[v17,11/12] config: Make configuration file locations configurable

24318 diff mbox series

To support easy switching of configurations, let's introduce
LIBCAMERA_CONFIG_DIR and LIBCAMERA_CONFIG_NAME environment variables.

LIBCAMERA_CONFIG_DIR environment variable specifies a directory or a
list of directories separated by colons where to look for the libcamera
configuration file before trying the standard locations.  This override
can be useful in a meson devenv.

LIBCAMERA_CONFIG_NAME
- specifies the path of the configuration file to load if it is an
  absolute path (useful to quickly try some configuration); or
- prevents any configuration file from loading if it is defined and
  empty (useful to disable all configuration files); or
- specifies the path of the configuration file to load, relative to
  the configuration directories (useful to quickly select between
  different configurations).

If a configuration file specified by those environment variables doesn't
exist, no custom configuration is loaded.

Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
---
 Documentation/runtime_configuration.rst | 13 +++++++
 src/libcamera/global_configuration.cpp  | 50 +++++++++++++++++--------
 2 files changed, 47 insertions(+), 16 deletions(-)

Hi Milan,

Thanks for the patch.

Quoting Milan Zamazal (2025-09-11 18:29:41)
> To support easy switching of configurations, let's introduce
> LIBCAMERA_CONFIG_DIR and LIBCAMERA_CONFIG_NAME environment variables.
> 
> LIBCAMERA_CONFIG_DIR environment variable specifies a directory or a
> list of directories separated by colons where to look for the libcamera
> configuration file before trying the standard locations.  This override
> can be useful in a meson devenv.
> 
> LIBCAMERA_CONFIG_NAME
> - specifies the path of the configuration file to load if it is an
>   absolute path (useful to quickly try some configuration); or
> - prevents any configuration file from loading if it is defined and
>   empty (useful to disable all configuration files); or
> - specifies the path of the configuration file to load, relative to
>   the configuration directories (useful to quickly select between
>   different configurations).
> 
> If a configuration file specified by those environment variables doesn't
> exist, no custom configuration is loaded.

I assume you mean that in this scenario no configuration file is loaded at all,
so s/custom// is clearer.

With that, looks good to me.

Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>

> 
> Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
> ---
>  Documentation/runtime_configuration.rst | 13 +++++++
>  src/libcamera/global_configuration.cpp  | 50 +++++++++++++++++--------
>  2 files changed, 47 insertions(+), 16 deletions(-)
> 
> diff --git a/Documentation/runtime_configuration.rst b/Documentation/runtime_configuration.rst
> index 702139544..5307f3645 100644
> --- a/Documentation/runtime_configuration.rst
> +++ b/Documentation/runtime_configuration.rst
> @@ -19,6 +19,19 @@ order:
>  - LIBCAMERA_SYSCONF_DIR/configuration.yaml
>  - LIBCAMERA_DATA_DIR/libcamera/configuration.yaml
>  
> +If LIBCAMERA_CONFIG_DIR environment variable is non-empty then it
> +specifies additional directories where to look for the configuration
> +file, before looking at the standard locations. It can be a single
> +directory or multiple directories separated by colons.
> +
> +The default name of the configuration file, configuration.yaml, can be
> +overridden in LIBCAMERA_CONFIG_NAME environment variable. The variable
> +can specify just an alternative configuration file name to be looked up
> +in the locations above, or a whole absolute path. If an absolute path is
> +specified then it is the only location that is used; if the given file
> +doesn't exist then no configuration file is read. If the variable is
> +defined but empty, no configuration is loaded.
> +
>  The first configuration file found wins, configuration files in other
>  locations are ignored.
>  
> diff --git a/src/libcamera/global_configuration.cpp b/src/libcamera/global_configuration.cpp
> index 592edcf30..8c2670e03 100644
> --- a/src/libcamera/global_configuration.cpp
> +++ b/src/libcamera/global_configuration.cpp
> @@ -23,13 +23,6 @@
>  
>  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)
>  
>  /**
> @@ -80,6 +73,33 @@ bool GlobalConfiguration::loadFile(const std::filesystem::path &fileName)
>  
>  void GlobalConfiguration::load()
>  {
> +       const char *libcameraConfigName =
> +               utils::secure_getenv("LIBCAMERA_CONFIG_NAME");
> +       if (libcameraConfigName && libcameraConfigName[0] == '\0')
> +               return;
> +       if (!libcameraConfigName)
> +               libcameraConfigName = "";
> +
> +       std::filesystem::path configName(libcameraConfigName);
> +
> +       if (configName.is_absolute()) {
> +               loadFile(configName);
> +               return;
> +       }
> +
> +       if (configName.empty())
> +               configName = std::filesystem::path("configuration.yaml");
> +
> +       std::vector<std::filesystem::path> configurationDirectories;
> +
> +       const char *configDir = utils::secure_getenv("LIBCAMERA_CONFIG_DIR");
> +       if (configDir) {
> +               for (auto const &path : utils::split(configDir, ":")) {
> +                       if (!path.empty())
> +                               configurationDirectories.push_back(path);
> +               }
> +       }
> +
>         std::filesystem::path userConfigurationDirectory;
>         const char *xdgConfigHome = utils::secure_getenv("XDG_CONFIG_HOME");
>         if (xdgConfigHome) {
> @@ -90,18 +110,16 @@ void GlobalConfiguration::load()
>                         userConfigurationDirectory =
>                                 std::filesystem::path(home) / ".config";
>         }
> +       if (!userConfigurationDirectory.empty())
> +               configurationDirectories.push_back(
> +                       userConfigurationDirectory / "libcamera");
>  
> -       if (!userConfigurationDirectory.empty()) {
> -               std::filesystem::path user_configuration_file =
> -                       userConfigurationDirectory / "libcamera" / "configuration.yaml";
> -               if (loadFile(user_configuration_file))
> -                       return;
> -       }
> +       configurationDirectories.push_back(LIBCAMERA_SYSCONF_DIR);
> +       configurationDirectories.push_back(LIBCAMERA_DATA_DIR);
>  
> -       for (const auto &path : globalConfigurationFiles) {
> -               if (loadFile(path))
> +       for (const auto &path : configurationDirectories)
> +               if (loadFile(path / configName))
>                         return;
> -       }
>  }
>  
>  /**
> -- 
> 2.51.0
>