[PATCH] dmaengine: Clarify cyclic transfer residue documentation

[PATCH] dmaengine: Clarify cyclic transfer residue documentation

[Paul Kocialkowski]

The current documentation for the residue reported in a cyclic transfer
case mentions that the reported residue should be relative to the current
period only. However the definition of DMA_RESIDUE_GRANULARITY_SEGMENT
specifies that the residue should be updated after each period for
a cyclic transfer, which is in direct contradiction.

Moreover the pcm_dmaengine common code uses the residue relative to
the whole cyclic buffer size, not one period.

Correct the residue-related documentation to reflect this.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
---
 Documentation/driver-api/dmaengine/provider.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/driver-api/dmaengine/provider.rst b/Documentation/driver-api/dmaengine/provider.rst
index 0072c9c7efd3..d3fa80e333b1 100644
--- a/Documentation/driver-api/dmaengine/provider.rst
+++ b/Documentation/driver-api/dmaengine/provider.rst
@@ -457,7 +457,7 @@ supported.
   - Should use dma_set_residue to report it
 
   - In the case of a cyclic transfer, it should only take into
-    account the current period.
+    account the total size of the cyclic buffer.
 
   - Should return DMA_OUT_OF_ORDER if the device does not support in order
     completion and is completing the operation out of order.
-- 
2.35.1

Re: [PATCH] dmaengine: Clarify cyclic transfer residue documentation

[Vinod Koul]

On 31-03-22, 15:41, Paul Kocialkowski wrote:
> The current documentation for the residue reported in a cyclic transfer
> case mentions that the reported residue should be relative to the current
> period only. However the definition of DMA_RESIDUE_GRANULARITY_SEGMENT
> specifies that the residue should be updated after each period for
> a cyclic transfer, which is in direct contradiction.
> 
> Moreover the pcm_dmaengine common code uses the residue relative to
> the whole cyclic buffer size, not one period.
> 
> Correct the residue-related documentation to reflect this.

Applied, thanks

-- 
~Vinod