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diff --git a/src/libcamera/media_object.cpp b/src/libcamera/media_object.cpp
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+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2018, Google Inc.
+ *
+ * media_object.cpp - Media device objects: entities, pads and links
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/stat.h>
+
+#include <string>
+#include <vector>
+
+#include <linux/media.h>
+
+#include "log.h"
+#include "media_object.h"
+
+/**
+ * \file media_object.h
+ * \brief Provides a class hierarchy that represents the  media objects exposed
+ * by the Linux kernel Media Controller APIs.
+ *
+ * The abstract MediaObject class represents any Media Controller graph object
+ * identified by an id unique in the media device context. It is subclassed by
+ * the MediaEntity, MediaPad and MediaLink classes that represent the entities,
+ * pads and links respectively. They are populated based on the media graph
+ * information exposed by the Linux kernel through the MEDIA_IOC_G_TOPOLOGY
+ * ioctl.
+ *
+ * As the media objects represent their kernel counterpart, information about
+ * the properties they expose can be found in the Linux kernel documentation.
+ *
+ * All media objects are meant to be created and destroyed solely by the
+ * MediaDevice and thus have private constructors and destructors.
+ */
+
+namespace libcamera {
+
+/**
+ * \class MediaObject
+ * \brief Base class for all media objects
+ *
+ * MediaObject is an abstract base class for all media objects in the media
+ * graph. Every media graph object is identified by an id unique in the media
+ * device context, and this base class provides that.
+ *
+ * \sa MediaEntity, MediaPad, MediaLink
+ */
+
+/**
+ * \fn MediaObject::MediaObject()
+ * \brief Construct a MediaObject with \a id
+ * \param id The media object id
+ *
+ * The caller shall ensure unicity of the object id in the media device context.
+ * This constraint is neither enforced nor checked by the MediaObject.
+ */
+
+/**
+ * \fn MediaObject::id()
+ * \brief Retrieve the media object id
+ * \return The media object id
+ */
+
+/**
+ * \var MediaObject::id_
+ * \brief The media object id
+ */
+
+/**
+ * \class MediaLink
+ * \brief The MediaLink represents a link between two pads in the media graph.
+ *
+ * Links are created from the information provided by the Media Controller API
+ * in the media_v2_link structure. They reference the source() and sink() pads
+ * they connect and track the link status through link flags().
+ *
+ * Each link is referenced in the link array of both of the pads it connect.
+ */
+
+/**
+ * \brief Construct a MediaLink
+ * \param link The media link kernel data
+ * \param source The source pad at the origin of the link
+ * \param sink The sink pad at the destination of the link
+ */
+MediaLink::MediaLink(const struct media_v2_link *link, MediaPad *source,
+		     MediaPad *sink)
+	: MediaObject(link->id), source_(source),
+	  sink_(sink), flags_(link->flags)
+{
+}
+
+/**
+ * \fn MediaLink::source()
+ * \brief Retrieve the link's source pad
+ * \return The source pad at the origin of the link
+ */
+
+/**
+ * \fn MediaLink::sink()
+ * \brief Retrieve the link's sink pad
+ * \return The sink pad at the destination of the link
+ */
+
+/**
+ * \fn MediaLink::flags()
+ * \brief Retrieve the link's flags
+ *
+ * Link flags are a bitmask of flags defined by the Media Controller API
+ * MEDIA_LNK_FL_* macros.
+ *
+ * \return The link flags
+ */
+
+/**
+ * \class MediaPad
+ * \brief The MediaPad represents a pad of an entity in the media graph
+ *
+ * Pads are created from the information provided by the Media Controller API
+ * in the media_v2_pad structure. They reference the entity() they belong to.
+ *
+ * In addition to its graph id, every media graph pad is identified by an index
+ * unique in the context of the entity the pad belongs to.
+ *
+ * A pad can be either a 'source' pad or a 'sink' pad. This information is
+ * captured in the pad flags().
+ *
+ * Pads are connected through links. Links originating from a source pad are
+ * outbound links, and links arriving at a sink pad are inbound links. Pads
+ * reference all the links() that are connected to them.
+ */
+
+/**
+ * \brief Construct a MediaPad
+ * \param pad The media pad kernel data
+ * \param entity The entity the pad belongs to
+ */
+MediaPad::MediaPad(const struct media_v2_pad *pad, MediaEntity *entity)
+	: MediaObject(pad->id), index_(pad->index), entity_(entity),
+	  flags_(pad->flags)
+{
+}
+
+MediaPad::~MediaPad()
+{
+	/*
+	 * Don't delete the links as we only borrow the reference owned by
+	 * MediaDevice.
+	 */
+	links_.clear();
+}
+
+/**
+ * \fn MediaPad::index()
+ * \brief Retrieve the pad index
+ * \return The 0-based pad index identifying the pad in the context of the
+ * entity it belongs to
+ */
+
+/**
+ * \fn MediaPad::entity()
+ * \brief Retrieve the entity the pad belongs to
+ * \return The MediaEntity the pad belongs to
+ */
+
+/**
+ * \fn MediaPad::flags()
+ * \brief Retrieve the pad flags
+ *
+ * Pad flags are a bitmask of flags defined by the Media Controller API
+ * MEDIA_PAD_FL_* macros.
+ *
+ * \return The pad flags
+ */
+
+/**
+ * \fn MediaPad::links()
+ * \brief Retrieve all links in the pad
+ * \return A list of links connected to the pad
+ */
+
+/**
+ * \brief Add a new link to this pad
+ * \param link The MediaLink to add
+ */
+void MediaPad::addLink(MediaLink *link)
+{
+	links_.push_back(link);
+}
+
+/**
+ * \class MediaEntity
+ * \brief The MediaEntity represents an entity in the media graph
+ *
+ * Entities are created from the information provided by the Media Controller
+ * API in the media_v2_entity structure. They reference the pads() they contain.
+ *
+ * In addition to its graph id, every media graph entity is identified by a
+ * name() unique in the media device context.
+ *
+ * \todo Add support for associating a devnode to the entity when integrating
+ * with DeviceEnumerator.
+ */
+
+/**
+ * \fn MediaEntity::name()
+ * \brief Retrieve the entity name
+ * \return The entity name
+ */
+
+/**
+ * \fn MediaEntity::pads()
+ * \brief Retrieve all pads of the entity
+ * \return The list of the entity's pads
+ */
+
+/**
+ * \brief Get a pad in this entity by its index
+ * \param index The 0-based pad index
+ * \return The pad identified by \a index, or nullptr if no such pad exist
+ */
+const MediaPad *MediaEntity::getPadByIndex(unsigned int index) const
+{
+	for (MediaPad *p : pads_) {
+		if (p->index() == index)
+			return p;
+	}
+
+	return nullptr;
+}
+
+/**
+ * \brief Get a pad in this entity by its object id
+ * \param id The pad id
+ * \return The pad identified by \a id, or nullptr if no such pad exist
+ */
+const MediaPad *MediaEntity::getPadById(unsigned int id) const
+{
+	for (MediaPad *p : pads_) {
+		if (p->id() == id)
+			return p;
+	}
+
+	return nullptr;
+}
+
+/**
+ * \brief Construct a MediaEntity
+ * \param entity The media entity kernel data
+ */
+MediaEntity::MediaEntity(const struct media_v2_entity *entity)
+	: MediaObject(entity->id), name_(entity->name)
+{
+}
+
+MediaEntity::~MediaEntity()
+{
+	/*
+	 * Don't delete the pads as we only borrow the reference owned by
+	 * MediaDevice.
+	 */
+	pads_.clear();
+}
+
+/**
+ * \brief Add \a pad to the entity's list of pads
+ * \param pad The pad to add to the list
+ *
+ * This function is meant to add pads to the entity during parsing of the media
+ * graph, after the MediaPad objects are constructed and before the MediaDevice
+ * is made available externally.
+ */
+void MediaEntity::addPad(MediaPad *pad)
+{
+	pads_.push_back(pad);
+}
+
+} /* namespace libcamera */