[libcamera-devel] [PATCH v2 0/6] Introduce ancillary links

[Daniel Scally]

Hello all

At present there's no means in the kernel of describing the supporting
relationship between subdevices that work together to form an effective single
unit - the type example in this case being a camera sensor and its
corresponding vcm. To attempt to solve that, this series adds a new type of
media link called MEDIA_LNK_FL_ANCILLARY_LINK, which connects two instances of
struct media_entity.

The mechanism of connection I have modelled as a notifier and async subdev,
which seemed the best route since sensor drivers already typically will call
v4l2_async_register_subdev_sensor() on probe, and that function already looks
for a reference to a firmware node with the reference named "lens-focus". To
avoid boilerplate in the sensor drivers, I added some new functions in
v4l2-async that are called in v4l2_async_match_notify() to create the ancillary
links - checking the entity.function of both notifier and subdev to make sure
that's appropriate. I haven't gone further than that yet, but I suspect we could
cut down on code elsewhere by, for example, also creating pad-to-pad links in
the same place.

Series-level changes since v1:

	- New patch adding some documentation to the uAPI pages.

Dan

Daniel Scally (6):
  media: entity: Skip non-data links in graph iteration
  media: media.h: Add new media link type
  media: docs: Add entries documenting ancillary links
  media: entity: Add link_type_name() helper
  media: entity: Add support for ancillary links
  media: v4l2-async: Create links during v4l2_async_match_notify()

 .../media/mediactl/media-controller-model.rst |  6 ++
 .../media/mediactl/media-types.rst            |  9 ++-
 drivers/media/mc/mc-entity.c                  | 46 ++++++++++++++-
 drivers/media/v4l2-core/v4l2-async.c          | 56 +++++++++++++++++++
 include/media/media-entity.h                  | 21 +++++++
 include/uapi/linux/media.h                    |  1 +
 6 files changed, 135 insertions(+), 4 deletions(-)

-- 
2.25.1