CEC: Allow no parameters with <System Audio Mode Request>.

Bug: 18266992
Change-Id: I4399e34d1178f3d4b17b4749ca543c2bb14c0765
diff --git a/services/core/java/com/android/server/hdmi/HdmiCecMessageValidator.java b/services/core/java/com/android/server/hdmi/HdmiCecMessageValidator.java
index f1529a7..53740fe 100644
--- a/services/core/java/com/android/server/hdmi/HdmiCecMessageValidator.java
+++ b/services/core/java/com/android/server/hdmi/HdmiCecMessageValidator.java
@@ -79,7 +79,7 @@
         addValidationInfo(Constants.MESSAGE_SET_STREAM_PATH,
                 physicalAddressValidator, DEST_BROADCAST);
         addValidationInfo(Constants.MESSAGE_SYSTEM_AUDIO_MODE_REQUEST,
-                physicalAddressValidator, DEST_DIRECT);
+                new SystemAudioModeRequestValidator(), DEST_DIRECT);
 
         // Messages have no parameter.
         FixedLengthValidator noneValidator = new FixedLengthValidator(0);
@@ -303,6 +303,17 @@
         }
     }
 
+    private class SystemAudioModeRequestValidator extends PhysicalAddressValidator {
+        @Override
+        public int isValid(byte[] params) {
+            // TV can send <System Audio Mode Request> with no parameters to terminate system audio.
+            if (params.length == 0) {
+                return OK;
+            }
+            return super.isValid(params);
+        }
+    }
+
     private class ReportPhysicalAddressValidator implements ParameterValidator {
         @Override
         public int isValid(byte[] params) {