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| -rw-r--r-- | Documentation/driver-api/dmaengine/client.rst | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/Documentation/driver-api/dmaengine/client.rst b/Documentation/driver-api/dmaengine/client.rst index e5953e7e4bf4..2104830a99ae 100644 --- a/Documentation/driver-api/dmaengine/client.rst +++ b/Documentation/driver-api/dmaengine/client.rst @@ -151,8 +151,8 @@ The details of these operations are: Note that callbacks will always be invoked from the DMA engines tasklet, never from interrupt context. -Optional: per descriptor metadata ---------------------------------- + **Optional: per descriptor metadata** + DMAengine provides two ways for metadata support. DESC_METADATA_CLIENT @@ -199,12 +199,15 @@ Optional: per descriptor metadata DESC_METADATA_CLIENT - DMA_MEM_TO_DEV / DEV_MEM_TO_MEM: + 1. prepare the descriptor (dmaengine_prep_*) construct the metadata in the client's buffer 2. use dmaengine_desc_attach_metadata() to attach the buffer to the descriptor 3. submit the transfer + - DMA_DEV_TO_MEM: + 1. prepare the descriptor (dmaengine_prep_*) 2. use dmaengine_desc_attach_metadata() to attach the buffer to the descriptor @@ -215,6 +218,7 @@ Optional: per descriptor metadata DESC_METADATA_ENGINE - DMA_MEM_TO_DEV / DEV_MEM_TO_MEM: + 1. prepare the descriptor (dmaengine_prep_*) 2. use dmaengine_desc_get_metadata_ptr() to get the pointer to the engine's metadata area @@ -222,7 +226,9 @@ Optional: per descriptor metadata 4. use dmaengine_desc_set_metadata_len() to tell the DMA engine the amount of data the client has placed into the metadata buffer 5. submit the transfer + - DMA_DEV_TO_MEM: + 1. prepare the descriptor (dmaengine_prep_*) 2. submit the transfer 3. on transfer completion, use dmaengine_desc_get_metadata_ptr() to get @@ -278,8 +284,8 @@ Optional: per descriptor metadata void dma_async_issue_pending(struct dma_chan *chan); -Further APIs: -------------- +Further APIs +------------ 1. Terminate APIs |