Android開發(fā)graphics?bufferqueue整體流程

更新時(shí)間：2023年07月09日 16:21:24 作者：Yink_Liu

這篇文章主要為大家介紹了Android開發(fā)graphics?bufferqueue整體流程詳解，有需要的朋友可以借鑒參考下，希望能夠有所幫助，祝大家多多進(jìn)步，早日升職加薪

一、引言

1、bufferqueue 的四大流程；

2、簡(jiǎn)要介紹四大流程的調(diào)用過程；

本文主要講解安卓圖形繪制中的buffer queue

頁面數(shù)據(jù)通過canvas/Open GL ES/vulkan繪制后，形成一幀buffer，交給buffer queue，buffer queue再把數(shù)據(jù)送到屏幕上顯示。所以buffer queue是圖形繪制中很核心的一環(huán)，它本身就是一個(gè)緩沖區(qū)池與隊(duì)列相結(jié)合的數(shù)據(jù)結(jié)構(gòu)。

Buffer queue:

圖像緩沖區(qū)，系統(tǒng)中絕大部分圖形數(shù)據(jù)都會(huì)緩沖于此。等待surfaceflinger組織進(jìn)一步的合成和顯示

備注：本文摘錄的代碼只摘錄關(guān)鍵代碼和路徑，需讀者自行結(jié)合閱讀.由于本文的重點(diǎn)在bufferqueue，其它和bufferqueue相關(guān)的流程提到的時(shí)候會(huì)精簡(jiǎn)列出，作為輔助理解。

二、Buffer queue

2.1、buffer queue的創(chuàng)建

bufferquque構(gòu)建

//BufferQueue.cpp    frameworks\native\libs\gui
void BufferQueue::createBufferQueue(sp<IGraphicBufferProducer>* outProducer,
        sp<IGraphicBufferConsumer>* outConsumer,
        bool consumerIsSurfaceFlinger) {
    sp<BufferQueueCore> core(new BufferQueueCore());
    sp<IGraphicBufferProducer> producer(new BufferQueueProducer(core, consumerIsSurfaceFlinger));
    sp<IGraphicBufferConsumer> consumer(new BufferQueueConsumer(core));
    *outProducer = producer;
    *outConsumer = consumer;
}

構(gòu)建調(diào)用流程

下面堆棧表示了底層surface創(chuàng)建bufferqueue的一個(gè)過程

04-20 11:45:54.739   674   707 E createBufferQueue: #00 pc 0004ca33  /system/lib/libgui.so (android::BufferQueue::createBufferQueue(android::sp<android::IGraphicBufferProducer>*, android::sp<android::IGraphicBufferConsumer>*, bool)+74)
04-20 11:45:54.739   674   707 E createBufferQueue: #01 pc 00068539  /system/lib/libsurfaceflinger.so (android::BufferQueueLayer::onFirstRef()+40)
04-20 11:45:54.739   674   707 E createBufferQueue: #02 pc 000d5ad1  /system/lib/libsurfaceflinger.so (android::surfaceflinger::DefaultFactory::createBufferQueueLayer(android::LayerCreationArgs const&)+52)
04-20 11:45:54.739   674   707 E createBufferQueue: #03 pc 000c11d5  /system/lib/libsurfaceflinger.so (android::SurfaceFlinger::createLayer(android::String8 const&, android::sp<android::Client> const&, unsigned int, unsigned int, int, unsigned int, android::LayerMetadata, android::sp<android::IBinder>*, android::sp<android::IGraphicBufferProducer>*, android::sp<android::IBinder> const&, android::sp<android::Layer> const&, unsigned int*)+1056)
04-20 11:45:54.739   674   707 E createBufferQueue: #04 pc 0006e197  /system/lib/libsurfaceflinger.so (android::Client::createSurface(android::String8 const&, unsigned int, unsigned int, int, unsigned int, android::sp<android::IBinder> const&, android::LayerMetadata, android::sp<android::IBinder>*, android::sp<android::IGraphicBufferProducer>*, unsigned int*)+122)
04-20 11:45:54.739   674   707 E createBufferQueue: #05 pc 0007b34f  /system/lib/libgui.so (int android::SafeBnInterface<android::ISurfaceComposerClient>::MethodCaller<std::__1::tuple<android::String8 const&, unsigned int, unsigned int, int, unsigned int, android::sp<android::IGraphicBufferProducer> const&, android::LayerMetadata, android::sp<android::IBinder>*, android::sp<android::IGraphicBufferProducer>*, unsigned int*> >::callHelper<android::SafeBnInterface<android::ISurfaceComposerClient>, int (android::ISurfaceComposerClient::*)(android::String8 const&, unsigned int, unsigned int, int, unsigned int, android::sp<android::IGraphicBufferProducer> const&, android::LayerMetadata, android::sp<android::IBinder>*, android::sp<android::IGraphicBufferProducer>*, unsigned int*), std::__1::tuple<android::String8, unsigned int, unsigned int, int, unsigned int, android::sp<android::IGraphicBufferProducer>, android::LayerMetadata, android::sp<android::IBinder>, android::sp<android::IGraphicBufferProducer>, unsigned int>, 0u, 1u, 2u, 3u, 4u, 5u, 6u, 7u, 8u, 9u>(android
04-20 11:45:54.739   674   707 E createBufferQueue: #06 pc 00079e2f  /system/lib/libgui.so (int android::SafeBnInterface<android::ISurfaceComposerClient>::callLocal<int (android::ISurfaceComposerClient::*)(android::String8 const&, unsigned int, unsigned int, int, unsigned int, android::sp<android::IBinder> const&, android::LayerMetadata, android::sp<android::IBinder>*, android::sp<android::IGraphicBufferProducer>*, unsigned int*)>(android::Parcel const&, android::Parcel*, int (android::ISurfaceComposerClient::*)(android::String8 const&, unsigned int, unsigned int, int, unsigned int, android::sp<android::IBinder> const&, android::LayerMetadata, android::sp<android::IBinder>*, android::sp<android::IGraphicBufferProducer>*, unsigned int*))+158)
04-20 11:45:54.739   674   707 E createBufferQueue: #07 pc 00079d3f  /system/lib/libgui.so (android::BnSurfaceComposerClient::onTransact(unsigned int, android::Parcel const&, android::Parcel*, unsigned int)+46)

BufferQueueCore:bufferqueue的實(shí)際實(shí)例，由他來銜接生產(chǎn)者和消費(fèi)者

BufferQueueProducer:bufferqueue工廠模式的接口，生產(chǎn)者

BufferQueueConsumer:bufferqueue消費(fèi)接口，消費(fèi)者

BufferQueueCore 負(fù)責(zé)維護(hù) BufferQueue 的基本數(shù)據(jù)結(jié)構(gòu)，而 BufferQueueProducer 和 BufferQueueConsumer 則負(fù)責(zé)提供操作 BufferQueue 的基本接口。

2.2、buffer queue整體流程

2.2.1、流程概要

image.png

這張圖片清晰的表述的buffer queue的工作方式，兩大功能：生產(chǎn)buffer、消費(fèi)buffer。

dequeueBuffer:向buffer queue請(qǐng)求一個(gè)緩沖區(qū)，并指定緩沖區(qū)的寬度、高度、像素格式和用法標(biāo)志

queueBuffer:把緩沖區(qū)返回到隊(duì)列

acquireBuffer:獲取緩沖區(qū)內(nèi)容

releaseBuffer:把數(shù)據(jù)返回到隊(duì)列

這里有兩次返回隊(duì)列，其實(shí)都是返回buffer queue的數(shù)據(jù)結(jié)構(gòu)中。簡(jiǎn)述兩個(gè)流程

1、dequeue、queue等于先申請(qǐng)緩沖區(qū)，并告訴producer申請(qǐng)成功，producer就把數(shù)據(jù)queue給buffer queue數(shù)據(jù)結(jié)構(gòu)中
2、當(dāng)consumer要的時(shí)候先去acquere獲取緩沖區(qū)內(nèi)容，獲取后進(jìn)行合成，合成完了需要釋放，就給回buffer queue來釋放
3、buffer queue操作數(shù)據(jù)時(shí)不會(huì)復(fù)制一份數(shù)據(jù)，只會(huì)操作數(shù)據(jù)本身。

通篇文章，我們就在理解BufferQueueProducer 和 BufferQueueConsumer如何操作上面這四個(gè)流程requestBuffer

int Surface::dequeueBuffer(android_native_buffer_t** buffer, int* fenceFd) {
    status_t result = mGraphicBufferProducer->dequeueBuffer(&buf, &fence, reqWidth, reqHeight,
                                                            reqFormat, reqUsage, &mBufferAge,
                                                            enableFrameTimestamps ? &frameTimestamps
                                                                                  : nullptr);
    ...
    if ((result & IGraphicBufferProducer::BUFFER_NEEDS_REALLOCATION) || gbuf == nullptr) {
        if (mReportRemovedBuffers && (gbuf != nullptr)) {
            mRemovedBuffers.push_back(gbuf);
        }
        result = mGraphicBufferProducer->requestBuffer(buf, &gbuf);

requestBuffer單獨(dú)提一下這個(gè)流程，當(dāng)我們首次dequeueBuffer過后，surface會(huì)調(diào)用requestBuffer,requestBuffer的主要作用就是把GraphicBuffer傳給應(yīng)用側(cè)，
這個(gè)動(dòng)作只需要做一次，應(yīng)用側(cè)拿到GraphicBuffer過后就可以把共享內(nèi)存mmap到應(yīng)用側(cè)的內(nèi)存空間，然后才可以繪制圖像。

2.2.2、bufferqueue被調(diào)用流程

本小結(jié)主要目的是，在我們認(rèn)識(shí)bufferqueu的是如何工作的同時(shí)，不脫離surfaceflinger整體框架。簡(jiǎn)單提一下它是如果調(diào)用來的。以便我們更深入理解。

1、dequeueBuffer&&queueBuffe

r當(dāng)app創(chuàng)建window的時(shí)候，會(huì)創(chuàng)建surface來顯示。實(shí)則會(huì)創(chuàng)建底層的surface。底層surface創(chuàng)建時(shí)會(huì)hook住dequeueBuffer和queueBuffer方法。

surface持有mGraphicBufferProducer對(duì)象來創(chuàng)建bufferqueue
dequeueBuffer方法位置：BufferQueueProducer::dequeueBuffer

04-20 09:48:38.909  6053  6263 E graphic dequeueBuffer: #00 pc 0006dea5  /system/lib/libgui.so (android::BpGraphicBufferProducer::dequeueBuffer(int*, android::sp<android::Fence>*, unsigned int, unsigned int, int, unsigned long long, unsigned long long*, android::FrameEventHistoryDelta*)+136)
04-20 09:48:38.909  6053  6263 E graphic dequeueBuffer: #01 pc 000842ed  /system/lib/libgui.so (android::Surface::dequeueBuffer(ANativeWindowBuffer**, int*)+316)
04-20 09:48:38.909  6053  6263 E graphic dequeueBuffer: #02 pc 0015004b  /system/lib/libhwui.so (android::uirenderer::renderthread::ReliableSurface::hook_dequeueBuffer(ANativeWindow*, int (*)(ANativeWindow*, ANativeWindowBuffer**, int*), void*, ANativeWindowBuffer**, int*)+42)
04-20 09:48:38.909  6053  6263 E graphic dequeueBuffer: #03 pc 00083181  /system/lib/libgui.so (android::Surface::hook_dequeueBuffer(ANativeWindow*, ANativeWindowBuffer**, int*)+60)
//接上面，binder調(diào)用到BufferQueueProducer
04-20 09:48:38.946   668   697 E dequeueBuffer: #00 pc 00052653  /system/lib/libgui.so (android::BufferQueueProducer::dequeueBuffer(int*, android::sp<android::Fence>*, unsigned int, unsigned int, int, unsigned long long, unsigned long long*, android::FrameEventHistoryDelta*)+250)
04-20 09:48:38.946   668   697 E dequeueBuffer: #01 pc 0006d117  /system/lib/libgui.so (android::BnGraphicBufferProducer::onTransact(unsigned int, android::Parcel const&, android::Parcel*, unsigned int)+374)

queueBuffer方法位置：BufferQueueProducer::queueBuffer

04-20 09:48:38.987  6053  6263 E queueBuffer: #00 pc 0006e4e1  /system/lib/libgui.so (android::BpGraphicBufferProducer::queueBuffer(int, android::IGraphicBufferProducer::QueueBufferInput const&, android::IGraphicBufferProducer::QueueBufferOutput*)+128)
04-20 09:48:38.987  6053  6263 E queueBuffer: #01 pc 00084d83  /system/lib/libgui.so (android::Surface::queueBuffer(ANativeWindowBuffer*, int)+722)
04-20 09:48:38.987  6053  6263 E queueBuffer: #02 pc 00083259  /system/lib/libgui.so (android::Surface::hook_queueBuffer(ANativeWindow*, ANativeWindowBuffer*, int)+60)
//接上面，binder調(diào)用到BufferQueueProducer
04-20 09:48:39.017   668   697 E queueBuffer: #00 pc 00053877  /system/lib/libgui.so (android::BufferQueueProducer::queueBuffer(int, android::IGraphicBufferProducer::QueueBufferInput const&, android::IGraphicBufferProducer::QueueBufferOutput*)+266)
04-20 09:48:39.017   668   697 E queueBuffer: #01 pc 0006d345  /system/lib/libgui.so (android::BnGraphicBufferProducer::onTransact(unsigned int, android::Parcel const&, android::Parcel*, unsigned int)+932)

2、acquireBuffer&&releaseBuffer

1、我們知道系統(tǒng)的刷新由Vsync信號(hào)控制，一個(gè)Vsync信號(hào)來時(shí)。surfaceflinger代碼會(huì)走INVALIDATE/REFRESH,最終都是走refresh
2、下面接收vsync的MessageQueue隊(duì)列，實(shí)際就是surfaceflinger初始化時(shí)創(chuàng)建的mEventQueue。
3、EventThread通過Connection通知VSYNC信號(hào)到達(dá)時(shí)可以觸發(fā)回調(diào)通知MessageQueue
4、vsync這個(gè)流程對(duì)應(yīng)bufferqueue流程中的acquireBuffer、releaseBuffer，調(diào)用流程堆棧下面已列出。

//SurfaceFlinger.cpp
void SurfaceFlinger::onMessageReceived(int32_t what, nsecs_t expectedVSyncTime) {
    ATRACE_CALL();
    switch (what) {
        case MessageQueue::INVALIDATE: {
            onMessageInvalidate(expectedVSyncTime);
            break;
        }
        case MessageQueue::REFRESH: {
            onMessageRefresh();
            break;
        }
    }
}

acquireBuffer方法位置：BufferQueueConsumer::acquireBuffer

04-19 19:33:38.926   666   666 E acquireBuffer: #00 pc 0004d34f  /system/lib/libgui.so (android::BufferQueueConsumer::acquireBuffer(android::BufferItem*, long long, unsigned long long)+74)
04-19 19:33:38.926   666   666 E acquireBuffer: #01 pc 000645cf  /system/lib/libgui.so (android::ConsumerBase::acquireBufferLocked(android::BufferItem*, long long, unsigned long long)+62)
04-19 19:33:38.926   666   666 E acquireBuffer: #02 pc 0007a7a1  /system/lib/libsurfaceflinger.so (android::FramebufferSurface::advanceFrame(bool)+112)
04-19 19:33:38.926   666   666 E acquireBuffer: #03 pc 000edf1f  /system/lib/libsurfaceflinger.so (android::compositionengine::impl::RenderSurface::queueBuffer(android::base::unique_fd_impl<android::base::DefaultCloser>, bool)+358)
04-19 19:33:38.926   666   666 E acquireBuffer: #04 pc 000e46e7  /system/lib/libsurfaceflinger.so (android::compositionengine::impl::Output::finishFrame(android::compositionengine::CompositionRefreshArgs const&)+454)
04-19 19:33:38.926   666   666 E acquireBuffer: #05 pc 000de3e5  /system/lib/libsurfaceflinger.so (android::compositionengine::impl::Display::finishFrame(android::compositionengine::CompositionRefreshArgs const&)+72)
04-19 19:33:38.926   666   666 E acquireBuffer: #06 pc 000e3011  /system/lib/libsurfaceflinger.so (android::compositionengine::impl::Output::present(android::compositionengine::CompositionRefreshArgs const&)+92)
04-19 19:33:38.926   666   666 E acquireBuffer: #07 pc 000dcfa1  /system/lib/libsurfaceflinger.so (android::compositionengine::impl::CompositionEngine::present(android::compositionengine::CompositionRefreshArgs&)+144)
04-19 19:33:38.926   666   666 E acquireBuffer: #08 pc 000baf81  /system/lib/libsurfaceflinger.so (android::SurfaceFlinger::onMessageRefresh()+1280)
04-19 19:33:38.926   666   666 E acquireBuffer: #09 pc 000b8b1d  /system/lib/libsurfaceflinger.so (android::SurfaceFlinger::onMessageReceived(int, long long)+52)

releaseBuffer方法位置：BufferQueueConsumer::releaseBuffer

04-19 19:33:38.996   666   666 E releaseBuffer: #00 pc 0004e429  /system/lib/libgui.so (android::BufferQueueConsumer::releaseBuffer(int, unsigned long long, android::sp<android::Fence> const&, void*, void*)+72)
04-19 19:33:38.996   666   666 E releaseBuffer: #01 pc 0004f3af  /system/lib/libgui.so (android::BufferQueueConsumer::releaseBuffer(int, unsigned long long, void*, void*, android::sp<android::Fence> const&)+36)
04-19 19:33:38.996   666   666 E releaseBuffer: #02 pc 0006498d  /system/lib/libgui.so (android::ConsumerBase::releaseBufferLocked(int, android::sp<android::GraphicBuffer>, void*, void*)+140)
04-19 19:33:38.996   666   666 E releaseBuffer: #03 pc 00066cab  /system/lib/libsurfaceflinger.so (android::BufferLayerConsumer::releasePendingBuffer()+78)
04-19 19:33:38.996   666   666 E releaseBuffer: #04 pc 00067b1d  /system/lib/libsurfaceflinger.so (android::BufferQueueLayer::releasePendingBuffer(long long)+28)
04-19 19:33:38.996   666   666 E releaseBuffer: #05 pc 000bb0bb  /system/lib/libsurfaceflinger.so (android::SurfaceFlinger::onMessageRefresh()+1594)
04-19 19:33:38.996   666   666 E releaseBuffer: #06 pc 000b8b1d  /system/lib/libsurfaceflinger.so (android::SurfaceFlinger::onMessageReceived(int, long long)+52)

2.2.3、認(rèn)識(shí)BufferQueueCore

BufferQueueCore是bufferqueue實(shí)現(xiàn)的具體類。BufferQueueCore管理了幾個(gè)數(shù)據(jù)結(jié)構(gòu)。操作這幾個(gè)數(shù)據(jù)結(jié)構(gòu)，來實(shí)現(xiàn)bufferqueue的dequebuffer等方法。

以dequeueBuffer過程來講，它就是向bufferqueue申請(qǐng)一個(gè)GraphicBuffer,用GraphicBuffer來繪制圖像。

BufferQueueCore中六個(gè)對(duì)象比較重要：mQueue、mSlot、FreeSlots、FreeBuffers、ActiveBuffers、UnusedBuffers 下面我會(huì)一一介紹

namespace android {
class IConsumerListener;
class IProducerListener;
class BufferQueueCore : public virtual RefBase {
private:
    BufferQueueDefs::SlotsType mSlots;
    Fifo mQueue;
    std::set<int> mFreeSlots;
    std::list<int> mFreeBuffers;
    std::list<int> mUnusedSlots;
    std::set<int> mActiveBuffers;

1、mQueue&&mSlot我們先認(rèn)識(shí)這兩個(gè)最核心的數(shù)據(jù)結(jié)構(gòu)。

class BufferItem {
public:
    enum { INVALID_BUFFER_SLOT = -1 };
    BufferItem() : mGraphicBuffer(nullptr), mFence(Fence::NO_FENCE) {}
    ~BufferItem() {}
    sp<GraphicBuffer> mGraphicBuffer;
    sp<Fence> mFence;
    Rect mCrop;
typedef Vector<BufferItem> Fifo;
Fifo mQueue;
namespace BufferQueueDefs {
    typedef BufferSlot SlotsType[NUM_BUFFER_SLOTS];
}
BufferQueueDefs::SlotsType mSlots;

我們平時(shí)說的bufferqueue隊(duì)列其實(shí)就是說的BufferItem這個(gè)mQueue數(shù)據(jù)容器。BufferItem擁有GraphicBuffer對(duì)象

而mSlot是一個(gè)BufferSlot大小為NUM_BUFFER_SLOTS(等于64)的數(shù)組，BufferSlot主要用來綁定GraphicBuffer,BufferSlot和GraphicBuffer一一對(duì)應(yīng)。

BufferSlot中有一個(gè)BufferState對(duì)象，它專門用來表示GraphicBuffer的狀態(tài)

struct BufferSlot {
    BufferState mBufferState;
// BufferState tracks the states in which a buffer slot can be.
struct BufferState {
    // All slots are initially FREE (not dequeued, queued, acquired, or shared).
    BufferState()
    : mDequeueCount(0),
      mQueueCount(0),
      mAcquireCount(0),
      mShared(false) {
    }
    uint32_t mDequeueCount;
    uint32_t mQueueCount;
    uint32_t mAcquireCount;
    bool mShared;
    // A buffer can be in one of five states, represented as below:
    //
    //         | mShared | mDequeueCount | mQueueCount | mAcquireCount |
    // --------|---------|---------------|-------------|---------------|
    // FREE    |  false  |       0       |      0      |       0       |
    // DEQUEUED|  false  |       1       |      0      |       0       |
    // QUEUED  |  false  |       0       |      1      |       0       |
    // ACQUIRED|  false  |       0       |      0      |       1       |
    // SHARED  |  true   |      any      |     any     |      any      |

2、FreeSlots、FreeBuffers、ActiveBuffers、UnusedBuffers

知道了mQueue&&mSlot作用后，我們?cè)賮碚J(rèn)識(shí)他們四個(gè)容易了,首先成立這樣一個(gè)等式
mSlots = mFreeSlots + mFreeBuffers + mActiveBuffers + mUnusedSlots
mSlots是所有BufferSlot，而其它四個(gè)BufferSlot，則表示不同的狀態(tài)的BufferSlot。

mFreeSlots：BufferSlot狀態(tài)為FREE，且沒有GraphicBuffer與之相綁定的slot集合

mFreeBuffers：BufferSlot狀態(tài)為FREE，且有GraphicBuffer與之相綁定的slot集合

mActiveBuffers：BufferSlot狀態(tài)不為FREE（即DEQUEUED、QUEUED、ACQUIRED、SHARED）的slot集合。既然狀態(tài)不是FREE，那么該BufferSlot必然有一個(gè)GraphicBuffer與之相綁定

mUnusedSlots：未參與使用的slot集合，由 mMaxBufferCount 決定

2.2.4、BufferQueueProducer生產(chǎn)者

生產(chǎn)者這邊，在bufferqueue流程中，主要負(fù)責(zé)dequeueBuffer、queueBuffer等流程

class BufferQueueProducer : public BnGraphicBufferProducer {
public:
    friend class BufferQueue; // Needed to access binderDied
    explicit BufferQueueProducer(const sp<BufferQueueCore>& core,
                                 bool consumerIsSurfaceFlinger = false);
    ~BufferQueueProducer() override;
    virtual status_t requestBuffer(int slot, sp<GraphicBuffer>* buf);
    virtual status_t dequeueBuffer(int* outSlot, sp<Fence>* outFence, uint32_t width,
                                   uint32_t height, PixelFormat format, uint64_t usage,
                                   uint64_t* outBufferAge,
                                   FrameEventHistoryDelta* outTimestamps) override;
    virtual status_t queueBuffer(int slot,
            const QueueBufferInput& input, QueueBufferOutput* output);
    ...//等方法

1、dequeueBuffer

status_t BufferQueueProducer::dequeueBuffer(int* outSlot, sp<android::Fence>* outFence,
                                            uint32_t width, uint32_t height, PixelFormat format,
                                            uint64_t usage, uint64_t* outBufferAge,
                                            FrameEventHistoryDelta* outTimestamps) {
    // 獲取下一個(gè)buffer slot,如果有freeSlot直接拿來用
    while (found == BufferItem::INVALID_BUFFER_SLOT) {
            status_t status = waitForFreeSlotThenRelock(FreeSlotCaller::Dequeue, lock, &found);
            if (status != NO_ERROR) {
                return status;
            }
    ...
    // IGraphicBufferProducer::BUFFER_NEEDS_REALLOCATION 和IGraphicBufferProducer::RELEASE_ALL_BUFFERS標(biāo)記會(huì)走 requestBuffer流程來獲取graphicBuffer對(duì)應(yīng)的slot
    if ((buffer == nullptr) ||
                buffer->needsReallocation(width, height, format, BQ_LAYER_COUNT, usage))
        {
            mSlots[found].mAcquireCalled = false;
            mSlots[found].mGraphicBuffer = nullptr;
            mSlots[found].mRequestBufferCalled = false;
            mSlots[found].mEglDisplay = EGL_NO_DISPLAY;
            mSlots[found].mEglFence = EGL_NO_SYNC_KHR;
            mSlots[found].mFence = Fence::NO_FENCE;
            mCore->mBufferAge = 0;
            mCore->mIsAllocating = true;
            returnFlags |= BUFFER_NEEDS_REALLOCATION;
        }

上面摘抄了dequebuffer流程主要的兩件事情

1、獲取下一個(gè)buffer slot,如果有freeSlot直接拿來用
2、IGraphicBufferProducer::BUFFER_NEEDS_REALLOCATION 和IGraphicBufferProducer::RELEASE_ALL_BUFFERS標(biāo)記會(huì)走 requestBuffer流程來獲取graphicBuffer對(duì)應(yīng)的slot

2、queueBuffer

queueBuffer將已填充的緩沖區(qū)返回給BufferQueue，即把bufferslot封裝成BufferItem返回到BufferItem隊(duì)列mQueue。

status_t BufferQueueProducer::queueBuffer(int slot,
        const QueueBufferInput &input, QueueBufferOutput *output) {
    // 構(gòu)建bufferitem并賦值
    BufferItem item;
    item.mAcquireCalled = mSlots[slot].mAcquireCalled;
    item.mGraphicBuffer = mSlots[slot].mGraphicBuffer;
    ...
    item.mSlot = slot;
    item.mFence = acquireFence;
    item.mFenceTime = acquireFenceTime;
    //bufferItem 入隊(duì)
    if (mCore->mQueue.empty()) {
            // When the queue is empty, we can ignore mDequeueBufferCannotBlock
            // and simply queue this buffer
            mCore->mQueue.push_back(item);
            frameAvailableListener = mCore->mConsumerListener;
        } else {
            // When the queue is not empty, we need to look at the last buffer
            // in the queue to see if we need to replace it
            const BufferItem& last = mCore->mQueue.itemAt(
                    mCore->mQueue.size() - 1);
            if (last.mIsDroppable) {
                if (!last.mIsStale) {
                    mSlots[last.mSlot].mBufferState.freeQueued();

queueBuffer比較簡(jiǎn)單，主要兩步

1、構(gòu)建bufferItem，賦值等

2、把bufferItem返回到mQueue隊(duì)列中

2.2.4、BufferQueueConsumer消費(fèi)者

1、acquireBuffer

acquireBuffer方法從緩沖隊(duì)列中嘗試取下一個(gè)掛起的BufferItem有這些情況：

隊(duì)列為空直接返回；如果緩沖已被獲取，返回之前獲取的緩沖項(xiàng)；如果expectedPresent標(biāo)記為非0，緩沖會(huì)即將顯示；如果緩沖時(shí)間戳在將來，不會(huì)被獲??；

status_t BufferQueueConsumer::acquireBuffer(BufferItem* outBuffer,
        nsecs_t expectedPresent, uint64_t maxFrameNumber) {
    // 新舊緩沖區(qū)顯示邏輯，決定顯示的buffer
    if (expectedPresent != 0 && !mCore->mQueue.empty()) {
            while (mCore->mQueue.size() > 1 && !mCore->mQueue[0].mIsAutoTimestamp) {
                const BufferItem& bufferItem(mCore->mQueue[1]);
    ...

此段邏輯比較簡(jiǎn)單，就是拿緩存，邏輯主要是怎么拿，最后回調(diào)

2、releaseBuffer

releaseBuffer將bufferslot返回到bufferqueue隊(duì)列?？梢栽赽ufferqueue任在訪問時(shí)進(jìn)行，當(dāng)buffer不再可用，fence機(jī)制會(huì)發(fā)出信號(hào)。

如果releaseBuffer收到STALE_BUFFER_SLOT信號(hào)，那么consumer必須直接放棄所有引用。直接釋放。

代碼就是release為主

status_t BufferQueueConsumer::releaseBuffer(int slot, uint64_t frameNumber,
        const sp<Fence>& releaseFence, EGLDisplay eglDisplay,
        EGLSyncKHR eglFence) {
    sp<IProducerListener> listener;
    { // Autolock scope
        std::lock_guard<std::mutex> lock(mCore->mMutex);
        if (frameNumber != mSlots[slot].mFrameNumber &&
                !mSlots[slot].mBufferState.isShared()) {
            return STALE_BUFFER_SLOT;
        }
        if (!mSlots[slot].mBufferState.isAcquired()) {
            BQ_LOGE("releaseBuffer: attempted to release buffer slot %d "
                    "but its state was %s", slot,
                    mSlots[slot].mBufferState.string());
            return BAD_VALUE;
        }
        mSlots[slot].mEglDisplay = eglDisplay;
        mSlots[slot].mEglFence = eglFence;
        mSlots[slot].mFence = releaseFence;
        mSlots[slot].mBufferState.release();

三、bufferqueue總結(jié)

bufferqueue是整個(gè)安卓圖形處理的核心，把數(shù)據(jù)生產(chǎn)者和數(shù)據(jù)消費(fèi)者連接起來。
生產(chǎn)者dequeuebuffer申請(qǐng)一個(gè)緩沖區(qū)，并指定寬高等。填充緩沖區(qū)數(shù)據(jù)后用queueBuffer返回到隊(duì)列。隨后aquirebuffer獲取緩沖區(qū)，消費(fèi)者處理完后。則返回到隊(duì)列release

以上就是Android開發(fā)graphics bufferqueue整體流程的詳細(xì)內(nèi)容，更多關(guān)于Android graphics bufferqueue的資料請(qǐng)關(guān)注腳本之家其它相關(guān)文章！

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Android開發(fā)graphics?bufferqueue整體流程

目錄

一、引言

二、Buffer queue

2.1、buffer queue的創(chuàng)建

2.2、buffer queue整體流程

2.2.1、流程概要

2.2.2、bufferqueue被調(diào)用流程

2.2.3、認(rèn)識(shí)BufferQueueCore

2.2.4、BufferQueueProducer生產(chǎn)者

2.2.4、BufferQueueConsumer消費(fèi)者

三、bufferqueue總結(jié)

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Android開發(fā)graphics?bufferqueue整體流程

目錄

一、引言

二、Buffer queue

2.1、buffer queue的創(chuàng)建

2.2、buffer queue整體流程

2.2.1、流程概要

2.2.2、bufferqueue被調(diào)用流程

2.2.3、認(rèn)識(shí)BufferQueueCore

2.2.4、BufferQueueProducer生產(chǎn)者

2.2.4、BufferQueueConsumer消費(fèi)者

三、bufferqueue總結(jié)

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一、引言

二、Buffer queue

2.2、buffer queue整體流程

2.2.1、流程概要

2.2.2、bufferqueue被調(diào)用流程

2.2.3、認(rèn)識(shí)BufferQueueCore

2.2.4、BufferQueueProducer生產(chǎn)者

三、bufferqueue總結(jié)