libcamera: control_ids: Add comment to specify control direction

Document that controls are bi-directional by default. If a control
is only returned in metadata, this must be specified in the control's
description.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

src/libcamera/control_ids.cpp.in

@@ -33,6 +33,9 @@ ${controls_def}
 
 /**
  * \brief List of all supported libcamera controls
+ *
+ * Unless otherwise stated, all controls are bi-directional, i.e. they can be
+ * set through Request::controls() and returned out through Request::metadata().
  */
 extern const ControlIdMap controls {
 ${controls_map}

src/libcamera/control_ids.yaml

@@ -4,6 +4,8 @@
 #
 %YAML 1.2
 ---
+# Unless otherwise stated, all controls are bi-directional, i.e. they can be
+# set through Request::controls() and returned out through Request::metadata().
 controls:
   - AeEnable:
       type: bool