Re: block: DMA alignment of IO buffer allocated from slab

[Matthew Wilcox]

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.