Documentation: update scatterlist struct description in DMA-API-HOWTO
Now we have <asm-generic/scatterlist.h>. Architectures should use it
instead of inventing the own scatterlist struct. Let's update the
description.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt
index a38ddad..c3ab456 100644
--- a/Documentation/DMA-API-HOWTO.txt
+++ b/Documentation/DMA-API-HOWTO.txt
@@ -703,19 +703,10 @@
1) Struct scatterlist requirements.
- Struct scatterlist must contain, at a minimum, the following
- members:
-
- struct page *page;
- unsigned int offset;
- unsigned int length;
-
- The base address is specified by a "page+offset" pair.
-
- Previous versions of struct scatterlist contained a "void *address"
- field that was sometimes used instead of page+offset. As of Linux
- 2.5., page+offset is always used, and the "address" field has been
- deleted.
+ Don't invent the architecture specific struct scatterlist; just use
+ <asm-generic/scatterlist.h>. You need to enable
+ CONFIG_NEED_SG_DMA_LENGTH if the architecture supports IOMMUs
+ (including software IOMMU).
2) More to come...