htc: implement htclow listener thread

libraries/libstratosphere/include/stratosphere/htclow/htclow_channel_types.hpp

@@ -27,4 +27,25 @@ namespace ams::htclow {
         ChannelId _channel_id;
     };
 
+    enum ChannelState {
+        ChannelState_Connectable   = 0,
+        ChannelState_Unconnectable = 1,
+        ChannelState_Connected     = 2,
+        ChannelState_Shutdown      = 3,
+    };
+
+    constexpr bool IsStateTransitionAllowed(ChannelState from, ChannelState to) {
+        switch (from) {
+            case ChannelState_Connectable:
+                return to == ChannelState_Unconnectable || to == ChannelState_Connected || to == ChannelState_Shutdown;
+            case ChannelState_Unconnectable:
+                return to == ChannelState_Connectable || to == ChannelState_Shutdown;
+            case ChannelState_Connected:
+                return to == ChannelState_Shutdown;
+            case ChannelState_Shutdown:
+                return to == ChannelState_Shutdown;
+            AMS_UNREACHABLE_DEFAULT_CASE();
+        }
+    }
+
 }