[lkml]   [2004]   [Jun]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: DMA API issues
    James Bottomley wrote:
    > On Fri, 2004-06-18 at 16:08, David Brownell wrote:
    >>I'm not following you. This isn't using the PCI DMA calls.
    >>These dots don't connect: different hardware needs different
    >>solutions. How would those calls make dma_alloc_coherent work?
    > The statement was "That's dma_alloc_coherent at its core ... it should
    > allocate from that 32K region." and what I was pointing out is that not
    > all platforms can treat an on-chip memory region as a real memory area.

    But this one can, and it sure seems like the appropriate
    solution. For reasons like the one not quoted above: it's
    a good way to eliminate what would otherwise be a case
    where a dmabounce is needed. And hey wow, it even uses
    the API designed to reduce such DMA "mapping" costs, and
    there are drivers already using it for such purposes.

    > That's why we have the iomem accessor functions.

    You mentioned ioremap(), which doesn't help here since
    the need is for a block of memory, not just address space,
    and also memcpy_toio(), which just another tool to implement
    the dma bouncing (which is on the "strongly avoid!" list).

    As I said, those still don't make dma_alloc_coherent() work.

    - Dave

    > James

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2005-03-22 14:03    [W:0.048 / U:8.932 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site