path: root/libs/gui/include/gui/BufferQueueCore.h

/*
 * 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/BufferItem.h>
#include <gui/BufferQueueDefs.h>
#include <gui/BufferSlot.h>
#include <gui/OccupancyTracker.h>

#include <utils/NativeHandle.h>
#include <utils/RefBase.h>
#include <utils/String8.h>
#include <utils/StrongPointer.h>
#include <utils/Trace.h>
#include <utils/Vector.h>

#include <list>
#include <set>
#include <mutex>
#include <condition_variable>

#define ATRACE_BUFFER_INDEX(index)                                                         \
    do {                                                                                   \
        if (ATRACE_ENABLED()) {                                                            \
            char ___traceBuf[1024];                                                        \
            snprintf(___traceBuf, 1024, "%s: %d", mCore->mConsumerName.string(), (index)); \
            android::ScopedTrace ___bufTracer(ATRACE_TAG, ___traceBuf);                    \
        }                                                                                  \
    } while (false)

namespace android {

class IConsumerListener;
class IProducerListener;

class BufferQueueCore : public virtual RefBase {

    friend class BufferQueueProducer;
    friend class BufferQueueConsumer;

public:
    // Used as a placeholder slot number when the value isn't pointing to an
    // existing buffer.
    enum { INVALID_BUFFER_SLOT = BufferItem::INVALID_BUFFER_SLOT };

    // We reserve two slots in order to guarantee that the producer and
    // consumer can run asynchronously.
    enum { MAX_MAX_ACQUIRED_BUFFERS = BufferQueueDefs::NUM_BUFFER_SLOTS - 2 };

    enum {
        // The API number used to indicate the currently connected producer
        CURRENTLY_CONNECTED_API = -1,

        // The API number used to indicate that no producer is connected
        NO_CONNECTED_API        = 0,
    };

    typedef Vector<BufferItem> Fifo;

    // BufferQueueCore manages a pool of gralloc memory slots to be used by
    // producers and consumers.
    BufferQueueCore();
    virtual ~BufferQueueCore();

private:
    // Dump our state in a string
    void dumpState(const String8& prefix, String8* outResult) const;

    // getMinUndequeuedBufferCountLocked returns the minimum number of buffers
    // that must remain in a state other than DEQUEUED. The async parameter
    // tells whether we're in asynchronous mode.
    int getMinUndequeuedBufferCountLocked() const;

    // getMinMaxBufferCountLocked returns the minimum number of buffers allowed
    // given the current BufferQueue state. The async parameter tells whether
    // we're in asynchonous mode.
    int getMinMaxBufferCountLocked() const;

    // getMaxBufferCountLocked returns the maximum number of buffers that can be
    // allocated at once. This value depends on the following member variables:
    //
    //     mMaxDequeuedBufferCount
    //     mMaxAcquiredBufferCount
    //     mMaxBufferCount
    //     mAsyncMode
    //     mDequeueBufferCannotBlock
    //
    // Any time one of these member variables is changed while a producer is
    // connected, mDequeueCondition must be broadcast.
    int getMaxBufferCountLocked() const;

    // This performs the same computation but uses the given arguments instead
    // of the member variables for mMaxBufferCount, mAsyncMode, and
    // mDequeueBufferCannotBlock.
    int getMaxBufferCountLocked(bool asyncMode,
            bool dequeueBufferCannotBlock, int maxBufferCount) const;

    // clearBufferSlotLocked frees the GraphicBuffer and sync resources for the
    // given slot.
    void clearBufferSlotLocked(int slot);

    // freeAllBuffersLocked frees the GraphicBuffer and sync resources for
    // all slots, even if they're currently dequeued, queued, or acquired.
    void freeAllBuffersLocked();

    // discardFreeBuffersLocked releases all currently-free buffers held by the
    // queue, in order to reduce the memory consumption of the queue to the
    // minimum possible without discarding data.
    void discardFreeBuffersLocked();

    // If delta is positive, makes more slots available. If negative, takes
    // away slots. Returns false if the request can't be met.
    bool adjustAvailableSlotsLocked(int delta);

    // waitWhileAllocatingLocked blocks until mIsAllocating is false.
    void waitWhileAllocatingLocked(std::unique_lock<std::mutex>& lock) const;

#if DEBUG_ONLY_CODE
    // validateConsistencyLocked ensures that the free lists are in sync with
    // the information stored in mSlots
    void validateConsistencyLocked() const;
#endif

    // mMutex is the mutex used to prevent concurrent access to the member
    // variables of BufferQueueCore objects. It must be locked whenever any
    // member variable is accessed.
    mutable std::mutex mMutex;

    // mIsAbandoned indicates that the BufferQueue will no longer be used to
    // consume image buffers pushed to it using the IGraphicBufferProducer
    // interface. It is initialized to false, and set to true in the
    // consumerDisconnect method. A BufferQueue that is abandoned will return
    // the NO_INIT error from all IGraphicBufferProducer methods capable of
    // returning an error.
    bool mIsAbandoned;

    // mConsumerControlledByApp indicates whether the connected consumer is
    // controlled by the application.
    bool mConsumerControlledByApp;

    // mConsumerName is a string used to identify the BufferQueue in log
    // messages. It is set by the IGraphicBufferConsumer::setConsumerName
    // method.
    String8 mConsumerName;

    // mConsumerListener is used to notify the connected consumer of
    // asynchronous events that it may wish to react to. It is initially
    // set to NULL and is written by consumerConnect and consumerDisconnect.
    sp<IConsumerListener> mConsumerListener;

    // mConsumerUsageBits contains flags that the consumer wants for
    // GraphicBuffers.
    uint64_t mConsumerUsageBits;

    // mConsumerIsProtected indicates the consumer is ready to handle protected
    // buffer.
    bool mConsumerIsProtected;

    // mConnectedApi indicates the producer API that is currently connected
    // to this BufferQueue. It defaults to NO_CONNECTED_API, and gets updated
    // by the connect and disconnect methods.
    int mConnectedApi;
    // PID of the process which last successfully called connect(...)
    pid_t mConnectedPid;

    // mLinkedToDeath is used to set a binder death notification on
    // the producer.
    sp<IProducerListener> mLinkedToDeath;

    // mConnectedProducerListener is used to handle the onBufferReleased
    // and onBuffersDiscarded notification.
    sp<IProducerListener> mConnectedProducerListener;
    // mBufferReleasedCbEnabled is used to indicate whether onBufferReleased()
    // callback is registered by the listener. When set to false,
    // mConnectedProducerListener will not trigger onBufferReleased() callback.
    bool mBufferReleasedCbEnabled;

    // mSlots is an array of buffer slots that must be mirrored on the producer
    // side. This allows buffer ownership to be transferred between the producer
    // and consumer without sending a GraphicBuffer over Binder. The entire
    // array is initialized to NULL at construction time, and buffers are
    // allocated for a slot when requestBuffer is called with that slot's index.
    BufferQueueDefs::SlotsType mSlots;

    // mQueue is a FIFO of queued buffers used in synchronous mode.
    Fifo mQueue;

    // mFreeSlots contains all of the slots which are FREE and do not currently
    // have a buffer attached.
    std::set<int> mFreeSlots;

    // mFreeBuffers contains all of the slots which are FREE and currently have
    // a buffer attached.
    std::list<int> mFreeBuffers;

    // mUnusedSlots contains all slots that are currently unused. They should be
    // free and not have a buffer attached.
    std::list<int> mUnusedSlots;

    // mActiveBuffers contains all slots which have a non-FREE buffer attached.
    std::set<int> mActiveBuffers;

    // mDequeueCondition is a condition variable used for dequeueBuffer in
    // synchronous mode.
    mutable std::condition_variable mDequeueCondition;

    // mDequeueBufferCannotBlock indicates whether dequeueBuffer is allowed to
    // block. This flag is set during connect when both the producer and
    // consumer are controlled by the application.
    bool mDequeueBufferCannotBlock;

    // mQueueBufferCanDrop indicates whether queueBuffer is allowed to drop
    // buffers in non-async mode. This flag is set during connect when both the
    // producer and consumer are controlled by application.
    bool mQueueBufferCanDrop;

    // mLegacyBufferDrop indicates whether mQueueBufferCanDrop is in effect.
    // If this flag is set mQueueBufferCanDrop is working as explained. If not
    // queueBuffer will not drop buffers unless consumer is SurfaceFlinger and
    // mQueueBufferCanDrop is set.
    bool mLegacyBufferDrop;

    // mDefaultBufferFormat can be set so it will override the buffer format
    // when it isn't specified in dequeueBuffer.
    PixelFormat mDefaultBufferFormat;

    // mDefaultWidth holds the default width of allocated buffers. It is used
    // in dequeueBuffer if a width and height of 0 are specified.
    uint32_t mDefaultWidth;

    // mDefaultHeight holds the default height of allocated buffers. It is used
    // in dequeueBuffer if a width and height of 0 are specified.
    uint32_t mDefaultHeight;

    // mDefaultBufferDataSpace holds the default dataSpace of queued buffers.
    // It is used in queueBuffer if a dataspace of 0 (HAL_DATASPACE_UNKNOWN)
    // is specified.
    android_dataspace mDefaultBufferDataSpace;

    // mMaxBufferCount is the limit on the number of buffers that will be
    // allocated at one time. This limit can be set by the consumer.
    int mMaxBufferCount;

    // mMaxAcquiredBufferCount is the number of buffers that the consumer may
    // acquire at one time. It defaults to 1, and can be changed by the consumer
    // via setMaxAcquiredBufferCount, but this may only be done while no
    // producer is connected to the BufferQueue. This value is used to derive
    // the value returned for the MIN_UNDEQUEUED_BUFFERS query to the producer.
    int mMaxAcquiredBufferCount;

    // mMaxDequeuedBufferCount is the number of buffers that the producer may
    // dequeue at one time. It defaults to 1, and can be changed by the producer
    // via setMaxDequeuedBufferCount.
    int mMaxDequeuedBufferCount;

    // mBufferHasBeenQueued is true once a buffer has been queued. It is reset
    // when something causes all buffers to be freed (e.g., changing the buffer
    // count).
    bool mBufferHasBeenQueued;

    // mFrameCounter is the free running counter, incremented on every
    // successful queueBuffer call and buffer allocation.
    uint64_t mFrameCounter;

    // mTransformHint is used to optimize for screen rotations.
    uint32_t mTransformHint;

    // mSidebandStream is a handle to the sideband buffer stream, if any
    sp<NativeHandle> mSidebandStream;

    // mIsAllocating indicates whether a producer is currently trying to allocate buffers (which
    // releases mMutex while doing the allocation proper). Producers should not modify any of the
    // FREE slots while this is true. mIsAllocatingCondition is signaled when this value changes to
    // false.
    bool mIsAllocating;

    // mIsAllocatingCondition is a condition variable used by producers to wait until mIsAllocating
    // becomes false.
    mutable std::condition_variable mIsAllocatingCondition;

    // mAllowAllocation determines whether dequeueBuffer is allowed to allocate
    // new buffers
    bool mAllowAllocation;

    // mBufferAge tracks the age of the contents of the most recently dequeued
    // 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;

    // mAsyncMode indicates whether or not async mode is enabled.
    // In async mode an extra buffer will be allocated to allow the producer to
    // enqueue buffers without blocking.
    bool mAsyncMode;

    // mSharedBufferMode indicates whether or not shared buffer mode is enabled.
    bool mSharedBufferMode;

    // When shared buffer mode is enabled, this indicates whether the consumer
    // should acquire buffers even if BufferQueue doesn't indicate that they are
    // available.
    bool mAutoRefresh;

    // When shared buffer mode is enabled, this tracks which slot contains the
    // shared buffer.
    int mSharedBufferSlot;

    // Cached data about the shared buffer in shared buffer mode
    struct SharedBufferCache {
        SharedBufferCache(Rect _crop, uint32_t _transform,
                uint32_t _scalingMode, android_dataspace _dataspace)
        : crop(_crop),
          transform(_transform),
          scalingMode(_scalingMode),
          dataspace(_dataspace) {
        }

        Rect crop;
        uint32_t transform;
        uint32_t scalingMode;
        android_dataspace dataspace;
    } mSharedBufferCache;

    // The slot of the last queued buffer
    int mLastQueuedSlot;

    OccupancyTracker mOccupancyTracker;

    const uint64_t mUniqueId;

    // When buffer size is driven by the consumer and mTransformHint specifies
    // a 90 or 270 degree rotation, this indicates whether the width and height
    // used by dequeueBuffer will be additionally swapped.
    bool mAutoPrerotation;

    // mTransformHintInUse is to cache the mTransformHint used by the producer.
    uint32_t mTransformHintInUse;

}; // class BufferQueueCore

} // namespace android

#endif