X-Git-Url: https://bbs.cooldavid.org/git/?a=blobdiff_plain;f=Documentation%2FDMA-API-HOWTO.txt;h=d568bc235bc008a215b981bcf303352c54bbda3a;hb=b382b191ea9e9ccefc437433d23befe91f4a8925;hp=98ce51796f711317f567a3b5144955178d0fd8da;hpb=60eab877a9581b479c6c7d7913ce8070a0ace960;p=net-next-2.6.git

diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt
index 98ce51796f7..d568bc235bc 100644
--- a/Documentation/DMA-API-HOWTO.txt
+++ b/Documentation/DMA-API-HOWTO.txt
@@ -738,21 +738,31 @@ to "Closing".
    CONFIG_NEED_SG_DMA_LENGTH if the architecture supports IOMMUs
    (including software IOMMU).
 
-2) ARCH_KMALLOC_MINALIGN
+2) ARCH_DMA_MINALIGN
 
    Architectures must ensure that kmalloc'ed buffer is
    DMA-safe. Drivers and subsystems depend on it. If an architecture
    isn't fully DMA-coherent (i.e. hardware doesn't ensure that data in
    the CPU cache is identical to data in main memory),
-   ARCH_KMALLOC_MINALIGN must be set so that the memory allocator
+   ARCH_DMA_MINALIGN must be set so that the memory allocator
    makes sure that kmalloc'ed buffer doesn't share a cache line with
    the others. See arch/arm/include/asm/cache.h as an example.
 
-   Note that ARCH_KMALLOC_MINALIGN is about DMA memory alignment
+   Note that ARCH_DMA_MINALIGN is about DMA memory alignment
    constraints. You don't need to worry about the architecture data
    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