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Diffstat (limited to 'Documentation/DMA-API.txt')
| -rw-r--r-- | Documentation/DMA-API.txt | 21 |
1 files changed, 1 insertions, 20 deletions
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index dddf52e768d6..ac66ae2509a9 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 -failure. - -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 |