[PATCH 0/2] vb2: add (un)prepare_streaming vb2_queue ops

[Hans Verkuil <hverkuil-cisco@xs4all.nl>]

Add support for two new (un)prepare_streaming queue ops that are called
when the user calls VIDIOC_STREAMON and STREAMOFF (or closes the fh).

This gives drivers a callback to validate the video pipeline and claim
or release streaming resources at the time that userspace indicates
that it wants to start streaming (VIDIOC_STREAMON) rather than when
the actual DMA engine kicks in (the start_streaming callback). This
is relevant for drivers that needs a minimum of X buffers before the
DMA can start. The actual pipeline validation needs to happen sooner
to avoid unnecessary errors at VIDIOC_QBUF time.

As a bonus this allows us to move the horrible call to
v4l_vb2q_enable_media_source() in vb2_core_streamon() to the au0828
driver (currently the only driver that uses this feature).

That call never belonged in vb2, but it had the same purpose as the
new prepare_streaming op: validate the pipeline.

This is a follow-up from my previous RFCv2:

https://patchwork.linuxtv.org/project/linux-media/patch/ba4bca14-488f-94ea-48d9-e7343103c5aa@xs4all.nl/

I would like to get consensus for this series.

Regards,

	Hans

Hans Verkuil (2):
  vb2: add (un)prepare_streaming queue ops
  vb2/au0828: move the v4l_vb2q_enable_media_source to the au0828 driver

 .../media/common/videobuf2/videobuf2-core.c   | 26 ++++++++++++++-----
 drivers/media/usb/au0828/au0828-vbi.c         |  2 ++
 drivers/media/usb/au0828/au0828-video.c       |  1 +
 include/media/videobuf2-core.h                | 14 ++++++++++
 4 files changed, 37 insertions(+), 6 deletions(-)

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2.35.1