Split BufferQueue into core + producer + consumer

Change-Id: Idc39f1e511d68ce4f02202d35425a419bc0bcd92

5 files changed, 672 insertions, 0 deletions

diff --git a/include/gui/BufferItem.h b/include/gui/BufferItem.h
new file mode 100644
index 0000000..5effd10
--- /dev/null
+++ b/include/gui/BufferItem.h
@@ -0,0 +1,103 @@
+/*
+ * Copyright 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_GUI_BUFFERITEM_H
+#define ANDROID_GUI_BUFFERITEM_H
+
+#include <EGL/egl.h>
+#include <EGL/eglext.h>
+
+#include <gui/IGraphicBufferConsumer.h>
+
+#include <ui/Rect.h>
+
+#include <utils/Flattenable.h>
+#include <utils/StrongPointer.h>
+
+namespace android {
+
+class Fence;
+class GraphicBuffer;
+
+class BufferItem : public Flattenable<BufferItem> {
+    friend class Flattenable<BufferItem>;
+    size_t getPodSize() const;
+    size_t getFlattenedSize() const;
+    size_t getFdCount() const;
+    status_t flatten(void*& buffer, size_t& size, int*& fds, size_t& count) const;
+    status_t unflatten(void const*& buffer, size_t& size, int const*& fds, size_t& count);
+
+    public:
+    // The default value of mBuf, used to indicate this doesn't correspond to a slot.
+    enum { INVALID_BUFFER_SLOT = -1 };
+    BufferItem();
+    operator IGraphicBufferConsumer::BufferItem() const;
+
+    static const char* scalingModeName(uint32_t scalingMode);
+
+    // mGraphicBuffer points to the buffer allocated for this slot, or is NULL
+    // if the buffer in this slot has been acquired in the past (see
+    // BufferSlot.mAcquireCalled).
+    sp<GraphicBuffer> mGraphicBuffer;
+
+    // mFence is a fence that will signal when the buffer is idle.
+    sp<Fence> mFence;
+
+    // mCrop is the current crop rectangle for this buffer slot.
+    Rect mCrop;
+
+    // mTransform is the current transform flags for this buffer slot.
+    // refer to NATIVE_WINDOW_TRANSFORM_* in <window.h>
+    uint32_t mTransform;
+
+    // mScalingMode is the current scaling mode for this buffer slot.
+    // refer to NATIVE_WINDOW_SCALING_* in <window.h>
+    uint32_t mScalingMode;
+
+    // mTimestamp is the current timestamp for this buffer slot. This gets
+    // to set by queueBuffer each time this slot is queued. This value
+    // is guaranteed to be monotonically increasing for each newly
+    // acquired buffer.
+    int64_t mTimestamp;
+
+    // mIsAutoTimestamp indicates whether mTimestamp was generated
+    // automatically when the buffer was queued.
+    bool mIsAutoTimestamp;
+
+    // mFrameNumber is the number of the queued frame for this slot.
+    uint64_t mFrameNumber;
+
+    // mSlot is the slot index of this buffer (default INVALID_BUFFER_SLOT).
+    int mSlot;
+
+    // mIsDroppable whether this buffer was queued with the
+    // property that it can be replaced by a new buffer for the purpose of
+    // making sure dequeueBuffer() won't block.
+    // i.e.: was the BufferQueue in "mDequeueBufferCannotBlock" when this buffer
+    // was queued.
+    bool mIsDroppable;
+
+    // Indicates whether this buffer has been seen by a consumer yet
+    bool mAcquireCalled;
+
+    // Indicates this buffer must be transformed by the inverse transform of the screen
+    // it is displayed onto. This is applied after mTransform.
+    bool mTransformToDisplayInverse;
+};
+
+} // namespace android
+
+#endif
diff --git a/include/gui/BufferQueueConsumer.h b/include/gui/BufferQueueConsumer.h
new file mode 100644
index 0000000..0980ebb
--- /dev/null
+++ b/include/gui/BufferQueueConsumer.h
@@ -0,0 +1,148 @@
+/*
+ * Copyright 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_GUI_BUFFERQUEUECONSUMER_H
+#define ANDROID_GUI_BUFFERQUEUECONSUMER_H
+
+#include <EGL/egl.h>
+#include <EGL/eglext.h>
+
+#include <gui/BufferQueueCore.h>
+#include <gui/IGraphicBufferConsumer.h>
+
+namespace android {
+
+class BufferQueueCore;
+
+class BufferQueueConsumer : public BnGraphicBufferConsumer {
+
+public:
+    BufferQueueConsumer(const sp<BufferQueueCore>& core);
+    virtual ~BufferQueueConsumer();
+
+    // acquireBuffer attempts to acquire ownership of the next pending buffer in
+    // the BufferQueue. If no buffer is pending then it returns
+    // NO_BUFFER_AVAILABLE. If a buffer is successfully acquired, the
+    // information about the buffer is returned in BufferItem.  If the buffer
+    // returned had previously been acquired then the BufferItem::mGraphicBuffer
+    // field of buffer is set to NULL and it is assumed that the consumer still
+    // holds a reference to the buffer.
+    //
+    // If expectedPresent is nonzero, it indicates the time when the buffer
+    // will be displayed on screen. If the buffer's timestamp is farther in the
+    // future, the buffer won't be acquired, and PRESENT_LATER will be
+    // returned.  The presentation time is in nanoseconds, and the time base
+    // is CLOCK_MONOTONIC.
+    virtual status_t acquireBuffer(BufferItem* outBuffer,
+            nsecs_t expectedPresent);
+
+    // releaseBuffer releases a buffer slot from the consumer back to the
+    // BufferQueue.  This may be done while the buffer's contents are still
+    // being accessed.  The fence will signal when the buffer is no longer
+    // in use. frameNumber is used to indentify the exact buffer returned.
+    //
+    // If releaseBuffer returns STALE_BUFFER_SLOT, then the consumer must free
+    // any references to the just-released buffer that it might have, as if it
+    // had received a onBuffersReleased() call with a mask set for the released
+    // buffer.
+    //
+    // Note that the dependencies on EGL will be removed once we switch to using
+    // the Android HW Sync HAL.
+    virtual status_t releaseBuffer(int slot, uint64_t frameNumber,
+            const sp<Fence>& releaseFence, EGLDisplay display,
+            EGLSyncKHR fence);
+
+    // connect connects a consumer to the BufferQueue.  Only one
+    // consumer may be connected, and when that consumer disconnects the
+    // BufferQueue is placed into the "abandoned" state, causing most
+    // interactions with the BufferQueue by the producer to fail.
+    // controlledByApp indicates whether the consumer is controlled by
+    // the application.
+    //
+    // consumerListener may not be NULL.
+    virtual status_t connect(const sp<IConsumerListener>& consumerListener,
+            bool controlledByApp);
+
+    // disconnect disconnects a consumer from the BufferQueue. All
+    // buffers will be freed and the BufferQueue is placed in the "abandoned"
+    // state, causing most interactions with the BufferQueue by the producer to
+    // fail.
+    virtual status_t disconnect();
+
+    // getReleasedBuffers sets the value pointed to by outSlotMask to a bit mask
+    // indicating which buffer slots have been released by the BufferQueue
+    // but have not yet been released by the consumer.
+    //
+    // This should be called from the onBuffersReleased() callback.
+    virtual status_t getReleasedBuffers(uint32_t* outSlotMask);
+
+    // setDefaultBufferSize is used to set the size of buffers returned by
+    // dequeueBuffer when a width and height of zero is requested.  Default
+    // is 1x1.
+    virtual status_t setDefaultBufferSize(uint32_t width, uint32_t height);
+
+    // setDefaultMaxBufferCount sets the default value for the maximum buffer
+    // count (the initial default is 2). If the producer has requested a
+    // buffer count using setBufferCount, the default buffer count will only
+    // take effect if the producer sets the count back to zero.
+    //
+    // The count must be between 2 and NUM_BUFFER_SLOTS, inclusive.
+    virtual status_t setDefaultMaxBufferCount(int bufferCount);
+
+    // disableAsyncBuffer disables the extra buffer used in async mode
+    // (when both producer and consumer have set their "isControlledByApp"
+    // flag) and has dequeueBuffer() return WOULD_BLOCK instead.
+    //
+    // This can only be called before connect().
+    virtual status_t disableAsyncBuffer();
+
+    // setMaxAcquiredBufferCount sets the maximum number of buffers that can
+    // be acquired by the consumer at one time (default 1).  This call will
+    // fail if a producer is connected to the BufferQueue.
+    virtual status_t setMaxAcquiredBufferCount(int maxAcquiredBuffers);
+
+    // setConsumerName sets the name used in logging
+    virtual void setConsumerName(const String8& name);
+
+    // setDefaultBufferFormat allows the BufferQueue to create
+    // GraphicBuffers of a defaultFormat if no format is specified
+    // in dequeueBuffer.  Formats are enumerated in graphics.h; the
+    // initial default is HAL_PIXEL_FORMAT_RGBA_8888.
+    virtual status_t setDefaultBufferFormat(uint32_t defaultFormat);
+
+    // setConsumerUsageBits will turn on additional usage bits for dequeueBuffer.
+    // These are merged with the bits passed to dequeueBuffer.  The values are
+    // enumerated in gralloc.h, e.g. GRALLOC_USAGE_HW_RENDER; the default is 0.
+    virtual status_t setConsumerUsageBits(uint32_t usage);
+
+    // setTransformHint bakes in rotation to buffers so overlays can be used.
+    // The values are enumerated in window.h, e.g.
+    // NATIVE_WINDOW_TRANSFORM_ROT_90.  The default is 0 (no transform).
+    virtual status_t setTransformHint(uint32_t hint);
+
+    // dump our state in a String
+    virtual void dump(String8& result, const char* prefix) const;
+
+private:
+    sp<BufferQueueCore> mCore;
+    BufferQueueCore::SlotsType& mSlots;
+    String8 mConsumerName; // Cached from mCore. Updated on setConsumerName.
+
+}; // class BufferQueueConsumer
+
+} // namespace android
+
+#endif
diff --git a/include/gui/BufferQueueCore.h b/include/gui/BufferQueueCore.h
new file mode 100644
index 0000000..ef11c61
--- /dev/null
+++ b/include/gui/BufferQueueCore.h
@@ -0,0 +1,120 @@
+/*
+ * Copyright 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_GUI_BUFFERQUEUECORE_H
+#define ANDROID_GUI_BUFFERQUEUECORE_H
+
+#include <gui/BufferSlot.h>
+
+#include <utils/Condition.h>
+#include <utils/Mutex.h>
+#include <utils/RefBase.h>
+#include <utils/String8.h>
+#include <utils/StrongPointer.h>
+#include <utils/Trace.h>
+#include <utils/Vector.h>
+
+#define BQ_LOGV(x, ...) ALOGV("[%s] "x, mConsumerName.string(), ##__VA_ARGS__)
+#define BQ_LOGD(x, ...) ALOGD("[%s] "x, mConsumerName.string(), ##__VA_ARGS__)
+#define BQ_LOGI(x, ...) ALOGI("[%s] "x, mConsumerName.string(), ##__VA_ARGS__)
+#define BQ_LOGW(x, ...) ALOGW("[%s] "x, mConsumerName.string(), ##__VA_ARGS__)
+#define BQ_LOGE(x, ...) ALOGE("[%s] "x, mConsumerName.string(), ##__VA_ARGS__)
+
+#define ATRACE_BUFFER_INDEX(index)                                   \
+    if (ATRACE_ENABLED()) {                                          \
+        char ___traceBuf[1024];                                      \
+        snprintf(___traceBuf, 1024, "%s: %d",                        \
+                mCore->mConsumerName.string(), (index));             \
+        android::ScopedTrace ___bufTracer(ATRACE_TAG, ___traceBuf);  \
+    }
+
+namespace android {
+
+class BufferItem;
+class IBinder;
+class IConsumerListener;
+class IGraphicBufferAlloc;
+
+class BufferQueueCore : public virtual RefBase {
+
+    friend class BufferQueueProducer;
+    friend class BufferQueueConsumer;
+
+public:
+    // BufferQueue will keep track of at most this value of buffers. Attempts
+    // at runtime to increase the number of buffers past this will fail.
+    enum { NUM_BUFFER_SLOTS = 32 };
+
+    // Used as a placeholder slot number when the value isn't pointing to an
+    // existing buffer.
+    enum { INVALID_BUFFER_SLOT = -1 }; // TODO: Extract from IGBC::BufferItem
+
+    // We reserve two slots in order to guarantee that the producer and
+    // consumer can run asynchronously.
+    enum { MAX_MAX_ACQUIRED_BUFFERS = NUM_BUFFER_SLOTS - 2 };
+
+    // The default API number used to indicate that no producer is connected
+    enum { NO_CONNECTED_API = 0 };
+
+    typedef BufferSlot SlotsType[NUM_BUFFER_SLOTS];
+    typedef Vector<BufferItem> Fifo;
+
+    // BufferQueueCore manages a pool of gralloc memory slots to be used by
+    // producers and consumers. allocator is used to allocate all the needed
+    // gralloc buffers.
+    BufferQueueCore(const sp<IGraphicBufferAlloc>& allocator = NULL);
+    virtual ~BufferQueueCore();
+
+private:
+    void dump(String8& result, const char* prefix) const;
+
+    int getMinUndequeuedBufferCountLocked(bool async) const;
+    int getMinMaxBufferCountLocked(bool async) const;
+    int getMaxBufferCountLocked(bool async) const;
+    status_t setDefaultMaxBufferCountLocked(int count);
+    void freeBufferLocked(int slot);
+    void freeAllBuffersLocked();
+    bool stillTracking(const BufferItem* item) const;
+
+    const sp<IGraphicBufferAlloc>& mAllocator;
+    mutable Mutex mMutex;
+    bool mIsAbandoned;
+    bool mConsumerControlledByApp;
+    String8 mConsumerName;
+    sp<IConsumerListener> mConsumerListener;
+    uint32_t mConsumerUsageBits;
+    int mConnectedApi;
+    sp<IBinder> mConnectedProducerToken;
+    BufferSlot mSlots[NUM_BUFFER_SLOTS];
+    Fifo mQueue;
+    int mOverrideMaxBufferCount;
+    mutable Condition mDequeueCondition;
+    bool mUseAsyncBuffer;
+    bool mDequeueBufferCannotBlock;
+    uint32_t mDefaultBufferFormat;
+    int mDefaultWidth;
+    int mDefaultHeight;
+    int mDefaultMaxBufferCount;
+    int mMaxAcquiredBufferCount;
+    bool mBufferHasBeenQueued;
+    uint64_t mFrameCounter;
+    uint32_t mTransformHint;
+
+}; // class BufferQueueCore
+
+} // namespace android
+
+#endif
diff --git a/include/gui/BufferQueueProducer.h b/include/gui/BufferQueueProducer.h
new file mode 100644
index 0000000..7f063aa
--- /dev/null
+++ b/include/gui/BufferQueueProducer.h
@@ -0,0 +1,165 @@
+/*
+ * Copyright 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_GUI_BUFFERQUEUEPRODUCER_H
+#define ANDROID_GUI_BUFFERQUEUEPRODUCER_H
+
+#include <gui/BufferQueueCore.h>
+#include <gui/IGraphicBufferProducer.h>
+
+namespace android {
+
+class BufferSlot;
+
+class BufferQueueProducer : public BnGraphicBufferProducer,
+                            private IBinder::DeathRecipient {
+
+public:
+    BufferQueueProducer(const sp<BufferQueueCore>& core);
+    virtual ~BufferQueueProducer();
+
+    // requestBuffer returns the GraphicBuffer for slot N.
+    //
+    // In normal operation, this is called the first time slot N is returned
+    // by dequeueBuffer.  It must be called again if dequeueBuffer returns
+    // flags indicating that previously-returned buffers are no longer valid.
+    virtual status_t requestBuffer(int slot, sp<GraphicBuffer>* buf);
+
+    // setBufferCount updates the number of available buffer slots.  If this
+    // method succeeds, buffer slots will be both unallocated and owned by
+    // the BufferQueue object (i.e. they are not owned by the producer or
+    // consumer).
+    //
+    // This will fail if the producer has dequeued any buffers, or if
+    // bufferCount is invalid.  bufferCount must generally be a value
+    // between the minimum undequeued buffer count (exclusive) and NUM_BUFFER_SLOTS
+    // (inclusive).  It may also be set to zero (the default) to indicate
+    // that the producer does not wish to set a value.  The minimum value
+    // can be obtained by calling query(NATIVE_WINDOW_MIN_UNDEQUEUED_BUFFERS,
+    // ...).
+    //
+    // This may only be called by the producer.  The consumer will be told
+    // to discard buffers through the onBuffersReleased callback.
+    virtual status_t setBufferCount(int bufferCount);
+
+    // dequeueBuffer gets the next buffer slot index for the producer to use.
+    // If a buffer slot is available then that slot index is written to the
+    // location pointed to by the buf argument and a status of OK is returned.
+    // If no slot is available then a status of -EBUSY is returned and buf is
+    // unmodified.
+    //
+    // The outFence parameter will be updated to hold the fence associated with
+    // the buffer. The contents of the buffer must not be overwritten until the
+    // fence signals. If the fence is Fence::NO_FENCE, the buffer may be
+    // written immediately.
+    //
+    // The width and height parameters must be no greater than the minimum of
+    // GL_MAX_VIEWPORT_DIMS and GL_MAX_TEXTURE_SIZE (see: glGetIntegerv).
+    // An error due to invalid dimensions might not be reported until
+    // updateTexImage() is called.  If width and height are both zero, the
+    // default values specified by setDefaultBufferSize() are used instead.
+    //
+    // The pixel formats are enumerated in graphics.h, e.g.
+    // HAL_PIXEL_FORMAT_RGBA_8888.  If the format is 0, the default format
+    // will be used.
+    //
+    // The usage argument specifies gralloc buffer usage flags.  The values
+    // are enumerated in gralloc.h, e.g. GRALLOC_USAGE_HW_RENDER.  These
+    // will be merged with the usage flags specified by setConsumerUsageBits.
+    //
+    // The return value may be a negative error value or a non-negative
+    // collection of flags.  If the flags are set, the return values are
+    // valid, but additional actions must be performed.
+    //
+    // If IGraphicBufferProducer::BUFFER_NEEDS_REALLOCATION is set, the
+    // producer must discard cached GraphicBuffer references for the slot
+    // returned in buf.
+    // If IGraphicBufferProducer::RELEASE_ALL_BUFFERS is set, the producer
+    // must discard cached GraphicBuffer references for all slots.
+    //
+    // In both cases, the producer will need to call requestBuffer to get a
+    // GraphicBuffer handle for the returned slot.
+    virtual status_t dequeueBuffer(int *outSlot, sp<Fence>* outFence, bool async,
+            uint32_t width, uint32_t height, uint32_t format, uint32_t usage);
+
+    // queueBuffer returns a filled buffer to the BufferQueue.
+    //
+    // Additional data is provided in the QueueBufferInput struct.  Notably,
+    // a timestamp must be provided for the buffer. The timestamp is in
+    // nanoseconds, and must be monotonically increasing. Its other semantics
+    // (zero point, etc) are producer-specific and should be documented by the
+    // producer.
+    //
+    // The caller may provide a fence that signals when all rendering
+    // operations have completed.  Alternatively, NO_FENCE may be used,
+    // indicating that the buffer is ready immediately.
+    //
+    // Some values are returned in the output struct: the current settings
+    // for default width and height, the current transform hint, and the
+    // number of queued buffers.
+    virtual status_t queueBuffer(int slot,
+            const QueueBufferInput& input, QueueBufferOutput* output);
+
+    // cancelBuffer returns a dequeued buffer to the BufferQueue, but doesn't
+    // queue it for use by the consumer.
+    //
+    // The buffer will not be overwritten until the fence signals.  The fence
+    // will usually be the one obtained from dequeueBuffer.
+    virtual void cancelBuffer(int slot, const sp<Fence>& fence);
+
+    // Query native window attributes.  The "what" values are enumerated in
+    // window.h (e.g. NATIVE_WINDOW_FORMAT).
+    virtual int query(int what, int* outValue);
+
+    // connect attempts to connect a producer API to the BufferQueue.  This
+    // must be called before any other IGraphicBufferProducer methods are
+    // called except for getAllocator.  A consumer must already be connected.
+    //
+    // This method will fail if connect was previously called on the
+    // BufferQueue and no corresponding disconnect call was made (i.e. if
+    // it's still connected to a producer).
+    //
+    // APIs are enumerated in window.h (e.g. NATIVE_WINDOW_API_CPU).
+    virtual status_t connect(const sp<IBinder>& token,
+            int api, bool producerControlledByApp, QueueBufferOutput* output);
+
+    // disconnect attempts to disconnect a producer API from the BufferQueue.
+    // Calling this method will cause any subsequent calls to other
+    // IGraphicBufferProducer methods to fail except for getAllocator and connect.
+    // Successfully calling connect after this will allow the other methods to
+    // succeed again.
+    //
+    // This method will fail if the the BufferQueue is not currently
+    // connected to the specified producer API.
+    virtual status_t disconnect(int api);
+
+private:
+    // This is required by the IBinder::DeathRecipient interface
+    virtual void binderDied(const wp<IBinder>& who);
+
+    sp<BufferQueueCore> mCore;
+    BufferQueueCore::SlotsType& mSlots;
+
+    // This is a cached copy of the name stored in the BufferQueueCore.
+    // It's updated during connect and dequeueBuffer (which should catch
+    // most updates).
+    String8 mConsumerName;
+
+}; // class BufferQueueProducer
+
+} // namespace android
+
+#endif
diff --git a/include/gui/BufferSlot.h b/include/gui/BufferSlot.h
new file mode 100644
index 0000000..2c4b43f
--- /dev/null
+++ b/include/gui/BufferSlot.h
@@ -0,0 +1,136 @@
+/*
+ * Copyright 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_GUI_BUFFERSLOT_H
+#define ANDROID_GUI_BUFFERSLOT_H
+
+#include <ui/Fence.h>
+#include <ui/GraphicBuffer.h>
+
+#include <EGL/egl.h>
+#include <EGL/eglext.h>
+
+#include <utils/StrongPointer.h>
+
+namespace android {
+
+class Fence;
+
+struct BufferSlot {
+
+    BufferSlot()
+    : mEglDisplay(EGL_NO_DISPLAY),
+      mBufferState(BufferSlot::FREE),
+      mRequestBufferCalled(false),
+      mFrameNumber(0),
+      mEglFence(EGL_NO_SYNC_KHR),
+      mAcquireCalled(false),
+      mNeedsCleanupOnRelease(false) {
+    }
+
+    // mGraphicBuffer points to the buffer allocated for this slot or is NULL
+    // if no buffer has been allocated.
+    sp<GraphicBuffer> mGraphicBuffer;
+
+    // mEglDisplay is the EGLDisplay used to create EGLSyncKHR objects.
+    EGLDisplay mEglDisplay;
+
+    // BufferState represents the different states in which a buffer slot
+    // can be.  All slots are initially FREE.
+    enum BufferState {
+        // FREE indicates that the buffer is available to be dequeued
+        // by the producer.  The buffer may be in use by the consumer for
+        // a finite time, so the buffer must not be modified until the
+        // associated fence is signaled.
+        //
+        // The slot is "owned" by BufferQueue.  It transitions to DEQUEUED
+        // when dequeueBuffer is called.
+        FREE = 0,
+
+        // DEQUEUED indicates that the buffer has been dequeued by the
+        // producer, but has not yet been queued or canceled.  The
+        // producer may modify the buffer's contents as soon as the
+        // associated ready fence is signaled.
+        //
+        // The slot is "owned" by the producer.  It can transition to
+        // QUEUED (via queueBuffer) or back to FREE (via cancelBuffer).
+        DEQUEUED = 1,
+
+        // QUEUED indicates that the buffer has been filled by the
+        // producer and queued for use by the consumer.  The buffer
+        // contents may continue to be modified for a finite time, so
+        // the contents must not be accessed until the associated fence
+        // is signaled.
+        //
+        // The slot is "owned" by BufferQueue.  It can transition to
+        // ACQUIRED (via acquireBuffer) or to FREE (if another buffer is
+        // queued in asynchronous mode).
+        QUEUED = 2,
+
+        // ACQUIRED indicates that the buffer has been acquired by the
+        // consumer.  As with QUEUED, the contents must not be accessed
+        // by the consumer until the fence is signaled.
+        //
+        // The slot is "owned" by the consumer.  It transitions to FREE
+        // when releaseBuffer is called.
+        ACQUIRED = 3
+    };
+
+    static const char* bufferStateName(BufferState state);
+
+    // mBufferState is the current state of this buffer slot.
+    BufferState mBufferState;
+
+    // mRequestBufferCalled is used for validating that the producer did
+    // call requestBuffer() when told to do so. Technically this is not
+    // needed but useful for debugging and catching producer bugs.
+    bool mRequestBufferCalled;
+
+    // mFrameNumber is the number of the queued frame for this slot.  This
+    // is used to dequeue buffers in LRU order (useful because buffers
+    // may be released before their release fence is signaled).
+    uint64_t mFrameNumber;
+
+    // mEglFence is the EGL sync object that must signal before the buffer
+    // associated with this buffer slot may be dequeued. It is initialized
+    // to EGL_NO_SYNC_KHR when the buffer is created and may be set to a
+    // new sync object in releaseBuffer.  (This is deprecated in favor of
+    // mFence, below.)
+    EGLSyncKHR mEglFence;
+
+    // mFence is a fence which will signal when work initiated by the
+    // previous owner of the buffer is finished. When the buffer is FREE,
+    // the fence indicates when the consumer has finished reading
+    // from the buffer, or when the producer has finished writing if it
+    // called cancelBuffer after queueing some writes. When the buffer is
+    // QUEUED, it indicates when the producer has finished filling the
+    // buffer. When the buffer is DEQUEUED or ACQUIRED, the fence has been
+    // passed to the consumer or producer along with ownership of the
+    // buffer, and mFence is set to NO_FENCE.
+    sp<Fence> mFence;
+
+    // Indicates whether this buffer has been seen by a consumer yet
+    bool mAcquireCalled;
+
+    // Indicates whether this buffer needs to be cleaned up by the
+    // consumer.  This is set when a buffer in ACQUIRED state is freed.
+    // It causes releaseBuffer to return STALE_BUFFER_SLOT.
+    bool mNeedsCleanupOnRelease;
+};
+
+} // namespace android
+
+#endif