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    SubjectRe: [PATCH 1/4 v2] dmaengine: add a tx_free method to struct dma_async_tx_descriptor
    On Wed, Dec 10, 2008 at 3:36 AM, Guennadi Liakhovetski
    <g.liakhovetski@gmx.de> wrote:
    > From: Guennadi Liakhovetski <lg@denx.de>
    >
    > Some users reuse DMA transaction descriptors multiple times and need an
    > explicit call to release them. An example of such a user is Video4Linux, which
    > has to be able to release descriptors on ioctl(VIDIOC_DQBUF).
    >
    > Signed-off-by: Guennadi Liakhovetski <lg@denx.de>


    Hi Guennadi,

    Other dmaengine drivers have tasklets that scan the list of completed
    descriptors and free the "acked" ones. This happens in the cleanup
    tasklet...
    /me looks
    ...hmm this driver does not have a cleanup routine? Ideally support
    for ioctl(VIDIOC_DQBUF) could be achieved through this mechanism
    without needing to increase the size of dma_async_tx_descriptor (which
    has cache utilization impacts on other drivers).

    --
    Dan


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