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>
This commit is contained in:
FUJITA Tomonori 2010-05-26 14:44:21 -07:00 committed by Linus Torvalds
parent 7cdcc8e476
commit b02de87161

View File

@ -703,19 +703,10 @@ to "Closing".
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...