On Wed, May 02, 2018 at 11:20:18PM +0100, James Hogan wrote: > On Wed, Apr 25, 2018 at 07:15:37AM +0200, Christoph Hellwig wrote: > > Only mips and unicore32 select CONFIG_NEED_SG_DMA_LENGTH when building > > swiotlb. swiotlb itself never merges segements and doesn't accesses the > > dma_length field directly, so drop the dependency. > > Is that at odds with Documentation/DMA-API-HOWTO.txt, which seems to > suggest arch ports should enable it for IOMMUs? swiotlb isn't really an iommu.. That being said iommus don't have to merge segments either if they don't want to, and we have various implementations that don't. The whole dma api documentation needs a major overhaul, including merging the various files and dropping a lot of dead wood. It has been on my todo list for a while, with an inner hope that someone else would do it before me.
