[otns] add default implementation for otPlatOtnsStatus (#5155)

This commit adds a default implementation for otPlatOtnsStatus, which
emits OTNS status messages to log, so that OTNS=1 could be used with
real devices. This is required for the Silk-OTNS integration work, as
Silk will pick up these messages and reroute them to OTNS for
visualization purposes.

src/core/common/logging.hpp

@@ -1158,6 +1158,19 @@ extern "C" {
 #define otLogDebgPlat(...)
 #endif
 
+/**
+ * @def otLogOtns
+ *
+ * This method generates a log with level none for the Core region,
+ * and is specifically for OTNS visualization use.
+ *
+ * @param[in]  ...       Arguments for the format specification.
+ *
+ */
+#if (OPENTHREAD_MTD || OPENTHREAD_FTD) && OPENTHREAD_CONFIG_OTNS_ENABLE
+#define otLogOtns(...) _otLogFormatter(OT_LOG_LEVEL_NONE, OT_LOG_REGION_CORE, _OT_LEVEL_NONE_PREFIX __VA_ARGS__, NULL)
+#endif
+
 /**
  * @def otDumpCrit
  *

src/core/utils/otns.cpp

@@ -38,6 +38,7 @@
 
 #include "common/debug.hpp"
 #include "common/locator-getters.hpp"
+#include "common/logging.hpp"
 
 namespace ot {
 namespace Utils {
@@ -133,4 +134,9 @@ void Otns::EmitNeighborChange(otNeighborTableEvent aEvent, Neighbor &aNeighbor)
 } // namespace Utils
 } // namespace ot
 
+OT_TOOL_WEAK void otPlatOtnsStatus(const char *aStatus)
+{
+    otLogOtns("[OTNS] %s", aStatus);
+}
+
 #endif // (OPENTHREAD_MTD || OPENTHREAD_FTD) && OPENTHREAD_CONFIG_OTNS_ENABLE