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SubjectRe: [PATCH 08/18] dma-mapping: add a new dma_alloc_noncoherent API
On 2020-09-15 16:51, Christoph Hellwig wrote:
> +These APIs allow to allocate pages in the kernel direct mapping that are
> +guaranteed to be DMA addressable. This means that unlike dma_alloc_coherent,
> +virt_to_page can be called on the resulting address, and the resulting

Nit: if we explicitly describe this as if it's a guarantee that can be
relied upon...

> +struct page can be used for everything a struct page is suitable for.

> +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 kernels direct mapping. Drivers must not call virt_to_page on
> +the returned memory region.

...then forbid this document's target audience from relying on it,
something seems off. At the very least it's unhelpfully unclear :/

Given patch #17, I suspect that the first paragraph is the one that's no
longer true.


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