[RFC PATCH 10/12] staging: android: ion: Use CMA APIs directly

On 03/03/2017 08:41 AM, Laurent Pinchart wrote:

Hi Laura,

Thank you for the patch.

On Thursday 02 Mar 2017 13:44:42 Laura Abbott wrote:

quoted

When CMA was first introduced, its primary use was for DMA allocation
and the only way to get CMA memory was to call dma_alloc_coherent. This
put Ion in an awkward position since there was no device structure
readily available and setting one up messed up the coherency model.
These days, CMA can be allocated directly from the APIs. Switch to using
this model to avoid needing a dummy device. This also avoids awkward
caching questions.

If the DMA mapping API isn't suitable for today's requirements anymore, I 
believe that's what needs to be fixed, instead of working around the problem 
by introducing another use-case-specific API.

I don't think this is a usecase specific API. CMA has been decoupled from
DMA already because it's used in other places. The trying to go through
DMA was just another layer of abstraction, especially since there isn't
a device available for allocation.

Thanks,
Laura