福州军区炮兵司令员:Pmem使用小结
来源:百度文库 编辑:偶看新闻 时间:2024/04/29 01:37:45
Pmem很好的满足高通芯片中MDP、GPU等需要连续物理内存的设备,这里我稍微小结一些自己的理解,做个记录:
1.如何使用,这里要分两种情况:
第一种:在一个进程中自己分配自己使用,直接open之后mmap就ok了。
pmem_fd = open("/dev/pmem_device", O_RDWR, 0)
pmem_base = mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED, pmem_fd, 0)
第二种:需要在不同的进程中共享。这需要用到Pmem的Connect功能,先来理解下面的代码:
pmem_fd0 = open("/dev/pmem_device", O_RDWR, 0)
pmem_base = mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED, pmem_fd0, 0)
pmem_fd1 = open("/dev/pmem_device", O_RDWR, 0)
ret = ioctl(pmem_fd1, PMEM_CONNECT, pmem_fd0)
ret = ioctl(pmem_fd1 , PMEM_MAP, ®ion1)
通过Connect之后,pmem_fd1就获得了和pmem_fd0同样的Pmem空间。一个进程打开Pmem设备,通过mmap操作映射内存到进程空间后,该进程成为了该Pmem的Master进程。其他进程通过Connect操作将自己的Pmem data和Master的Pmemdata连接之后,就成为该Pmem的Client进程。在Android中,通过Binder, 实现了跨进程传递Pmemfd。相关代码见MemoryHeapBase.cpp和MemoryHeapPmem.cpp,具体使用可以看下面的简化代码:
masterHeap = new MemoryHeapBase(Pmem_device,size,xxx)//对应主进程,申请Pmem
clientHeap = new MemoryHeapPmem(masterHeap,xxx)//对应client进程,函数实现了connect操作
clientHeap->slap() //对应mmap操作
2. 理解了上面,就不难理解下面surface操作的过程了:
client = new SurfaceComposerClient()
//向Surfaceflinger申请一个Surface,surface类型为PushBuffers
surfaceControl = client->createSurface(getpid(), 0, W, H,PIXEL_FORMAT_RGBA_565, ISurfaceComposer::ePushBuffers)
//获取ISurface对象
isurface = Test::getISurface(surfaceControl)
heap = new MemoryHeapBase(pmem_device, W * H)
sp pmemHeap = new MemoryHeapPmem(heap, 0)
pmemHeap->slap()
mBufferHeap = ISurface::BufferHeap(W,H,PIXEL_FORMAT_BGRA_565, pmemHeap)
isurface->registerBuffers(mBufferHeap)
//得到buffer指针
char * bp = static_cast(mBufferHeap.heap->base())
//向buffer写位图数据,注意要是32位的
XXXXXXXXXX
//提交修改,通知Surface Flinger更新屏幕
isurface->postBuffer(0)
1.如何使用,这里要分两种情况:
第一种:在一个进程中自己分配自己使用,直接open之后mmap就ok了。
pmem_fd = open("/dev/pmem_device", O_RDWR, 0)
pmem_base = mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED, pmem_fd, 0)
第二种:需要在不同的进程中共享。这需要用到Pmem的Connect功能,先来理解下面的代码:
pmem_fd0 = open("/dev/pmem_device", O_RDWR, 0)
pmem_base = mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED, pmem_fd0, 0)
pmem_fd1 = open("/dev/pmem_device", O_RDWR, 0)
ret = ioctl(pmem_fd1, PMEM_CONNECT, pmem_fd0)
ret = ioctl(pmem_fd1 , PMEM_MAP, ®ion1)
通过Connect之后,pmem_fd1就获得了和pmem_fd0同样的Pmem空间。一个进程打开Pmem设备,通过mmap操作映射内存到进程空间后,该进程成为了该Pmem的Master进程。其他进程通过Connect操作将自己的Pmem data和Master的Pmemdata连接之后,就成为该Pmem的Client进程。在Android中,通过Binder, 实现了跨进程传递Pmemfd。相关代码见MemoryHeapBase.cpp和MemoryHeapPmem.cpp,具体使用可以看下面的简化代码:
masterHeap = new MemoryHeapBase(Pmem_device,size,xxx)//对应主进程,申请Pmem
clientHeap = new MemoryHeapPmem(masterHeap,xxx)//对应client进程,函数实现了connect操作
clientHeap->slap() //对应mmap操作
2. 理解了上面,就不难理解下面surface操作的过程了:
client = new SurfaceComposerClient()
//向Surfaceflinger申请一个Surface,surface类型为PushBuffers
surfaceControl = client->createSurface(getpid(), 0, W, H,PIXEL_FORMAT_RGBA_565, ISurfaceComposer::ePushBuffers)
//获取ISurface对象
isurface = Test::getISurface(surfaceControl)
heap = new MemoryHeapBase(pmem_device, W * H)
sp pmemHeap = new MemoryHeapPmem(heap, 0)
pmemHeap->slap()
mBufferHeap = ISurface::BufferHeap(W,H,PIXEL_FORMAT_BGRA_565, pmemHeap)
isurface->registerBuffers(mBufferHeap)
//得到buffer指针
char * bp = static_cast(mBufferHeap.heap->base())
//向buffer写位图数据,注意要是32位的
XXXXXXXXXX
//提交修改,通知Surface Flinger更新屏幕
isurface->postBuffer(0)