[PATCH] scatterlist: Comment on pages for sg_set_page()

[Alan Mikhak <alan.mikhak@sifive.com>]

From: Alan Mikhak <alan.mikhak@sifive.com>

Update the description of sg_set_page() to communicate current
requirements for the page pointer parameter.

Signed-off-by: Alan Mikhak <alan.mikhak@sifive.com>
---
 include/linux/scatterlist.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 6eec50fb36c8..6dda865893aa 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -112,6 +112,12 @@ static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
  *   of the page pointer. See sg_page() for looking up the page belonging
  *   to an sg entry.
  *
+ *   Scatterlist currently expects the page parameter to be a pointer to
+ *   a page that is backed by a page struct.
+ *
+ *   Page pointers derived from addresses obtained from ioremap() are
+ *   currently not supported since they require use of iomem safe memcpy.
+ *
  **/
 static inline void sg_set_page(struct scatterlist *sg, struct page *page,
 			       unsigned int len, unsigned int offset)
-- 
2.7.4