lkml.org 
[lkml]   [2007]   [Aug]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 2/3] dma: override "dma_flags_set_dmaflush" for sn-ia64
    On Tue, 21 Aug 2007 12:35:22 -0700 akepner@sgi.com wrote:

    >
    > > I'm a little concerned about changing the API for the dma_ foo
    > > functions, which are defined cross platform. If you want to change
    > > that, I think it will require updating the documentation explaining
    > > it.....
    >
    > What do you think of the following? (And is there anyone else
    > I should be cc-ing for review?)

    probably the document's author (cc added)


    > Document semantics of dma_flags_set_dmaflush()
    >
    > Signed-off-by: Arthur Kepner <akepner@sgi.com>
    > --
    > DMA-API.txt | 22 ++++++++++++++++++++++
    > 1 files changed, 22 insertions(+)
    >
    > diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
    > index cc7a8c3..e117b72 100644
    > --- a/Documentation/DMA-API.txt
    > +++ b/Documentation/DMA-API.txt
    > @@ -392,6 +392,28 @@ Notes: You must do this:
    >
    > See also dma_map_single().
    >
    > +int
    > +dma_flags_set_dmaflush(int dir)
    > +
    > +Amend dir (one of the enum dma_data_direction values), with a platform-

    no comma.

    > +specific "dmaflush" attribute. Unless the platform supports "posted DMA"

    add comma after "posted DMA" and drop lots of trailing spaces.

    > +this is a no-op.
    > +
    > +On platforms that support posted DMA, dma_flags_set_dmaflush() causes
    > +device writes to the associated memory region to flush in-flight DMA.
    > +This can be important, for example, when (DMA) writes to the memory
    > +region indicate that DMA of data is complete. If DMA of data and DMA of
    > +the completion indication race, as they can do when the platform supports
    > +posted DMA, then the completion indication may arrive in host memory
    > +ahead of some data.
    > +
    > +To prevent this, you might map the memory region used for completion
    > +indications as follows:
    > +
    > + int count, flags = dma_flags_set_dmaflush(DMA_BIDIRECTIONAL);
    > + .....
    > + count = dma_map_sg(dev, sglist, nents, flags);
    > +
    >
    > Part II - Advanced dma_ usage
    > -----------------------------
    > --
    > Arthur


    ---
    ~Randy
    *** Remember to use Documentation/SubmitChecklist when testing your code ***
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-08-21 22:29    [W:0.024 / U:0.236 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site