Subject: Re: [PATCH 2/2] arm-nommu: Add use_reserved_mem() to check if device support reserved memory

From: Christoph Hellwig <[email-masked]>
Date: Tue, 9 Jun 2020 19:34:55 +0200

On Tue, Jun 09, 2020 at 05:25:04PM +0100, Vladimir Murzin wrote:
> Even though commit mentions ARM, I do not see how mmap would continue
> to work for NOMMU with dma-direct. ARM NOMMU needs it's own DMA operations
> only in cases where caches are implemented or active, in other cases it
> fully relies on dma-direct.

> It looks to me that we either should provide NOMMU variant for mmap in
> dma/direct or (carefully) fix dma/mapping.

I think dma-direct is the right place, the common helpers in
dma/mapping.c are basically the red headed stepchilds for misc
IOMMU drivers not covered by dma-iommu only.

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