Re: [PATCH 1/9] dma-direct: provide page based alloc/free helpers

[Christoph Hellwig]

On Fri, Nov 30, 2018 at 07:04:41PM +0000, Robin Murphy wrote:
> On 05/11/2018 12:19, Christoph Hellwig wrote:
>> Some architectures support remapping highmem into DMA coherent
>> allocations.  To use the common code for them we need variants of
>> dma_direct_{alloc,free}_pages that do not use kernel virtual addresses.
>
> FWIW it's as much about non-cacheable remapping of lowmem as it is about 
> highmem. Regardless, the diff looks OK to me.

Yes, but as long as you remap lowmem the current interface work ok,
but once you have highmem a kernel virtual address doesn't cut it,
and we need a page struct or physical address.