[RFC] ARM DMA mapping TODO, v1

[Russell King - ARM Linux]

On Thu, Apr 28, 2011 at 07:31:06AM +1000, Benjamin Herrenschmidt wrote:
> The question remains, if we ever want to do more complex demand-paged
> operations, should we also expose a lower level set of functions to get
> struct page out of a dma_alloc_coherent() allocation and to get the
> pgprot for the user dma mapping ?

I don't think so - that places the requirement that dma_alloc_coherent()
must be backed by memory with a set of struct page, which may not always
be the case.

Think about dma_alloc_coherent() with dma_declare_coherent_memory() used
with memory which is not part of system RAM.