As said before I don't think these low-level helpers are the right API to export, but even if they did you'd just cover a tiny subset of the architectures.
Also to distil the previous thread - if you remap memory to uncached the helper to use is arch_dma_prep_coherent, which does a writeback+ invalidate everywhere, and there is no need to clean up after a long-term uncached mapping. We might still get speculations into that area, if we don't remap the direct mapping, but it isn't like invalidting that just before freeing the memory is going to help anyone. Also it seems like patches 5 and 6 are missing in my inbox.
