dmaengine: add helper function to request a slave DMA channel

Currently slave DMA channels are requested by calling dma_request_channel()
and requires DMA clients to pass various filter parameters to obtain the
appropriate channel.

With device-tree being used by architectures such as arm and the addition of
device-tree helper functions to extract the relevant DMA client information
from device-tree, add a new function to request a slave DMA channel using
device-tree. This function is currently a simple wrapper that calls the
device-tree of_dma_request_slave_channel() function.

Cc: Nicolas Ferre <[email protected]>
Cc: Benoit Cousson <[email protected]>
Cc: Stephen Warren <[email protected]>
Cc: Grant Likely <[email protected]>
Cc: Russell King <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Vinod Koul <[email protected]>
Cc: Dan Williams <[email protected]>

Acked-by: Arnd Bergmann <[email protected]>
Signed-off-by: Jon Hunter <[email protected]>
Reviewed-by: Stephen Warren <[email protected]>
Acked-by: Rob Herring <[email protected]>
Signed-off-by: Vinod Koul <[email protected]>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index d3201e438d16..8cd0e2556d04 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -974,6 +974,7 @@ enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie);
 enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx);
 void dma_issue_pending_all(void);
 struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param);
+struct dma_chan *dma_request_slave_channel(struct device *dev, char *name);
 void dma_release_channel(struct dma_chan *chan);
 #else
 static inline enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx)
@@ -988,6 +989,11 @@ static inline struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask,
 {
 	return NULL;
 }
+static inline struct dma_chan *dma_request_slave_channel(struct device *dev,
+							 char *name)
+{
+	return NULL
+}
 static inline void dma_release_channel(struct dma_chan *chan)
 {
 }