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authorVinod Koul <vinod.koul@intel.com>2015-06-25 06:51:37 +0300
committerVinod Koul <vinod.koul@intel.com>2015-06-25 06:51:37 +0300
commit9324fdf5267b12f6db660fe52e882bbfffcc109a (patch)
tree877a81ac336724efdb02403eceb8ca0b1e7b10eb /Documentation
parent4983a501afede12f95d26e1e213f8f2e9eda1871 (diff)
parent5f88d9706fa48084eaab2dbbec27779809c5106b (diff)
downloadlinux-9324fdf5267b12f6db660fe52e882bbfffcc109a.tar.xz
Merge branch 'topic/core' into for-linus
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/dmaengine/provider.txt11
1 files changed, 6 insertions, 5 deletions
diff --git a/Documentation/dmaengine/provider.txt b/Documentation/dmaengine/provider.txt
index 05d2280190f1..ca67b0f04c6e 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 transfer can be reused after being completed.
+ - There is a guarantee the transfer 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() in between 2 transfers, because the DMA'd data wasn't used,
+ it can resubmit the transfer right after its completion.
General Design Notes
--------------------