[PATCH 3/8] libcamera: pipeline_handler: Add metadataAvailable() function

[Cheng-Hao Yang]

Hi Jacopo,

Thank you for the patch.

On Fri, Dec 6, 2024 at 5:07 PM Jacopo Mondi
<jacopo.mondi at ideasonboard.com> wrote:
>
> Currently the way pipeline handlers have to store metadata results
> for a Request is to access the Request::metadata_ list directly and
> either merge a ControlList or set a single control value there.
>
> Direct access to Request::metadata_ is however problematic as even if
> metadata would be available earlier, pipeline handlers can only
> accumulate the results in Request::metadata_ and they're only available
> for applications at Request complete time.
>
> Instead of letting pipeline handlers access Request::metadata_ directly
> provide two helper functions, similar in spirit to
> PipelineHandler::completeBuffer() and
> PipelineHandler::completeRequest(), to allow pipeline handlers to
> notify early availability of metadata.
>
> Provide two overloads, one that accepts a ControlList and merges it into
> Request::metadata_ and one that allows to set a single metadata result
> there without going through an intermediate copy.
>
> The newly provided helpers trigger the Camera::availableMetadata signal
> from where applications can retrieve the list of ControlIds that have
> just been made available by the pipeline handler.
>
> Signed-off-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
> ---
>  include/libcamera/internal/pipeline_handler.h | 41 ++++++++++
>  src/libcamera/pipeline_handler.cpp            | 74 +++++++++++++++++++
>  2 files changed, 115 insertions(+)
>
> diff --git a/include/libcamera/internal/pipeline_handler.h b/include/libcamera/internal/pipeline_handler.h
> index fb28a18d0f46..3ca6a0290b2b 100644
> --- a/include/libcamera/internal/pipeline_handler.h
> +++ b/include/libcamera/internal/pipeline_handler.h
> @@ -11,13 +11,17 @@
>  #include <queue>
>  #include <string>
>  #include <sys/types.h>
> +#include <unordered_set>
>  #include <vector>
>
>  #include <libcamera/base/object.h>
>
> +#include <libcamera/camera.h>
>  #include <libcamera/controls.h>
>  #include <libcamera/stream.h>
>
> +#include "libcamera/internal/request.h"
> +
>  namespace libcamera {
>
>  class Camera;
> @@ -58,6 +62,43 @@ public:
>         void registerRequest(Request *request);
>         void queueRequest(Request *request);
>
> +       void metadataAvailable(Request *request, const ControlList &metadata);
> +
> +       template<typename T>
> +       void metadataAvailable(Request *request, const Control<T> &ctrl,
> +                              const T &value)
> +       {
> +               if (request->metadata().contains(ctrl.id()))
> +                       return;
> +
> +               std::unordered_set<const ControlId *> ids;
> +               ids.insert(&ctrl);
> +
> +               request->metadata().set<T, T>(ctrl, value);
> +
> +               Camera *camera = request->_d()->camera();
> +               camera->metadataAvailable.emit(request, ids);
> +       }

One question: Have you considered wrapping `ctrls` and `value` into a
ControlList, and reuse `void metadataAvailable(Request *request, const
ControlList &metadata)` above?
I think this function doesn't check `request->metadata()->idMap()`
while the above function does.

Same for the function below.

BR,
Harvey


> +
> +#ifndef __DOXYGEN__
> +       template<typename T, std::size_t Size>
> +       void metadataAvailable(Request *request,
> +                              const Control<Span<const T, Size>> &ctrl,
> +                              const Span<const T, Size> &value)
> +       {
> +               if (request->metadata().contains(ctrl.id()))
> +                       return;
> +
> +               std::unordered_set<const ControlId *> ids;
> +               ids.insert(&ctrl);
> +
> +               request->metadata().set(ctrl, value);
> +
> +               Camera *camera = request->_d()->camera();
> +               camera->metadataAvailable.emit(request, ids);
> +       }
> +#endif
> +
>         bool completeBuffer(Request *request, FrameBuffer *buffer);
>         void completeRequest(Request *request);
>         void cancelRequest(Request *request);
> diff --git a/src/libcamera/pipeline_handler.cpp b/src/libcamera/pipeline_handler.cpp
> index caa5c20e7483..a69d789116ad 100644
> --- a/src/libcamera/pipeline_handler.cpp
> +++ b/src/libcamera/pipeline_handler.cpp
> @@ -507,6 +507,80 @@ void PipelineHandler::doQueueRequests()
>   * \return 0 on success or a negative error code otherwise
>   */
>
> +/**
> + * \brief Notify the availability of a list of metadata for \a request
> + * \param[in] request The request the metadata belongs to
> + * \param[in] metadata The metadata list
> + *
> + * This function should be called multiple times by pipeline handlers to signal
> + * the availability of a list of metadata results. It notifies applications
> + * by triggering the Camera::availableMetadata signal and accumulates the
> + * metadata results in Request::metadata().
> + *
> + * Early metadata completion allows pipeline handlers to fast track delivery of
> + * metadata results as soon as they are available before the completion of \a
> + * request. The full list of metadata results of a Request is available at
> + * Request completion time in Request::metadata().
> + *
> + * A metadata key is expected to be notified at most once. Metadata keys
> + * notified multiple times are ignored.
> + *
> + * This overload allows to signal the availability of a list of metadata and
> + * merges them in the Request::metadata() list. This operations is expensive
> + * as controls are copied from \a metadata to Request::metadata().
> + *
> + * \context This function shall be called from the CameraManager thread.
> + */
> +void PipelineHandler::metadataAvailable(Request *request, const ControlList &metadata)
> +{
> +       std::unordered_set<const ControlId *> ids;
> +       const ControlIdMap *idmap = request->metadata().idMap();
> +
> +       for (const auto &ctrl : metadata) {
> +               if (request->metadata().contains(ctrl.first))
> +                       continue;
> +
> +               ASSERT(idmap->count(ctrl.first));
> +
> +               ids.insert(idmap->at(ctrl.first));
> +       }
> +
> +       if (ids.empty())
> +               return;
> +
> +       request->metadata().merge(metadata);
> +
> +       Camera *camera = request->_d()->camera();
> +       camera->metadataAvailable.emit(request, ids);
> +}
> +
> +/**
> + * \fn void PipelineHandler::metadataAvailable(Request *request, const Control<T> &ctrl, const T &value)
> + * \brief Notify the availability of a metadata result for \a request
> + * \param[in] request The request the metadata belongs to
> + * \param[in] ctrl The control id to notify
> + * \param[in] value the control value
> + *
> + * This function should be called multiple times by pipeline handlers to signal
> + * the availability of a metadata result. It notifies applications
> + * by triggering the Camera::availableMetadata signal and accumulates the
> + * metadata result in Request::metadata().
> + *
> + * Early metadata completion allows pipeline handlers to fast track delivery of
> + * metadata results as soon as they are available before the completion of \a
> + * request. The full list of metadata results of a Request is available at
> + * Request completion time in Request::metadata().
> + *
> + * A metadata key is expected to be notified at most once. Metadata keys
> + * notified multiple times are ignored.
> + *
> + * This overload allows to signal the availability of a single metadata and
> + * merge \a value in the Request::metadata() list. This operations copies \a
> + * value in the Request::metadata() list without creating intermediate copies.
> + *
> + * \context This function shall be called from the CameraManager thread.
> + */
> +
>  /**
>   * \brief Complete a buffer for a request
>   * \param[in] request The request the buffer belongs to
> --
> 2.47.1
>