The tran_init_pkt(9E) entry point is the HBA driver function that allocates and initializes, on behalf of the target driver, a scsi_pkt(9S) structure and DMA resources for a target driver request.
Each call of the tran_init_pkt(9E) entry point is a request to perform one or more of three possible services:
Allocation and initialization of a scsi_pkt(9S) structure
Allocation of DMA resources for data transfer
Reallocation of DMA resources for the next portion of the data transfer