4 files changed, 442 insertions, 0 deletions
diff --git a/include/libcamera/internal/converter.h b/include/libcamera/internal/converter.h
new file mode 100644
index 00000000..834ec5ab
--- /dev/null
+++ b/include/libcamera/internal/converter.h
@@ -0,0 +1,108 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2020, Laurent Pinchart
+ * Copyright 2022 NXP
+ *
+ * converter.h - Generic format converter interface
+ */
+
+#pragma once
+
+#include <functional>
+#include <initializer_list>
+#include <map>
+#include <memory>
+#include <string>
+#include <tuple>
+#include <vector>
+
+#include <libcamera/base/class.h>
+#include <libcamera/base/signal.h>
+
+#include <libcamera/geometry.h>
+
+namespace libcamera {
+
+class FrameBuffer;
+class MediaDevice;
+class PixelFormat;
+struct StreamConfiguration;
+
+class Converter
+{
+public:
+	Converter(MediaDevice *media);
+	virtual ~Converter();
+
+	virtual int loadConfiguration(const std::string &filename) = 0;
+
+	virtual bool isValid() const = 0;
+
+	virtual std::vector<PixelFormat> formats(PixelFormat input) = 0;
+	virtual SizeRange sizes(const Size &input) = 0;
+
+	virtual std::tuple<unsigned int, unsigned int>
+	strideAndFrameSize(const PixelFormat &pixelFormat, const Size &size) = 0;
+
+	virtual int configure(const StreamConfiguration &inputCfg,
+			      const std::vector<std::reference_wrapper<StreamConfiguration>> &outputCfgs) = 0;
+	virtual int exportBuffers(unsigned int output, unsigned int count,
+				  std::vector<std::unique_ptr<FrameBuffer>> *buffers) = 0;
+
+	virtual int start() = 0;
+	virtual void stop() = 0;
+
+	virtual int queueBuffers(FrameBuffer *input,
+				 const std::map<unsigned int, FrameBuffer *> &outputs) = 0;
+
+	Signal<FrameBuffer *> inputBufferReady;
+	Signal<FrameBuffer *> outputBufferReady;
+
+	const std::string &deviceNode() const { return deviceNode_; }
+
+private:
+	std::string deviceNode_;
+};
+
+class ConverterFactoryBase
+{
+public:
+	ConverterFactoryBase(const std::string name, std::initializer_list<std::string> compatibles);
+	virtual ~ConverterFactoryBase() = default;
+
+	const std::vector<std::string> &compatibles() const { return compatibles_; }
+
+	static std::unique_ptr<Converter> create(MediaDevice *media);
+	static std::vector<ConverterFactoryBase *> &factories();
+	static std::vector<std::string> names();
+
+private:
+	LIBCAMERA_DISABLE_COPY_AND_MOVE(ConverterFactoryBase)
+
+	static void registerType(ConverterFactoryBase *factory);
+
+	virtual std::unique_ptr<Converter> createInstance(MediaDevice *media) const = 0;
+
+	std::string name_;
+	std::vector<std::string> compatibles_;
+};
+
+template<typename _Converter>
+class ConverterFactory : public ConverterFactoryBase
+{
+public:
+	ConverterFactory(const char *name, std::initializer_list<std::string> compatibles)
+		: ConverterFactoryBase(name, compatibles)
+	{
+	}
+
+	std::unique_ptr<Converter> createInstance(MediaDevice *media) const override
+	{
+		return std::make_unique<_Converter>(media);
+	}
+};
+
+#define REGISTER_CONVERTER(name, converter, compatibles) \
+	static ConverterFactory<converter> global_##converter##Factory(name, compatibles);
+
+} /* namespace libcamera */
diff --git a/include/libcamera/internal/meson.build b/include/libcamera/internal/meson.build
index f8be86e0..341af8a2 100644
--- a/include/libcamera/internal/meson.build
+++ b/include/libcamera/internal/meson.build
@@ -19,6 +19,7 @@ libcamera_internal_headers = files([
     'camera_sensor_properties.h',
     'control_serializer.h',
     'control_validator.h',
+    'converter.h',
     'delayed_controls.h',
     'device_enumerator.h',
     'device_enumerator_sysfs.h',
diff --git a/src/libcamera/converter.cpp b/src/libcamera/converter.cpp
new file mode 100644
index 00000000..3de39cff
--- /dev/null
+++ b/src/libcamera/converter.cpp
@@ -0,0 +1,332 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright 2022 NXP
+ *
+ * converter.cpp - Generic format converter interface
+ */
+
+#include "libcamera/internal/converter.h"
+
+#include <algorithm>
+
+#include <libcamera/base/log.h>
+
+#include "libcamera/internal/media_device.h"
+
+#include "linux/media.h"
+
+/**
+ * \file internal/converter.h
+ * \brief Abstract converter
+ */
+
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(Converter)
+
+/**
+ * \class Converter
+ * \brief Abstract Base Class for converter
+ *
+ * The Converter class is an Abstract Base Class defining the interfaces of
+ * converter implementations.
+ *
+ * Converters offer scaling and pixel format conversion services on an input
+ * stream. The converter can output multiple streams with individual conversion
+ * parameters from the same input stream.
+ */
+
+/**
+ * \brief Construct a Converter instance
+ * \param[in] media The media device implementing the converter
+ *
+ * This searches for the entity implementing the data streaming function in the
+ * media graph entities and use its device node as the converter device node.
+ */
+Converter::Converter(MediaDevice *media)
+{
+	const std::vector<MediaEntity *> &entities = media->entities();
+	auto it = std::find_if(entities.begin(), entities.end(),
+			       [](MediaEntity *entity) {
+				       return entity->function() == MEDIA_ENT_F_IO_V4L;
+			       });
+	if (it == entities.end()) {
+		LOG(Converter, Error)
+			<< "No entity suitable for implementing a converter in "
+			<< media->driver() << " entities list.";
+		return;
+	}
+
+	deviceNode_ = (*it)->deviceNode();
+}
+
+Converter::~Converter()
+{
+}
+
+/**
+ * \fn Converter::loadConfiguration()
+ * \brief Load converter configuration from file
+ * \param[in] filename The file name path
+ *
+ * Load converter dependent configuration parameters to apply on the hardware.
+ *
+ * \return 0 on success or a negative error code otherwise
+ */
+
+/**
+ * \fn Converter::isValid()
+ * \brief Check if the converter configuration is valid
+ * \return True is the converter is valid, false otherwise
+ */
+
+/**
+ * \fn Converter::formats()
+ * \brief Retrieve the list of supported pixel formats for an input pixel format
+ * \param[in] input Input pixel format to retrieve output pixel format list for
+ * \return The list of supported output pixel formats
+ */
+
+/**
+ * \fn Converter::sizes()
+ * \brief Retrieve the range of minimum and maximum output sizes for an input size
+ * \param[in] input Input stream size to retrieve range for
+ * \return A range of output image sizes
+ */
+
+/**
+ * \fn Converter::strideAndFrameSize()
+ * \brief Retrieve the output stride and frame size for an input configutation
+ * \param[in] pixelFormat Input stream pixel format
+ * \param[in] size Input stream size
+ * \return A tuple indicating the stride and frame size or an empty tuple on error
+ */
+
+/**
+ * \fn Converter::configure()
+ * \brief Configure a set of output stream conversion from an input stream
+ * \param[in] inputCfg Input stream configuration
+ * \param[out] outputCfgs A list of output stream configurations
+ * \return 0 on success or a negative error code otherwise
+ */
+
+/**
+ * \fn Converter::exportBuffers()
+ * \brief Export buffers from the converter device
+ * \param[in] output Output stream index exporting the buffers
+ * \param[in] count Number of buffers to allocate
+ * \param[out] buffers Vector to store allocated buffers
+ *
+ * This function operates similarly to V4L2VideoDevice::exportBuffers() on the
+ * output stream indicated by the \a output index.
+ *
+ * \return The number of allocated buffers on success or a negative error code
+ * otherwise
+ */
+
+/**
+ * \fn Converter::start()
+ * \brief Start the converter streaming operation
+ * \return 0 on success or a negative error code otherwise
+ */
+
+/**
+ * \fn Converter::stop()
+ * \brief Stop the converter streaming operation
+ */
+
+/**
+ * \fn Converter::queueBuffers()
+ * \brief Queue buffers to converter device
+ * \param[in] input The frame buffer to apply the conversion
+ * \param[out] outputs The container holding the output stream indexes and
+ * their respective frame buffer outputs.
+ *
+ * This function queues the \a input frame buffer on the output streams of the
+ * \a outputs map key and retrieve the output frame buffer indicated by the
+ * buffer map value.
+ *
+ * \return 0 on success or a negative error code otherwise
+ */
+
+/**
+ * \var Converter::inputBufferReady
+ * \brief A signal emitted when the input frame buffer completes
+ */
+
+/**
+ * \var Converter::outputBufferReady
+ * \brief A signal emitted on each frame buffer completion of the output queue
+ */
+
+/**
+ * \fn Converter::deviceNode()
+ * \brief The converter device node attribute accessor
+ * \return The converter device node string
+ */
+
+/**
+ * \class ConverterFactoryBase
+ * \brief Base class for converter factories
+ *
+ * The ConverterFactoryBase class is the base of all specializations of the
+ * ConverterFactory class template. It implements the factory registration,
+ * maintains a registry of factories, and provides access to the registered
+ * factories.
+ */
+
+/**
+ * \brief Construct a converter factory base
+ * \param[in] name Name of the converter class
+ * \param[in] compatibles Name aliases of the converter class
+ *
+ * Creating an instance of the factory base registers it with the global list of
+ * factories, accessible through the factories() function.
+ *
+ * The factory \a name is used as unique identifier. If the converter
+ * implementation fully relies on a generic framework, the name should be the
+ * same as the framework. Otherwise, if the implementation is specialized, the
+ * factory name should match the driver name implementing the function.
+ *
+ * The factory \a compatibles holds a list of driver names implementing a generic
+ * subsystem without any personalizations.
+ */
+ConverterFactoryBase::ConverterFactoryBase(const std::string name, std::initializer_list<std::string> compatibles)
+	: name_(name), compatibles_(compatibles)
+{
+	registerType(this);
+}
+
+/**
+ * \fn ConverterFactoryBase::compatibles()
+ * \return The names compatibles
+ */
+
+/**
+ * \brief Create an instance of the converter corresponding to a named factory
+ * \param[in] media Name of the factory
+ *
+ * \return A unique pointer to a new instance of the converter subclass
+ * corresponding to the named factory or one of its alias. Otherwise a null
+ * pointer if no such factory exists
+ */
+std::unique_ptr<Converter> ConverterFactoryBase::create(MediaDevice *media)
+{
+	const std::vector<ConverterFactoryBase *> &factories =
+		ConverterFactoryBase::factories();
+
+	for (const ConverterFactoryBase *factory : factories) {
+		const std::vector<std::string> &compatibles = factory->compatibles();
+		auto it = std::find(compatibles.begin(), compatibles.end(), media->driver());
+
+		if (it == compatibles.end() && media->driver() != factory->name_)
+			continue;
+
+		LOG(Converter, Debug)
+			<< "Creating converter from "
+			<< factory->name_ << " factory with "
+			<< (it == compatibles.end() ? "no" : media->driver()) << " alias.";
+
+		return factory->createInstance(media);
+	}
+
+	return nullptr;
+}
+
+/**
+ * \brief Add a converter class to the registry
+ * \param[in] factory Factory to use to construct the converter class
+ *
+ * The caller is responsible to guarantee the uniqueness of the converter name.
+ */
+void ConverterFactoryBase::registerType(ConverterFactoryBase *factory)
+{
+	std::vector<ConverterFactoryBase *> &factories =
+		ConverterFactoryBase::factories();
+
+	factories.push_back(factory);
+}
+
+/**
+ * \brief Retrieve the list of all converter factory names
+ * \return The list of all converter factory names
+ */
+std::vector<std::string> ConverterFactoryBase::names()
+{
+	std::vector<std::string> list;
+
+	std::vector<ConverterFactoryBase *> &factories =
+		ConverterFactoryBase::factories();
+
+	for (ConverterFactoryBase *factory : factories) {
+		list.push_back(factory->name_);
+		for (auto alias : factory->compatibles())
+			list.push_back(alias);
+	}
+
+	return list;
+}
+
+/**
+ * \brief Retrieve the list of all converter factories
+ * \return The list of converter factories
+ */
+std::vector<ConverterFactoryBase *> &ConverterFactoryBase::factories()
+{
+	/*
+	 * The static factories map is defined inside the function to ensure
+	 * it gets initialized on first use, without any dependency on link
+	 * order.
+	 */
+	static std::vector<ConverterFactoryBase *> factories;
+	return factories;
+}
+
+/**
+ * \var ConverterFactoryBase::name_
+ * \brief The name of the factory
+ */
+
+/**
+ * \var ConverterFactoryBase::compatibles_
+ * \brief The list holding the factory compatibles
+ */
+
+/**
+ * \class ConverterFactory
+ * \brief Registration of ConverterFactory classes and creation of instances
+ * \param _Converter The converter class type for this factory
+ *
+ * To facilitate discovery and instantiation of Converter classes, the
+ * ConverterFactory class implements auto-registration of converter helpers.
+ * Each Converter subclass shall register itself using the REGISTER_CONVERTER()
+ * macro, which will create a corresponding instance of a ConverterFactory
+ * subclass and register it with the static list of factories.
+ */
+
+/**
+ * \fn ConverterFactory::ConverterFactory(const char *name, std::initializer_list<std::string> compatibles)
+ * \brief Construct a converter factory
+ * \details \copydetails ConverterFactoryBase::ConverterFactoryBase
+ */
+
+/**
+ * \fn ConverterFactory::createInstance() const
+ * \brief Create an instance of the Converter corresponding to the factory
+ * \param[in] media Media device pointer
+ * \return A unique pointer to a newly constructed instance of the Converter
+ * subclass corresponding to the factory
+ */
+
+/**
+ * \def REGISTER_CONVERTER
+ * \brief Register a converter with the Converter factory
+ * \param[in] name Converter name used to register the class
+ * \param[in] converter Class name of Converter derived class to register
+ * \param[in] compatibles List of compatible names
+ *
+ * Register a Converter subclass with the factory and make it available to try
+ * and match converters.
+ */
+
+} /* namespace libcamera */
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index 0494e808..e9d0324e 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -13,6 +13,7 @@ libcamera_sources = files([
     'controls.cpp',
     'control_serializer.cpp',
     'control_validator.cpp',
+    'converter.cpp',
     'delayed_controls.cpp',
     'device_enumerator.cpp',
     'device_enumerator_sysfs.cpp',