+ * When an "change" event is received on an accelerometer,
+ * open its device node, and from the value, as well as the previous
+ * value of the property, calculate the device's new orientation,
+ * and export it as ID_INPUT_ACCELEROMETER_ORIENTATION.
+ *
+ * Possible values are:
+ * undefined
+ * * normal
+ * * bottom-up
+ * * left-up
+ * * right-up
+ *
+ * The property will be persistent across sessions, and the new
+ * orientations can be deducted from the previous one (it allows
+ * for a threshold for switching between opposite ends of the
+ * orientation).
+ *