diff --git a/audio/4.0/IStreamOutCallback.hal b/audio/4.0/IStreamOutCallback.hal
new file mode 100644
index 0000000..9a19d32
--- /dev/null
+++ b/audio/4.0/IStreamOutCallback.hal
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2018 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.
+ */
+
+package android.hardware.audio@4.0;
+
+/**
+ * Asynchronous write callback interface.
+ */
+interface IStreamOutCallback {
+    /**
+     * Non blocking write completed.
+     */
+    oneway onWriteReady();
+
+    /**
+     * Drain completed.
+     */
+    oneway onDrainReady();
+
+    /**
+     * Stream hit an error.
+     */
+    oneway onError();
+};