new file mode 100644
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Ideas on Board Oy
+ *
+ * Media pipeline support
+ */
+
+#pragma once
+
+#include <list>
+#include <string>
+
+#include <libcamera/base/log.h>
+
+namespace libcamera {
+
+class CameraSensor;
+class MediaEntity;
+class MediaLink;
+class MediaPad;
+struct V4L2SubdeviceFormat;
+
+class MediaPipeline
+{
+public:
+ int init(MediaEntity *source, std::string sink);
+ int initLinks();
+ int configure(CameraSensor *sensor, V4L2SubdeviceFormat *);
+
+private:
+ struct Entity {
+ /* The media entity, always valid. */
+ MediaEntity *entity;
+ /*
+ * Whether or not the entity is a subdev that supports the
+ * routing API.
+ */
+ bool supportsRouting;
+ /*
+ * The local sink pad connected to the upstream entity, null for
+ * the camera sensor at the beginning of the pipeline.
+ */
+ const MediaPad *sink;
+ /*
+ * The local source pad connected to the downstream entity, null
+ * for the video node at the end of the pipeline.
+ */
+ const MediaPad *source;
+ /*
+ * The link on the source pad, to the downstream entity, null
+ * for the video node at the end of the pipeline.
+ */
+ MediaLink *sourceLink;
+ };
+
+ std::vector<const MediaPad *> routedSourcePads(MediaPad *sink);
+ std::list<Entity> entities_;
+};
+
+} /* namespace libcamera */
@@ -32,6 +32,7 @@ libcamera_internal_headers = files([
'matrix.h',
'media_device.h',
'media_object.h',
+ 'media_pipeline.h',
'pipeline_handler.h',
'process.h',
'pub_key.h',
new file mode 100644
@@ -0,0 +1,302 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Ideas on Board Oy
+ *
+ * Media pipeline support
+ */
+
+#include "libcamera/internal/media_pipeline.h"
+
+#include <algorithm>
+#include <errno.h>
+#include <queue>
+#include <string>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
+
+#include <linux/media.h>
+
+#include <libcamera/base/log.h>
+
+#include "libcamera/internal/camera_sensor.h"
+#include "libcamera/internal/media_device.h"
+#include "libcamera/internal/media_object.h"
+#include "libcamera/internal/v4l2_subdevice.h"
+
+/**
+ * \file media_pipeline.h
+ * \brief Provide a representation of a pipeline of devices using the Media
+ * Controller.
+ */
+
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(MediaPipeline)
+
+/**
+ * \class MediaPipeline
+ * \brief The MediaPipeline represents a set of entities that together form a
+ * data path for stream data.
+ *
+ * A MediaPipeline instance is constructed from a sink and a source between
+ * two entities in a media graph.
+ */
+
+/**
+ * \brief Retrieve all source pads connected to a sink pad through active routes
+ *
+ * Examine the entity using the V4L2 Subdevice Routing API to collect all the
+ * source pads which are connected with an active route to the sink pad.
+ *
+ * \return A vector of source MediaPads
+ */
+std::vector<const MediaPad *> MediaPipeline::routedSourcePads(MediaPad *sink)
+{
+ MediaEntity *entity = sink->entity();
+ std::unique_ptr<V4L2Subdevice> subdev =
+ std::make_unique<V4L2Subdevice>(entity);
+
+ int ret = subdev->open();
+ if (ret < 0)
+ return {};
+
+ V4L2Subdevice::Routing routing = {};
+ ret = subdev->getRouting(&routing, V4L2Subdevice::ActiveFormat);
+ if (ret < 0)
+ return {};
+
+ std::vector<const MediaPad *> pads;
+
+ for (const V4L2Subdevice::Route &route : routing) {
+ if (sink->index() != route.sink.pad ||
+ !(route.flags & V4L2_SUBDEV_ROUTE_FL_ACTIVE))
+ continue;
+
+ const MediaPad *pad = entity->getPadByIndex(route.source.pad);
+ if (!pad) {
+ LOG(MediaPipeline, Error)
+ << "Entity " << entity->name()
+ << " has invalid route source pad "
+ << route.source.pad;
+ return {};
+ }
+
+ pads.push_back(pad);
+ }
+
+ return pads;
+}
+
+/**
+ * \brief Find the path from source to sink
+ *
+ * Starting from a source entity, determine the shortest path to the target
+ * described by \a sink.
+ *
+ * If \a sink can not be found, or a route from source to sink can not be
+ * achieved an error of -ENOLINK will be returned.
+ *
+ * When successful, the MediaPipeline will internally store the representation
+ * of entities and links to describe the path between the two entities.
+ *
+ * \return 0 on success, a negative errno otherwise
+ */
+int MediaPipeline::init(MediaEntity *source, std::string sink)
+{
+ /*
+ * Find the shortest path between from the Camera Sensor and the
+ * target entity.
+ */
+ std::unordered_set<MediaEntity *> visited;
+ std::queue<std::tuple<MediaEntity *, MediaPad *>> queue;
+
+ /* Remember at each entity where we came from. */
+ std::unordered_map<MediaEntity *, Entity> parents;
+ MediaEntity *entity = nullptr;
+ MediaEntity *target = nullptr;
+ MediaPad *sinkPad;
+
+ queue.push({ source, nullptr });
+
+ while (!queue.empty()) {
+ std::tie(entity, sinkPad) = queue.front();
+ queue.pop();
+
+ /* Found the target device. */
+ if (entity->name() == sink) {
+ LOG(MediaPipeline, Debug)
+ << "Found Pipeline target " << entity->name();
+ target = entity;
+ break;
+ }
+
+ visited.insert(entity);
+
+ /*
+ * Add direct downstream entities to the search queue. If the
+ * current entity supports the subdev internal routing API,
+ * restrict the search to downstream entities reachable through
+ * active routes.
+ */
+
+ std::vector<const MediaPad *> pads;
+ bool supportsRouting = false;
+
+ if (sinkPad) {
+ pads = routedSourcePads(sinkPad);
+ if (!pads.empty())
+ supportsRouting = true;
+ }
+
+ if (pads.empty()) {
+ for (const MediaPad *pad : entity->pads()) {
+ if (!(pad->flags() & MEDIA_PAD_FL_SOURCE))
+ continue;
+ pads.push_back(pad);
+ }
+ }
+
+ for (const MediaPad *pad : pads) {
+ for (MediaLink *link : pad->links()) {
+ MediaEntity *next = link->sink()->entity();
+ if (visited.find(next) == visited.end()) {
+ queue.push({ next, link->sink() });
+
+ Entity e{ entity, supportsRouting, sinkPad, pad, link };
+ parents.insert({ next, e });
+ }
+ }
+ }
+ }
+
+ if (!target) {
+ LOG(MediaPipeline, Error) << "Failed to connect " << source->name();
+ return -ENOLINK;
+ }
+
+ /*
+ * With the parents, we can follow back our way from the capture device
+ * to the sensor. Store all the entities in the pipeline, from the
+ * camera sensor to the video node, in entities_.
+ */
+ entities_.push_front({ entity, false, sinkPad, nullptr, nullptr });
+
+ for (auto it = parents.find(entity); it != parents.end();
+ it = parents.find(entity)) {
+ const Entity &e = it->second;
+ entities_.push_front(e);
+ entity = e.entity;
+ }
+
+ LOG(MediaPipeline, Info)
+ << "Found pipeline: "
+ << utils::join(entities_, " -> ",
+ [](const Entity &e) {
+ std::string s = "[";
+ if (e.sink)
+ s += std::to_string(e.sink->index()) + "|";
+ s += e.entity->name();
+ if (e.source)
+ s += "|" + std::to_string(e.source->index());
+ s += "]";
+ return s;
+ });
+
+ return 0;
+}
+
+/**
+ * \brief Initialise and enable all links through the MediaPipeline
+ * \return 0 on success, or a negative errno otherwise
+ */
+int MediaPipeline::initLinks()
+{
+ int ret = 0;
+
+ MediaLink *sinkLink = nullptr;
+ for (Entity &e : entities_) {
+ /* Sensor entities have no connected sink. */
+ if (!sinkLink) {
+ sinkLink = e.sourceLink;
+ continue;
+ }
+
+ LOG(MediaPipeline, Debug) << "Enabling : " << *sinkLink;
+
+ if (!(sinkLink->flags() & MEDIA_LNK_FL_ENABLED)) {
+ ret = sinkLink->setEnabled(true);
+ if (ret < 0)
+ return ret;
+ }
+
+ sinkLink = e.sourceLink;
+ }
+
+ return ret;
+}
+
+/**
+ * \brief Configure the entities of this MediaPipeline
+ *
+ * Propagate formats through each of the entities of the Pipeline, validating
+ * that each one was not adjusted by the driver from the desired format.
+ *
+ * \return 0 on success or a negative errno otherwise
+ */
+int MediaPipeline::configure(CameraSensor *sensor, V4L2SubdeviceFormat *format)
+{
+ int ret;
+
+ for (const Entity &e : entities_) {
+ /* The sensor is configured through the CameraSensor */
+ if (!e.sourceLink)
+ break;
+
+ MediaLink *link = e.sourceLink;
+ MediaPad *source = link->source();
+ MediaPad *sink = link->sink();
+
+ /* 'format' already contains the sensor configuration */
+ if (source->entity() != sensor->entity()) {
+ /* \todo Add MediaDevice cache to reduce FD pressure */
+ V4L2Subdevice subdev(source->entity());
+ ret = subdev.open();
+ if (ret)
+ return ret;
+
+ ret = subdev.getFormat(source->index(), format);
+ if (ret < 0)
+ return ret;
+ }
+
+ V4L2SubdeviceFormat sourceFormat = *format;
+ /* \todo Add MediaDevice cache to reduce FD pressure */
+ V4L2Subdevice subdev(sink->entity());
+ ret = subdev.open();
+ if (ret)
+ return ret;
+
+ ret = subdev.setFormat(sink->index(), format);
+ if (ret < 0)
+ return ret;
+
+ if (format->code != sourceFormat.code ||
+ format->size != sourceFormat.size) {
+ LOG(MediaPipeline, Debug)
+ << "Source '" << *source
+ << " produces " << sourceFormat
+ << ", sink '" << *sink
+ << " requires " << format;
+ return -EINVAL;
+ }
+
+ LOG(MediaPipeline, Debug)
+ << "Link " << *link << " configured with format "
+ << format;
+ }
+
+ return 0;
+}
+
+} /* namespace libcamera */
@@ -43,6 +43,7 @@ libcamera_internal_sources = files([
'matrix.cpp',
'media_device.cpp',
'media_object.cpp',
+ 'media_pipeline.cpp',
'pipeline_handler.cpp',
'process.cpp',
'pub_key.cpp',