pmem杂记

froyo:

drivers/misc/pmem.c

frameworks/base/libs/binder:

 

这是一个简单的使用：

pmem_fd = open("/dev/pmem_adsp", O_RDWR, 0);//打开设备，为了操作硬件引擎，要noncache的
ioctl(pmem_fd, PMEM_GET_TOTAL_SIZE, &region)  //获取全部空间

pmem_base = mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED, pmem_fd, 0);//mmap操作

ioctl(pmem_fd, PMEM_GET_PHYS, &region) //获取物理地址

munmap

 

考虑使用PMEM_CONNECT的话，有
1。 multiple references with multiple allocations

fd0 = open("/dev/pmem_xxx", ...)

mmap();

...

fd1 = open("/dev/pmem_xxx", ...)

mmap();

 

2。 multiple references with one allocation in oneprocess or one process group

 

fd0 = open("/dev/pmem_xxx", ...)

mmap();

...

 

fd1 = open("/dev/pmem_xxx", ...);

ret = ioctl(fd1, PMEM_CONNECT, fd0);

if (ret != 0) goto error;

struct pmem_region region1 = { offset1, size1 };

ret = ioctl(fd1, PMEM_MAP, &region1);

...

 

3. multiple references with one allocation inmultiple processes

a think it's a little tricky 

 

 

 

MemoryHeapBase

MemoryHeapBase ：BnMemoryHeap

 

MemoryHeapPmem ：MemoryHeapBase

MemoryHeapPmem ::MemoryPmem :BnMemory :BnInterface<IMemory>

 

 

 

struct pmem_region region;sp<MemoryHeapBase> base = new MemoryHeapBase(PMEM_DEVICE,mPreviewFrameSize_align * (kPreviewBufCnt));if (base->heapID() < 0) { LOGE("Failed to allocate pmem from %s", PMEM_DEVICE);}mPreviewHeap = new MemoryHeapPmem(base, 0);int fd_pmem = mPreviewHeap->getHeapID();if (ioctl(fd_pmem, PMEM_GET_PHYS, &region)) { LOGE("%s: Failed to get PMEM physical address", __FUNCTION__);} /* * Make an IMemory for each streaming buffer so that we can reuse * them in callbacks. */ for (int i = 0; i < kPreviewBufCnt; i++) { mBuffers[i] = (static_cast<MemoryHeapPmem *>(mPreviewHeap.get()))-> mapMemory(i * mPreviewFrameSize_align, mPreviewFrameSize); mBufferPhyAddr[i] = (void *)(region.offset + i * mPreviewFrameSize_align); }