drm@1.4: API to retrieve plugin log messages

Log messages can be exported by apps during error diagnosis.

Bug: 162255728
Test: GtsMediaTestCases MediaDrmTest#testGetLogMessages
Change-Id: Id7576b237501f4af6a7399207fbad5ac3b92c20b
diff --git a/drm/1.4/IDrmPlugin.hal b/drm/1.4/IDrmPlugin.hal
index e8af230..df04b9f 100644
--- a/drm/1.4/IDrmPlugin.hal
+++ b/drm/1.4/IDrmPlugin.hal
@@ -19,6 +19,8 @@
 import @1.0::SessionId;
 import @1.1::SecurityLevel;
 import @1.2::IDrmPlugin;
+import @1.4::LogMessage;
+import @1.4::Status;
 
 /**
  * IDrmPlugin is used to interact with a specific drm plugin that was
@@ -61,4 +63,14 @@
      */
     setPlaybackId(SessionId sessionId, string playbackId) generates (@1.0::Status status);
 
+    /**
+     * @return logMessages latest plugin level log messages. Can be used
+     *     by apps in diagnosis of errors.
+     * @return status the status of the call. The status must be:
+     *     OK on success;
+     *     GENERAL_OEM_ERROR on OEM-provided, low-level component failures;
+     *     GENERAL_PLUGIN_ERROR on unexpected plugin-level errors.
+     */
+    getLogMessages() generates (@1.4::Status status, vec<LogMessage> logMessages);
+
 };