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Commit 5f88d970 authored by Robert Jarzmik's avatar Robert Jarzmik Committed by Vinod Koul
Browse files

Documentation: dmaengine: document DMA_CTRL_ACK 



Add documentation about acking the transfers, and their
reusability.

Signed-off-by: default avatarRobert Jarzmik <robert.jarzmik@free.fr>
Acked-by: default avatarMaxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: default avatarVinod Koul <vinod.koul@intel.com>
parent b9855f03

Documentation/dmaengine/provider.txt

+6 −5
Original line number Diff line number Diff line
@@ -345,11 +345,12 @@ where to put them) 
      that abstracts it away.



  * DMA_CTRL_ACK

    - Undocumented feature

    - No one really has an idea of what it's about, besides being

      related to reusing the DMA transaction descriptors or having

      additional transactions added to it in the async-tx API

    - Useless in the case of the slave API

    - If set, the transfer can be reused after being completed.

    - There is a guarantee the transfer won't be freed until it is acked

      by async_tx_ack().

    - As a consequence, if a device driver wants to skip the dma_map_sg() and

      dma_unmap_sg() in between 2 transfers, because the DMA'd data wasn't used,

      it can resubmit the transfer right after its completion.



General Design Notes

--------------------