external_libcamera/src/libcamera/control_serializer.cpp

/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2019, Google Inc.
 *
 * Control (de)serializer
 */

#include "libcamera/internal/control_serializer.h"

#include <algorithm>
#include <memory>
#include <vector>

#include <libcamera/base/log.h>
#include <libcamera/base/span.h>

#include <libcamera/control_ids.h>
#include <libcamera/controls.h>
#include <libcamera/property_ids.h>

#include <libcamera/ipa/ipa_controls.h>

#include "libcamera/internal/byte_stream_buffer.h"

/**
 * \file control_serializer.h
 * \brief Serialization and deserialization helpers for controls
 */

namespace libcamera {

LOG_DEFINE_CATEGORY(Serializer)

/**
 * \class ControlSerializer
 * \brief Serializer and deserializer for control-related classes
 *
 * The control serializer is a helper to serialize and deserialize
 * ControlInfoMap and ControlValue instances for the purpose of communication
 * with IPA modules.
 *
 * Neither the ControlInfoMap nor the ControlList are self-contained data
 * container. ControlInfoMap references an external ControlId in each of its
 * entries, and ControlList references a ControlInfoMap for the purpose of
 * validation. Serializing and deserializing those objects thus requires a
 * context that maintains the associations between them. The control serializer
 * fulfils this task.
 *
 * ControlInfoMap instances can be serialized on their own, but require
 * ControlId instances to be provided at deserialization time. The serializer
 * recreates those ControlId instances and stores them in an internal cache,
 * from which the ControlInfoMap is populated.
 *
 * ControlList instances need to be associated with a ControlInfoMap when
 * deserialized. To make this possible, the control lists are serialized with a
 * handle to their ControlInfoMap, and the map is looked up from the handle at
 * deserialization time. To make this possible, the serializer assigns a
 * numerical handle to ControlInfoMap instances when they are serialized, and
 * stores the mapping between handle and ControlInfoMap both when serializing
 * (for the pipeline handler side) and deserializing (for the IPA side) them.
 * This mapping is used when serializing a ControlList to include the
 * corresponding ControlInfoMap handle in the binary data, and when
 * deserializing to retrieve the corresponding ControlInfoMap.
 *
 * As independent ControlSerializer instances are used on both sides of the IPC
 * boundary, and the two instances operate without a shared point of control,
 * there is a potential risk of collision of the numerical handles assigned to
 * each serialized ControlInfoMap. For this reason the control serializer is
 * initialized with a seed and the handle is incremented by 2, so that instances
 * initialized with a different seed operate on a separate numerical space,
 * avoiding any collision risk.
 *
 * In order to perform those tasks, the serializer keeps an internal state that
 * needs to be properly populated. This mechanism requires the ControlInfoMap
 * corresponding to a ControlList to have been serialized or deserialized
 * before the ControlList is serialized or deserialized. Failure to comply with
 * that constraint results in serialization or deserialization failure of the
 * ControlList.
 *
 * The serializer can be reset() to clear its internal state. This may be
 * performed when reconfiguring an IPA to avoid constant growth of the internal
 * state, especially if the contents of the ControlInfoMap instances change at
 * that time. A reset of the serializer invalidates all ControlList and
 * ControlInfoMap that have been previously deserialized. The caller shall thus
 * proceed with care to avoid stale references.
 */

/**
 * \enum ControlSerializer::Role
 * \brief Define the role of the IPC component using the control serializer
 *
 * The role of the component that creates the serializer is used to initialize
 * the handles numerical space.
 *
 * \var ControlSerializer::Role::Proxy
 * \brief The control serializer is used by the IPC Proxy classes
 *
 * \var ControlSerializer::Role::Worker
 * \brief The control serializer is used by the IPC ProxyWorker classes
 */

/**
 * \brief Construct a new ControlSerializer
 * \param[in] role The role of the IPC component using the serializer
 */
ControlSerializer::ControlSerializer(Role role)
{
	/*
	 * Initialize the handle numerical space using the role of the
	 * component that created the instance.
	 *
	 * Instances initialized for a different role will use a different
	 * numerical handle space, avoiding any collision risk when, in example,
	 * two instances of the ControlSerializer class are used at the IPC
	 * boundaries.
	 *
	 * Start counting handles from '1' as '0' is a special value used as
	 * place holder when serializing lists that do not have a ControlInfoMap
	 * associated (in example list of libcamera controls::controls).
	 *
	 * \todo This is a temporary hack and should probably be better
	 * engineered, but for the time being it avoids collisions on the handle
	 * value when using IPC.
	 */
	serialSeed_ = role == Role::Proxy ? 1 : 2;
	serial_ = serialSeed_;
}

/**
 * \brief Reset the serializer
 *
 * Reset the internal state of the serializer. This invalidates all the
 * ControlList and ControlInfoMap that have been previously deserialized.
 */
void ControlSerializer::reset()
{
	serial_ = serialSeed_;

	infoMapHandles_.clear();
	infoMaps_.clear();
	controlIds_.clear();
	controlIdMaps_.clear();
}

size_t ControlSerializer::binarySize(const ControlValue &value)
{
	return sizeof(ControlType) + value.data().size_bytes();
}

size_t ControlSerializer::binarySize(const ControlInfo &info)
{
	return binarySize(info.min()) + binarySize(info.max()) + binarySize(info.def());
}

/**
 * \brief Retrieve the size in bytes required to serialize a ControlInfoMap
 * \param[in] infoMap The control info map
 *
 * Compute and return the size in bytes required to store the serialized
 * ControlInfoMap.
 *
 * \return The size in bytes required to store the serialized ControlInfoMap
 */
size_t ControlSerializer::binarySize(const ControlInfoMap &infoMap)
{
	size_t size = sizeof(struct ipa_controls_header)
		    + infoMap.size() * sizeof(struct ipa_control_info_entry);

	for (const auto &ctrl : infoMap)
		size += binarySize(ctrl.second);

	return size;
}

/**
 * \brief Retrieve the size in bytes required to serialize a ControlList
 * \param[in] list The control list
 *
 * Compute and return the size in bytes required to store the serialized
 * ControlList.
 *
 * \return The size in bytes required to store the serialized ControlList
 */
size_t ControlSerializer::binarySize(const ControlList &list)
{
	size_t size = sizeof(struct ipa_controls_header)
		    + list.size() * sizeof(struct ipa_control_value_entry);

	for (const auto &ctrl : list)
		size += binarySize(ctrl.second);

	return size;
}

void ControlSerializer::store(const ControlValue &value,
			      ByteStreamBuffer &buffer)
{
	const ControlType type = value.type();
	buffer.write(&type);
	buffer.write(value.data());
}

void ControlSerializer::store(const ControlInfo &info, ByteStreamBuffer &buffer)
{
	store(info.min(), buffer);
	store(info.max(), buffer);
	store(info.def(), buffer);
}

/**
 * \brief Serialize a ControlInfoMap in a buffer
 * \param[in] infoMap The control info map to serialize
 * \param[in] buffer The memory buffer where to serialize the ControlInfoMap
 *
 * Serialize the \a infoMap into the \a buffer using the serialization format
 * defined by the IPA context interface in ipa_controls.h.
 *
 * The serializer stores a reference to the \a infoMap internally. The caller
 * shall ensure that \a infoMap stays valid until the serializer is reset().
 *
 * \return 0 on success, a negative error code otherwise
 * \retval -ENOSPC Not enough space is available in the buffer
 */
int ControlSerializer::serialize(const ControlInfoMap &infoMap,
				 ByteStreamBuffer &buffer)
{
	if (isCached(infoMap)) {
		LOG(Serializer, Debug)
			<< "Skipping already serialized ControlInfoMap";
		return 0;
	}

	/* Compute entries and data required sizes. */
	size_t entriesSize = infoMap.size()
			   * sizeof(struct ipa_control_info_entry);
	size_t valuesSize = 0;
	for (const auto &ctrl : infoMap)
		valuesSize += binarySize(ctrl.second);

	const ControlIdMap *idmap = &infoMap.idmap();
	enum ipa_controls_id_map_type idMapType;
	if (idmap == &controls::controls)
		idMapType = IPA_CONTROL_ID_MAP_CONTROLS;
	else if (idmap == &properties::properties)
		idMapType = IPA_CONTROL_ID_MAP_PROPERTIES;
	else
		idMapType = IPA_CONTROL_ID_MAP_V4L2;

	/* Prepare the packet header. */
	struct ipa_controls_header hdr;
	hdr.version = IPA_CONTROLS_FORMAT_VERSION;
	hdr.handle = serial_;
	hdr.entries = infoMap.size();
	hdr.size = sizeof(hdr) + entriesSize + valuesSize;
	hdr.data_offset = sizeof(hdr) + entriesSize;
	hdr.id_map_type = idMapType;

	buffer.write(&hdr);

	/*
	 * Increment the handle for the ControlInfoMap by 2 to keep the handles
	 * numerical space partitioned between instances initialized for a
	 * different role.
	 *
	 * \sa ControlSerializer::Role
	 */
	serial_ += 2;

	/*
	 * Serialize all entries.
	 * \todo Serialize the control name too
	 */
	ByteStreamBuffer entries = buffer.carveOut(entriesSize);
	ByteStreamBuffer values = buffer.carveOut(valuesSize);

	for (const auto &ctrl : infoMap) {
		const ControlId *id = ctrl.first;
		const ControlInfo &info = ctrl.second;

		struct ipa_control_info_entry entry;
		entry.id = id->id();
		entry.type = id->type();
		entry.offset = values.offset();
		entries.write(&entry);

		store(info, values);
	}

	if (buffer.overflow())
		return -ENOSPC;

	/*
	 * Store the map to handle association, to be used to serialize and
	 * deserialize control lists.
	 */
	infoMapHandles_[&infoMap] = hdr.handle;

	return 0;
}

/**
 * \brief Serialize a ControlList in a buffer
 * \param[in] list The control list to serialize
 * \param[in] buffer The memory buffer where to serialize the ControlList
 *
 * Serialize the \a list into the \a buffer using the serialization format
 * defined by the IPA context interface in ipa_controls.h.
 *
 * \return 0 on success, a negative error code otherwise
 * \retval -ENOENT The ControlList is related to an unknown ControlInfoMap
 * \retval -ENOSPC Not enough space is available in the buffer
 */
int ControlSerializer::serialize(const ControlList &list,
				 ByteStreamBuffer &buffer)
{
	/*
	 * Find the ControlInfoMap handle for the ControlList if it has one, or
	 * use 0 for ControlList without a ControlInfoMap.
	 */
	unsigned int infoMapHandle;
	if (list.infoMap()) {
		auto iter = infoMapHandles_.find(list.infoMap());
		if (iter == infoMapHandles_.end()) {
			LOG(Serializer, Error)
				<< "Can't serialize ControlList: unknown ControlInfoMap";
			return -ENOENT;
		}

		infoMapHandle = iter->second;
	} else {
		infoMapHandle = 0;
	}

	const ControlIdMap *idmap = list.idMap();
	enum ipa_controls_id_map_type idMapType;
	if (idmap == &controls::controls)
		idMapType = IPA_CONTROL_ID_MAP_CONTROLS;
	else if (idmap == &properties::properties)
		idMapType = IPA_CONTROL_ID_MAP_PROPERTIES;
	else
		idMapType = IPA_CONTROL_ID_MAP_V4L2;

	size_t entriesSize = list.size() * sizeof(struct ipa_control_value_entry);
	size_t valuesSize = 0;
	for (const auto &ctrl : list)
		valuesSize += binarySize(ctrl.second);

	/* Prepare the packet header. */
	struct ipa_controls_header hdr;
	hdr.version = IPA_CONTROLS_FORMAT_VERSION;
	hdr.handle = infoMapHandle;
	hdr.entries = list.size();
	hdr.size = sizeof(hdr) + entriesSize + valuesSize;
	hdr.data_offset = sizeof(hdr) + entriesSize;
	hdr.id_map_type = idMapType;

	buffer.write(&hdr);

	ByteStreamBuffer entries = buffer.carveOut(entriesSize);
	ByteStreamBuffer values = buffer.carveOut(valuesSize);

	/* Serialize all entries. */
	for (const auto &ctrl : list) {
		unsigned int id = ctrl.first;
		const ControlValue &value = ctrl.second;

		struct ipa_control_value_entry entry;
		entry.id = id;
		entry.type = value.type();
		entry.is_array = value.isArray();
		entry.count = value.numElements();
		entry.offset = values.offset();
		entries.write(&entry);

		store(value, values);
	}

	if (buffer.overflow())
		return -ENOSPC;

	return 0;
}

ControlValue ControlSerializer::loadControlValue(ByteStreamBuffer &buffer,
						 bool isArray,
						 unsigned int count)
{
	ControlType type;
	buffer.read(&type);

	ControlValue value;

	value.reserve(type, isArray, count);
	buffer.read(value.data());

	return value;
}

ControlInfo ControlSerializer::loadControlInfo(ByteStreamBuffer &b)
{
	ControlValue min = loadControlValue(b);
	ControlValue max = loadControlValue(b);
	ControlValue def = loadControlValue(b);

	return ControlInfo(min, max, def);
}

/**
 * \fn template<typename T> T ControlSerializer::deserialize(ByteStreamBuffer &buffer)
 * \brief Deserialize an object from a binary buffer
 * \param[in] buffer The memory buffer that contains the object
 *
 * This function is only valid when specialized for ControlInfoMap or
 * ControlList. Any other typename \a T is not supported.
 */

/**
 * \brief Deserialize a ControlInfoMap from a binary buffer
 * \param[in] buffer The memory buffer that contains the serialized map
 *
 * Re-construct a ControlInfoMap from a binary \a buffer containing data
 * serialized using the serialize() function.
 *
 * \return The deserialized ControlInfoMap
 */
template<>
ControlInfoMap ControlSerializer::deserialize<ControlInfoMap>(ByteStreamBuffer &buffer)
{
	const struct ipa_controls_header *hdr = buffer.read<decltype(*hdr)>();
	if (!hdr) {
		LOG(Serializer, Error) << "Out of data";
		return {};
	}

	auto iter = infoMaps_.find(hdr->handle);
	if (iter != infoMaps_.end()) {
		LOG(Serializer, Debug) << "Use cached ControlInfoMap";
		return iter->second;
	}

	if (hdr->version != IPA_CONTROLS_FORMAT_VERSION) {
		LOG(Serializer, Error)
			<< "Unsupported controls format version "
			<< hdr->version;
		return {};
	}

	/*
	 * Use the ControlIdMap corresponding to the id map type. If the type
	 * references a globally defined id map (such as controls::controls
	 * or properties::properties), use it. Otherwise, create a local id map
	 * that will be populated with dynamically created ControlId instances
	 * when deserializing individual ControlInfoMap entries.
	 */
	const ControlIdMap *idMap = nullptr;
	ControlIdMap *localIdMap = nullptr;
	switch (hdr->id_map_type) {
	case IPA_CONTROL_ID_MAP_CONTROLS:
		idMap = &controls::controls;
		break;
	case IPA_CONTROL_ID_MAP_PROPERTIES:
		idMap = &properties::properties;
		break;
	case IPA_CONTROL_ID_MAP_V4L2:
		controlIdMaps_.emplace_back(std::make_unique<ControlIdMap>());
		localIdMap = controlIdMaps_.back().get();
		idMap = localIdMap;
		break;
	default:
		LOG(Serializer, Error)
			<< "Unknown id map type: " << hdr->id_map_type;
		return {};
	}

	ByteStreamBuffer entries = buffer.carveOut(hdr->data_offset - sizeof(*hdr));
	ByteStreamBuffer values = buffer.carveOut(hdr->size - hdr->data_offset);

	if (buffer.overflow()) {
		LOG(Serializer, Error) << "Out of data";
		return {};
	}

	ControlInfoMap::Map ctrls;
	for (unsigned int i = 0; i < hdr->entries; ++i) {
		const struct ipa_control_info_entry *entry =
			entries.read<decltype(*entry)>();
		if (!entry) {
			LOG(Serializer, Error) << "Out of data";
			return {};
		}

		ControlType type = static_cast<ControlType>(entry->type);

		/* If we're using a local id map, populate it. */
		if (localIdMap) {
			/**
			 * \todo Find a way to preserve the control name for
			 * debugging purpose.
			 */
			controlIds_.emplace_back(std::make_unique<ControlId>(entry->id,
									     "", "local", type));
			(*localIdMap)[entry->id] = controlIds_.back().get();
		}

		const ControlId *controlId = idMap->at(entry->id);
		ASSERT(controlId);

		if (entry->offset != values.offset()) {
			LOG(Serializer, Error)
				<< "Bad data, entry offset mismatch (entry "
				<< i << ")";
			return {};
		}

		/* Create and store the ControlInfo. */
		ctrls.emplace(controlId, loadControlInfo(values));
	}

	/*
	 * Create the ControlInfoMap in the cache, and store the map to handle
	 * association.
	 */
	infoMaps_[hdr->handle] = ControlInfoMap(std::move(ctrls), *idMap);
	ControlInfoMap &map = infoMaps_[hdr->handle];
	infoMapHandles_[&map] = hdr->handle;

	return map;
}

/**
 * \brief Deserialize a ControlList from a binary buffer
 * \param[in] buffer The memory buffer that contains the serialized list
 *
 * Re-construct a ControlList from a binary \a buffer containing data
 * serialized using the serialize() function.
 *
 * \return The deserialized ControlList
 */
template<>
ControlList ControlSerializer::deserialize<ControlList>(ByteStreamBuffer &buffer)
{
	const struct ipa_controls_header *hdr = buffer.read<decltype(*hdr)>();
	if (!hdr) {
		LOG(Serializer, Error) << "Out of data";
		return {};
	}

	if (hdr->version != IPA_CONTROLS_FORMAT_VERSION) {
		LOG(Serializer, Error)
			<< "Unsupported controls format version "
			<< hdr->version;
		return {};
	}

	ByteStreamBuffer entries = buffer.carveOut(hdr->data_offset - sizeof(*hdr));
	ByteStreamBuffer values = buffer.carveOut(hdr->size - hdr->data_offset);

	if (buffer.overflow()) {
		LOG(Serializer, Error) << "Out of data";
		return {};
	}

	/*
	 * Retrieve the ControlIdMap associated with the ControlList.
	 *
	 * The idmap is either retrieved from the list's ControlInfoMap when
	 * a valid handle has been initialized at serialization time, or by
	 * using the header's id_map_type field for lists that refer to the
	 * globally defined libcamera controls and properties, for which no
	 * ControlInfoMap is available.
	 */
	const ControlIdMap *idMap;
	if (hdr->handle) {
		auto iter = std::find_if(infoMapHandles_.begin(), infoMapHandles_.end(),
					 [&](decltype(infoMapHandles_)::value_type &entry) {
						 return entry.second == hdr->handle;
					 });
		if (iter == infoMapHandles_.end()) {
			LOG(Serializer, Error)
				<< "Can't deserialize ControlList: unknown ControlInfoMap";
			return {};
		}

		const ControlInfoMap *infoMap = iter->first;
		idMap = &infoMap->idmap();
	} else {
		switch (hdr->id_map_type) {
		case IPA_CONTROL_ID_MAP_CONTROLS:
			idMap = &controls::controls;
			break;

		case IPA_CONTROL_ID_MAP_PROPERTIES:
			idMap = &properties::properties;
			break;

		case IPA_CONTROL_ID_MAP_V4L2:
		default:
			LOG(Serializer, Fatal)
				<< "A list of V4L2 controls requires an ControlInfoMap";
			return {};
		}
	}

	/*
	 * \todo When available, initialize the list with the ControlInfoMap
	 * so that controls can be validated against their limits.
	 * Currently no validation is performed, so it's fine relying on the
	 * idmap only.
	 */
	ControlList ctrls(*idMap);

	for (unsigned int i = 0; i < hdr->entries; ++i) {
		const struct ipa_control_value_entry *entry =
			entries.read<decltype(*entry)>();
		if (!entry) {
			LOG(Serializer, Error) << "Out of data";
			return {};
		}

		if (entry->offset != values.offset()) {
			LOG(Serializer, Error)
				<< "Bad data, entry offset mismatch (entry "
				<< i << ")";
			return {};
		}

		ctrls.set(entry->id,
			  loadControlValue(values, entry->is_array, entry->count));
	}

	return ctrls;
}

/**
 * \brief Check if a ControlInfoMap is cached
 * \param[in] infoMap The ControlInfoMap to check
 *
 * The ControlSerializer caches all ControlInfoMaps that it has (de)serialized.
 * This function checks if \a infoMap is in the cache.
 *
 * \return True if \a infoMap is in the cache or false otherwise
 */
bool ControlSerializer::isCached(const ControlInfoMap &infoMap)
{
	return infoMapHandles_.count(&infoMap);
}

} /* namespace libcamera */