Documentation: DMA-API-HOWTO.txt: add multiple types of IOMMUs support
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 98ce517..3c4e071 100644
--- a/Documentation/DMA-API-HOWTO.txt
+++ b/Documentation/DMA-API-HOWTO.txt
@@ -753,6 +753,16 @@
alignment constraints (e.g. the alignment constraints about 64-bit
objects).
+3) Supporting multiple types of IOMMUs
+
+ If your architecture needs to support multiple types of IOMMUs, you
+ can use include/linux/asm-generic/dma-mapping-common.h. It's a
+ library to support the DMA API with multiple types of IOMMUs. Lots
+ of architectures (x86, powerpc, sh, alpha, ia64, microblaze and
+ sparc) use it. Choose one to see how it can be used. If you need to
+ support multiple types of IOMMUs in a single system, the example of
+ x86 or powerpc helps.
+
Closing
This document, and the API itself, would not be in its current