[RFC PATCH 04/15] lib/scatterlist: Add flag for indicating P2PDMA segments in an SGL

[Logan Gunthorpe]

We make use of the top bit of the dma_length to indicate a P2PDMA
segment. Code that uses this will need to use sg_dma_p2pdma_len() to
get the length and ensure no lengths exceed 2GB.

An sg_dma_is_p2pdma() helper is included to check if a particular
segment is p2pdma().

Signed-off-by: Logan Gunthorpe <logang at deltatee.com>
---
 include/linux/scatterlist.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 36c47e7e66a2..e738159d56f9 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -39,6 +39,10 @@ struct scatterlist {
 #define sg_dma_len(sg)		((sg)->length)
 #endif
 
+#define SG_P2PDMA_FLAG	(1U << 31)
+#define sg_dma_p2pdma_len(sg)	(sg_dma_len(sg) & ~SG_P2PDMA_FLAG)
+#define sg_dma_is_p2pdma(sg)	(sg_dma_len(sg) & SG_P2PDMA_FLAG)
+
 struct sg_table {
 	struct scatterlist *sgl;	/* the list */
 	unsigned int nents;		/* number of mapped entries */
-- 
2.20.1