X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=Documentation%2FDMA-attributes.txt;h=725580de75af0ff2d6aad098597b7bdde0966946;hb=08ab6bcf6ad5f910c0924d47c99772bddb2deeb2;hp=b768cc0e402b8e6f1cfa8ae0b0f23c4e1c50168a;hpb=a4e0d9af403d099e751797f6cc69e4a8e2d78ef1;p=pandora-kernel.git

diff --git a/Documentation/DMA-attributes.txt b/Documentation/DMA-attributes.txt
index b768cc0e402b..725580de75af 100644
--- a/Documentation/DMA-attributes.txt
+++ b/Documentation/DMA-attributes.txt
@@ -31,3 +31,39 @@ may be weakly ordered, that is that reads and writes may pass each other.
 Since it is optional for platforms to implement DMA_ATTR_WEAK_ORDERING,
 those that do not will simply ignore the attribute and exhibit default
 behavior.
+
+DMA_ATTR_WRITE_COMBINE
+----------------------
+
+DMA_ATTR_WRITE_COMBINE specifies that writes to the mapping may be
+buffered to improve performance.
+
+Since it is optional for platforms to implement DMA_ATTR_WRITE_COMBINE,
+those that do not will simply ignore the attribute and exhibit default
+behavior.
+
+DMA_ATTR_NON_CONSISTENT
+-----------------------
+
+DMA_ATTR_NON_CONSISTENT lets the platform to choose to return either
+consistent or non-consistent memory as it sees fit.  By using this API,
+you are guaranteeing to the platform that you have all the correct and
+necessary sync points for this memory in the driver.
+
+DMA_ATTR_NO_KERNEL_MAPPING
+--------------------------
+
+DMA_ATTR_NO_KERNEL_MAPPING lets the platform to avoid creating a kernel
+virtual mapping for the allocated buffer. On some architectures creating
+such mapping is non-trivial task and consumes very limited resources
+(like kernel virtual address space or dma consistent address space).
+Buffers allocated with this attribute can be only passed to user space
+by calling dma_mmap_attrs(). By using this API, you are guaranteeing
+that you won't dereference the pointer returned by dma_alloc_attr(). You
+can threat it as a cookie that must be passed to dma_mmap_attrs() and
+dma_free_attrs(). Make sure that both of these also get this attribute
+set on each call.
+
+Since it is optional for platforms to implement
+DMA_ATTR_NO_KERNEL_MAPPING, those that do not will simply ignore the
+attribute and exhibit default behavior.