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-rw-r--r--Documentation/DMA-API-HOWTO.txt10
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt
index 98ce51796f71..3c4e07123e59 100644
--- a/Documentation/DMA-API-HOWTO.txt
+++ b/Documentation/DMA-API-HOWTO.txt
@@ -753,6 +753,16 @@ to "Closing".
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