dmaengine: documentation to the new callback mechanism
Adding documentation in dmaengine/provider.txt on the usage of callback
with result, callback_result, function pointer to retrieve transanction
result from a DMA submission.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
diff --git a/Documentation/dmaengine/provider.txt b/Documentation/dmaengine/provider.txt
index 91ce82d..c4fd475 100644
--- a/Documentation/dmaengine/provider.txt
+++ b/Documentation/dmaengine/provider.txt
@@ -282,6 +282,17 @@
that is supposed to push the current
transaction descriptor to a pending queue, waiting
for issue_pending to be called.
+ - In this structure the function pointer callback_result can be
+ initialized in order for the submitter to be notified that a
+ transaction has completed. In the earlier code the function pointer
+ callback has been used. However it does not provide any status to the
+ transaction and will be deprecated. The result structure defined as
+ dmaengine_result that is passed in to callback_result has two fields:
+ + result: This provides the transfer result defined by
+ dmaengine_tx_result. Either success or some error
+ condition.
+ + residue: Provides the residue bytes of the transfer for those that
+ support residue.
* device_issue_pending
- Takes the first transaction descriptor in the pending queue,