On Mon, 13 Apr 2009, Robert Jarzmik wrote: > After DMA redesign, the pxa_camera dynamic behaviour should > be documented so that future contributors understand how it > works, and improve it. > > Signed-off-by: Robert Jarzmik <robert.jarzmik@xxxxxxx> > --- > Documentation/video4linux/pxa_camera.txt | 49 ++++++++++++++++++++++++++++++ > 1 files changed, 49 insertions(+), 0 deletions(-) > > diff --git a/Documentation/video4linux/pxa_camera.txt b/Documentation/video4linux/pxa_camera.txt > index b1137f9..b595e94 100644 > --- a/Documentation/video4linux/pxa_camera.txt > +++ b/Documentation/video4linux/pxa_camera.txt > @@ -26,6 +26,55 @@ Global video workflow > > Once the last buffer is filled in, the QCI interface stops. > > + c) Capture global finite state machine schema > + > + +----+ +---+ +----+ > + | DQ | | Q | | DQ | > + | v | v | v > + +-----------+ +------------------------+ > + | STOP | | Wait for capture start | > + +-----------+ Q +------------------------+ > ++-> | QCI: stop | ------------------> | QCI: run | <------------+ > +| | DMA: stop | | DMA: stop | | > +| +-----------+ +-----> +------------------------+ | > +| / | | > +| / +---+ +----+ | | > +|capture list empty / | Q | | DQ | | QCI Irq EOF | > +| / | v | v v | > +| +--------------------+ +----------------------+ | > +| | DMA hotlink missed | | Capture running | | > +| +--------------------+ +----------------------+ | > +| | QCI: run | +-----> | QCI: run | <-+ | > +| | DMA: stop | / | DMA: run | | | > +| +--------------------+ / +----------------------+ | Other | > +| ^ /DMA still | | channels | > +| | capture list / running | DMA Irq End | not | > +| | not empty / | | finished | > +| | / v | yet | > +| +----------------------+ +----------------------+ | | > +| | Videobuf released | | Channel completed | | | > +| +----------------------+ +----------------------+ | | > +| | QCI: run | | QCI: run | --+ | > +| | DMA: run | | DMA: run | | > +| +----------------------+ +----------------------+ | > +| ^ / | | > +| | no overrun / | overrun | > +| | / v | > +| +--------------------+ / +----------------------+ | > +| | Frame completed | / | Frame overran | | > +| +--------------------+ <-----+ +----------------------+ restart frame | > ++-- | QCI: run | | QCI: stop | --------------+ > + | DMA: run | | DMA: stop | > + +--------------------+ +----------------------+ > + > + Legend: - each box is a FSM state > + - each arrow is the condition to transition to another state > + - an arrow with a comment is a mandatory transition (no condition) > + - arrow "Q" means : a buffer was enqueued > + - arrow "DQ" means : a buffer was dequeued > + - "QCI: stop" means the QCI interface is not enabled > + - "DMA: stop" means all 3 DMA channels are stopped > + - "DMA: run" means at least 1 DMA channel is still running > > DMA usage > --------- Cool, nice:-) One question though: shouldn't the "capture list empty" transition start from "Videobuf released" state? Or maybe you want to reorginise the "Videobuf released" and "Frame completed" states a bit to separate cases - capture list empty - capture list not empty - DMA still running - hot-linking success - DMA stopped - restart Thanks Guennadi --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
