[libcamera-devel] [PATCH v2 6/6] documentation: Document vendor specific control and properties handling

[Laurent Pinchart]

Hi Naush,

Thank you for the patch.

On Tue, Nov 21, 2023 at 02:53:50PM +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

s/vendor specific/vendor-specific/

If that's a "proper English vs. US English" issue, please feel free to
correct me :-)

> small example.
> 
> Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> ---
>  Documentation/guides/pipeline-handler.rst | 52 +++++++++++++++++++++++
>  1 file changed, 52 insertions(+)
> 
> diff --git a/Documentation/guides/pipeline-handler.rst b/Documentation/guides/pipeline-handler.rst
> index 10b9c75c2a7f..26977164accf 100644
> --- a/Documentation/guides/pipeline-handler.rst
> +++ b/Documentation/guides/pipeline-handler.rst
> @@ -672,6 +672,58 @@ 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.
> +
> +For example, adding a Raspberry Pi vendor control file for the PiSP pipeline
> +handler is done with the following mapping:
> +
> +.. code-block:: meson
> +
> +   vendor_controls_mapping = {
> +      # Mapping of vendor (pipeline handler) specific controls files
> +      'controls':
> +      {
> +         'rpi/pisp': 'control_ids_rpi.yaml',
> +      },
> +      # Mapping of vendor (pipeline handler) specific properties files
> +      'properties':
> +      {
> +
> +      }
> +   }
> +
> +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.

Indentiation looks wrong here, the '- PispConfigDumpFile:' line is
under-indented, and so are the three lines of the description text.

> +
> +
> +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.
> +
> +Note that libcamera core controls are defined with the `vendor: libcamera` tag
> +and libcamera draft controls are defined with the `vendor: draft` tag.

I'm not sure I would have mentioned this here, as it's not really
related to pipeline handlers. Up to you.

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

> +
>  Generating a default configuration
>  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  

-- 
Regards,

Laurent Pinchart