Detailed Description

DMA peripheral ingest / egress - implementation.

PC_DMA_SIMULATE (default) runs an in-memory model of the peripheral: an ingress staging ring feeds the ping-pong RX buffers, egress DMA drains the TX buffer into a capture ring, and a loopback channel routes its own TX back into its RX. pc_dma_poll() advances that engine and fires the completion callbacks - so the whole pipeline is host- and device-testable with no physical loopback. When the flag is 0, the front end dispatches to the weak pc_dma_hw_* hooks a real silicon driver overrides.

Definition in file dma.cpp.