[lkml]   [2012]   [Jun]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [alsa-devel] [PATCH 2/2] ASoC: dmaengine-pcm: Add support for querying stream position from DMA device
    On 06/11/2012 04:57 PM, Mark Brown wrote:
    > On Mon, Jun 11, 2012 at 02:24:09PM +0100, Russell King - ARM Linux wrote:
    >> What we need to do is to get rid of this idea that reporting the residue
    >> is optional for DMA engine drivers. Let's make it absolutely required
    >> in order to support cyclic transfers.
    > I tend to agree, if we are going to let things not implement this we
    > need to provide an out of bounds way for them to signal that they don't
    > support it and make it an error to use the interface at all. Otherwise
    > the interface complexity increases as you get into special cases and so
    > on. We only need to fix the drivers that are used with ASoC immediately
    > and there's not so many of them which is easier than being forced to get
    > every driver upgraded at once.

    I think the previous discussions have made it clear that we don't want to
    make it optional for drivers to implement residue reporting for cyclic

    Another option is to provide the current implementation of the pcm_pointer
    as a standalone legacy function, which can be used by the old platforms
    until their dmaengine drivers have cached up. And add a new residue-only
    implementation which will be mandatory for new drivers. That would make it
    more explicit that those platforms are sort of broken and need to be fixed.
    After all of them have been fixed the legacy pcm_pointer implementation can
    be removed.

    I still think though that residue should never be reported as 0 for active
    cyclic transfers.

    - Lars

     \ /
      Last update: 2012-06-11 18:03    [W:0.022 / U:2.792 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site