Document AudioSystem::newAudioSessionId() failures

Change-Id: Iaa168722f362c36bdfa87fe20dc0a59b43cf1ca3

3 files changed, 8 insertions, 2 deletions

diff --git a/include/media/AudioSystem.h b/include/media/AudioSystem.h
index 28fdfd4..3faaa7e 100644
--- a/include/media/AudioSystem.h
+++ b/include/media/AudioSystem.h
@@ -141,7 +141,13 @@ public:
     // return the number of input frames lost by HAL implementation, or 0 if the handle is invalid
     static uint32_t getInputFramesLost(audio_io_handle_t ioHandle);
 
+    // Allocate a new audio session ID and return that new ID.
+    // If unable to contact AudioFlinger, returns AUDIO_SESSION_ALLOCATE instead.
+    // FIXME If AudioFlinger were to ever exhaust the session ID namespace,
+    //       this method could fail by returning either AUDIO_SESSION_ALLOCATE
+    //       or an unspecified existing session ID.
     static int newAudioSessionId();
+
     static void acquireAudioSessionId(int audioSession, pid_t pid);
     static void releaseAudioSessionId(int audioSession, pid_t pid);
 
diff --git a/media/libmedia/AudioSystem.cpp b/media/libmedia/AudioSystem.cpp
index 140fb66..c418466 100644
--- a/media/libmedia/AudioSystem.cpp
+++ b/media/libmedia/AudioSystem.cpp
@@ -431,7 +431,7 @@ uint32_t AudioSystem::getInputFramesLost(audio_io_handle_t ioHandle)
 int AudioSystem::newAudioSessionId()
 {
     const sp<IAudioFlinger>& af = AudioSystem::get_audio_flinger();
-    if (af == 0) return 0;
+    if (af == 0) return AUDIO_SESSION_ALLOCATE;
     return af->newAudioSessionId();
 }
 
diff --git a/media/libmedia/IAudioFlinger.cpp b/media/libmedia/IAudioFlinger.cpp
index 762681e..f28b82d 100644
--- a/media/libmedia/IAudioFlinger.cpp
+++ b/media/libmedia/IAudioFlinger.cpp
@@ -599,7 +599,7 @@ public:
         Parcel data, reply;
         data.writeInterfaceToken(IAudioFlinger::getInterfaceDescriptor());
         status_t status = remote()->transact(NEW_AUDIO_SESSION_ID, data, &reply);
-        int id = 0;
+        int id = AUDIO_SESSION_ALLOCATE;
         if (status == NO_ERROR) {
             id = reply.readInt32();
         }