On 04/15/2018 08:29 PM, Christoph Hellwig wrote: > This way we have one central definition of it, and user can select it as > needed. Note that we also add a second ARCH_HAS_SWIOTLB symbol to > indicate the architecture supports swiotlb at all, so that we can still > make the usage optional for a few architectures that want this feature > to be user selectable. > > Signed-off-by: Christoph Hellwig <h...@lst.de>
snip > + > +config SWIOTLB > + bool "SWIOTLB support" > + default ARCH_HAS_SWIOTLB > + select DMA_DIRECT_OPS > + select NEED_DMA_MAP_STATE > + select NEED_SG_DMA_LENGTH > + ---help--- > + Support for IO bounce buffering for systems without an IOMMU. > + This allows us to DMA to the full physical address space on > + platforms where the size of a physical address is larger > + than the bus address. If unsure, say Y. > + > config CHECK_SIGNATURE > bool Pulling DMA_DIRECT_OPS config option by default when SWIOTLB is enabled makes sense. This option was also needed to be enabled separately even to use swiotlb_dma_ops.