On Wed, Jun 17, 2015 at 05:50:01PM +0800, Herbert Xu wrote: > On Wed, Jun 17, 2015 at 09:45:33AM +0200, Boris Brezillon wrote: > > > > + 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 :) It's worse than that... You're right on that point, but there's an additional point. If dma_map_sg() coalesces scatterlist entries, then ret will be smaller than src_nents, and ret indicates how many scatterlist entries to be walked during DMA - you should not use src_nents for that. I couldn't see where the driver used that information. In fact, the driver seems to be capable of walking more than src_nents/ret numbers of scatterlist entries: it just keeps going with sg_next() until it hits the end of the allocated scatterlist. -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
