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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2018, Google Inc.
*
* device_enumerator.cpp - Enumeration and matching
*/
#include "libcamera/internal/device_enumerator.h"
#include "libcamera/internal/device_enumerator_sysfs.h"
#include "libcamera/internal/device_enumerator_udev.h"
#include <string.h>
#include "libcamera/internal/log.h"
#include "libcamera/internal/media_device.h"
/**
* \file device_enumerator.h
* \brief Enumeration and matching of media devices
*
* The purpose of device enumeration and matching is to find media devices in
* the system and map them to pipeline handlers.
*
* At the core of the enumeration is the DeviceEnumerator class, responsible
* for enumerating all media devices in the system. It handles all interactions
* with the operating system in a platform-specific way. For each media device
* found an instance of MediaDevice is created to store information about the
* device gathered from the kernel through the Media Controller API.
*
* The DeviceEnumerator can enumerate all or specific media devices in the
* system. When a new media device is added the enumerator creates a
* corresponding MediaDevice instance.
*
* The enumerator supports searching among enumerated devices based on criteria
* expressed in a DeviceMatch object.
*/
namespace libcamera {
LOG_DEFINE_CATEGORY(DeviceEnumerator)
/**
* \class DeviceMatch
* \brief Description of a media device search pattern
*
* The DeviceMatch class describes a media device using properties from the
* Media Controller struct media_device_info, entity names in the media graph
* or other properties that can be used to identify a media device.
*
* The description is meant to be filled by pipeline managers and passed to a
* device enumerator to find matching media devices.
*
* A DeviceMatch is created with a specific Linux device driver in mind,
* therefore the name of the driver is a required property. One or more Entity
* names can be added as match criteria.
*
* Pipeline handlers are recommended to add entities to DeviceMatch as
* appropriare to ensure that the media device they need can be uniquely
* identified. This is useful when the corresponding kernel driver can produce
* different graphs, for instance as a result of different driver versions or
* hardware configurations, and not all those graphs are suitable for a pipeline
* handler.
*/
/**
* \brief Construct a media device search pattern
* \param[in] driver The Linux device driver name that created the media device
*/
DeviceMatch::DeviceMatch(const std::string &driver)
: driver_(driver)
{
}
/**
* \brief Add a media entity name to the search pattern
* \param[in] entity The name of the entity in the media graph
*/
void DeviceMatch::add(const std::string &entity)
{
entities_.push_back(entity);
}
/**
* \brief Compare a search pattern with a media device
* \param[in] device The media device
*
* Matching is performed on the Linux device driver name and entity names from
* the media graph. A match is found if both the driver name matches and the
* media device contains all the entities listed in the search pattern.
*
* \return true if the media device matches the search pattern, false otherwise
*/
bool DeviceMatch::match(const MediaDevice *device) const
{
if (driver_ != device->driver())
return false;
for (const std::string &name : entities_) {
bool found = false;
for (const MediaEntity *entity : device->entities()) {
if (name == entity->name()) {
found = true;
break;
}
}
if (!found)
return false;
}
return true;
}
/**
* \class DeviceEnumerator
* \brief Enumerate, store and search media devices
*
* The DeviceEnumerator class is responsible for all interactions with the
* operating system related to media devices. It enumerates all media devices
* in the system, and for each device found creates an instance of the
* MediaDevice class and stores it internally. The list of media devices can
* then be searched using DeviceMatch search patterns.
*
* The enumerator also associates media device entities with device node paths.
*/
/**
* \brief Create a new device enumerator matching the systems capabilities
*
* Depending on how the operating system handles device detection, hot-plug
* notification and device node lookup, different device enumerator
* implementations may be needed. This function creates the best enumerator for
* the operating system based on the available resources. Not all different
* enumerator types are guaranteed to support all features.
*
* \return A pointer to the newly created device enumerator on success, or
* nullptr if an error occurs
*/
std::unique_ptr<DeviceEnumerator> DeviceEnumerator::create()
{
std::unique_ptr<DeviceEnumerator> enumerator;
#ifdef HAVE_LIBUDEV
enumerator = std::make_unique<DeviceEnumeratorUdev>();
if (!enumerator->init())
return enumerator;
#endif
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