[PATCH] doc:dmaengine: clarify DMA desc. pointer after submission

Federico Vaga
2019-02-08T15:30:56Z

It clarifies that the DMA description pointer returned by
`dmaengine_prep_*` function should not be used after submission.

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>
---
Documentation/driver-api/dmaengine/client.rst | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/Documentation/driver-api/dmaengine/client.rst b/Documentation/driver-api/dmaengine/client.rst
index fbbb2831f29f..d728e50105eb 100644
--- a/Documentation/driver-api/dmaengine/client.rst
+++ b/Documentation/driver-api/dmaengine/client.rst
@@ -168,6 +168,13 @@ The details of these operations are:
dmaengine_submit() will not start the DMA operation, it merely adds
it to the pending queue. For this, see step 5, dma_async_issue_pending.

+ .. note::
+
+ After calling ``dmaengine_submit()`` the submitted transfer descriptor
+ (``struct dma_async_tx_descriptor``) belongs to the DMA engine.
+ Consequentially, the client must consider invalid the pointer to that
+ descriptor.
+
5. Issue pending DMA requests and wait for callback notification

The transactions in the pending queue can be activated by calling the
--
2.15.0