On Fri, 2007-12-21 at 09:39 +0000, Russell King wrote: > > +#ifndef ARCH_MIN_DMA_ALIGNMENT > > +#define __dma_aligned > > +#define __dma_buffer > > +#else > > +#define __dma_aligned __attribute__((aligned(ARCH_MIN_DMA_ALIGNMENT))) > > +#define __dma_buffer __dma_buffer_line(__LINE__) > > +#define __dma_buffer_line(line) __dma_aligned;\ > > + char __dma_pad_##line[0] __dma_aligned > > You introduce __dma_buffer_line() if ARCH_MIN_DMA_ALIGNMENT is set but > not if it isn't... Yup, it's not meant to be used outside of __dma_buffer... .../... > > +then dev->buffer will be safe for DMA on all architectures. On a > > +cache-coherent architecture the members of dev will be aligned exactly > > +as they would have been without __dma_buffer; on a non-cache-coherent > > +architecture buffer and field2 will be aligned so that buffer does not > > +share a cache line with any other data. > > + > > ... but it's not described. What's the purpose of it, and why would it > only be used on CPUs with ARCH_MIN_DMA_ALIGNMENT set? Hrm, I'm not the best at writing exlanations, care to send a patch ? :-) Cheers, Ben - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
