dmaengine: Use dma_sg_len(sg) instead of sg->length

sg->length may or may not contain the length of the dma region to transfer,
depending on the architecture - dma_sg_len(sg) always will though. For the
architectures which use the drivers modified by this patch it probably is the
case that sg->length contains the dma transfer length. But to be consistent and
future proof change them to use dma_sg_len.

To quote Russel King:
	sg->length is meaningless to something performing DMA.

	In cases where sg_dma_len(sg) and sg->length are the same storage, then
	there's no problem. But scatterlists _can_ (and one some architectures) do
	split them - especially when you have an IOMMU which can allow you to
	combine a scatterlist into fewer entries.

	So, anything using sg->length for the size of a scatterlist's DMA transfer
	_after_ a call to dma_map_sg() is almost certainly buggy.

The patch has been generated using the following coccinelle patch:
<smpl>
@@
struct scatterlist *sg;
expression X;
@@
-sg[X].length
+sg_dma_len(&sg[X])
@@
struct scatterlist *sg;
@@
-sg->length
+sg_dma_len(sg)
</smpl>

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/drivers/dma/imx-dma.c b/drivers/dma/imx-dma.c
index bb787d8..fcfeb3c 100644
--- a/drivers/dma/imx-dma.c
+++ b/drivers/dma/imx-dma.c
@@ -227,7 +227,7 @@ static inline int imxdma_sg_next(struct imxdma_desc *d)
 	struct scatterlist *sg = d->sg;
 	unsigned long now;
 
-	now = min(d->len, sg->length);
+	now = min(d->len, sg_dma_len(sg));
 	if (d->len != IMX_DMA_LENGTH_LOOP)
 		d->len -= now;
 
@@ -763,16 +763,16 @@ static struct dma_async_tx_descriptor *imxdma_prep_slave_sg(
 	desc = list_first_entry(&imxdmac->ld_free, struct imxdma_desc, node);
 
 	for_each_sg(sgl, sg, sg_len, i) {
-		dma_length += sg->length;
+		dma_length += sg_dma_len(sg);
 	}
 
 	switch (imxdmac->word_size) {
 	case DMA_SLAVE_BUSWIDTH_4_BYTES:
-		if (sgl->length & 3 || sgl->dma_address & 3)
+		if (sg_dma_len(sgl) & 3 || sgl->dma_address & 3)
 			return NULL;
 		break;
 	case DMA_SLAVE_BUSWIDTH_2_BYTES:
-		if (sgl->length & 1 || sgl->dma_address & 1)
+		if (sg_dma_len(sgl) & 1 || sgl->dma_address & 1)
 			return NULL;
 		break;
 	case DMA_SLAVE_BUSWIDTH_1_BYTE:
@@ -831,13 +831,13 @@ static struct dma_async_tx_descriptor *imxdma_prep_dma_cyclic(
 		imxdmac->sg_list[i].page_link = 0;
 		imxdmac->sg_list[i].offset = 0;
 		imxdmac->sg_list[i].dma_address = dma_addr;
-		imxdmac->sg_list[i].length = period_len;
+		sg_dma_len(&imxdmac->sg_list[i]) = period_len;
 		dma_addr += period_len;
 	}
 
 	/* close the loop */
 	imxdmac->sg_list[periods].offset = 0;
-	imxdmac->sg_list[periods].length = 0;
+	sg_dma_len(&imxdmac->sg_list[periods]) = 0;
 	imxdmac->sg_list[periods].page_link =
 		((unsigned long)imxdmac->sg_list | 0x01) & ~0x02;