[v18,01/12] config: Introduce global runtime configuration

24352 diff mbox series

diff --git a/include/libcamera/internal/global_configuration.h b/include/libcamera/internal/global_configuration.h
new file mode 100644
index 000000000..f695498c4
--- /dev/null
+++ b/include/libcamera/internal/global_configuration.h
@@ -0,0 +1,34 @@ 
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024-2025 Red Hat, inc.
+ *
+ * Global configuration handling
+ */
+
+#pragma once
+
+#include <filesystem>
+
+#include "libcamera/internal/yaml_parser.h"
+
+namespace libcamera {
+
+class GlobalConfiguration
+{
+public:
+	using Configuration = const YamlObject &;
+
+	GlobalConfiguration();
+
+	unsigned int version() const;
+	Configuration configuration() const;
+
+private:
+	bool loadFile(const std::filesystem::path &fileName);
+	void load();
+
+	std::unique_ptr<YamlObject> yamlConfiguration_ =
+		std::make_unique<YamlObject>();
+};
+
+} /* namespace libcamera */
diff --git a/include/libcamera/internal/meson.build b/include/libcamera/internal/meson.build
index 5c80a28c4..45c299f6a 100644
--- a/include/libcamera/internal/meson.build
+++ b/include/libcamera/internal/meson.build
@@ -23,6 +23,7 @@  libcamera_internal_headers = files([
     'dma_buf_allocator.h',
     'formats.h',
     'framebuffer.h',
+    'global_configuration.h',
     'ipa_data_serializer.h',
     'ipa_manager.h',
     'ipa_module.h',
diff --git a/src/libcamera/global_configuration.cpp b/src/libcamera/global_configuration.cpp
new file mode 100644
index 000000000..d02668111
--- /dev/null
+++ b/src/libcamera/global_configuration.cpp
@@ -0,0 +1,148 @@ 
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024-2025 Red Hat, inc.
+ *
+ * Global configuration handling
+ */
+
+#include "libcamera/internal/global_configuration.h"
+
+#include <filesystem>
+#include <string_view>
+#include <sys/types.h>
+
+#include <libcamera/base/file.h>
+#include <libcamera/base/log.h>
+#include <libcamera/base/utils.h>
+
+#include "libcamera/internal/yaml_parser.h"
+
+namespace libcamera {
+
+namespace {
+const std::vector<std::filesystem::path> globalConfigurationFiles = {
+	std::filesystem::path(LIBCAMERA_SYSCONF_DIR) / "configuration.yaml",
+	std::filesystem::path(LIBCAMERA_DATA_DIR) / "configuration.yaml",
+};
+}
+
+LOG_DEFINE_CATEGORY(Configuration)
+
+/**
+ * \class GlobalConfiguration
+ * \brief Support for global libcamera configuration
+ *
+ * The configuration file is a YAML file and the configuration itself is stored
+ * under `configuration' top-level item.
+ *
+ * The configuration file is looked up in user's home directory first and if it
+ * is not found then in system-wide configuration directories. If multiple
+ * configuration files exist then only the first one found is used and no
+ * configuration merging is performed.
+ *
+ * If the first found configuration file cannot be opened or parsed, an error is
+ * reported and no configuration file is used. This is to prevent libcamera from
+ * using an unintended configuration file.
+ */
+
+bool GlobalConfiguration::loadFile(const std::filesystem::path &fileName)
+{
+	File file(fileName);
+	if (!file.open(File::OpenModeFlag::ReadOnly)) {
+		if (file.error() == -ENOENT)
+			return false;
+
+		LOG(Configuration, Error)
+			<< "Failed to open configuration file " << fileName;
+		return true;
+	}
+
+	std::unique_ptr<YamlObject> configuration = YamlParser::parse(file);
+	if (!configuration) {
+		LOG(Configuration, Error)
+			<< "Failed to parse configuration file " << fileName;
+		return true;
+	}
+
+	yamlConfiguration_ = std::move(configuration);
+	return true;
+}
+
+void GlobalConfiguration::load()
+{
+	std::filesystem::path userConfigurationDirectory;
+	const char *xdgConfigHome = utils::secure_getenv("XDG_CONFIG_HOME");
+	if (xdgConfigHome) {
+		userConfigurationDirectory = xdgConfigHome;
+	} else {
+		const char *home = utils::secure_getenv("HOME");
+		if (home)
+			userConfigurationDirectory =
+				std::filesystem::path(home) / ".config";
+	}
+
+	if (!userConfigurationDirectory.empty()) {
+		std::filesystem::path user_configuration_file =
+			userConfigurationDirectory / "libcamera" / "configuration.yaml";
+		if (loadFile(user_configuration_file))
+			return;
+	}
+
+	for (const auto &path : globalConfigurationFiles) {
+		if (loadFile(path))
+			return;
+	}
+}
+
+/**
+ * \brief Initialize the global configuration
+ */
+GlobalConfiguration::GlobalConfiguration()
+{
+	load();
+}
+
+/**
+ * \typedef GlobalConfiguration::Configuration
+ * \brief Type representing global libcamera configuration
+ *
+ * All code outside GlobalConfiguration must use this type declaration and not
+ * the underlying type.
+ */
+
+/**
+ * \brief Return configuration version
+ *
+ * The version is (optionally) declared in the configuration file in the
+ * top-level section `version', alongside `configuration'. This has currently no
+ * real use but may be needed in future if configuration incompatibilities
+ * occur.
+ *
+ * \return Configuration version as declared in the configuration file or 0 if
+ * no version is declared there
+ */
+unsigned int GlobalConfiguration::version() const
+{
+	return (*yamlConfiguration_)["version"].get<unsigned int>().value_or(0);
+}
+
+/**
+ * \brief Return libcamera global configuration
+ *
+ * This returns the whole configuration stored in the top-level section
+ * `configuration' of the YAML configuration file.
+ *
+ * The requested part of the configuration can be accessed using \a YamlObject
+ * methods.
+ *
+ * \note \a YamlObject type itself shouldn't be used in type declarations to
+ * avoid trouble if we decide to change the underlying data objects in future.
+ *
+ * \return The whole configuration section
+ */
+GlobalConfiguration::Configuration GlobalConfiguration::configuration() const
+{
+	return (*yamlConfiguration_)["configuration"];
+}
+
+} /* namespace libcamera */
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index b3ca27f21..5b9b86f21 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -31,6 +31,7 @@  libcamera_internal_sources = files([
     'device_enumerator_sysfs.cpp',
     'dma_buf_allocator.cpp',
     'formats.cpp',
+    'global_configuration.cpp',
     'ipa_controls.cpp',
     'ipa_data_serializer.cpp',
     'ipa_interface.cpp',