[RFC PATCH 2/4] libcamera: internal: Allow to limit the number of queued requests

[Sven Püschel]

Hi Stefan,

On 5/26/25 23:42, Stefan Klug wrote:
> Allow pipeline handler classes to limit the maximum number of requests that
> get queued using queueRequestDevice().
>
> Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
> ---
>   include/libcamera/internal/pipeline_handler.h | 5 +++++
>   src/libcamera/pipeline_handler.cpp            | 3 +++
>   2 files changed, 8 insertions(+)
>
> diff --git a/include/libcamera/internal/pipeline_handler.h b/include/libcamera/internal/pipeline_handler.h
> index dedc29e815fb..86b86d5971dc 100644
> --- a/include/libcamera/internal/pipeline_handler.h
> +++ b/include/libcamera/internal/pipeline_handler.h
> @@ -79,6 +79,11 @@ protected:
>   	virtual bool acquireDevice(Camera *camera);
>   	virtual void releaseDevice(Camera *camera);
>   
> +	virtual unsigned int maxQueuedRequestsDevice() const
> +	{
> +		return std::numeric_limits<unsigned int>::max();
> +	}
> +
is there a benefit of having a virtual function instead of a variable 
(initialized to max by default and potentially changed in the subclass 
constructors)?
>   	CameraManager *manager_;
>   
>   private:
> diff --git a/src/libcamera/pipeline_handler.cpp b/src/libcamera/pipeline_handler.cpp
> index 14d8602e67d8..1853bca71371 100644
> --- a/src/libcamera/pipeline_handler.cpp
> +++ b/src/libcamera/pipeline_handler.cpp
> @@ -490,6 +490,9 @@ void PipelineHandler::doQueueRequests()
>   
>   		Camera::Private *data = camera->_d();
>   		while (!data->waitingRequests_.empty()) {
> +			if (data->queuedRequests_.size() == maxQueuedRequestsDevice())
> +				break;
> +
>   			Request *request = data->waitingRequests_.front();
>   			if (!request->_d()->prepared_)
>   				break;