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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 "media_object.h"

#include <errno.h>
#include <string.h>
#include <unistd.h>

#include <string>
#include <vector>

#include <linux/media.h>

#include "log.h"
#include "media_device.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 {

LOG_DECLARE_CATEGORY(MediaDevice)

/**
 * \class MediaObject
 * \brief Base class for all media objects
 *
 * MediaObject is an abstract base class for all media objects in the
 * media graph. Each object is identified by a reference to the media
 * device it belongs to and a unique id within that media device.
 * This base class provide helpers to media objects to keep track of
 * these identifiers.
 *
 * \sa MediaEntity, MediaPad, MediaLink
 */

/**
 * \fn MediaObject::MediaObject()
 * \brief Construct a MediaObject part of the MediaDevice \a dev,
 * identified by the \a id unique within the device
 * \param[in] dev The media device this object belongs to
 * \param[in] 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::device()
 * \brief Retrieve the media device the media object belongs to
 * \return The MediaDevice
 */

/**
 * \fn MediaObject::id()
 * \brief Retrieve the media object id
 * \return The media object id
 */

/**
 * \var MediaObject::dev_
 * \brief The media device the media object belongs to
 */

/**
 * \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 Enable or disable a link
 * \param[in] enable True to enable the link, false to disable it
 *
 * Set the status of a link according to the value of \a enable.
 * Links between two pads can be set to the enabled or disabled state freely,
 * unless they're immutable links, whose status cannot be changed.
 * Enabling an immutable link is not considered an error, while trying to
 * disable it is.
 *
 * Enabling a link establishes a data connection between two pads, while
 * disabling it interrupts that connection.
 *
 * \return 0 on success or a negative error code otherwise
 */
int MediaLink::setEnabled(bool enable)
{
	unsigned int flags = enable ? MEDIA_LNK_FL_ENABLED : 0;

	int ret = dev_->setupLink(this, flags);
	if (ret)
		return ret;

	flags_ = flags;

	return 0;
}

/**
 * \brief Construct a MediaLink
 * \param[in] link The media link kernel data
 * \param[in] source The source pad at the origin of the link
 * \param[in] sink The sink pad at the destination of the link
 */
MediaLink::MediaLink(const struct media_v2_link *link, MediaPad *source,
		     MediaPad *sink)
	: MediaObject(source->device(), 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