On 02/18/2011 02:04 AM, FUJITA Tomonori wrote: > On Thu, 17 Feb 2011 16:05:37 +0100 > Tomas Henzl <thenzl@xxxxxxxxxx> wrote: > > >> the discussion is mostly if 'dma_alloc_coherent' >> ... >> dma_coherent = dma_alloc_coherent(&pdev->dev, acb->uncache_size, &dma_coherent_handle, GFP_KERNEL); >> ... >> returns a page address - dma_coherent with last, I think five bits, zeroed. >> Could you help us with that? >> > Documentation/DMA-API-HOWTO.txt is not clear enough? > > = > dma_alloc_coherent returns two values: the virtual address which you > can use to access it from the CPU and dma_handle which you pass to the > card. > > The cpu return address and the DMA bus master address are both > guaranteed to be aligned to the smallest PAGE_SIZE order which > is greater than or equal to the requested size. This invariant > exists (for example) to guarantee that if you allocate a chunk > which is smaller than or equal to 64 kilobytes, the extent of the > buffer you receive will not cross a 64K boundary. > -- > 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 > It's clear enough I think, I asked this question because Nick doesn't have a "100% confidence in that.". So I wanted a help to convince him. -- 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
