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. Thoughts and comments very welcome Dan Daniel Scally (5): media: media.h: Add new media link type media: entity: Add link_type() helper media: entity: Skip non-data links in graph iteration media: entity: Add support for ancillary links media: v4l2-async: Create links during v4l2_async_match_notify() drivers/media/mc/mc-entity.c | 56 ++++++++++++++++++++++++++-- drivers/media/v4l2-core/v4l2-async.c | 51 +++++++++++++++++++++++++ include/media/media-entity.h | 29 ++++++++++++++ include/uapi/linux/media.h | 1 + 4 files changed, 134 insertions(+), 3 deletions(-) -- 2.25.1
