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    SubjectRe: [PATCH 1/3] DMAENGINE: generic slave channel control v2
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    Hi Linus,

    On Wed, Jul 21, 2010 at 12:22 PM, Linus Walleij
    <linus.walleij@stericsson.com> wrote:
    > This adds an interface to the DMAengine to make it possible to
    > reconfigure a slave channel at runtime. We add a few foreseen
    > config parameters to the passed struct, with a void * pointer
    > for custom per-device or per-platform runtime slave data.
    >
    > Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
    > ---
    > This version was revised after discussion, it splits the control
    > arguments in source/destination pairs to prepare for (among other
    > things) device to device transfers.
    > ---
    >  include/linux/dmaengine.h |   75 +++++++++++++++++++++++++++++++++++++++++++++
    >  1 files changed, 75 insertions(+), 0 deletions(-)
    >
    > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
    > index 5204f01..406b820 100644
    > --- a/include/linux/dmaengine.h
    > +++ b/include/linux/dmaengine.h
    > @@ -114,11 +114,17 @@ enum dma_ctrl_flags {
    >  * @DMA_TERMINATE_ALL: terminate all ongoing transfers
    >  * @DMA_PAUSE: pause ongoing transfers
    >  * @DMA_RESUME: resume paused transfer
    > + * @DMA_SLAVE_CONFIG: this command is only implemented by DMA controllers
    > + * that need to runtime reconfigure the slave channels (as opposed to passing
    > + * configuration data in statically from the platform). An additional
    > + * argument of struct dma_slave_config must be passed in with this
    > + * command.
    >  */
    >  enum dma_ctrl_cmd {
    >        DMA_TERMINATE_ALL,
    >        DMA_PAUSE,
    >        DMA_RESUME,
    > +       DMA_SLAVE_CONFIG,
    >  };
    >
    >  /**
    > @@ -199,6 +205,75 @@ struct dma_chan_dev {
    >        atomic_t *idr_ref;
    >  };
    >
    > +/**
    > + * enum dma_slave_buswidth - defines bus with of the DMA slave
    > + * device, source or target busses

    s/busses/buses/

    > + */
    > +enum dma_slave_buswidth {
    > +       DMA_SLAVE_BUSWIDTH_UNDEFINED = 0,
    > +       DMA_SLAVE_BUSWIDTH_1_BYTE = 1,
    > +       DMA_SLAVE_BUSWIDTH_2_BYTES = 2,
    > +       DMA_SLAVE_BUSWIDTH_4_BYTES = 4,
    > +       DMA_SLAVE_BUSWIDTH_8_BYTES = 8,
    > +};
    > +
    > +/**
    > + * struct dma_slave_config - dma slave channel runtime config
    > + * @direction: whether the data shall go in or out on this slave
    > + * channel, right now. DMA_TO_DEVICE and DMA_FROM_DEVICE are
    > + * legal values, DMA_BIDIRECTIONAL is not acceptable since we
    > + * need to differentiate source and target addresses.
    > + * @src_addr: this is the physical address where DMA slave data
    > + * should be read (RX), if the source is memory this argument is
    > + * ignored.
    > + * @dst_addr: this is the physical address where DMA slave data
    > + * should be written (TX), if the source is memory this argument
    > + * is ignored.
    > + * @src_addr_width: this is the width in bytes of the source (RX)
    > + * register where DMA data shall be read. If the source
    > + * is memory this may be ignored depending on architecture.
    > + * Legal values: 1, 2, 4, 8.
    > + * @dst_addr_width: same as src_addr_width but for destination
    > + * target (TX) mutatis mutandis.

    /me wikipedias "mutatis mutandis", ah sort of latin for the s/// operator :-).

    > + * @src_maxburst: the maximum number of words (note: words, as in
    > + * units of the src_addr_width member, not bytes) that can be sent
    > + * in one burst to the device. Typically something like half the
    > + * FIFO depth on I/O peripherals so you don't overflow it. This
    > + * may or may not be applicable on memory sources.
    > + * @dst_maxburst: same as src_maxburst but for destination target
    > + * mutatus mutandis.

    s/mutatus/mutatis/

    > + * @private_config: if you need to pass in specialized configuration
    > + * at runtime, apart from the generic things supported in this
    > + * struct, you provide it in this pointer and dereference it inside
    > + * your dmaengine driver to get the proper configuration bits out.
    > + *

    Will there be any users of this field initially, I'd just as soon
    leave it out? Like I mentioned to Vinod I think requiring
    dma_slave_config to be wrapped is a better way to extend this
    structure.

    --
    Dan
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