On Wed, 19 May 2010 14:49:08 +0100 David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote: > Commit 3843384a055496dfed3c93ae883d964d8290fdab ("Input: ad7877 - keep > dma rx buffers in seperate cache lines")[sic] introduced the use of > ____cacheline_aligned to ensure that buffers used for DMA as part of a > structure were suitably separated from the rest of the structure. > > However, aligning to the cache line size isn't necessary on > cache-coherent architectures. To avoid wasting space, the correct value > to use for the alignment is ARCH_KMALLOC_MINALIGN. > > This patch provides a __dma_aligned macro which does the right thing. > > Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx> > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index ca32ed7..4487cf3 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -5,6 +5,9 @@ > #include <linux/err.h> > #include <linux/dma-attrs.h> > #include <linux/scatterlist.h> > +#include <linux/slab.h> > + > +#define __dma_aligned __attribute__((__aligned__(ARCH_KMALLOC_MINALIGN))) As wrote in other mail, such was proposed several times: http://www.mail-archive.com/linux-scsi@xxxxxxxxxxxxxxx/msg12633.html http://lwn.net/Articles/2269/ And rejected. http://lwn.net/Articles/2270/ -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html