BF609使用CCES开发，看别人的例子里adi_mdma_Open()这个函数里有个回调函数的操作,想请教一下什么时候调用这个回调函数，有什么作用？

ADI_DMA_RESULT adi_mdma_Open(
    ADI_DMA_STREAM_ID               eStreamID,
    void                            *pStreamMemory,
    ADI_DMA_STREAM_HANDLE           *phStream,
    ADI_DMA_CHANNEL_HANDLE          *phSrcChannel,
    ADI_DMA_CHANNEL_HANDLE          *phDestChannel,
    ADI_CALLBACK                    pfCallback,
    void                            *pCBParam);

typedef void(* ADI_CALLBACK)(void *pCBParam,uint32_t Event,void *pArg)

Pointer to the event specific argument