driver-api/dmaengine/provider.rst

11 They have a given number of channels to use for the DMA transfers, and
41 really efficient, you'll get several bigger transfers. This is done
44 transfer into smaller sub-transfers.
46 Our theoretical DMA controller would then only be able to do transfers
48 transfers we usually have are not, and want to copy data from
52 DMAEngine, at least for mem2dev transfers, require support for
80 memory-to-device (mem2dev) kind of transfers. Most devices often
81 support other kind of transfers or memory operations that dmaengine
91 Over time, the need for memory to device transfers arose, and
125   (i.e. excluding mem2mem transfers)
215   - The devices only supports slave transfers, and as such isn't
216     available for async transfers.
227   - The device can handle device to memory transfers, including
228     scatter-gather transfers.
240   - The device can handle cyclic transfers.
245   - It's usually used for audio transfers, where you want to operate
252   - These transfers can transfer data from a non-contiguous buffer
257   - It's usually used for 2d content transfers, in which case you
279   - The device supports repeated transfers. A repeated transfer, indicated by
284   - This feature is limited to interleaved transfers, this flag should thus not
291   - The device supports replacing repeated transfers at end of transfer (EOT)
468     currently queued transfers, but only on subsequent ones
499   - Aborts all the pending and ongoing transfers on the channel
501   - For aborted transfers the complete callback should not be called
535   ignored in the slave transfers case.
569   ``dma_map_sg()`` and ``dma_unmap_sg()`` in between 2 transfers,
599     client terminates all transfers.
609   - This is the default behaviour for non-repeated transfers, specifying
610     DMA_PREP_LOAD_EOT for non-repeated transfers will thus make no difference.
612   - When using repeated transfers, DMA clients will usually need to set the
613     DMA_PREP_LOAD_EOT flag on all transfers, otherwise the channel will keep
614     repeating the last repeated transfer and ignore the new transfers being