how to specific virtual address to the nvBuffer?

Hi Nvidia:
Function NvBufferMemMap(int dmabuf_fd, unsigned int plane, NvBufferMemFlags memflag, void ** pVirtAddr) is used for getting mem mapped virtual Address of the plane. Is there any way to specific the virtual Address to the plane? because during my using process of a NvBuffer(its memory type is DMA type,and create it with function NvBufferCreateEx), I do not want to copy data from an adrress known to the NvBuffer virtual Address.
if there is a way,How?
Thanks a lot! Expected your reply!

Hi Nvidia:
Is ther any one can give me answer?
Thanks! Expected your reply soon!

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