libcamera: controls: Add templates to convert a type T to a ControlType

These will be used to implement ControlValue::get() and set() as
template functions.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

Documentation/Doxyfile.in

@@ -881,7 +881,7 @@ EXCLUDE_SYMBOLS        = libcamera::BoundMethodArgs \
                          libcamera::BoundMethodStatic \
                          libcamera::SignalBase \
                          libcamera::*::Private \
-                         libcamera::*::details::* \
+                         *::details::* \
                          std::*
 
 # The EXAMPLE_PATH tag can be used to specify one or more files or directories

include/libcamera/controls.h

@@ -22,6 +22,34 @@ enum ControlType {
 	ControlTypeInteger64,
 };
 
+namespace details {
+
+template<typename T>
+struct control_type {
+};
+
+template<>
+struct control_type<void> {
+	static constexpr ControlType value = ControlTypeNone;
+};
+
+template<>
+struct control_type<bool> {
+	static constexpr ControlType value = ControlTypeBool;
+};
+
+template<>
+struct control_type<int32_t> {
+	static constexpr ControlType value = ControlTypeInteger32;
+};
+
+template<>
+struct control_type<int64_t> {
+	static constexpr ControlType value = ControlTypeInteger64;
+};
+
+} /* namespace details */
+
 class ControlValue
 {
 public: