uORB::Publication*: template parameter automatically obtains the queue size according to the type

src/modules/uORB/Publication.hpp

@@ -48,6 +48,24 @@
 namespace uORB
 {
 
+template <typename U> class DefaultQueueSize
+{
+private:
+	template <typename T>
+	static constexpr uint8_t get_queue_size(decltype(T::ORB_QUEUE_LENGTH) *)
+	{
+		return T::ORB_QUEUE_LENGTH;
+	}
+
+	template <typename T> static constexpr uint8_t get_queue_size(...)
+	{
+		return 1;
+	}
+
+public:
+	static constexpr unsigned value = get_queue_size<U>(nullptr);
+};
+
 class PublicationBase
 {
 public:
@@ -79,7 +97,7 @@ protected:
 /**
  * uORB publication wrapper class
  */
-template<typename T, uint8_t ORB_QSIZE = 1>
+template<typename T, uint8_t ORB_QSIZE = DefaultQueueSize<T>::value>
 class Publication : public PublicationBase
 {
 public:

src/modules/uORB/PublicationMulti.hpp

@@ -50,7 +50,7 @@ namespace uORB
 /**
  * Base publication multi wrapper class
  */
-template<typename T, uint8_t QSIZE = 1>
+template<typename T, uint8_t QSIZE = DefaultQueueSize<T>::value>
 class PublicationMulti : public PublicationBase
 {
 public: