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

[Naushir Patuck]

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>
---
 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.
+
+
+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.
+
 Generating a default configuration
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-- 
2.34.1