This adds a sensor driver for the hyt271, hyt221, and hyt939 sensor module from
vendor iST (Innovative Sensor Technology). This sensor type is connected via i2c
bus and allows the measurement of relative humidity and temperature.
Each driver instance supports two different character device for each type
(/dev/sensor/tempX and /dev/sensor/humiX).
This driver also supports changing the i2c address of one connected sensor on
the bus. This requires a callback to the platform-specific board logic which
must ensure a power-on reset.
Optional the driver allows setting up a read interval for fetching sensor data.
This is done by a worker thread and can be useful when watching several sensors
via poll() by the userspace application.
Signed-off-by: Marco Krahl <ocram.lhark@gmail.com>
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