Android0顯示系統(tǒng)三管理圖像緩沖區(qū)

1、Android6.0Android6.0顯示系統(tǒng)(三)管理圖像緩沖區(qū)、BufferQueueCoreBufferQueueProducerBufferQueueConsumer上篇博客在Layer的onFirstRef函數(shù)中，調(diào)用了下面函數(shù)，創(chuàng)建了3個(gè)對(duì)象BufferQueueCoreBufferQueueProducerBufferQueueConsumer。其中BufferCore是核心，把BufferQueueProducer和BufferQueueConsumer對(duì)象連接在一起。cppviewplaincopy在CODE上查看代碼片派生到我的代碼片voidBufferQueue:cre

2、ateBufferQueue(sp*outProducer,sp*outConsumer,constsp&allocator)spcore(newBufferQueueCore(allocator);spproducer(newBufferQueueProducer(core);spconsumer(newBufferQueueConsumer(core);*outProducer=producer;*outConsumer=consumer;1.1生產(chǎn)者和core的聯(lián)系IGraphicBufferProducer的大致接口如下，BufferQueueProducer類(lèi)是接口IGrap

3、hicBufferProducer的實(shí)現(xiàn)，使用BufferQueueProducer之前先要調(diào)用connect函數(shù)，使用結(jié)束后調(diào)用disconnect斷開(kāi)連接。cppviewplaincopy在CODE上查看代碼片派生到我的代碼片classIGraphicBufferProducer:publicIInterfacepublic:virtualstatus_trequestBuffer(intslot,sp*buf)=0;virtualstatus_tsetBufferCount(intbufferCount)=0;virtualstatus_tdequeueBuffer(int*slot,s

4、p*fence,boolasync,uint32_tw,uint32_th,PixelFormatformat,uint32_tusage)=0;virtualstatus_tdetachBuffer(intslot)=0;virtualstatus_tdetachNextBuffer(sp*outBuffer,sp*outFence)=0;virtualstatus_tattachBuffer(int*outSlot,constsp&buffer)=0;virtualstatus_tqueueBuffer(intslot,constQueueBufferInput&input

5、,QueueBufferOutput*output)=0;virtualvoidcancelBuffer(intslot,constsp&fence)=0;virtualintquery(intwhat,int*value)=0;virtualstatus_tconnect(constsp&listener,intapi,boolproducerControlledByApp,QueueBufferOutput*output)=0;virtualstatus_tdisconnect(intapi)=0;virtualstatus_tsetSidebandStream(const

6、sp&stream)=0;virtualvoidallocateBuffers(boolasync,uint32_twidth,uint32_theight,PixelFormatformat,uint32_tusage)=0;virtualstatus_tallowAllocation(boolallow)=0;virtualstatus_tsetGenerationNumber(uint32_tgenerationNumber)=0;virtualString8getConsumerName()const=0;在BufferQueueCore類(lèi)中定義了一個(gè)64項(xiàng)的數(shù)據(jù)mSlots。

7、cppviewplaincopy在CODE上查看代碼片派生到我的代碼片BufferQueueDefs:SlotsTypemSlots;cppviewplaincopy在CODE上查看代碼片派生到我的代碼片typedefBufferSlotSlotsTypeNUM_BUFFER_SLOTS;每個(gè)緩沖區(qū)的類(lèi)型是BufferSlot類(lèi)型。它有兩個(gè)重要的成員變量，mGraphicBuffer是指向圖像緩沖區(qū)GraphicBuffer的指針，mBufferState表示圖像緩沖區(qū)的狀態(tài)。cppviewplaincopy在CODE上查看代碼片派生到我的代碼片spmGraphicBuffer;BufferS

8、tatemBufferState;BufferState的狀態(tài)有下面幾個(gè)cppviewplaincopy在CODE上查看代碼片派生到我的代碼片enumBufferStateFREE=0,空閑DEQUEUED=1,生產(chǎn)狀態(tài)，被生產(chǎn)者擁有QUEUED=2,/保存數(shù)據(jù)狀態(tài)，被BufferQueue擁有ACQUIRED=3/消費(fèi)狀態(tài)，被消費(fèi)者擁有;BufferQueueProducer的dequeueBuffer函數(shù)用來(lái)向BufferQueueCore申請(qǐng)一個(gè)空閑的slot,這個(gè)slot可能已經(jīng)有緩沖區(qū)，也可能沒(méi)有，如果沒(méi)有緩沖區(qū)，dequeueBuffer函數(shù)會(huì)分配一塊新的緩沖區(qū)。得到空閑的slot

9、后，還需要調(diào)用requestBuffer函數(shù)來(lái)取得一塊緩沖區(qū)。得到緩沖區(qū)，如果不需要了，可以使用cancelBuffer函數(shù)來(lái)釋放這個(gè)slot。調(diào)用dequeueBuffer函數(shù)之后，緩沖區(qū)的擁有者是生產(chǎn)者，緩沖區(qū)處于DEQUEUED狀態(tài)。一旦緩沖區(qū)復(fù)制數(shù)據(jù)完成，通過(guò)queueBuffer函數(shù)把緩沖區(qū)的控制權(quán)交還給BufferQueueCore,這時(shí)候緩沖區(qū)將處于QUEUED狀態(tài)。1.2消費(fèi)者和core的聯(lián)系下面是IGraphicBufferComsumer接口的幾個(gè)主要函數(shù)：cppviewplaincopy在CODE上查看代碼片派生到我的代碼片virtualstatus_tacquireBu

10、ffer(BufferItem*outBuffer,nsecs_texpectedPresent,uint64_tmaxFrameNumber=0)override;virtualstatus_treleaseBuffer(intslot,uint64_tframeNumber,constsp&releaseFence,EGLDisplaydisplay,EGLSyncKHRfence);virtualstatus_tconnect(constsp&consumerListener,boolcontrolledByApp);virtualstatus_tdisconnect()

11、;BufferQueueConsumer類(lèi)是接口IGraphicBufferComsumer的實(shí)現(xiàn)，在使用它之前，先要調(diào)用connect函數(shù)建立聯(lián)系，這里傳遞的參數(shù)是IConsumerListener對(duì)象，是一個(gè)回調(diào)接口，如果BufferQueue中有數(shù)據(jù)準(zhǔn)備好了就會(huì)調(diào)用它的onFrameAvailable函數(shù)來(lái)通知消費(fèi)者取走數(shù)據(jù)。取走數(shù)據(jù)的時(shí)候，需要調(diào)用acquireBuffer函數(shù)，將緩沖區(qū)狀態(tài)變成ACQUIRED,使用完之后調(diào)用releaseBuffer函數(shù)可以吧緩沖區(qū)數(shù)據(jù)歸還給BufferQueueCore,這樣緩沖區(qū)就變成FREE。1.3三者聯(lián)系對(duì)象BufferQueueProduc

12、er和BufferQueueConsumer好像沒(méi)有直接聯(lián)系，其實(shí)都是通過(guò)共同的BufferQueueCore對(duì)象連接在一起的，很多操作時(shí)直接使用BufferQueueCore對(duì)象的成員變量而不是函數(shù)來(lái)完成的。二、GraphicBuffer對(duì)象的創(chuàng)建對(duì)Surface而言，圖像緩沖區(qū)是一個(gè)重要的數(shù)據(jù)結(jié)構(gòu)，它是用戶(hù)進(jìn)程和圖像顯示器之間的紐帶,下面我們來(lái)看看Surface的圖像緩沖區(qū)是如何創(chuàng)建的。2.1內(nèi)存緩沖區(qū)的創(chuàng)建前面介紹了過(guò)dequeueBuffer函數(shù)， 圖像緩沖區(qū)GraphicBuffer就是在這個(gè)函數(shù)中創(chuàng)建的， 當(dāng)從BufferQueueCore中獲取到空間的slot時(shí)，如果這個(gè)slot

13、沒(méi)有緩沖區(qū)就要新建一個(gè)。下面是dequeueBuffer函數(shù)的部分代碼， 在從BufferQueueCore中獲取到slot的時(shí)候， 如果需要重新分配圖像緩沖區(qū)就會(huì)調(diào)用mCore-mAllocator-createGraphicBuffer函數(shù)來(lái)重新創(chuàng)建一個(gè)圖像緩沖區(qū)。cppviewplaincopy在CODE上查看代碼片派生到我的代碼片*outSlot=found;/found復(fù)制到outslotATRACE_BUFFER_INDEX(found);attachedByConsumer=mSlotsfound.mAttachedByConsumer;mSlotsfound.mBufferSt

14、ate=BufferSlot:DEQUEUED;/slot的狀態(tài)修改變成生產(chǎn)狀態(tài)constsp&buffer(mSlotsfound.mGraphicBuffer);if(buffer=NULL)|/為空，或者需要重新分配buffer-needsReallocation(width,height,format,usage)mSlotsfound.mAcquireCalled=false;mSlotsfound.mGraphicBuffer=NULL;mSlotsfound.mRequestBufferCalled=false;mSlotsfound.mEglDisplay=EGL_NO

15、_DISPLAY;mSlotsfound.mEglFence=EGL_NO_SYNC_KHR;mSlotsfound.mFence=Fence:NO_FENCE;mCore-mBufferAge=0;returnFlags|=BUFFER_NEEDS_REALLOCATION;/需要重啟分配緩沖區(qū)else/Weadd1becausethatwillbetheframenumberwhenthisbuffer/isqueuedmCore-mBufferAge=mCore-mFrameCounter+1-mSlotsfound.mFrameNumber;BQ_LOGV(dequeueBuffer:

16、settingbufferageto%PRIu64,mCore-mBufferAge);if(CC_UNLIKELY(mSlotsfound.mFence=NULL)BQ_LOGE(dequeueBuffer:abouttoreturnaNULLfence-slot=%dw=%dh=%dformat=%u,found,buffer-width,buffer-height,buffer-format);eglDisplay=mSlotsfound.mEglDisplay;eglFence=mSlotsfound.mEglFence;*outFence=mSlotsfound.mFence;mSl

17、otsfound.mEglFence=EGL_NO_SYNC_KHR;mSlotsfound.mFence=Fence:NO_FENCE;mCore-validateConsistencyLocked();/Autolockscopeif(returnFlags&BUFFER_NEEDS_REALLOCATION)/如果需要重啟分配圖像緩沖區(qū)status_terror;BQ_LOGV(dequeueBuffer:allocatinganewbufferforslot%d,*outSlot);spgraphicBuffer(mCore-mAllocator-createGraphicBu

18、ffer(/創(chuàng)建圖像緩沖區(qū)width,height,format,usage,&error);if(graphicBuffer=NULL)BQ_LOGE(dequeueBuffer:createGraphicBufferfailed);returnerror;/AutolockscopeMutex:Autolocklock(mCore-mMutex);if(mCore-mIsAbandoned)BQ_LOGE(dequeueBuffer:BufferQueuehasbeenabandoned);returnNO_INIT;graphicBuffer-setGenerationNumbe

19、r(mCore-mGenerationNumber);mSlots*outSlot.mGraphicBuffer=graphicBuffer;/AutolockscopemAllocator的類(lèi)型是IGraphicBufferA110c,也是一個(gè)Binder對(duì)象， 它是在BufferQueueCore的構(gòu)造函數(shù)中得到的，這個(gè)時(shí)候allocator為空的，具體要從Layer的構(gòu)造函數(shù)中調(diào)用BufferQueue:createBufferQueue函數(shù)是，那個(gè)時(shí)候allocator參數(shù)就為空。然后通過(guò)getComposerService來(lái)調(diào)用createGraphicBufferAlloc函數(shù)來(lái)創(chuàng)

20、建這個(gè)mAllocator對(duì)象。之前的博客分析過(guò)getComposerService返回的是和SurfaceFlinger進(jìn)程的Binder對(duì)象，因此最后是到SurfaceFlinger的createGraphicBufferAlloc函數(shù)中去了（但是這里有點(diǎn)搞不明白明明是在一個(gè)進(jìn)程中為什么要用Binder呢？）。cppviewplaincopy在CODE上查看代碼片派生到我的代碼片if(allocator=NULL)spcomposer(ComposerService:getComposerService();mAllocator=mposer-createGraphicBufferA110

21、c();if(mAllocator=NULL)BQ_LOGE(createGraphicBufferAllocfailed);下面我們來(lái)看SurfaceFlinger的createGraphicBufferAlloc函數(shù)。cppviewplaincopy在CODE上查看代碼片派生到我的代碼片spSurfaceFlinger:createGraphicBufferA110c()spgba(newGraphicBufferAlloc();returngba;)因此最后BufferQueueProducer中的dequeueBuffer函數(shù)中調(diào)用mCore-mAllocator的createGrap

22、hicBuffer函數(shù)就是調(diào)用了GraphicBufferAlloc的createGraphicBufferAlloc函數(shù)。cppviewplaincopy在CODE上查看代碼片派生到我的代碼片spGraphicBufferAlloc:createGraphicBuffer(uint32_twidth,uint32_theight,PixelFormatformat,uint32_tusage,status_t*error)spgraphicBuffer(newGraphicBuffer(width,height,format,usage);status_terr=graphicBuffer-

23、initCheck();*error=err;錯(cuò)誤處理returngraphicBuffer;)我們來(lái)看下GraphicBuffer對(duì)象的構(gòu)造函數(shù)中調(diào)用了initSize函數(shù)。cppviewplaincopy在CODE上查看代碼片派生到我的代碼片GraphicBuffer:GraphicBuffer(uint32_tinWidth,uint32_tinHeight,PixelFormatinFormat,uint32_tinUsage):BASE(),mOwner(ownData),mBufferMapper(GraphicBufferMapper:get(),mInitCheck(NO_ER

24、ROR),mId(getUniqueId()mInitCheck=initSize(inWidth,inHeight,inFormat,inUsage);)在initSize函數(shù)中調(diào)用GraphicBufferAllocator的alloc來(lái)分配內(nèi)存。cppviewplaincopy在CODE上查看代碼片派生到我的代碼片status_tGraphicBuffer:initSize(uint32_tinWidth,uint32_tinHeight,PixelFormatinFormat,int32_tinUsage)GraphicBufferAllocator&allocator=Gra

25、phicBufferAllocator:get();uint32_toutStride=0;status_terr=allocator.alloc(inWidth,inHeight,inFormat,inUsage,&handle,&outStride);if(err=NO_ERROR)width=static_cast(inWidth);height=static_cast(inHeight);format=inFormat;usage=static_cast(inUsage);stride=static_cast(outStride);)returnerr;)alloc又調(diào)

26、用了成員變量mAllocDev的alloc函數(shù)。cppviewplaincopy在CODE上查看代碼片派生到我的代碼片status_tGraphicBufferAllocator:alloc(uint32_twidth,uint32_theight,PixelFormatformat,uint32_tusage,buffer_handle_t*handle,uint32_t*stride)err=mAllocDev-alloc(mAllocDev,static_cast(width),static_cast(height),format,static_cast(usage),handle,&a

27、mp;outStride);在GraphicBufferAllocator的構(gòu)造函數(shù)中裝載了Gralloc模塊，因此mAllocDev指向了Gralloc模塊。這個(gè)會(huì)在后面的博客中分析cppviewplaincopy在CODE上查看代碼片派生到我的代碼片GraphicBufferAllocator:GraphicBufferAllocator():mAllocDev(0)hw_module_tconst*module;interr=hw_get_module(GRALLOC_HARDWARE_MODULE_ID,&module);ALOGE_IF(err,FATAL:cantfindt

28、he%smodule,GRALLOC_HARDWARE_MODULE_ID);if(err=0)gralloc_open(module,&mAllocDev);這里調(diào)用alloc分配了一塊共享的內(nèi)存緩沖區(qū)，alloc函數(shù)將返回共享區(qū)的fd和緩沖區(qū)的指針。既然GraphicBuffer中的緩沖區(qū)是共享內(nèi)存，我們知道使用共享內(nèi)存需要傳遞共享內(nèi)存的句柄fd。下面我們看看是如何傳到客戶(hù)進(jìn)程的。2.2內(nèi)存緩沖區(qū)的fd傳遞到客戶(hù)進(jìn)程GraphicBuffer類(lèi)從模板類(lèi)Flattenable派生，這個(gè)派生類(lèi)可以通過(guò)Parcel傳遞，通常派生類(lèi)需要重載flatten和unflatten方法，用于對(duì)象的

29、序列化和反序列化。cppviewplaincopy在CODE上查看代碼片派生到我的代碼片classGraphicBuffer:publicANativeObjectBase,publicFlattenable我們先來(lái)看下flatten函數(shù)，fds參數(shù)用來(lái)傳遞文件句柄，函數(shù)把handle中的句柄復(fù)制到fds中，因此這些句柄就能通過(guò)binder傳遞到目標(biāo)進(jìn)程中去。cppviewplaincopy在CODE上查看代碼片派生到我的代碼片status_tGraphicBuffer:flatten(void*&buffer,size_t&size,int*&fds,size_t&a

30、mp;count)constsize_tsizeNeeded=GraphicBuffer:getFlattenedSize();if(sizesizeNeeded)returnNO_MEMORY;size_tfdCountNeeded=GraphicBuffer:getFdCount();if(countfdCountNeeded)returnNO_MEMORY;int32_t*buf=static_cast(buffer);buf0=GBFR;buf1=width;buf2=height;buf3=stride;buf4=format;buf5=usage;buf6=static_cast(

31、mId32);buf7=static_cast(mId&0 xFFFFFFFFull);buf8=static_cast(mGenerationNumber);buf9=0;buf10=0;if(handle)buf9=handle-numFds;buf10=handle-numInts;memcpy(fds,handle-data,把handle中的中復(fù)制到fds中static_cast(handle-numFds)*sizeof(int);memcpy(&buf11,handle-data+handle-numFds,static_cast(handle-numInts)*sizeof(int);)buffer=static_cast(static_cast(buffer)+sizeNeeded);size-=sizeNeeded;if(ndle)fds+=hand