Messages in this thread | | | Subject | Re: [PATCH] dmaengine: Add API documentation for slave dma usage | From | "Koul, Vinod" <> | Date | Tue, 24 May 2011 21:36:11 +0530 |
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On Tue, 2011-05-24 at 17:40 +0200, Per Forlin wrote: > Hi Vinod, > > On Tue, May 24, 2011 at 2:04 PM, Koul, Vinod <vinod.koul@intel.com> wrote: > > From: Vinod Koul <vinod.koul@intel.com> > > > > Signed-off-by: Vinod Koul <vinod.koul@intel.com> > > --- > > Documentation/dma-slave-api.txt | 74 +++++++++++++++++++++++++++++++++++++++ > > 1 files changed, 74 insertions(+), 0 deletions(-) > > create mode 100644 Documentation/dma-slave-api.txt > I suggest putting this in subsection of dmaengine.txt instead. > dmaengine.txt would be the natural place to look at. Agreed, that would make it easier for people to find
> > +4. Submit the transaction(s) and wait for callback notification when slave API > > +is 3 above returns, the non NULL value would imply a "descriptor" for the > > +transaction. These transaction(s) would need to be submitted which pushes them > > +into queue in DMA driver. If DMA is idle then the first descriptor submit will > > +be pushed to DMA and subsequent ones will be queued. On completion of the DMA > > +operation the next in queue is submitted and a tasklet triggered. The tasklet > > +would then call the client driver completion callback routine for notification, > > +if set. > > + > Does submit really start the transfer as well? My interpretation of > submit is that is only adds desc to a pending queue. When calling > issue_pending all these descs will be schedule for DMA transfer. Calls > to submit after this point will added to the pending queue again and > not be issued until calling issue_pending once more. For slave dma devices, submit() is used to start the transaction if the channel is idle. If its already doing a transaction then it will queue it up and submit once cureent excuting one is completed. It is not required to call issue_pending once more. I am not sure if this is true for non slave usage, Dan would that be correct for you as well?
-- ~Vinod
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