path: root/Documentation/DMA-API.txt
diff options
authorChristoph Hellwig <hch@lst.de>2017-08-25 15:13:09 (GMT)
committerChristoph Hellwig <hch@lst.de>2017-09-01 09:59:17 (GMT)
commit2436bdcda53ff4abb7897c87fa29ef3de8055344 (patch)
treeaa9204da61d1e888fea12ac09c948f5d77e793c5 /Documentation/DMA-API.txt
parentb32dbc1e0bf0eaa8bdd725491b361d5fc2f57a85 (diff)
dma-coherent: remove the DMA_MEMORY_MAP and DMA_MEMORY_IO flags
DMA_MEMORY_IO was never used in the tree, so remove it. That means there is no need for the DMA_MEMORY_MAP flag either now, so remove it as well and change dma_declare_coherent_memory to return a normal errno value. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com>
Diffstat (limited to 'Documentation/DMA-API.txt')
1 files changed, 1 insertions, 20 deletions
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index dddf52e..ac66ae2 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -592,30 +592,11 @@ size is the size of the area (must be multiples of PAGE_SIZE).
flags can be ORed together and are:
-- DMA_MEMORY_MAP - request that the memory returned from
- dma_alloc_coherent() be directly writable.
-- DMA_MEMORY_IO - request that the memory returned from
- dma_alloc_coherent() be addressable using read()/write()/memcpy_toio() etc.
-One or both of these flags must be present.
- DMA_MEMORY_EXCLUSIVE - only allocate memory from the declared regions.
Do not allow dma_alloc_coherent() to fall back to system memory when
it's out of memory in the declared region.
-The return value will be either DMA_MEMORY_MAP or DMA_MEMORY_IO and
-must correspond to a passed in flag (i.e. no returning DMA_MEMORY_IO
-if only DMA_MEMORY_MAP were passed in) for success or zero for
-Note, for DMA_MEMORY_IO returns, all subsequent memory returned by
-dma_alloc_coherent() may no longer be accessed directly, but instead
-must be accessed using the correct bus functions. If your driver
-isn't prepared to handle this contingency, it should not specify
-DMA_MEMORY_IO in the input flags.
-As a simplification for the platforms, only **one** such region of
+As a simplification for the platforms, only *one* such region of
memory may be declared per device.
For reasons of efficiency, most platforms choose to track the declared