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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2018, Google Inc.
 *
 * media_device.cpp - Media device handler
 */

#include "libcamera/internal/media_device.h"

#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <string>
#include <string.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <vector>

#include <linux/media.h>

#include "libcamera/internal/log.h"

/**
 * \file media_device.h
 * \brief Provide a representation of a Linux kernel Media Controller device
 * that exposes the full graph topology.
 */

namespace libcamera {

LOG_DEFINE_CATEGORY(MediaDevice)

/**
 * \class MediaDevice
 * \brief The MediaDevice represents a Media Controller device with its full
 * graph of connected objects.
 *
 * A MediaDevice instance is associated with a media controller device node when
 * created, and that association is kept for the lifetime of the MediaDevice
 * instance.
 *
 * The instance is created with an empty media graph. Before performing any
 * other operation, it must be populate by calling populate(). Instances of
 * MediaEntity, MediaPad and MediaLink are created to model the media graph,
 * and stored in a map indexed by object id.
 *
 * The graph is valid once successfully populated, as reported by the valid()
 * function. It can be queried to list all entities(), or entities can be
 * looked up by name with getEntityByName(). The graph can be traversed from
 * entity to entity through pads and links as exposed by the corresponding
 * classes.
 *
 * Media device can be claimed for exclusive use with acquire(), released with
 * release() and tested with busy(). This mechanism is aimed at pipeline
 * managers to claim media devices they support during enumeration.
 */