libgui: Add generation numbers to BufferQueue

This change allows producers to set a generation number on a
BufferQueue. This number will be embedded in any new GraphicBuffers
created in that BufferQueue, and attempts to attach buffers which have
a different generation number will fail.

It also plumbs the setGenerationNumber method through Surface, with the
additional effect that any buffers attached to the Surface after
setting a new generation number will automatically be updated with the
new number (as opposed to failing, as would happen on through IGBP).

Bug: 20923096
Change-Id: I32bf726b035f99c3e5834beaf76afb9f01adcbc2

5 files changed, 31 insertions, 3 deletions

diff --git a/include/gui/BufferQueueCore.h b/include/gui/BufferQueueCore.h
index d7686ec..99134ea 100644
--- a/include/gui/BufferQueueCore.h
+++ b/include/gui/BufferQueueCore.h
@@ -275,6 +275,11 @@ private:
     // buffer as the number of frames that have elapsed since it was last queued
     uint64_t mBufferAge;
 
+    // mGenerationNumber stores the current generation number of the attached
+    // producer. Any attempt to attach a buffer with a different generation
+    // number will fail.
+    uint32_t mGenerationNumber;
+
 }; // class BufferQueueCore
 
 } // namespace android
diff --git a/include/gui/BufferQueueProducer.h b/include/gui/BufferQueueProducer.h
index ed660fb..afa7eb1 100644
--- a/include/gui/BufferQueueProducer.h
+++ b/include/gui/BufferQueueProducer.h
@@ -175,6 +175,9 @@ public:
     // See IGraphicBufferProducer::allowAllocation
     virtual status_t allowAllocation(bool allow);
 
+    // See IGraphicBufferProducer::setGenerationNumber
+    virtual status_t setGenerationNumber(uint32_t generationNumber);
+
 private:
     // This is required by the IBinder::DeathRecipient interface
     virtual void binderDied(const wp<IBinder>& who);
diff --git a/include/gui/IGraphicBufferConsumer.h b/include/gui/IGraphicBufferConsumer.h
index 6363a3a..60ec9cc 100644
--- a/include/gui/IGraphicBufferConsumer.h
+++ b/include/gui/IGraphicBufferConsumer.h
@@ -110,7 +110,8 @@ public:
     // will be deallocated as stale.
     //
     // Return of a value other than NO_ERROR means an error has occurred:
-    // * BAD_VALUE - outSlot or buffer were NULL
+    // * BAD_VALUE - outSlot or buffer were NULL, or the generation number of
+    //               the buffer did not match the buffer queue.
     // * INVALID_OPERATION - cannot attach the buffer because it would cause too
     //                       many buffers to be acquired.
     // * NO_MEMORY - no free slots available
diff --git a/include/gui/IGraphicBufferProducer.h b/include/gui/IGraphicBufferProducer.h
index 5c50b2b..4ca4cd5 100644
--- a/include/gui/IGraphicBufferProducer.h
+++ b/include/gui/IGraphicBufferProducer.h
@@ -218,8 +218,9 @@ public:
     //
     // Return of a negative value means an error has occurred:
     // * NO_INIT - the buffer queue has been abandoned.
-    // * BAD_VALUE - outSlot or buffer were NULL or invalid combination of
-    //               async mode and buffer count override.
+    // * BAD_VALUE - outSlot or buffer were NULL, invalid combination of
+    //               async mode and buffer count override, or the generation
+    //               number of the buffer did not match the buffer queue.
     // * INVALID_OPERATION - cannot attach the buffer because it would cause
     //                       too many buffers to be dequeued, either because
     //                       the producer already has a single buffer dequeued
@@ -470,6 +471,15 @@ public:
     // eligible slot is available, dequeueBuffer will block or return an error
     // as usual.
     virtual status_t allowAllocation(bool allow) = 0;
+
+    // Sets the current generation number of the BufferQueue.
+    //
+    // This generation number will be inserted into any buffers allocated by the
+    // BufferQueue, and any attempts to attach a buffer with a different
+    // generation number will fail. Buffers already in the queue are not
+    // affected and will retain their current generation number. The generation
+    // number defaults to 0.
+    virtual status_t setGenerationNumber(uint32_t generationNumber) = 0;
 };
 
 // ----------------------------------------------------------------------------
diff --git a/include/gui/Surface.h b/include/gui/Surface.h
index fd6d48c..261b07c 100644
--- a/include/gui/Surface.h
+++ b/include/gui/Surface.h
@@ -101,6 +101,11 @@ public:
      */
     void allocateBuffers();
 
+    /* Sets the generation number on the IGraphicBufferProducer and updates the
+     * generation number on any buffers attached to the Surface after this call.
+     * See IGBP::setGenerationNumber for more information. */
+    status_t setGenerationNumber(uint32_t generationNumber);
+
 protected:
     virtual ~Surface();
 
@@ -305,6 +310,10 @@ private:
     // When a non-CPU producer is attached, this reflects the surface damage
     // (the change since the previous frame) passed in by the producer.
     Region mDirtyRegion;
+
+    // Stores the current generation number. See setGenerationNumber and
+    // IGraphicBufferProducer::setGenerationNumber for more information.
+    uint32_t mGenerationNumber;
 };
 
 }; // namespace android