On Wed, 17 Jun 2015 17:50:01 +0800
Herbert Xu [off-list ref] wrote:

On Wed, Jun 17, 2015 at 09:45:33AM +0200, Boris Brezillon wrote:

quoted

+	ret = dma_map_sg(cesa_dev->dev, req->src, creq->src_nents,
+			 DMA_TO_DEVICE);
+	if (!ret)
+		return -ENOMEM;
+
+	creq->src_nents = ret;

DMA-API-HOWTO says that you must retain the original nents and
use it when you call dma_unmap_sg.  So I'm afraid one more repost
is needed :)

My bad (again :-/).
Actually, I think I don't need to save the dma_map_sg return val, since
I'm using the sg_next function to iterate over the scatterlist. Am I
right ?
IOW, is the ->map_sg() function (in dma_map_ops) supposed to merge the
contiguous entries and then flag the unused entries with the is_chain
flag ?
If that's not the case, and the ->map_sg() just marks the merged entries
as empty (length = 0), then I'll have to rework my iterator algorithm.

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com