Re: [PATCH 12/21] dma-iommu: factor atomic pool allocations into helpers

[Christoph Hellwig]

On Thu, Apr 18, 2019 at 05:41:00PM +0100, Robin Murphy wrote:
>>  From a very high level POV this looks ok, but sometimes a bit to
>> convoluted to me.  The major issue why I went with the version I posted
>> is that I can cleanly ifdef out the remap code in just a few sections.
>> In this version it is spread out a lot more, and the use of IS_ENABLED
>> means that we'd need a lot more stubs for functionality that won't
>> ever be called but needs to be compilable.
>
> What functionality do you have planned in that regard? I did do a quick 
> build test of my arm64 config with DMA_DIRECT_REMAP hacked out, and 
> dma-iommu.o appeared to link OK (although other bits of arm64 and 
> dma-direct didn't, as expected). I will try x86 with IOMMU_DMA to make 
> sure, though.

Yeah, this seems to actually work, there just is a huge chunk of
remapping that is hopefully discarded by the compiler even without the
ifdefs.