add libsurfaceflinger_ddmconnection for PDK build

- the library is dlopened from libsurfaceflinger
- the library built only when libnativehelper exists

Bug: 7089510
Change-Id: Ib3ea1029d7e8f6e055f4b759d0bf68f5123fa8a1

services/surfaceflinger/Android.mk

@@ -52,3 +52,19 @@ LOCAL_SHARED_LIBRARIES := \
 LOCAL_MODULE:= libsurfaceflinger
 
 include $(BUILD_SHARED_LIBRARY)
+
+###############################################################
+# uses jni which may not be available in PDK
+ifneq ($(wildcard libnativehelper/include),)
+include $(CLEAR_VARS)
+LOCAL_SRC_FILES:= \
+    DdmConnection.cpp
+
+LOCAL_SHARED_LIBRARIES := \
+	libcutils \
+	libdl
+
+LOCAL_MODULE:= libsurfaceflinger_ddmconnection
+
+include $(BUILD_SHARED_LIBRARY)
+endif # libnativehelper

services/surfaceflinger/DdmConnection.cpp

@@ -23,6 +23,10 @@
 
 namespace android {
 
+void DdmConnection_start(const char* name) {
+    ALOGI("DdmConnection_start");
+    DdmConnection::start(name);
+}
 
 void DdmConnection::start(const char* name) {
     JavaVM* vm;

services/surfaceflinger/DdmConnection.h

@@ -19,6 +19,9 @@
 
 namespace android {
 
+// wrapper for dlsym
+extern "C" void DdmConnection_start(const char* name);
+
 class DdmConnection {
 public:
     static void start(const char* name);

services/surfaceflinger/SurfaceFlinger.cpp

@@ -20,6 +20,7 @@
 #include <sys/types.h>
 #include <errno.h>
 #include <math.h>
+#include <dlfcn.h>
 
 #include <EGL/egl.h>
 #include <GLES/gl.h>
@@ -108,9 +109,11 @@ SurfaceFlinger::SurfaceFlinger()
     property_get("debug.sf.ddms", value, "0");
     mDebugDDMS = atoi(value);
     if (mDebugDDMS) {
-        DdmConnection::start(getServiceName());
+        if (!startDdmConnection()) {
+            // start failed, and DDMS debugging not enabled
+            mDebugDDMS = 0;
+        }
     }
-
     ALOGI_IF(mDebugRegion, "showupdates enabled");
     ALOGI_IF(mDebugDDMS, "DDMS debugging enabled");
 }
@@ -2061,6 +2064,24 @@ void SurfaceFlinger::dumpAllLocked(
     hw->dump(result);
 }
 
+bool SurfaceFlinger::startDdmConnection()
+{
+    void* libddmconnection_dso =
+            dlopen("libsurfaceflinger_ddmconnection.so", RTLD_NOW);
+    if (!libddmconnection_dso) {
+        return false;
+    }
+    void (*DdmConnection_start)(const char* name);
+    DdmConnection_start =
+            (typeof DdmConnection_start)dlsym(libddmconnection_dso, "DdmConnection_start");
+    if (!DdmConnection_start) {
+        dlclose(libddmconnection_dso);
+        return false;
+    }
+    (*DdmConnection_start)(getServiceName());
+    return true;
+}
+
 status_t SurfaceFlinger::onTransact(
     uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
 {

services/surfaceflinger/SurfaceFlinger.h

@@ -388,6 +388,7 @@ private:
     void clearStatsLocked(const Vector<String16>& args, size_t& index,
         String8& result, char* buffer, size_t SIZE) const;
     void dumpAllLocked(String8& result, char* buffer, size_t SIZE) const;
+    bool startDdmConnection();
 
     /* ------------------------------------------------------------------------
      * Attributes