DMA-list transfers

A DMA list is a sequence of transfer elements (or list elements) that, together with an initiating DMA-list command, specifies a sequence of DMA transfers between a single area of LS and possibly discontinuous areas in main storage.

Such DMA lists are stored in an SPE's LS, and the sequence of transfers is initiated with a DMA-list command, such as getl or putl.

DMA-list commands can only be issued by programs running on an SPE, but the PPE or other devices can create and store the lists in an SPE's LS. DMA lists can be used to implement scatter-gather functions between main storage and the LS.

1. Creating the DMA list
   Each transfer element in the DMA list contains a transfer size, the low half of an effective address, and a stall-and-notify bit that can be used to suspend list execution after transferring a list element whose stall-and-notify bit is set.
2. Initiating the transfers specified in the DMA list
   After the list is stored in the LS, the execution of the list is initiated by a DMA-list command, such as getl or putl, from the SPE whose LS contains the list.
3. DMA-list transfers: programming example
   The C-language sample program included here creates a DMA list and, in the last line, uses an spu_mfcdma32 intrinsic to issue a single DMA-list command (getl) to transfer a main-storage region into LS.