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| author | Robert Jarzmik <robert.jarzmik@free.fr> | 2009-04-24 19:58:35 +0400 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@redhat.com> | 2009-06-17 01:20:44 +0400 |
| commit | 56600093644c6929a7d1809dab5b8265532df045 (patch) | |
| tree | 12d9986af549cc57642720889d646af3bc64bfc9 | |
| parent | c09b77806e692d8e58c55b4f4592a855b95f13cd (diff) | |
| download | linux-56600093644c6929a7d1809dab5b8265532df045.tar.xz | |
V4L/DVB (11613): pxa_camera: Documentation of the FSM
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@free.fr>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
| -rw-r--r-- | 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 b1137f9a53eb..4f6d0ca01956 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 --------- |