Add AIDL implementation for the vendor HAL service.

Bug: 205044134
Test: Pass AIDL VTS tests and regression tests.
Change-Id: Iad04ce01f71fc220443e05a4be05d7d5545227e8
diff --git a/wifi/aidl/default/aidl_sync_util.h b/wifi/aidl/default/aidl_sync_util.h
new file mode 100644
index 0000000..a61cd3f
--- /dev/null
+++ b/wifi/aidl/default/aidl_sync_util.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef AIDL_SYNC_UTIL_H_
+#define AIDL_SYNC_UTIL_H_
+
+#include <mutex>
+
+// Utility that provides a global lock to synchronize access between
+// the AIDL thread and the legacy HAL's event loop.
+namespace aidl {
+namespace android {
+namespace hardware {
+namespace wifi {
+namespace aidl_sync_util {
+std::unique_lock<std::recursive_mutex> acquireGlobalLock();
+}  // namespace aidl_sync_util
+}  // namespace wifi
+}  // namespace hardware
+}  // namespace android
+}  // namespace aidl
+#endif  // AIDL_SYNC_UTIL_H_