diff --git a/include/media/AudioPolicy.h b/include/media/AudioPolicy.h
index 800b27b..feed402 100644
--- a/include/media/AudioPolicy.h
+++ b/include/media/AudioPolicy.h
@@ -38,14 +38,17 @@
 #define MIX_TYPE_PLAYERS 0
 #define MIX_TYPE_RECORDERS 1
 
+// definition of the different events that can be reported on a dynamic policy from
+//   AudioSystem's implementation of the AudioPolicyClient interface
+// keep in sync with AudioSystem.java
+#define DYNAMIC_POLICY_EVENT_MIX_STATE_UPDATE 0
+
 #define MIX_STATE_DISABLED -1
 #define MIX_STATE_IDLE 0
 #define MIX_STATE_MIXING 1
 
-#define ROUTE_FLAG_RENDER 0x1
-#define ROUTE_FLAG_LOOP_BACK (0x1 << 1)
-
-#define MIX_FLAG_NOTIFY_ACTIVITY 0x1
+#define MIX_ROUTE_FLAG_RENDER 0x1
+#define MIX_ROUTE_FLAG_LOOP_BACK (0x1 << 1)
 
 #define MAX_MIXES_PER_POLICY 10
 #define MAX_CRITERIA_PER_MIX 20
@@ -67,11 +70,15 @@
 
 class AudioMix {
 public:
+    // flag on an AudioMix indicating the activity on this mix (IDLE, MIXING)
+    //   must be reported through the AudioPolicyClient interface
+    static const uint32_t kCbFlagNotifyActivity = 0x1;
+
     AudioMix() {}
     AudioMix(Vector<AttributeMatchCriterion> criteria, uint32_t mixType, audio_config_t format,
              uint32_t routeFlags, String8 registrationId, uint32_t flags) :
         mCriteria(criteria), mMixType(mixType), mFormat(format),
-        mRouteFlags(routeFlags), mRegistrationId(registrationId), mFlags(flags){}
+        mRouteFlags(routeFlags), mRegistrationId(registrationId), mCbFlags(flags){}
 
     status_t readFromParcel(Parcel *parcel);
     status_t writeToParcel(Parcel *parcel) const;
@@ -81,7 +88,7 @@
     audio_config_t  mFormat;
     uint32_t        mRouteFlags;
     String8         mRegistrationId;
-    uint32_t        mFlags;
+    uint32_t        mCbFlags; // flags indicating which callbacks to use, see kCbFlag*
 };
 
 }; // namespace android
diff --git a/include/media/AudioSystem.h b/include/media/AudioSystem.h
index 182133c..a3af1b2 100644
--- a/include/media/AudioSystem.h
+++ b/include/media/AudioSystem.h
@@ -29,6 +29,7 @@
 namespace android {
 
 typedef void (*audio_error_callback)(status_t err);
+typedef void (*dynamic_policy_callback)(int event, String8 regId, int val);
 
 class IAudioFlinger;
 class IAudioPolicyService;
@@ -89,6 +90,7 @@
     static String8  getParameters(const String8& keys);
 
     static void setErrorCallback(audio_error_callback cb);
+    static void setDynPolicyCallback(dynamic_policy_callback cb);
 
     // helper function to obtain AudioFlinger service handle
     static const sp<IAudioFlinger> get_audio_flinger();
@@ -408,6 +410,7 @@
     static Mutex gLockAPS;   // protects gAudioPolicyService and gAudioPolicyServiceClient
     static sp<IAudioFlinger> gAudioFlinger;
     static audio_error_callback gAudioErrorCallback;
+    static dynamic_policy_callback gDynPolicyCallback;
 
     static size_t gInBuffSize;
     // previous parameters for recording buffer size queries