+Handling autogain/gain-type Controls with Auto Clusters
+=======================================================
+
+A common type of control cluster is one that handles 'auto-foo/foo'-type
+controls. Typical examples are autogain/gain, autoexposure/exposure,
+autowhitebalance/red balance/blue balance. In all cases you have one controls
+that determines whether another control is handled automatically by the hardware,
+or whether it is under manual control from the user.
+
+If the cluster is in automatic mode, then the manual controls should be
+marked inactive. When the volatile controls are read the g_volatile_ctrl
+operation should return the value that the hardware's automatic mode set up
+automatically.
+
+If the cluster is put in manual mode, then the manual controls should become
+active again and the is_volatile flag should be ignored (so g_volatile_ctrl is
+no longer called while in manual mode).
+
+Finally the V4L2_CTRL_FLAG_UPDATE should be set for the auto control since
+changing that control affects the control flags of the manual controls.
+
+In order to simplify this a special variation of v4l2_ctrl_cluster was
+introduced:
+
+void v4l2_ctrl_auto_cluster(unsigned ncontrols, struct v4l2_ctrl **controls,
+ u8 manual_val, bool set_volatile);
+
+The first two arguments are identical to v4l2_ctrl_cluster. The third argument
+tells the framework which value switches the cluster into manual mode. The
+last argument will optionally set the is_volatile flag for the non-auto controls.
+
+The first control of the cluster is assumed to be the 'auto' control.
+
+Using this function will ensure that you don't need to handle all the complex
+flag and volatile handling.
+
+