libextsupport: Add waitServiceDefault which polls

libextsupport/GetServiceSupport.h

@@ -1,3 +1,6 @@
+#include <chrono>
+#include <thread>
+
 #include <type_traits>
 #include <string>
 
@@ -17,3 +20,24 @@ static inline std::shared_ptr<T> getServiceDefault(void)
 {
 	return getService<T>(std::string() + T::descriptor + "/default");
 }
+
+template <typename T>
+static std::shared_ptr<T> waitServiceDefault(int retries = 5)
+{
+	std::shared_ptr<T> kService = nullptr;
+	const auto kServiceDesc = std::string() + T::descriptor + "/default";
+
+	// If not declared, just return null
+	if (AServiceManager_isDeclared(kServiceDesc.c_str())) {
+		do {
+			kService = getService<T>(kServiceDesc);
+			if (kService == nullptr) {
+				std::this_thread::sleep_for(std::chrono::seconds(5));
+				--retries;
+			} else {
+				break;
+			}
+		} while (retries > 0);
+	}
+	return kService;
+}