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Diffstat (limited to 'Documentation/core-api/dma-api.rst')
| -rw-r--r-- | Documentation/core-api/dma-api.rst | 64 |
1 files changed, 22 insertions, 42 deletions
diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst index 75cb757bbff0..e6d23f117308 100644 --- a/Documentation/core-api/dma-api.rst +++ b/Documentation/core-api/dma-api.rst @@ -528,16 +528,14 @@ an I/O device, you should not be using this part of the API. :: - void * - dma_alloc_noncoherent(struct device *dev, size_t size, - dma_addr_t *dma_handle, enum dma_data_direction dir, - gfp_t gfp) + struct page * + dma_alloc_pages(struct device *dev, size_t size, dma_addr_t *dma_handle, + enum dma_data_direction dir, gfp_t gfp) -This routine allocates a region of <size> bytes of consistent memory. It -returns a pointer to the allocated region (in the processor's virtual address -space) or NULL if the allocation failed. The returned memory may or may not -be in the kernel direct mapping. Drivers must not call virt_to_page on -the returned memory region. +This routine allocates a region of <size> bytes of non-coherent memory. It +returns a pointer to first struct page for the region, or NULL if the +allocation failed. The resulting struct page can be used for everything a +struct page is suitable for. It also returns a <dma_handle> which may be cast to an unsigned integer the same width as the bus and given to the device as the DMA address base of @@ -558,51 +556,33 @@ reused. :: void - dma_free_noncoherent(struct device *dev, size_t size, void *cpu_addr, + dma_free_pages(struct device *dev, size_t size, struct page *page, dma_addr_t dma_handle, enum dma_data_direction dir) -Free a region of memory previously allocated using dma_alloc_noncoherent(). -dev, size and dma_handle and dir must all be the same as those passed into -dma_alloc_noncoherent(). cpu_addr must be the virtual address returned by -dma_alloc_noncoherent(). +Free a region of memory previously allocated using dma_alloc_pages(). +dev, size, dma_handle and dir must all be the same as those passed into +dma_alloc_pages(). page must be the pointer returned by dma_alloc_pages(). :: - struct page * - dma_alloc_pages(struct device *dev, size_t size, dma_addr_t *dma_handle, - enum dma_data_direction dir, gfp_t gfp) - -This routine allocates a region of <size> bytes of non-coherent memory. It -returns a pointer to first struct page for the region, or NULL if the -allocation failed. The resulting struct page can be used for everything a -struct page is suitable for. - -It also returns a <dma_handle> which may be cast to an unsigned integer the -same width as the bus and given to the device as the DMA address base of -the region. - -The dir parameter specified if data is read and/or written by the device, -see dma_map_single() for details. - -The gfp parameter allows the caller to specify the ``GFP_`` flags (see -kmalloc()) for the allocation, but rejects flags used to specify a memory -zone such as GFP_DMA or GFP_HIGHMEM. + void * + dma_alloc_noncoherent(struct device *dev, size_t size, + dma_addr_t *dma_handle, enum dma_data_direction dir, + gfp_t gfp) -Before giving the memory to the device, dma_sync_single_for_device() needs -to be called, and before reading memory written by the device, -dma_sync_single_for_cpu(), just like for streaming DMA mappings that are -reused. +This routine is a convenient wrapper around dma_alloc_pages that returns the +kernel virtual address for the allocated memory instead of the page structure. :: void - dma_free_pages(struct device *dev, size_t size, struct page *page, + dma_free_noncoherent(struct device *dev, size_t size, void *cpu_addr, dma_addr_t dma_handle, enum dma_data_direction dir) -Free a region of memory previously allocated using dma_alloc_pages(). -dev, size and dma_handle and dir must all be the same as those passed into -dma_alloc_noncoherent(). page must be the pointer returned by -dma_alloc_pages(). +Free a region of memory previously allocated using dma_alloc_noncoherent(). +dev, size, dma_handle and dir must all be the same as those passed into +dma_alloc_noncoherent(). cpu_addr must be the virtual address returned by +dma_alloc_noncoherent(). :: |