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If some ARM configs only give >>>>> order 4 folios or whatever then dmabuf heap doesn't care. >>>> >>>> The fundamental problem is that DMA allocations are highly >>>> architecture and device specific while Linux memory allocation APIs >>>> are generic. >>> >>> This isn't a dma allocation, this is a memory allocation. >> >> No, I mean this is a DMA-buf heaps allocation. It is a DMA >> allocation, we just don't know for which device. > > So? How is it any different from the existing alloc pages? That you need to specify that this is for DMA without encryption. >> So ideally we should use resources which work for most devices in >> the system. > > Which this does. > >> If a device has special allocation requirements (CMA, >> restricted addressing etc...) we need a specialized DMA-buf heaps >> for it. > > Those things don't really intersect with CC, but if they did their are > already heap names to request those, someone can add some shared > restricted CMA option if they need someday ? > >> That userspace provides this cc_shared flag is a NO-GO to begin >> with. > > What do you mean? We discussed this with the heap maintainers and we > all agreed this was a kind of heap just like any of the other kinds of > heaps that userspace can request. > > It is *exactly* the "special allocation requirements" you are talking > about above. I only see a fraction of the patch set (because no DMA-buf maintainer was CCed) and to me it looked like the cc_shared flag was added as an additional parameter to the allocation and not a separate heap created. If that is not the case then it is actually the correct approach. Christian. > > Jason