On Tue, Aug 20, 2019 at 04:58:09PM +0200, Nicolas Saenz Julienne wrote: > Some architectures have platform specific DMA addressing limitations. > This will allow for hardware description code to provide the constraints > in a generic manner, so as for arch code to properly setup it's memory > zones and DMA mask. I know this just spreads the arm code, but I still kinda hate it. MAX_DMA_ADDRESS is such an oddly defined concepts. We have the mm code that uses it to start allocating after the dma zones, but I think that would better be done using a function returning 1 << max(zone_dma_bits, 32) or so. Then we have about a handful of drivers using it that all seem rather bogus, and one of which I think are usable on arm64.