src/libcamera/pipeline_handler.cpp

/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2018, Google Inc.
 *
 * pipeline_handler.cpp - Pipeline handler infrastructure
 */

#include "libcamera/internal/pipeline_handler.h"

#include <sys/sysmacros.h>

#include <libcamera/buffer.h>
#include <libcamera/camera.h>
#include <libcamera/camera_manager.h>

#include "libcamera/internal/device_enumerator.h"
#include "libcamera/internal/log.h"
#include "libcamera/internal/media_device.h"
#include "libcamera/internal/tracepoints.h"
#include "libcamera/internal/utils.h"

/**
 * \file pipeline_handler.h
 * \brief Create pipelines and cameras from a set of media devices
 *
 * Each pipeline supported by libcamera needs to be backed by a pipeline
 * handler implementation that operate on a set of media devices. The pipeline
 * handler is responsible for matching the media devices it requires with the
 * devices present in the system, and once all those devices can be acquired,
 * create corresponding Camera instances.
 *
 * Every subclass of PipelineHandler shall be registered with libcamera using
 * the REGISTER_PIPELINE_HANDLER() macro.
 */

namespace libcamera {

LOG_DEFINE_CATEGORY(Pipeline)

/**
 * \class CameraData
 * \brief Base class for platform-specific data associated with a camera
 *
 * The CameraData base abstract class represents platform specific-data
 * a pipeline handler might want to associate with a Camera to access them
 * at a later time.
 *
 * Pipeline handlers are expected to extend this base class with platform
 * specific implementation, associate instances of the derived classes
 * using the registerCamera() method, and access them at a later time
 * with cameraData().
 */

/**
 * \fn CameraData::CameraData(PipelineHandler *pipe)
 * \brief Construct a CameraData instance for the given pipeline handler
 * \param[in] pipe The pipeline handler
 *
 * The reference to the pipeline handler is stored internally, the caller shall
 * guarantee that the pointer remains valid as long as the CameraData instance
 * exists.
 */

/**
 * \var CameraData::pipe_
 * \brief The pipeline handler related to this CameraData instance
 *
 * The pipe_ pointer provides access to the PipelineHandler object that this
 * instance is related to. It is set when the CameraData instance is created
 * and remains valid until the instance is destroyed.
 */

/**
 * \var CameraData::queuedRequests_
 * \brief The list of queued and not yet completed request
 *
 * The list of queued request is used to track requests queued in order to
 * ensure completion of all requests when the pipeline handler is stopped.
 *
 * \sa PipelineHandler::queueRequest(), PipelineHandler::stop(),
 * PipelineHandler::completeRequest()
 */

/**
 * \var CameraData::controlInfo_
 * \brief The set of controls supported by the camera
 *
 * The control information shall be initialised by the pipeline handler when
 * creating the camera, and shall not be modified afterwards.
 */

/**
 * \var CameraData::properties_
 * \brief The list of properties supported by the camera
 *
 * The list of camera properties shall be initialised by the pipeline handler
 * when creating the camera, and shall not be modified afterwards.
 */

/**
 * \var CameraData::requestSequence_
 * \brief The queuing sequence of the request
 *
 * When requests are queued, they are given a per-camera sequence number to
 * facilitate debugging of internal request usage.
 *
 * The requestSequence_ tracks the number of requests queued to a camera
 * over its lifetime.
 */

/**
 * \class PipelineHandler
 * \brief Create and manage cameras based on a set of media devices
 *
 * The PipelineHandler matches the media devices provided by a DeviceEnumerator
 * with the pipelines it supports and creates corresponding Camera devices.
 *
 * Pipeline handler instances are reference-counted through std::shared_ptr<>.
 * They implement std::enable_shared_from_this<> in order to create new
 * std::shared_ptr<> in code paths originating from member functions of the
 * PipelineHandler class where only the 'this' pointer is available.
 */

/**
 * \brief Construct a PipelineHandler instance
 * \param[in] manager The camera manager
 *
 * In order to honour the std::enable_shared_from_this<> contract,
 * PipelineHandler instances shall never be constructed manually, but always
 * through the PipelineHandlerFactory::create() method implemented by the
 * respective factories.
 */
PipelineHandler::PipelineHandler(CameraManager *manager)
	: manager_(manager)
{
}

PipelineHandler::~PipelineHandler()
{
	for (std::shared_ptr<MediaDevice> media : mediaDevices_)
		media->release();
}

/**
 * \fn PipelineHandler::match(DeviceEnumerator *enumerator)
 * \brief Match media devices and create camera instances
 * \param[in] enumerator The enumerator providing all media devices found in the
 * system
 *
 * This function is the main entry point of the pipeline handler. It is called
 * by the camera manager with the \a enumerator passed as an argument. It shall
 * acquire from the \a enumerator all the media devices it needs for a single
 * pipeline, create one or multiple Camera instances and register them with the
 * camera manager.
 *
 * If all media devices needed by the pipeline handler are found, they must all
 * be acquired by a call to MediaDevice::acquire(). This function shall then
 * create the corresponding Camera instances, store them internally, and return
 * true. Otherwise it shall not acquire any media device (or shall release all
 * the media devices is has acquired by calling MediaDevice::release()) and
 * return false.
 *
 * If multiple instances of a pipeline are available in the system, the
 * PipelineHandler class will be instantiated once per instance, and its match()
 * function called for every instance. Each call shall acquire media devices for
 * one pipeline instance, until all compatible media devices are exhausted.
 *
 * If this function returns true, a new instance of the pipeline handler will
 * be created and its match() function called.
 *
 * \context This function is called from the CameraManager thread.
 *
 * \return true if media devices have been acquired and camera instances
 * created, or false otherwise
 */

/**
 * \brief Search and acquire a MediaDevice matching a device pattern
 * \param[in] enumerator Enumerator containing all media devices in the system
 * \param[in] dm Device match pattern
 *
 * Search the device \a enumerator for an available media device matching the
 * device match pattern \a dm. Matching media device that have previously been
 * acquired by MediaDevice::acquire() are not considered. If a match is found,
 * the media device is acquired and returned. The caller shall not release the
 * device explicitly, it will be automatically released when the pipeline
 * handler is destroyed.
 *
 * \context This function shall be called from the CameraManager thread.
 *
 * \return A pointer to the matching MediaDevice, or nullptr if no match is found
 */
MediaDevice *PipelineHandler::acquireMediaDevice(DeviceEnumerator *enumerator,
						 const DeviceMatch &dm)
{
	std::shared_ptr<MediaDevice> media = enumerator->search(dm);
	if (!media)
		return nullptr;

	if (!media->acquire())
		return nullptr;

	mediaDevices_.push_back(media);

	return media.get();
}

/**
 * \brief Lock all media devices acquired by the pipeline
 *
 * This method shall not be called from pipeline handler implementation, as the
 * Camera class handles locking directly.
 *
 * \context This function is \threadsafe.
 *
 * \return True if the devices could be locked, false otherwise
 * \sa unlock()
 * \sa MediaDevice::lock()
 */
bool PipelineHandler::lock()
{
	for (std::shared_ptr<MediaDevice> &media : mediaDevices_) {
		if (!media->lock()) {
			unlock();
			return false;
		}
	}

	return true;
}

/**
 * \brief Unlock all media devices acquired by the pipeline
 *
 * This method shall not be called from pipeline handler implementation, as the
 * Camera class handles locking directly.
 *
 * \context This function is \threadsafe.
 *
 * \sa lock()
 */
void PipelineHandler::unlock()
{
	for (std::shared_ptr<MediaDevice> &media : mediaDevices_)
		media->unlock();
}

/**
 * \brief Retrieve the list of controls for a camera
 * \param[in] camera The camera
 * \context This function is \threadsafe.
 * \return A ControlInfoMap listing the controls support by \a camera
 */
const ControlInfoMap &PipelineHandler::controls(const Camera *camera) const
{
	const CameraData *data = cameraData(camera);
	return data->controlInfo_;
}

/**
 * \brief Retrieve the list of properties for a camera
 * \param[in] camera The camera
 * \return A ControlList of properties supported by \a camera
 */
const ControlList &PipelineHandler::properties(const Camera *camera) const
{
	const CameraData *data = cameraData(camera);
	return data->properties_;
}

/**
 * \fn PipelineHandler::generateConfiguration()
 * \brief Generate a camera configuration for a specified camera
 * \param[in] camera The camera to generate a default configuration for
 * \param[in] roles A list of stream roles
 *
 * Generate a default configuration for the \a camera for a specified list of
 * stream roles. The caller shall populate the \a roles with the use-cases it
 * wishes to fetch the default configuration for. The returned configuration
 * can then be examined by the caller to learn about the selected streams and
 * their default parameters.
 *
 * The intended companion to this is \a configure() which can be used to change
 * the group of streams parameters.
 *
 * \context This function may be called from any thread and shall be
 * \threadsafe. It shall not modify the state of the \a camera in the pipeline
 * handler.
 *
 * \return A valid CameraConfiguration if the requested roles can be satisfied,
 * or a null pointer otherwise. The ownership of the returned configuration is
 * passed to the caller.
 */

/**
 * \fn PipelineHandler::configure()
 * \brief Configure a group of streams for capture
 * \param[in] camera The camera to configure
 * \param[in] config The camera configurations to setup
 *
 * Configure the specified group of streams for \a camera according to the
 * configuration specified in \a config. The intended caller of this interface
 * is the Camera class which will receive configuration to apply from the
 * application.
 *
 * The configuration is guaranteed to have been validated with
 * CameraConfiguration::validate(). The pipeline handler implementation shall
 * not perform further validation and may rely on any custom field stored in its
 * custom CameraConfiguration derived class.
 *
 * When configuring the camera the pipeline handler shall associate a Stream
 * instance to each StreamConfiguration entry in the CameraConfiguration using
 * the StreamConfiguration::setStream() method.
 *
 * \context This function is called from the CameraManager thread.
 *
 * \return 0 on success or a negative error code otherwise
 */

/**
 * \fn PipelineHandler::exportFrameBuffers()
 * \brief Allocate and export buffers for \a stream
 * \param[in] camera The camera
 * \param[in] stream The stream to allocate buffers for
 * \param[out] buffers Array of buffers successfully allocated
 *
 * This method allocates buffers for the \a stream from the devices associated
 * with the stream in the corresponding pipeline handler. Those buffers shall be
 * suitable to be added to a Request for the stream, and shall be mappable to
 * the CPU through their associated dmabufs with mmap().
 *
 * The method may only be called after the Camera has been configured and before
 * it gets started, or after it gets stopped. It shall be called only for
 * streams that are part of the active camera configuration.
 *
 * The only intended caller is Camera::exportFrameBuffers().
 *
 * \context This function is called from the CameraManager thread.
 *
 * \return The number of allocated buffers on success or a negative error code
 * otherwise
 */

/**
 * \fn PipelineHandler::start()
 * \brief Start capturing from a group of streams
 * \param[in] camera The camera to start
 * \param[in] controls Controls to be applied before starting the Camera
 *
 * Start the group of streams that have been configured for capture by
 * \a configure(). The intended caller of this method is the Camera class which
 * will in turn be called from the application to indicate that it has
 * configured the streams and is ready to capture.
 *
 * \context This function is called from the CameraManager thread.
 *
 * \return 0 on success or a negative error code otherwise
 */

/**
 * \fn PipelineHandler::stop()
 * \brief Stop capturing from all running streams
 * \param[in] camera The camera to stop
 *
 * This method stops capturing and processing requests immediately. All pending
 * requests are cancelled and complete immediately in an error state.
 *
 * \context This function is called from the CameraManager thread.
 */

/**
 * \fn PipelineHandler::queueRequest()
 * \brief Queue a request
 * \param[in] request The request to queue
 *
 * This method queues a capture request to the pipeline handler for processing.
 * The request is first added to the internal list of queued requests, and
 * then passed to the pipeline handler with a call to queueRequestDevice().
 *
 * Keeping track of queued requests ensures automatic completion of all requests
 * when the pipeline handler is stopped with stop(). Request completion shall be
 * signalled by the pipeline handler using the completeRequest() method.
 *
 * \context This function is called from the CameraManager thread.
 */
void PipelineHandler::queueRequest(Request *request)
{
	LIBCAMERA_TRACEPOINT(request_queue, request);

	Camera *camera = request->camera_;
	CameraData *data = cameraData(camera);
	data->queuedRequests_.push_back(request);

	request->sequence_ = data->requestSequence_++;

	int ret = queueRequestDevice(camera, request);
	if (ret)
		data->queuedRequests_.remove(request);
}

/**
 * \fn PipelineHandler::queueRequestDevice()
 * \brief Queue a request to the device
 * \param[in] camera The camera to queue the request to
 * \param[in] request The request to queue
 *
 * This method queues a capture request to the device for processing. The
 * request contains a set of buffers associated with streams and a set of
 * parameters. The pipeline handler shall program the device to ensure that the
 * parameters will be applied to the frames captured in the buffers provided in
 * the request.
 *
 * \context This function is called from the CameraManager thread.
 *
 * \return 0 on success or a negative error code otherwise
 */

/**
 * \brief Complete a buffer for a request
 * \param[in] request The request the buffer belongs to
 * \param[in] buffer The buffer that has completed
 *
 * This method shall be called by pipeline handlers to signal completion of the
 * \a buffer part of the \a request. It notifies applications of buffer
 * completion and updates the request's internal buffer tracking. The request
 * is not completed automatically when the last buffer completes to give
 * pipeline handlers a chance to perform any operation that may still be
 * needed. They shall complete requests explicitly with completeRequest().
 *
 * \context This function shall be called from the CameraManager thread.
 *
 * \return True if all buffers contained in the request have completed, false
 * otherwise
 */
bool PipelineHandler::completeBuffer(Request *request, FrameBuffer *buffer)
{
	Camera *camera = request->camera_;
	camera->bufferCompleted.emit(request, buffer);
	return request->completeBuffer(buffer);
}

/**
 * \brief Signal request completion
 * \param[in] request The request that has completed
 *
 * The pipeline handler shall call this method to notify the \a camera that the
 * request has completed. The request is no longer managed by the pipeline
 * handler and shall not be accessed once this method returns.
 *
 * This method ensures that requests will be returned to the application in
 * submission order, the pipeline handler may call it on any complete request
 * without any ordering constraint.
 *
 * \context This function shall be called from the CameraManager thread.
 */
void PipelineHandler::completeRequest(Request *request)
{
	Camera *camera = request->camera_;

	request->complete();

	CameraData *data = cameraData(camera);

	while (!data->queuedRequests_.empty()) {
		Request *req = data->queuedRequests_.front();
		if (req->status() == Request::RequestPending)
			break;

		ASSERT(!req->hasPendingBuffers());
		data->queuedRequests_.pop_front();
		camera->requestComplete(req);
	}
}

/**
 * \brief Register a camera to the camera manager and pipeline handler
 * \param[in] camera The camera to be added
 * \param[in] data Pipeline-specific data for the camera
 *
 * This method is called by pipeline handlers to register the cameras they
 * handle with the camera manager. It associates the pipeline-specific \a data
 * with the camera, for later retrieval with cameraData(). Ownership of \a data
 * is transferred to the PipelineHandler.
 *
 * \context This function shall be called from the CameraManager thread.
 */
void PipelineHandler::registerCamera(std::shared_ptr<Camera> camera,
				     std::unique_ptr<CameraData> data)
{
	cameraData_[camera.get()] = std::move(data);
	cameras_.push_back(camera);

	if (mediaDevices_.empty())
		LOG(Pipeline, Fatal)
			<< "Registering camera with no media devices!";

	/*
	 * Walk the entity list and map the devnums of all capture video nodes
	 * to the camera.
	 */
	std::vector<dev_t> devnums;
	for (const std::shared_ptr<MediaDevice> &media : mediaDevices_) {
		for (const MediaEntity *entity : media->entities()) {
			if (entity->pads().size() == 1 &&
			    (entity->pads()[0]->flags() & MEDIA_PAD_FL_SINK) &&
			    entity->function() == MEDIA_ENT_F_IO_V4L) {
				devnums.push_back(makedev(entity->deviceMajor(),
							  entity->deviceMinor()));
			}
		}
	}

	manager_->addCamera(std::move(camera), devnums);
}

/**
 * \brief Enable hotplug handling for a media device
 * \param[in] media The media device
 *
 * This function enables hotplug handling, and especially hot-unplug handling,
 * of the \a media device. It shall be called by pipeline handlers for all the
 * media devices that can be disconnected.
 *
 * When a media device passed to this function is later unplugged, the pipeline
 * handler gets notified and automatically disconnects all the cameras it has
 * registered without requiring any manual intervention.
 */
void PipelineHandler::hotplugMediaDevice(MediaDevice *media)
{
	media->disconnected.connect(this, &PipelineHandler::mediaDeviceDisconnected);
}

/**
 * \brief Slot for the MediaDevice disconnected signal
 */
void PipelineHandler::mediaDeviceDisconnected(MediaDevice *media)
{
	media->disconnected.disconnect(this);

	if (cameras_.empty())
		return;

	disconnect();
}

/**
 * \brief Device disconnection handler
 *
 * This virtual function is called to notify the pipeline handler that the
 * device it handles has been disconnected. It notifies all cameras created by
 * the pipeline handler that they have been disconnected, and unregisters them
 * from the camera manager.
 *
 * The function can be overloaded by pipeline handlers to perform custom
 * operations at disconnection time. Any overloaded version shall call the
 * PipelineHandler::disconnect() base function for proper hot-unplug operation.
 */
void PipelineHandler::disconnect()
{
	/*
	 * Each camera holds a reference to its associated pipeline handler
	 * instance. Hence, when the last camera is dropped, the pipeline
	 * handler will get destroyed by the last manager_->removeCamera(camera)
	 * call in the loop below.
	 *
	 * This is acceptable as long as we make sure that the code path does not
	 * access any member of the (already destroyed) pipeline handler instance
	 * afterwards. Therefore, we move the cameras_ vector to a local temporary
	 * container to avoid accessing freed memory later i.e. to explicitly run
	 * cameras_.clear().
	 */
	std::vector<std::weak_ptr<Camera>> cameras{ std::move(cameras_) };

	for (std::weak_ptr<Camera> ptr : cameras) {
		std::shared_ptr<Camera> camera = ptr.lock();
		if (!camera)
			continue;

		camera->disconnect();
		manager_->removeCamera(camera);
	}
}

/**
 * \brief Retrieve the pipeline-specific data associated with a Camera
 * \param[in] camera The camera whose data to retrieve
 * \return A pointer to the pipeline-specific data passed to registerCamera().
 * The returned pointer is a borrowed reference and is guaranteed to remain
 * valid until the pipeline handler is destroyed. It shall not be deleted
 * manually by the caller.
 */
CameraData *PipelineHandler::cameraData(const Camera *camera)
{
	ASSERT(cameraData_.count(camera));
	return cameraData_[camera].get();
}

/**
 * \brief Retrieve the pipeline-specific data associated with a Camera
 * \param[in] camera The camera whose data to retrieve
 * \sa cameraData()
 * \return A const pointer to the pipeline-specific data passed to
 * registerCamera().
 */
const CameraData *PipelineHandler::cameraData(const Camera *camera) const
{
	ASSERT(cameraData_.count(camera));
	return cameraData_.at(camera).get();
}

/**
 * \var PipelineHandler::manager_
 * \brief The Camera manager associated with the pipeline handler
 *
 * The camera manager pointer is stored in the pipeline handler for the
 * convenience of pipeline handler implementations. It remains valid and
 * constant for the whole lifetime of the pipeline handler.
 */

/**
 * \fn PipelineHandler::name()
 * \brief Retrieve the pipeline handler name
 * \context This function shall be \threadsafe.
 * \return The pipeline handler name
 */

/**
 * \class PipelineHandlerFactory
 * \brief Registration of PipelineHandler classes and creation of instances
 *
 * To facilitate discovery and instantiation of PipelineHandler classes, the
 * PipelineHandlerFactory class maintains a registry of pipeline handler
 * classes. Each PipelineHandler subclass shall register itself using the
 * REGISTER_PIPELINE_HANDLER() macro, which will create a corresponding
 * instance of a PipelineHandlerFactory subclass and register it with the
 * static list of factories.
 */

/**
 * \brief Construct a pipeline handler factory
 * \param[in] name Name of the pipeline handler class
 *
 * Creating an instance of the factory registers is with the global list of
 * factories, accessible through the factories() function.
 *
 * The factory \a name is used for debug purpose and shall be unique.
 */
PipelineHandlerFactory::PipelineHandlerFactory(const char *name)
	: name_(name)
{
	registerType(this);
}

/**
 * \brief Create an instance of the PipelineHandler corresponding to the factory
 * \param[in] manager The camera manager
 *
 * \return A shared pointer to a new instance of the PipelineHandler subclass
 * corresponding to the factory
 */
std::shared_ptr<PipelineHandler> PipelineHandlerFactory::create(CameraManager *manager)
{
	PipelineHandler *handler = createInstance(manager);
	handler->name_ = name_.c_str();
	return std::shared_ptr<PipelineHandler>(handler);
}

/**
 * \fn PipelineHandlerFactory::name()
 * \brief Retrieve the factory name
 * \return The factory name
 */

/**
 * \brief Add a pipeline handler class to the registry
 * \param[in] factory Factory to use to construct the pipeline handler
 *
 * The caller is responsible to guarantee the uniqueness of the pipeline handler
 * name.
 */
void PipelineHandlerFactory::registerType(PipelineHandlerFactory *factory)
{
	std::vector<PipelineHandlerFactory *> &factories = PipelineHandlerFactory::factories();

	factories.push_back(factory);
}

/**
 * \brief Retrieve the list of all pipeline handler factories
 *
 * The static factories map is defined inside the function to ensures it gets
 * initialized on first use, without any dependency on link order.
 *
 * \return the list of pipeline handler factories
 */
std::vector<PipelineHandlerFactory *> &PipelineHandlerFactory::factories()
{
	static std::vector<PipelineHandlerFactory *> factories;
	return factories;
}

/**
 * \fn PipelineHandlerFactory::createInstance()
 * \brief Create an instance of the PipelineHandler corresponding to the factory
 * \param[in] manager The camera manager
 *
 * This virtual function is implemented by the REGISTER_PIPELINE_HANDLER()
 * macro. It creates a pipeline handler instance associated with the camera
 * \a manager.
 *
 * \return a pointer to a newly constructed instance of the PipelineHandler
 * subclass corresponding to the factory
 */

/**
 * \def REGISTER_PIPELINE_HANDLER
 * \brief Register a pipeline handler with the pipeline handler factory
 * \param[in] handler Class name of PipelineHandler derived class to register
 *
 * Register a PipelineHandler subclass with the factory and make it available to
 * try and match devices.
 */

} /* namespace libcamera */