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authorFederico Vaga <federico.vaga@cern.ch>2019-02-08 16:30:38 +0100
committerJonathan Corbet <corbet@lwn.net>2019-02-11 08:40:16 -0700
commitdb693aded3fb419c763963246281e417c1c0e126 (patch)
treefe7d307eb0af8517281cb9a8dcdf4daf42067c11 /Documentation/driver-api
parent2c71d305caf9cd5076873c6a57d22ab8cb7c906c (diff)
downloadlinux-db693aded3fb419c763963246281e417c1c0e126.tar.bz2
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>
Diffstat (limited to 'Documentation/driver-api')
-rw-r--r--Documentation/driver-api/dmaengine/client.rst7
1 files changed, 7 insertions, 0 deletions
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