semantics of dma_map_single()

Vineet Gupta Vineet.Gupta1 at
Mon Jul 17 09:06:29 PDT 2017

Hi Christoph,

On 07/16/2017 11:42 PM, Christoph Hellwig wrote:
> I would expect that it would support any contiguous range in
> the kernel mapping (e.g. no vmalloc and friends).  But it's not
> documented anywhere, and if no in kernel users makes use of that
> fact at the moment it might be better to document a page size
> limitation and add asserts to enforce it.

My first thought was indeed to add a BUG_ON for @size > PAGE_SIZE (also accounting 
for offset etc), but I have a feeling this will cause too many breakages. So 
perhaps it would be better to add the fact to Documentation that it can handle any 
physically contiguous range.


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