[RFC,01/11] config: Introduce global runtime configuration
diff mbox series

Message ID 20240326112419.503286-2-mzamazal@redhat.com
State Superseded
Headers show
Series
  • Add global configuration file
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Commit Message

Milan Zamazal March 26, 2024, 11:24 a.m. UTC
Currently, libcamera can be configured in runtime using several environment
variables.  With introducing more and more variables, this mechanism reaches its
limits.  It would be simpler and more flexible if it was possible to configure
libcamera in a single file.

For example, there have been a request for defining pipeline precedence in
runtime.  We want to have support for multiple pipelines compiled in order to
have single packages in distributions.  And then being able to select among them
as needed based on the particular hardware or operating system environment.
This can for example allow easy switching between hardware, CPU or GPU IPAs.
Another possible use case is tuning image output, especially with software ISP,
to user liking.  For example, some users may prefer higher contrast without the
need to use the corresponding knobs, if present at all, in every application.

This patch introduces basic support for configuration files.
GlobalConfiguration class reads, stores and adds access to the configuration.
Its instance is stored as a singleton and be accessed using a static method of
the class.

libcamera configuration can be specified using a system-wide configuration file
or a user configuration file.  The user configuration file take precedence if
present.  There is currently no way to merge multiple configuration files, the
one found is used as the only configuration file.  If no configuration file is
present, nothing changes to the current libcamera behavior (except for some log messages).

The configuration file is a YAML file, we already have a mechanism for handling
YAML configuration files in libcamera and the given infrastructure can be reused
for the purpose.  However, the configuration type is abstracted to make
contingent future change of the underlying class easier, if retaining (most of)
its API.

The configuration is versioned.  This has currently no particular meaning but is
likely to have its purpose in future, especially once configuration validation
is introduced.

The configuration YAML file looks as follows:

  ---
  version: 1
  configuration:
    WHATEVER CONFIGURATION NEEDED

This patch introduces just the basic idea.  Actually using the configuration in
the corresponding places (everything what is currently configurable via
environment variables should be configurable in the file configuration),
refining the mechanism (e.g. configuration file validation to avoid mistakes
caused by typos) and other improvements will be addressed in followup patches.

GlobalConfiguration is meant to be used as a globally accessible singleton.
There is currently no reason to have more than one instance.

Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
---
 .../libcamera/internal/global_configuration.h |  44 ++++++
 include/libcamera/internal/meson.build        |   1 +
 src/libcamera/global_configuration.cpp        | 132 ++++++++++++++++++
 src/libcamera/meson.build                     |   1 +
 4 files changed, 178 insertions(+)
 create mode 100644 include/libcamera/internal/global_configuration.h
 create mode 100644 src/libcamera/global_configuration.cpp

Patch
diff mbox series

diff --git a/include/libcamera/internal/global_configuration.h b/include/libcamera/internal/global_configuration.h
new file mode 100644
index 00000000..0a4f3c02
--- /dev/null
+++ b/include/libcamera/internal/global_configuration.h
@@ -0,0 +1,44 @@ 
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024 Red Hat, inc.
+ *
+ * global_configuration.h - Global configuration handling
+ */
+
+#pragma once
+
+#include <filesystem>
+#include <vector>
+
+#include "libcamera/internal/yaml_parser.h"
+
+namespace libcamera {
+
+class GlobalConfiguration
+{
+public:
+	/**
+	 * \brief Type representing global libcamera configuration.
+	 *
+	 * All code outside GlobalConfiguration must use this type and not the
+	 * underlying type.
+	 */
+	using Configuration = const YamlObject &;
+
+	static unsigned int version();
+	static Configuration configuration();
+
+private:
+	static const std::vector<std::filesystem::path> globalConfigurationFiles;
+
+	bool initialized_;
+	std::unique_ptr<YamlObject> configuration_;
+
+	GlobalConfiguration();
+	bool loadFile(const std::filesystem::path &fileName);
+	void load();
+	static const GlobalConfiguration &instance();
+	static Configuration get();
+};
+
+} /* namespace libcamera */
diff --git a/include/libcamera/internal/meson.build b/include/libcamera/internal/meson.build
index 160fdc37..640a54aa 100644
--- a/include/libcamera/internal/meson.build
+++ b/include/libcamera/internal/meson.build
@@ -28,6 +28,7 @@  libcamera_internal_headers = files([
     'dma_heaps.h',
     'formats.h',
     'framebuffer.h',
+    'global_configuration.h',
     'ipa_manager.h',
     'ipa_module.h',
     'ipa_proxy.h',
diff --git a/src/libcamera/global_configuration.cpp b/src/libcamera/global_configuration.cpp
new file mode 100644
index 00000000..72c3ce26
--- /dev/null
+++ b/src/libcamera/global_configuration.cpp
@@ -0,0 +1,132 @@ 
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024 Red Hat, inc.
+ *
+ * global_configuration.cpp - Global configuration handling
+ */
+
+#include "libcamera/internal/global_configuration.h"
+
+#include <cstdint>
+#include <filesystem>
+#include <memory>
+#include <sys/types.h>
+
+#include <libcamera/base/file.h>
+#include <libcamera/base/log.h>
+
+#include "libcamera/internal/yaml_parser.h"
+
+#include "libcamera/base/utils.h"
+
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(Configuration)
+
+/**
+ * \class GlobalConfiguration
+ * \brief Support for global libcamera configuration
+ *
+ * ...
+ */
+
+GlobalConfiguration::GlobalConfiguration()
+	: initialized_(false), configuration_(std::make_unique<YamlObject>())
+{
+}
+
+const std::vector<std::filesystem::path>
+	GlobalConfiguration::globalConfigurationFiles = {
+		std::filesystem::path(LIBCAMERA_SYSCONF_DIR) / "configuration.yaml",
+		std::filesystem::path("/etc/libcamera/configuration.yaml"),
+	};
+
+void GlobalConfiguration::load()
+{
+	std::filesystem::path userConfigurationDirectory;
+	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 (auto path : globalConfigurationFiles)
+		if (loadFile(path))
+			return;
+
+	initialized_ = true;
+	LOG(Configuration, Debug) << "No configuration file found";
+}
+
+bool GlobalConfiguration::loadFile(const std::filesystem::path &fileName)
+{
+	File file(fileName);
+	if (!file.exists()) {
+		return false;
+	}
+
+	if (!file.open(File::OpenModeFlag::ReadOnly)) {
+		LOG(Configuration, Warning)
+			<< "Failed to open configuration file '" << fileName << "'";
+		return true;
+	}
+
+	auto root = YamlParser::parse(file);
+	if (!root) {
+		LOG(Configuration, Warning) << "Failed to parse configuration file "
+					    << fileName;
+		return true;
+	}
+	configuration_ = std::move(root);
+	initialized_ = true;
+	LOG(Configuration, Info) << "Configuration file " << fileName << "loaded";
+
+	return true;
+}
+
+const GlobalConfiguration &GlobalConfiguration::instance()
+{
+	static GlobalConfiguration configuration;
+	if (!configuration.initialized_) {
+		configuration.load();
+	}
+	return configuration;
+}
+
+GlobalConfiguration::Configuration GlobalConfiguration::get()
+{
+	return (*instance().configuration_);
+}
+
+/**
+ * \brief Return configuration version.
+ *
+ * ...
+ */
+unsigned int GlobalConfiguration::version()
+{
+	return get()["version"].get<unsigned int>().value_or(0);
+}
+
+/**
+ * \brief Return libcamera global configuration.
+ *
+ * ...
+ */
+GlobalConfiguration::Configuration GlobalConfiguration::configuration()
+{
+	return get()["configuration"];
+}
+
+} /* namespace libcamera */
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index a3b12bc1..b81c75b8 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -21,6 +21,7 @@  libcamera_sources = files([
     'framebuffer.cpp',
     'framebuffer_allocator.cpp',
     'geometry.cpp',
+    'global_configuration.cpp',
     'ipa_controls.cpp',
     'ipa_data_serializer.cpp',
     'ipa_interface.cpp',