Messages in this thread |  | | Subject | Re: [PATCH 08/18] dma-mapping: add a new dma_alloc_noncoherent API | From | Robin Murphy <> | Date | Fri, 25 Sep 2020 12:15:37 +0100 |
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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.
Robin.
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