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    SubjectRe: RFC: usb: musb: Adding CPPI4.1 DMA driver under drivers/dma
    On Fri, Jan 13, 2012 at 10:09:32AM -0800, Greg KH wrote:
    > On Fri, Jan 13, 2012 at 10:40:50AM +0000, Gupta, Ajay Kumar wrote:
    > > Hi,
    > >
    > > CPPI4.1 (Communication Port Programming Interface) is a TI specific DMA
    > > controller used in multiple TI platform such as AM33x, DA8x, AM35x, TI81x.
    > > The DMA engine is mainly used by musb controller on above platform.
    > >
    > > Earlier version of the driver was submitted by Sergei Shtylyov at [1] but
    > > was not merged due to disagreement on the location of driver in kernel.
    > > Refer the discussions at [1] for more details.
    > >
    > > [1] http://marc.info/?l=linux-usb&m=125087318308323
    > >
    > > The new implementation of the CPPI4.1 DMA slave driver will be in the
    > > drivers/dma folder, complying to dmaengine framework.
    > > It would involve changes in existing musb driver also for which current
    > > plan is to maintain the compatibility of non-CPPI4.1 DMA in musb driver.
    > >
    > > The task is planned to be spitted into below subtasks.
    > >
    > > (1) Post RFC on the API details, changes envisaged in musb driver and other
    > > challenges
    > >
    > > (2) Implement and post RFC for the CPPI4.1 DMA driver and changes needed in
    > > musb driver.
    > >
    > > Let me know if you have any thoughts/comments on this.
    >
    > First off, don't highjack threads (you responded to a linux-usb thread
    > here, get a better email client please.)
    >
    > Second, that sounds fine, please post patches.

    I'm with Greg here, please post patches.

    What I suggest is:

    - first create a dma-engine.c file on drivers/usb/musb which will simply
    translate dmaengine into the MUSB-specific API.
    this will allow us to slowly convert other platforms without
    breaking the legacy stuff.

    - Then move CPPI to drivers/dma

    - Test it all out ;-)

    --
    balbi
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