diff options
Diffstat (limited to 'Documentation/driver-api/dmaengine')
| -rw-r--r-- | Documentation/driver-api/dmaengine/client.rst | 14 | ||||
| -rw-r--r-- | Documentation/driver-api/dmaengine/index.rst | 4 | ||||
| -rw-r--r-- | Documentation/driver-api/dmaengine/provider.rst | 12 |
3 files changed, 22 insertions, 8 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 diff --git a/Documentation/driver-api/dmaengine/index.rst b/Documentation/driver-api/dmaengine/index.rst index b9df904d0a79..bdc45d8b4cfb 100644 --- a/Documentation/driver-api/dmaengine/index.rst +++ b/Documentation/driver-api/dmaengine/index.rst @@ -5,8 +5,8 @@ DMAEngine documentation DMAEngine documentation provides documents for various aspects of DMAEngine framework. -DMAEngine documentation ------------------------ +DMAEngine development documentation +----------------------------------- This book helps with DMAengine internal APIs and guide for DMAEngine device driver writers. diff --git a/Documentation/driver-api/dmaengine/provider.rst b/Documentation/driver-api/dmaengine/provider.rst index 790a15089f1f..56e5833e8a07 100644 --- a/Documentation/driver-api/dmaengine/provider.rst +++ b/Documentation/driver-api/dmaengine/provider.rst @@ -266,11 +266,15 @@ to use. attached (via the dmaengine_desc_attach_metadata() helper to the descriptor. From the DMA driver the following is expected for this mode: + - DMA_MEM_TO_DEV / DEV_MEM_TO_MEM + The data from the provided metadata buffer should be prepared for the DMA controller to be sent alongside of the payload data. Either by copying to a hardware descriptor, or highly coupled packet. + - DMA_DEV_TO_MEM + On transfer completion the DMA driver must copy the metadata to the client provided metadata buffer before notifying the client about the completion. After the transfer completion, DMA drivers must not touch the metadata @@ -284,10 +288,14 @@ to use. and dmaengine_desc_set_metadata_len() is provided as helper functions. From the DMA driver the following is expected for this mode: - - get_metadata_ptr + + - get_metadata_ptr() + Should return a pointer for the metadata buffer, the maximum size of the metadata buffer and the currently used / valid (if any) bytes in the buffer. - - set_metadata_len + + - set_metadata_len() + It is called by the clients after it have placed the metadata to the buffer to let the DMA driver know the number of valid bytes provided. |