[libcamera-devel] [PATCH v2 2/5] libcamera: pipeline: simple: Document the pipeline traversal algorithm

[Kieran Bingham]

Quoting Laurent Pinchart via libcamera-devel (2022-06-12 16:23:08)
> Add a section to the documentation at the top of the file to describe in
> a bit more details how the media graph is traversed.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>  src/libcamera/pipeline/simple/simple.cpp | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
> index efb28ccd97e8..b09368aee20b 100644
> --- a/src/libcamera/pipeline/simple/simple.cpp
> +++ b/src/libcamera/pipeline/simple/simple.cpp
> @@ -95,6 +95,21 @@ LOG_DEFINE_CATEGORY(SimplePipeline)
>   * valid pipeline configurations are found, a Camera is registered for the
>   * SimpleCameraData instance.
>   *
> + * Pipeline Traversal
> + * ------------------
> + *
> + * During the breadth-first search, the pipeline is traversed from entity to
> + * entity, by following media graph links from source to sink, starting at the
> + * camera sensor. When reaching an entity (on its sink side), all its source
> + * pads are considered to continue the graph traversal.
> + *
> + * The shortest path between the camera sensor and a video node is stored in
> + * SimpleCameraData::entities_ as a list of SimpleCameraData::Entity structures,
> + * ordered along the data path from the camera sensor to the video node. The
> + * Entity structure stores a pointer to the MediaEntity, as well as information
> + * about how it is connected in that particular path for later usage when
> + * configuring the pipeline.
> + *

I still think a generalised pipeline traversal like proposed by Naush
might be helpful sometime.

But ... that's a separate topic, this documents the current behaviour,
sounds reasonable so it's good to add.


Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

>   * Pipeline Configuration
>   * ----------------------
>   *
> -- 
> Regards,
> 
> Laurent Pinchart
>