>
+ Pascal Sachs <pascal.sachs@sensirion.com>
+
+Description
+-----------
+
+This driver implements support for the Sensirion SHT3x-DIS chip, a humidity
+and temperature sensor. Temperature is measured in degrees celsius, relative
+humidity is expressed as a percentage. In the sysfs interface, all values are
+scaled by 1000, i.e. the value for 31.5 degrees celsius is 31500.
+
+The device communicates with the I2C protocol. Sensors can have the I2C
+addresses 0x44 or 0x45, depending on the wiring. See
+Documentation/i2c/instantiating-devices for methods to instantiate the device.
+
+There are two options configurable by means of sht3x_platform_data:
+1. blocking (pull the I2C clock line down while performing the measurement) or
+ non-blocking mode. Blocking mode will guarantee the fastest result but
+ the I2C bus will be busy during that time. By default, non-blocking mode
+ is used. Make sure clock-stretching works properly on your device if you
+ want to use blocking mode.
+2. high or low accuracy. High accuracy is used by default and using it is
+ strongly recommended.
+
+The sht3x sensor supports a single shot mode as well as 5 periodic measure
+modes, which can be controlled with the update_interval sysfs interface.
+The allowed update_interval in milliseconds are as follows:
+ * 0 single shot mode
+ * 2000 0.5 Hz periodic measurement
+ * 1000 1 Hz periodic measurement
+ * 500 2 Hz periodic measurement
+ * 250 4 Hz periodic measurement
+ * 100 10 Hz periodic measurement
+
+In the periodic measure mode, the sensor automatically triggers a measurement
+with the configured update interval on the chip. When a temperature or humidity
+reading exceeds the configured limits, the alert attribute is set to 1 and
+the alert pin on the sensor is set to high.
+When the temperature and humidity readings move back between the hysteresis
+values, the alert bit is set to 0 and the alert pin on the sensor is set to
+low.
+
+sysfs-Interface
+---------------
+
+temp1_input: temperature input
+humidity1_input: humidity input
+temp1_max: temperature max value
+temp1_max_hyst: temperature hysteresis value for max limit
+humidity1_max: humidity max value
+humidity1_max_hyst: humidity hysteresis value for max limit
+temp1_min: temperature min value
+temp1_min_hyst: temperature hysteresis value for min limit
+humidity1_min: humidity min value
+humidity1_min_hyst: humidity hysteresis value for min limit
+temp1_alarm: alarm flag is set to 1 if the temperature is outside the
+ configured limits. Alarm only works in periodic measure mode
+humidity1_alarm: alarm flag is set to 1 if the humidity is outside the
+ configured limits. Alarm only works in periodic measure mode
+update_interval: update interval, 0 for single shot, interval in msec
+ for periodic measurement. If the interval is not supported
+ by the sensor, the next faster interval is chosen