Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> writes: > On Tue, Jan 2, 2018 at 10:45 AM, Michael Ellerman <mpe@xxxxxxxxxxxxxx> wrote: >> Christoph Hellwig <hch@xxxxxx> writes: >> >>> We want to use the dma_direct_ namespace for a generic implementation, >>> so rename powerpc to the second best choice: dma_nommu_. >> >> I'm not a fan of "nommu". Some of the users of direct ops *are* using an >> IOMMU, they're just setting up a 1:1 mapping once at init time, rather >> than mapping dynamically. >> >> Though I don't have a good idea for a better name, maybe "1to1", >> "linear", "premapped" ? > > "identity"? I think that would be wrong, but thanks for trying to help :) The address on the device side is sometimes (often?) offset from the CPU address. So eg. the device can DMA to RAM address 0x0 using address 0x800000000000000. Identity would imply 0 == 0 etc. I think "bijective" is the correct term, but that's probably a bit esoteric. cheers
