[lkml]   [2009]   [Jun]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: is_device_dma_capable
    On Tue, 16 Jun 2009 16:54:24 +0930
    Malcom Blaney <> wrote:

    > I'm using the parport_pc driver with a dma buffer, which is provided
    > by calling dma_alloc_coherent in arch/x86/include/asm/dma-mapping.h.
    > This is no longer working for me in, the previous version I
    > was using is, which was fine with the same hardware.
    > The problem is that the call to is_device_dma_capable returns false,
    > so dma_alloc_coherent returns NULL. Do I need to set the dma_mask in
    > the driver for this to work correctly?

    You use X86_32, right?

    In 2.6.25, X86_32 and X86_64 had the own dma_alloc_coherent
    implementations; X86_32 accepted a device having dma_mask that is not
    initialized however X86_64 didn't, I think.

    When we merged them, we chose to prohibit a device having dma_mask
    that is not initialized. I'm not sure the DMA docs say this but IMO
    it's good to require drivers to set up dma_mask (and
    coherent_dma_mask) properly if the drivers want DMA.

     \ /
      Last update: 2009-06-16 10:15    [W:0.019 / U:40.824 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site