V4L2 Explicit Synchronization

Hi all,

The most relevant change for this round is that all the work done in the fence callback is now moved to a workqueue, that runs with the queue lock held.

Although this introduces some latency, it is however needed to take the vb2_queue mutex and safely call vb2 ops.

Given the fence callback can be called fully asynchronously, and given it needs to be associated with a vb2_buffer, we now need to refcount vb2_buffer. This allows to safely "attach" the vb2_buffer to the fence callback.

To prevent annoying deadlocks, and because the fence callback is called with the fence spinlock, it's best to avoid calling dma_fence_put in the fence callback itself. So the fence is now put in the DQBUF operation (or in cancel paths).

Hopefully, I took care of all the feedback provided by Hans and Brian on v9. Please let me know if you guys catch anything else.

Thanks!

Changes from v9:

* Move fence callback to workqueue, and call vb2_start_streaming if needed.
* Refcount vb2_buffer.
* Check return of get_unused_fd.
* Increase seqno for out-fences that reuse the context.
* Go back to is_unordered callback.
* Mark unordered formats in cobalt driver.
* Improve CAP_FENCES check.
* Minor documentation changes.

Ezequiel Garcia (1):
videobuf2: Make struct vb2_buffer refcounted

Gustavo Padovan (15):
xilinx: regroup caps on querycap
hackrf: group device capabilities
omap3isp: group device capabilities
vb2: move vb2_ops functions to videobuf2-core.[ch]
vb2: add is_unordered callback for drivers
v4l: add unordered flag to format description ioctl
v4l: mark unordered formats
cobalt: add .is_unordered() for cobalt
vb2: mark codec drivers as unordered
vb2: add explicit fence user API
vb2: add in-fence support to QBUF
vb2: add out-fence support to QBUF
v4l: introduce the fences capability
v4l: Add V4L2_CAP_FENCES to drivers
v4l: Document explicit synchronization behavior

 Documentation/media/uapi/v4l/buffer.rst            |  48 ++-
 Documentation/media/uapi/v4l/vidioc-enum-fmt.rst   |   7 +
 Documentation/media/uapi/v4l/vidioc-qbuf.rst       |  53 ++-
 Documentation/media/uapi/v4l/vidioc-querybuf.rst   |  12 +-
 Documentation/media/uapi/v4l/vidioc-querycap.rst   |   3 +
 drivers/media/common/videobuf2/Kconfig             |   1 +
 drivers/media/common/videobuf2/videobuf2-core.c    | 376 ++++++++++++++++++---
 drivers/media/common/videobuf2/videobuf2-v4l2.c    |  65 +++-
 drivers/media/dvb-core/dvb_vb2.c                   |   2 +-
 drivers/media/pci/cobalt/cobalt-v4l2.c             |   4 +
 drivers/media/platform/coda/coda-common.c          |   1 +
 drivers/media/platform/exynos-gsc/gsc-m2m.c        |   3 +-
 drivers/media/platform/m2m-deinterlace.c           |   3 +-
 drivers/media/platform/mtk-mdp/mtk_mdp_m2m.c       |   3 +-
 drivers/media/platform/mtk-vcodec/mtk_vcodec_dec.c |   1 +
 .../media/platform/mtk-vcodec/mtk_vcodec_dec_drv.c |   2 +-
 drivers/media/platform/mtk-vcodec/mtk_vcodec_enc.c |   1 +
 .../media/platform/mtk-vcodec/mtk_vcodec_enc_drv.c |   3 +-
 drivers/media/platform/mx2_emmaprp.c               |   3 +-
 drivers/media/platform/omap3isp/ispvideo.c         |  10 +-
 drivers/media/platform/qcom/venus/vdec.c           |   4 +-
 drivers/media/platform/qcom/venus/venc.c           |   4 +-
 drivers/media/platform/s5p-mfc/s5p_mfc_dec.c       |   1 +
 drivers/media/platform/s5p-mfc/s5p_mfc_enc.c       |   1 +
 drivers/media/platform/sh_veu.c                    |   3 +-
 drivers/media/platform/xilinx/xilinx-dma.c         |  10 +-
 drivers/media/usb/hackrf/hackrf.c                  |  11 +-
 drivers/media/v4l2-core/v4l2-compat-ioctl32.c      |   4 +-
 drivers/media/v4l2-core/v4l2-ioctl.c               |  98 +++++-
 include/media/videobuf2-core.h                     |  76 ++++-
 include/media/videobuf2-v4l2.h                     |  18 -
 include/uapi/linux/videodev2.h                     |  10 +-
 32 files changed, 708 insertions(+), 133 deletions(-)

2.16.3