fix [2068105] implement queueBuffer/lockBuffer/dequeueBuffer properly

Rewrote SurfaceFlinger's buffer management from the ground-up.
The design now support an arbitrary number of buffers per surface, however the current implementation is limited to four. Currently only 2 buffers are used in practice.

The main new feature is to be able to dequeue all buffers at once (very important when there are only two). 

A client can dequeue all buffers until there are none available, it can lock all buffers except the last one that is used for composition. The client will block then, until a new buffer is enqueued.

The current implementation requires that buffers are locked in the same order they are dequeued and enqueued in the same order they are locked. Only one buffer can be locked at a time.

eg. Allowed sequence:   DQ, DQ, LOCK, Q, LOCK, Q
eg. Forbidden sequence: DQ, DQ, LOCK, LOCK, Q, Q

1 files changed, 6 insertions, 4 deletions

diff --git a/libs/ui/ISurface.cpp b/libs/ui/ISurface.cpp
index b78e8b5..a2dbe7f 100644
--- a/libs/ui/ISurface.cpp
+++ b/libs/ui/ISurface.cpp
@@ -71,12 +71,13 @@ public:
     {
     }
 
-    virtual sp<SurfaceBuffer> getBuffer(int usage)
+    virtual sp<SurfaceBuffer> requestBuffer(int bufferIdx, int usage)
     {
         Parcel data, reply;
         data.writeInterfaceToken(ISurface::getInterfaceDescriptor());
+        data.writeInt32(bufferIdx);
         data.writeInt32(usage);
-        remote()->transact(GET_BUFFER, data, &reply);
+        remote()->transact(REQUEST_BUFFER, data, &reply);
         sp<SurfaceBuffer> buffer = new SurfaceBuffer(reply);
         return buffer;
     }
@@ -134,10 +135,11 @@ status_t BnSurface::onTransact(
     uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
 {
     switch(code) {
-        case GET_BUFFER: {
+        case REQUEST_BUFFER: {
             CHECK_INTERFACE(ISurface, data, reply);
+            int bufferIdx = data.readInt32();
             int usage = data.readInt32();
-            sp<SurfaceBuffer> buffer(getBuffer(usage));
+            sp<SurfaceBuffer> buffer(requestBuffer(bufferIdx, usage));
             return SurfaceBuffer::writeToParcel(reply, buffer.get());
         }
         case REGISTER_BUFFERS: {