While the .device_prep_slave_sg() callback rejects empty scatterlists,
it still accepts single-entry scatterlists with a zero-length segment.
These may happen if a driver calls dmaengine_prep_slave_single() with a
zero len parameter. The corresponding DMA request will never complete,
leading to messages like:
rcar-dmac e7300000.dma-controller: Channel Address Error happen
and DMA timeouts.
Although requesting a zero-length DMA request is a driver bug, rejecting
it early eases debugging. Note that the .device_prep_dma_memcpy()
callback already rejects requests to copy zero bytes.
Reported-by: Eugeniu Rosca <ero...@de.adit-jv.com>
Analyzed-by: Yoshihiro Shimoda <yoshihiro.shimoda...@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+rene...@glider.be>
---
See "[PATCH 0/2] serial: sh-sci: Fix .flush_buffer() issues"
(https://lore.kernel.org/linux-renesas-soc/20190624123540.20629-1-geert+rene...@glider.be/)
for the driver fix.
drivers/dma/sh/rcar-dmac.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index 67df54ac329400b7..9c41a4e425759fcc 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -1165,7 +1165,7 @@ rcar_dmac_prep_slave_sg(struct dma_chan *chan, struct
scatterlist *sgl,
struct rcar_dmac_chan *rchan = to_rcar_dmac_chan(chan);
/* Someone calling slave DMA on a generic channel? */
- if (rchan->mid_rid < 0 || !sg_len) {
+ if (rchan->mid_rid < 0 || !sg_len || !sg_dma_len(sgl)) {
dev_warn(chan->device->dev,
"%s: bad parameter: len=%d, id=%d\n",
__func__, sg_len, rchan->mid_rid);
--
2.17.1
