[PATCH v3 01/14] config: Introduce global runtime configuration
Milan Zamazal
mzamazal at redhat.com
Thu Jun 27 16:51:38 CEST 2024
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 compile in multiple pipelines, in order to have
them accessible within single packages in distributions. And then being
able to select among the pipelines manually as needed based on the
particular hardware or operating system environment. Having the
configuration file then allows easy switching between hardware, GPU or
CPU 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. The configuration file can also
be used to enable or disable experimental features and avoid the need to
track local patches changing configuration options hard-wired in the
code when working on new features.
This patch introduces basic support for configuration files.
GlobalConfiguration class reads, stores and accesses the configuration.
Its instance is stored as a private singleton accessed using a static
method of the class. There is currently no reason to have more than one
instance.
libcamera configuration can be specified using a system-wide
configuration file or a user configuration file. The user configuration
file takes 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 related to configuration file lookup).
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 while retaining (most of) the original 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.
Signed-off-by: Milan Zamazal <mzamazal at redhat.com>
---
.../libcamera/internal/global_configuration.h | 38 ++++
include/libcamera/internal/meson.build | 1 +
src/libcamera/global_configuration.cpp | 163 ++++++++++++++++++
src/libcamera/meson.build | 1 +
4 files changed, 203 insertions(+)
create mode 100644 include/libcamera/internal/global_configuration.h
create mode 100644 src/libcamera/global_configuration.cpp
diff --git a/include/libcamera/internal/global_configuration.h b/include/libcamera/internal/global_configuration.h
new file mode 100644
index 00000000..2f38056a
--- /dev/null
+++ b/include/libcamera/internal/global_configuration.h
@@ -0,0 +1,38 @@
+/* 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:
+ 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 9713ea1c..daab7150 100644
--- a/include/libcamera/internal/meson.build
+++ b/include/libcamera/internal/meson.build
@@ -28,6 +28,7 @@ libcamera_internal_headers = files([
'dma_buf_allocator.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..96088b36
--- /dev/null
+++ b/src/libcamera/global_configuration.cpp
@@ -0,0 +1,163 @@
+/* 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 <filesystem>
+#include <memory>
+#include <stdint.h>
+#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 {
+
+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.
+ *
+ * The class is used as a private singleton and the configuration can be
+ * accessed usingGlobalConfiguration::configuration().
+ */
+
+/**
+ * \typedef GlobalConfiguration::Configuration
+ * \brief Type representing global libcamera configuration
+ *
+ * All code outside GlobalConfiguration must use this type declaration and not
+ * the underlying type.
+ */
+
+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
+ *
+ * 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()
+{
+ return get()["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()
+{
+ return get()["configuration"];
+}
+
+} /* namespace libcamera */
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index 89504cee..32396ff2 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',
--
2.44.1
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