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From: Robert Jarzmik <robert.jarzmik@free.fr>
The DMA transfers in pxa_camera showed some weaknesses in
multiple queued buffers context :
- poll/select problem
The bug shows up with capture_example tool from v4l2 hg
tree. The process just "stalls" on a "select timeout".
- multiple buffers DMA starting
When multiple buffers were queued, the DMA channels were
always started right away. This is not optimal, as a
special case appears when the first EOF was not yet
reached, and the DMA channels were prematurely started.
- Maintainability
DMA code was a bit obfuscated. Rationalize the code to be
easily maintainable by anyone.
- DMA hot chaining
DMA is not stopped anymore to queue a buffer, the buffer
is queued with DMA running. As a tribute, a corner case
exists where chaining happens while DMA finishes the
chain, and the capture is restarted to deal with the
missed link buffer.
This patch attemps to address these issues / improvements.
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
---
Documentation/video4linux/pxa_camera.txt | 125 ++++++++++++
drivers/media/video/pxa_camera.c | 319 ++++++++++++++++++------------
2 files changed, 316 insertions(+), 128 deletions(-)
create mode 100644 Documentation/video4linux/pxa_camera.txt
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