libcamera: control_ids: Fix documentation for controls namespace

The controls namespace isn't documenting, making it impossible to
reference the variables it contains. Furthermore, within the
documentation page for the control_ids.h file, links from overview to
detailed variable documentation are broken for the same reason. Both
issues can be fixed by documenting the controls namespace.

Unfortunately doxygen then fails to parse the initialisers for the
controls global variables correctly and considers them as functions. To
work around this, modify the control_ids.cpp generation script to hide
the variables from doxygen, but still expose their documentation.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Tested-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/libcamera/control_ids.cpp.in

@@ -16,9 +16,20 @@
 
 namespace libcamera {
 
+/**
+ * \brief Namespace for libcamera controls
+ */
 namespace controls {
 
-${controls}
+${controls_doc}
+
+#ifndef __DOXYGEN__
+/*
+ * Keep the controls definitions hidden from doxygen as it incorrectly parses
+ * them as functions.
+ */
+${controls_def}
+#endif
 
 } /* namespace controls */