Coherent DMA mapping for existing struct page

Coherent DMA mapping for existing struct page

[Nikolaus Rath]

Hello,

How do I set up a coherent DMA mapping for an existing struct page?
dma_alloc_coherent() wants to allocate its own buffer, and
dma_map_page() sets up streaming mappings. Which function am I missing?


Thanks,

   -Nikolaus

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Re: Coherent DMA mapping for existing struct page

[Robert Hancock]

On 01/24/2011 02:26 PM, Nikolaus Rath wrote:
> Hello,
>
> How do I set up a coherent DMA mapping for an existing struct page?
> dma_alloc_coherent() wants to allocate its own buffer, and
> dma_map_page() sets up streaming mappings. Which function am I missing?

I don't think you can do this. On some platforms, only certain memory 
can be used for coherent DMA, so you can't just use any arbitrary page.