On Mon, Apr 18, 2022 at 01:44:27AM +0300, Serge Semin wrote: > > but a DMA controller might also want to access something in the MMIO range > > 0x0-0x7fffffff, of which it still has an identical non-offset view. If a > > driver was previously using dma_map_resource() for that, it would now start > > getting DMA_MAPPING_ERROR because the dma_range_map exists but doesn't > > describe the MMIO region. I agree that in hindsight it's not an ideal > > situation, but it's how things have ended up, so at this point I'm wary of > > making potentially-breaking changes. > > Hmm, what if the driver was previously using for instance the > dma_direct_map_sg() method for it? dma_map_resource is for mapping MMIO space, and must not be called on memory in the kernel map. For dma_map_sg (or all the other dma_map_* interface except for dma_map_resource), the reverse is true.
