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doc:dmaengine: clarify DMA desc. pointer after submission 

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>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Federico Vaga 2019-02-08 16:30:38 +01:00 committed by Jonathan Corbet
parent 2c71d305ca
commit db693aded3
1 changed files with 7 additions and 0 deletions
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7
Documentation/driver-api/dmaengine/client.rst
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@ -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