Configuration option types — WirePlumber 0.5.10 documentation

# Configuration option types

As seen in the previous sections, WirePlumber can be partly configured by enabling or disabling features, which affect which components are getting loaded. These components, however, can be further configured to fine-tune their behavior. This section describes the different types of configuration options that can be used to configure WirePlumber components.

## Dynamic options (“Settings”)

Dynamic options (also simply referred to as “settings”) are configuration options that can be changed at runtime. They are typically simple values like booleans, integers, strings, etc. and are all located under the `wireplumber.settings` section in the configuration file. Their purpose is to allow the user to change simple behavioral aspects of WirePlumber.

As the name suggests, these options are dynamic and can be changed at runtime using `wpctl` or the Settings API. For example, setting the `device.routes.default-sink-volume` setting to `0.5` can be done like this:

    $ wpctl settings device.routes.default-sink-volume 0.5

Under the hood, when WirePlumber starts, the `metadata.sm-settings` component (provided by `libwireplumber-module-settings`) reads this section from the configuration file and populates the `sm-settings` metadata object, which is exported to PipeWire. In addition, it reads the `wireplumber.settings.schema` section and populates the `schema-sm-settings` metadata object, which is used by the API to validate the settings. Any options that are missing from `wireplumber.settings` are also populated in `sm-settings` from their default values in the schema. Then the rest of the components read their configuration options from this metadata object via the Settings API.

Most of the components that use such dynamic options make sure to listen to changes in the metadata object so that they can immediately adapt their behavior. Other components, however, do not react immediately and the changes only take effect the next time the option is needed. For instance, some options affect created objects in a way that cannot be changed after the object has been created, so when the option is changed it applies only to new objects and not existing ones.

Changing the settings at runtime in the `sm-settings` metadata object is a non-persistent change. The changes will be lost when WirePlumber is restarted. However, the Settings API also supports saving settings to a state file, which will be loaded again when WirePlumber starts and override the settings from the configuration file. This is done by using yet another metadata object called `persistent-sm-settings`. When a setting is changed in the `persistent-sm-settings` metadata object, WirePlumber automatically saves the change to the state file and also changes the value in the `sm-settings` metadata object immediately.

To make such a persistent change using `wpctl`, the `--save` option can be used. For example, to set the `device.routes.default-sink-volume` setting to `0.5` and save it to the state file:

    $ wpctl settings --save device.routes.default-sink-volume 0.5

With `wpctl`, it is also possible to restore a setting to its default value (taken from the schema), by using the `--reset` option. For example, to reset the `device.routes.default-sink-volume` setting, the following command can be used:

    $ wpctl settings --reset device.routes.default-sink-volume

In addition, the `--delete` option can be used to delete a setting from the `persistent-sm-settings` metadata object, which will also remove it from the state file. After deleting, the value from the `wireplumber.settings` section of the configuration file will be used again. For example, to delete the `device.routes.default-sink-volume` setting, the following command can be used:

    $ wpctl settings --delete device.routes.default-sink-volume

A list of all the available settings can be found in the Well-known settings section.

## Static options

Static options are more complex configuration structures that reside only in the configuration file and cannot be changed at runtime. They are typically used to configure device monitors and provide rules that match objects and perform actions such as update their properties.

While these options could also in theory be stored in the metadata object and be made dynamic, this is not supported because these options are both complex and therefore hard to change on the command line, but also because they are typically used to configure objects that are created at startup and cannot be changed later.

Static options are located in their own top-level sections. Examples of such sections are `monitor.alsa.properties` and `monitor.alsa.rules` that are used to configure the `monitor.alsa` component. The next sections of this documentation describe in detail all the available static options.

### Component arguments

Components can also be configured statically by passing arguments to them when they are loaded. This is done by adding an `arguments` key to the component description in the `wireplumber.components` section (see Components & Profiles).

The arguments are mostly meant as a way to instantiate multiple instances of the same module or script with slightly different configuration to create a new unique component. For example, the `metadata.lua` script can be instantiated multiple times to create multiple metadata objects, each with a different name. The name of the metadata object is passed as an argument to the script.

While many more static options could be passed as arguments, this is not recommended because it is not possible to override the arguments by adding fragment configuration files. Therefore, it is recommended to use component-specific top-level sections, unless the option is not meant to be changed by the user.