On Mon, Sep 24, 2018 at 12:56:18PM -0700, Bart Van Assche wrote: > On Mon, 2018-09-24 at 11:57 -0700, Matthew Wilcox wrote: > > You're not supposed to use kmalloc memory for DMA. This is why we have > > dma_alloc_coherent() and friends. > > Are you claiming that all drivers that use DMA should use coherent DMA only? If > coherent DMA is the only DMA style that should be used, why do the following > function pointers exist in struct dma_map_ops? Good job snipping the part of my reply which addressed this. Go read DMA-API.txt yourself. Carefully.