On Tue, 21 Aug 2007 12:35:22 -0700 [EMAIL PROTECTED] 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 <[EMAIL PROTECTED]> > -- > 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 [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
