Add documentation about acking the transfers, and their
reusability.
Signed-off-by: Robert Jarzmik <robert.jarzmik@xxxxxxx>
---
Documentation/dmaengine/provider.txt | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/Documentation/dmaengine/provider.txt b/Documentation/dmaengine/provider.txt
index 05d2280..33a81ce 100644
--- a/Documentation/dmaengine/provider.txt
+++ b/Documentation/dmaengine/provider.txt
@@ -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 TX transfer can be reused after being completed.
+ - there is a guarantee the TX 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() because the DMA'd data wasn't used, it can resubmit the
+ transfer right after its completion.
General Design Notes
--------------------
--
2.1.4
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