[PATCH v1 1/1] libcamera: camera_manager: Add environment variable to order pipelines match

[Kieran Bingham]

Quoting Julien Vuillaumier (2024-03-04 18:18:16)
> To match the enumerated media devices, each pipeline handler registered
> is used in no specific order. It is a limitation when several pipelines
> can match the devices, and user has to select a specific pipeline.
> 
> For this purpose, environment variable LIBCAMERA_PIPELINES_MATCH_LIST is
> created that gives the option to define an ordered list of pipelines
> to invoke during the match process.
> 
> LIBCAMERA_PIPELINES_MATCH_LIST="<name1>[,<name2>[,<name3>...]]]"
> 
> Example:
> LIBCAMERA_PIPELINES_MATCH_LIST="PipelineHandlerRkISP1,SimplePipelineHandler"
> 
> Signed-off-by: Julien Vuillaumier <julien.vuillaumier at nxp.com>
> ---
>  Documentation/environment_variables.rst |  5 +++
>  src/libcamera/camera_manager.cpp        | 51 +++++++++++++++++++++----
>  2 files changed, 48 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/environment_variables.rst b/Documentation/environment_variables.rst
> index a9b230bc..f3a0d431 100644
> --- a/Documentation/environment_variables.rst
> +++ b/Documentation/environment_variables.rst
> @@ -37,6 +37,11 @@ LIBCAMERA_IPA_MODULE_PATH
>  
>     Example value: ``${HOME}/.libcamera/lib:/opt/libcamera/vendor/lib``
>  
> +LIBCAMERA_PIPELINES_MATCH_LIST
> +   Define ordered list of pipelines to be used to match the media devices.
> +
> +   Example value: ``PipelineHandlerRkISP1,SimplePipelineHandler``
> +
>  LIBCAMERA_RPI_CONFIG_FILE
>     Define a custom configuration file to use in the Raspberry Pi pipeline handler.
>  
> diff --git a/src/libcamera/camera_manager.cpp b/src/libcamera/camera_manager.cpp
> index 355f3ada..9568801e 100644
> --- a/src/libcamera/camera_manager.cpp
> +++ b/src/libcamera/camera_manager.cpp
> @@ -109,14 +109,7 @@ void CameraManager::Private::createPipelineHandlers()
>         const std::vector<PipelineHandlerFactoryBase *> &factories =
>                 PipelineHandlerFactoryBase::factories();
>  
> -       for (const PipelineHandlerFactoryBase *factory : factories) {
> -               LOG(Camera, Debug)
> -                       << "Found registered pipeline handler '"
> -                       << factory->name() << "'";
> -               /*
> -                * Try each pipeline handler until it exhaust
> -                * all pipelines it can provide.
> -                */
> +       auto pipeMatch = [&](const PipelineHandlerFactoryBase *factory) {

Does this need to be a lambda? is there a specific benefit, or can it be
a function? I find lambda's hard to parse :-( but perhaps that's just
me, so lets see what others say.


>                 while (1) {
>                         std::shared_ptr<PipelineHandler> pipe = factory->create(o);
>                         if (!pipe->match(enumerator_.get()))
> @@ -126,6 +119,48 @@ void CameraManager::Private::createPipelineHandlers()
>                                 << "Pipeline handler \"" << factory->name()
>                                 << "\" matched";
>                 }
> +       };
> +
> +       /*
> +        * When a list of preferred pipelines is defined, iterate through the
> +        * ordered list to match the devices enumerated.
> +        * Otherwise, devices matching is done in no specific order with each

s/devices/device/

> +        * pipeline handler registered.
> +        */
> +       const char *pipesLists =
> +               utils::secure_getenv("LIBCAMERA_PIPELINES_MATCH_LIST");
> +       if (pipesLists) {
> +               for (const auto &pipeName : utils::split(pipesLists, ",")) {
> +                       if (pipeName.empty())
> +                               continue;
> +
> +                       auto nameMatch = [pipeName](const PipelineHandlerFactoryBase *f) {
> +                               return (f->name() == pipeName);
> +                       };
> +
> +                       auto iter = std::find_if(factories.begin(),
> +                                                factories.end(),
> +                                                nameMatch);

If we do this - I'd probably add support to the PipelineHandlerFactory
to support getting by name as a preceeding patch.

> +
> +                       if (iter != factories.end()) {
> +                               LOG(Camera, Debug)
> +                                       << "Found pipeline handler from list '"
> +                                       << (*iter)->name() << "'";
> +                               pipeMatch(*iter);
> +                       }
> +               }
> +               return;
> +       }
> +
> +       for (const PipelineHandlerFactoryBase *factory : factories) {
> +               LOG(Camera, Debug)
> +                       << "Found registered pipeline handler '"
> +                       << factory->name() << "'";
> +               /*
> +                * Try each pipeline handler until it exhausts
> +                * all pipelines it can provide.
> +                */
> +               pipeMatch(factory);
>         }
>  }
>  
> -- 
> 2.34.1
>