[libcamera-devel] [PATCH v3 7/7] documentation: Document vendor specific controls and properties handling

[Jacopo Mondi]

Hi Naush

On Fri, Nov 24, 2023 at 12:37:13PM +0000, Naushir Patuck via libcamera-devel wrote:
> Add some documentation to the pipeline handler file describing how to
> implement and handle vendor specific controls and properties with a
> small example.
>
> Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>  Documentation/guides/pipeline-handler.rst | 48 +++++++++++++++++++++++
>  1 file changed, 48 insertions(+)
>
> diff --git a/Documentation/guides/pipeline-handler.rst b/Documentation/guides/pipeline-handler.rst
> index 66d428a19c4f..5a3d00b1b879 100644
> --- a/Documentation/guides/pipeline-handler.rst
> +++ b/Documentation/guides/pipeline-handler.rst
> @@ -672,6 +672,54 @@ handling controls:
>     #include <libcamera/controls.h>
>     #include <libcamera/control_ids.h>
>
> +Vendor-specific controls and properties
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +Vendor-specific controls and properties must be defined in a separate YAML file
> +and included in the build by defining the pipeline handler to file mapping in
> +include/libcamera/meson.build.
> +

The vendor-specific file has to be placed in src/libcamera I presume ?
Should we specify that ?

> +For example, adding a Raspberry Pi vendor control file for the PiSP pipeline
> +handler is done with the following mapping:
> +
> +.. code-block:: meson
> +
> +   controls_map = {
> +      'controls': {
> +         'draft': 'control_ids_draft.yaml',
> +         'libcamera': 'control_ids.yaml',
> +         'rpi/pisp': 'control_ids_rpi.yaml',

Should we say this item has to match the pipeline option as specified
in the meson build options ?

> +      },
> +
> +      'properties': {
> +         'draft': 'property_ids_draft.yaml',
> +         'libcamera': 'property_ids.yaml',
> +      }
> +   }
> +
> +Vendor-specific controls and properties must contain a `vendor: <vendor_string>`
> +tag in the YAML file. Every unique vendor tag must define a unique and
> +non-overlapping range of reserved control IDs in src/libcamera/control_ranges.yaml.
> +
> +For example, the following block defines a vendor-specific control with the
> +`rpi` vendor tag:
> +
> +.. code-block:: yaml
> +
> +    vendor: rpi
> +    controls:
> +      - PispConfigDumpFile:
> +          type: string
> +          description: |
> +            Triggers the Raspberry Pi PiSP pipeline handler to generate a JSON
> +            formatted dump of the Backend configuration to the filename given by the
> +            value of the control.
> +
> +This controls will be generated in the vendor-specific namespace
> +`libcamera::controls::rpi`. Additionally a `#define
> +LIBCAMERA_HAS_RPI_VENDOR_CONTROLS` will be available to allow applications to
> +test for the availability of these controls.
> +
>  Generating a default configuration
>  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> --
> 2.34.1
>