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    SubjectRe: [RFC PATCH 1/2] RapidIO: Add DMA Engine support for RIO data transfers
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    On Mon, 2011-10-17 at 21:22 +0530, Jassi Brar wrote:
    > On 15 October 2011 23:05, Vinod Koul <vinod.koul@intel.com> wrote:
    >
    > > Another alternate approach could be to add one more argument to
    > > prep_slave_sg API which allows us to pass additional runtime specific
    > > parameters. This can be NULL and unused for existing drivers and used in
    > > RIO and any future subsystems which want to use dmaengine.
    > > Thoughts...?
    > >
    > That doesn't sound much different than passing the data via
    > dma_chan.private during prep_slave_sg. Only now we add to
    > the number of arguments.
    Yes agreed, but we already decided and marked it as depreciated.

    > And then either this argument would be RapidIO specific (unfair
    > to other users) or generic. In latter case what would it look like ?
    My initial thoughts were to add an argument which only the specific dmac
    knows howto decode and is filled by its client. As i said for existing
    users and people who don't require dynamic information wouldn't bother.
    The pros
    - allows us to support RIO kind of subsystems where one needs to pass
    subsystem specific information for programing the dmac
    - doesn't require us to add subsystem specific stuff in dmaengine,
    today its RIO tomorrow some other folks may want to add. We want to
    maintain dmaengine as a generic framework, while also trying to support
    multiple audiences.
    Cons:
    - there is no guarantee; dmac expects foo and clients pass bar

    I am okay if we have alternate way to support this with above goal :)

    --
    ~Vinod



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