Hi Shawn,
On 11/04/16 03:47, Shawn Guo wrote:
The macro sg_dma_len(sg) is commonly used to retrieve length of sg,
which could be 'dma_length' or 'length' field, depending on whether
NEED_SG_DMA_LENGTH is enabled or not. On the other hand, many driver
code use helper function sg_set_page() to set an sg entry pointing at
a page, with offset and length set up in one call. But sg_set_page()
does not consider NEED_SG_DMA_LENGTH case and only set up 'length'
field. This causes problem on platforms like ARM64, where
NEED_SG_DMA_LENGTH is enabled by default, i.e. sg_set_page() sets up
'length' while sg_dma_len(sg) returns 'dma_length' field.
The patch changes sg_set_page() to use sg_dma_len() for sg length setup
as well, so that NEED_SG_DMA_LENGTH case can be handled.
Signed-off-by: Shawn Guo <[email protected]>
---
include/linux/scatterlist.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 556ec1ea2574..b0e32ea594c3 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -114,7 +114,7 @@ static inline void sg_set_page(struct scatterlist *sg,
struct page *page,
{
sg_assign_page(sg, page);
sg->offset = offset;
- sg->length = len;
+ sg_dma_len(sg) = len;
This looks wrong. If a driver is building a scatterlist, then it needs
to fill in the page, offset and length fields to describe the physical
layout - leaving sg->length uninitialised would be a recipe for disaster
- then pass it to the DMA API. Only the DMA API implementation should be
setting dma_addr and dma_len, and they may not correspond to the
physical layout at all (e.g. an IOMMU could concatenate the entire list
into a single much longer segment at whatever arbitrary DMA address it
chooses).
Is there some particular driver hiccup behind this?
Robin.
}
static inline struct page *sg_page(struct scatterlist *sg)
