async_tx: kill ASYNC_TX_DEP_ACK flag

In support of inter-channel chaining async_tx utilizes an ack flag to
gate whether a dependent operation can be chained to another.  While the
flag is not set the chain can be considered open for appending.  Setting
the ack flag closes the chain and flags the descriptor for garbage
collection.  The ASYNC_TX_DEP_ACK flag essentially means "close the
chain after adding this dependency".  Since each operation can only have
one child the api now implicitly sets the ack flag at dependency
submission time.  This removes an unnecessary management burden from
clients of the api.

[ Impact: clean up and enforce one dependency per operation ]

Reviewed-by: Andre Noll <maan@systemlinux.org>
Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 1 insertions, 3 deletions

diff --git a/include/linux/async_tx.h b/include/linux/async_tx.h
index 513150d8c25b..9f14cd540cd2 100644
--- a/include/linux/async_tx.h
+++ b/include/linux/async_tx.h
@@ -58,13 +58,11 @@ struct dma_chan_ref {
  * array.
  * @ASYNC_TX_ACK: immediately ack the descriptor, precludes setting up a
  * dependency chain
- * @ASYNC_TX_DEP_ACK: ack the dependency descriptor.  Useful for chaining.
  */
 enum async_tx_flags {
         ASYNC_TX_XOR_ZERO_DST    = (1 << 0),
         ASYNC_TX_XOR_DROP_DST    = (1 << 1),
-        ASYNC_TX_ACK             = (1 << 3),
-        ASYNC_TX_DEP_ACK         = (1 << 4),
+        ASYNC_TX_ACK             = (1 << 2),
 };
 
 #ifdef CONFIG_DMA_ENGINE