[libcamera-devel] [PATCH v2 10/11] Documentation: guides: pipeline-handler: Migrate to Camera::Private

[Jacopo Mondi]

Hi Laurent,

On Thu, Aug 05, 2021 at 08:58:47PM +0300, Laurent Pinchart wrote:
> Update the pipeline handler guide following the migration from the
> CameraData class to the Camera::Private class.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> Reviewed-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> ---
>  Documentation/guides/pipeline-handler.rst | 67 ++++++++++++-----------
>  1 file changed, 34 insertions(+), 33 deletions(-)
>
> diff --git a/Documentation/guides/pipeline-handler.rst b/Documentation/guides/pipeline-handler.rst
> index 152776935a33..7e9ff824dd50 100644
> --- a/Documentation/guides/pipeline-handler.rst
> +++ b/Documentation/guides/pipeline-handler.rst
> @@ -106,7 +106,7 @@ functionalities descibed above. Below is a brief overview of each of those:
>     Abstracts camera sensor handling by hiding the details of the V4L2 subdevice
>     kernel API and caching sensor information.
>
> --  `CameraData <http://libcamera.org/api-html/classlibcamera_1_1CameraData.html>`_:
> +-  `Camera::Private <http://libcamera.org/api-html/classlibcamera_1_1Camera_1_1Private.html>`_:
>     Represents device-specific data a pipeline handler associates to each Camera
>     instance.
>
> @@ -416,26 +416,26 @@ receivers port output.
>  The Pipeline Handler is responsible for defining the set of Streams associated
>  with the Camera.
>
> -Each Camera has instance-specific data represented using the `CameraData`_
> +Each Camera has instance-specific data represented using the `Camera::Private`_
>  class, which can be extended for the specific needs of the pipeline handler.
>
> -.. _CameraData: http://libcamera.org/api-html/classlibcamera_1_1CameraData.html
> +.. _Camera::Private: http://libcamera.org/api-html/classlibcamera_1_1Camera_1_1Private.html
>
>
> -To support the Camera we will later register, we need to create a CameraData
> +To support the Camera we will later register, we need to create a Camera::Private
>  class that we can implement for our specific Pipeline Handler.
>
> -Define a new ``VividCameraData()`` class derived from ``CameraData`` by adding
> -the following code before the PipelineHandlerVivid class definition where it
> -will be used:
> +Define a new ``VividCameraPrivate()`` class derived from ``Camera::Private`` by
> +adding the following code before the PipelineHandlerVivid class definition where
> +it will be used:
>
>  .. code-block:: cpp
>
> -   class VividCameraData : public CameraData
> +   class VividCameraData : public Camera::Private
>     {
>     public:
>            VividCameraData(PipelineHandler *pipe, MediaDevice *media)
> -                : CameraData(pipe), media_(media), video_(nullptr)
> +                : Camera::Private(pipe), media_(media), video_(nullptr)
>            {
>            }
>
> @@ -457,17 +457,17 @@ single stream, represented by the ``VividCameraData`` class members. More
>  complex pipeline handlers might register cameras composed of several video
>  devices and sub-devices, or multiple streams per camera that represent the
>  several components of the image capture pipeline. You should represent all these
> -components in the ``CameraData`` derived class when developing a custom
> +components in the ``Camera::Private`` derived class when developing a custom
>  PipelineHandler.
>
>  In our example VividCameraData we implement an ``init()`` function to prepare
> -the object from our PipelineHandler, however the CameraData class does not
> +the object from our PipelineHandler, however the Camera::Private class does not
>  specify the interface for initialisation and PipelineHandlers can manage this
> -based on their own needs. Derived CameraData classes are used only by their
> +based on their own needs. Derived Camera::Private classes are used only by their
>  respective pipeline handlers.
>
> -The CameraData class stores the context required for each camera instance and
> -is usually responsible for opening all Devices used in the capture pipeline.
> +The Camera::Private class stores the context required for each camera instance
> +and is usually responsible for opening all Devices used in the capture pipeline.
>
>  We can now implement the ``init`` method for our example Pipeline Handler to
>  create a new V4L2 video device from the media entity, which we can specify using
> @@ -488,11 +488,11 @@ capture device named 'vivid-000-vid-cap' by the device.
>            return 0;
>     }
>
> -The CameraData should be created and initialised before we move on to register a
> -new Camera device so we need to construct and initialise our
> +The VividCameraData should be created and initialised before we move on to
> +register a new Camera device so we need to construct and initialise our
>  VividCameraData after we have identified our device within
>  PipelineHandlerVivid::match(). The VividCameraData is wrapped by a
> -std::unique_ptr to help manage the lifetime of our CameraData instance.
> +std::unique_ptr to help manage the lifetime of the instance.

If the ownership is not transfered, this is really an implementation
detail of each pipeline's match() implementation

>
>  If the camera data initialization fails, return ``false`` to indicate the
>  failure to the ``match()`` method and prevent retrying of the pipeline handler.
> @@ -508,9 +508,9 @@ failure to the ``match()`` method and prevent retrying of the pipeline handler.
>  Once the camera data has been initialized, the Camera device instances and the
>  associated streams have to be registered. Create a set of streams for the
>  camera, which for this device is only one. You create a camera using the static
> -`Camera::create`_ method, passing the pipeline handler, the id of the camera,
> -and the streams available. Then register the camera and its data with the
> -pipeline handler and camera manager using `registerCamera`_.
> +`Camera::create`_ method, passing the Camera::Private instance, the id of the
> +camera, and the streams available. Then register the camera with the pipeline
> +handler and camera manager using `registerCamera`_.
>
>  Finally with a successful construction, we return 'true' indicating that the
>  PipelineHandler successfully matched and constructed a device.
> @@ -548,23 +548,24 @@ Our match function should now look like the following:
>
>     	/* Create and register the camera. */
>     	std::set<Stream *> streams{ &data->stream_ };
> -   	std::shared_ptr<Camera> camera = Camera::create(this, data->video_->deviceName(), streams);
> -   	registerCamera(std::move(camera), std::move(data));
> +        const std::string &id = data->video_->deviceName();

       ^ weird spacing

> +   	std::shared_ptr<Camera> camera = Camera::create(data.release(), id, streams);
> +   	registerCamera(std::move(camera));
>
>     	return true;
>     }
>
> -We will need to use our custom CameraData class frequently throughout the
> +We will need to use our custom VividCameraData class frequently throughout the
>  pipeline handler, so we add a private convenience helper to our Pipeline handler
> -to obtain and cast the custom CameraData instance from a Camera instance.
> +to obtain and cast the custom VividCameraData instance from a Camera::Private
> +instance.
>
>  .. code-block:: cpp
>
>     private:
> -       VividCameraData *cameraData(const Camera *camera)
> +       VividCameraData *cameraData(Camera *camera)
>         {
> -               return static_cast<VividCameraData *>(
> -                        PipelineHandler::cameraData(camera));
> +               return static_cast<VividCameraData *>(camera->_d());
>         }
>
>  At this point, you need to add the following new includes to provide the Camera
> @@ -594,12 +595,12 @@ are defined by src/libcamera/`properties_ids.yaml`_.
>
>  Pipeline handlers can optionally register the list of controls an application
>  can set as well as a list of immutable camera properties. Being both
> -Camera-specific values, they are represented in the ``CameraData`` base class,
> -which provides two members for this purpose: the `CameraData::controlInfo_`_ and
> -the `CameraData::properties_`_ fields.
> +Camera-specific values, they are represented in the ``Camera::Private`` base
> +class, which provides two members for this purpose: the
> +`Camera::Private::controlInfo_`_ and the `Camera::Private::properties_`_ fields.
>
> -.. _CameraData::controlInfo_: http://libcamera.org/api-html/classlibcamera_1_1CameraData.html#ab9fecd05c655df6084a2233872144a52
> -.. _CameraData::properties_: http://libcamera.org/api-html/classlibcamera_1_1CameraData.html#a84002c29f45bd35566c172bb65e7ec0b
> +.. _Camera::Private::controlInfo_: http://libcamera.org/api-html/classlibcamera_1_1Camera_1_1Private.html#ab4e183eb4dabe929d1b2bbbb519b969f
> +.. _Camera::Private::properties_: http://libcamera.org/api-html/classlibcamera_1_1Camera_1_1Private.html#ad31f12f5ed9c1fbe25750902f4791064
>
>  The ``controlInfo_`` field represents a map of ``ControlId`` instances
>  associated with the limits of valid values supported for the control. More
> @@ -617,7 +618,7 @@ Complete the initialization of the ``VividCameraData`` class by adding the
>  following code to the ``VividCameraData::init()`` method to initialise the
>  controls. For more complex control configurations, this could of course be
>  broken out to a separate function, but for now we just initialise the small set
> -inline in our CameraData init:
> +inline in our VividCameraData init:

The rest looks ok
Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>

Thanks
   j

>
>  .. code-block:: cpp
>
> --
> Regards,
>
> Laurent Pinchart
>