Am 10.07.20 um 14:43 schrieb Jason Gunthorpe:

On Thu, Jul 09, 2020 at 10:09:11AM +0200, Daniel Vetter wrote:

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Hi Jason,

Below the paragraph I've added after our discussions around dma-fences outside of drivers/gpu. Good enough for an ack on this, or want something changed?

Thanks, Daniel

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• • Note that only GPU drivers have a reasonable excuse for both requiring
• • &mmu_interval_notifier and &shrinker callbacks at the same time as having to
• • track asynchronous compute work using &dma_fence. No driver outside of
• • drivers/gpu should ever call dma_fence_wait() in such contexts.

I was hoping we'd get to 'no driver outside GPU should even use dma_fence()'

My last status was that V4L could come use dma_fences as well.

I'm not 100% sure, but wouldn't MMU notifier + dma_fence be a valid use case for things like custom FPGA interfaces as well?

Is that not reasonable?

When your annotations once anything uses dma_fence it has to assume the worst cases, right?

Well a defensive approach is usually the best idea, yes.

Christian.

Jason