[libcamera-devel] [PATCH 0/5] Introduce ancillary links

[Mauro Carvalho Chehab]

Em Mon, 13 Dec 2021 23:28:44 +0000
Daniel Scally <djrscally at gmail.com> escreveu:

> 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 

The idea of ancillary link sounds interesting. I did a quick look at
the series. 

Laurent already did some good points during his review.
Besides that, one thing it is missing, though, is an implementation on
a driver. At least vimc should gain an implementation at this series,
in order to allow media developers to test and see how the graph will
be after the patch series.

Regards,
Mauro

> 
> 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(-)
> 



Thanks,
Mauro