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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.
*/
/**
* \brief Construct a MediaDevice
* \param[in] deviceNode The media device node path
*
* Once constructed the media device is invalid, and must be populated with
* populate() before the media graph can be queried.
*/
MediaDevice::MediaDevice(const std::string &deviceNode)
: deviceNode_(deviceNode), fd_(-1), valid_(false), acquired_(false),
lockOwner_(false)
{
}
MediaDevice::~MediaDevice()
{
if (fd_ != -1)
::close(fd_);
clear();
}
std::string MediaDevice::logPrefix() const
{
return deviceNode() + "[" + driver() + "]";
}
/**
* \brief Claim a device for exclusive use
*
* The device claiming mechanism offers simple media device access arbitration
* between multiple users. When the media device is created, it is available to
* all users. Users can query the media graph to determine whether they can
* support the device and, if they do, claim the device for exclusive use. Other
* users are then expected to skip over media devices in use as reported by the
* busy() function.
*
* Once claimed the device shall be released by its user when not needed anymore
* by calling the release() function. Acquiring the media device opens a file
* descriptor to the device which is kept open until release() is called.
*
* Exclusive access is only guaranteed if all users of the media device abide by
* the device claiming mechanism, as it isn't enforced by the media device
* itself.
*
* \return true if the device was successfully claimed, or false if it was
* already in use
* \sa release(), busy()
*/
bool MediaDevice::acquire()
{
if (acquired_)
return false;
if (open())
return false;
acquired_ = true;
return true;
}
/**
* \brief Release a device previously claimed for exclusive use
* \sa acquire(), busy()
*/
void MediaDevice::release()
{
close();
acquired_ = false;
}
/**
* \brief Lock the device to prevent it from being used by other instances of
* libcamera
*
* Multiple instances of libcamera might be running on the same system, at the
* same time. To allow the different instances to coexist, system resources in
* the form of media devices must be accessible for enumerating the cameras
* they provide at all times, while still allowing an instance to lock a
* resource while it prepares to actively use a camera from the resource.
*
* This method shall not be called from a pipeline handler implementation
* directly, as the base PipelineHandler implementation handles this on the
* behalf of the specified implementation.
*
* \return True if the device could be locked, false otherwise
* \sa unlock()
*/
bool MediaDevice::lock()
{
if (fd_ == -1)
return false;
/* Do not allow nested locking in the same libcamera instance. */
if (lockOwner_)
return false;
if (lockf(fd_, F_TLOCK, 0))
return false;
lockOwner_ = true;
return true;
}
/**
* \brief Unlock the device and free it for use for libcamera instances
*
* This method shall not be called from a pipeline handler implementation
* directly, as the base PipelineHandler implementation handles this on the
* behalf of the specified implementation.
*
* \sa lock()
*/
void MediaDevice::unlock()
{
if (fd_ == -1)
return;
if (!lockOwner_)
return;
lockOwner_ = false;
lockf(fd_, F_ULOCK, 0);
}
/**
* \fn MediaDevice::busy()
* \brief Check if a device is in use
* \return true if the device has been claimed for exclusive use, or false if it
* is available
* \sa acquire(), release()
*/
/**
* \brief Populate the MediaDevice with device information and media objects
*
* This function retrieves the media device information and enumerates all
* media objects in the media device graph and creates their MediaObject
* representations. All entities, pads and links are stored as MediaEntity,
* MediaPad and MediaLink respectively, with cross-references between objects.
* Interfaces are not processed.
*
* Entities are stored in a separate list in the MediaDevice to ease lookup,
* while pads are accessible from the entity they belong to and links from the
* pads they connect.
*
* \return 0 on success or a negative error code otherwise
*/
int MediaDevice::populate()
{
struct media_v2_topology topology = {};
struct media_v2_entity *ents = nullptr;
struct media_v2_interface *interfaces = nullptr;
struct media_v2_link *links = nullptr;
struct media_v2_pad *pads = nullptr;
__u64 version = -1;
int ret;
clear();
ret = open();
if (ret)
return ret;
struct media_device_info info = {};
ret = ioctl(fd_, MEDIA_IOC_DEVICE_INFO, &info);
if (ret) {
ret = -errno;
LOG(MediaDevice, Error)
<< "Failed to get media device info " << strerror(-ret);
goto done;
}
driver_ = info.driver;
model_ = info.model;
version_ = info.media_version;
/*
* Keep calling G_TOPOLOGY until the version number stays stable.
*/
while (true) {
topology.topology_version = 0;
topology.ptr_entities = reinterpret_cast<uintptr_t>(ents);
topology.ptr_interfaces = reinterpret_cast<uintptr_t>(interfaces);
topology.ptr_links = reinterpret_cast<uintptr_t>(links);
topology.ptr_pads = reinterpret_cast<uintptr_t>(pads);
ret = ioctl(fd_, MEDIA_IOC_G_TOPOLOGY, &topology);
if (ret < 0) {
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