Display events can originate from many different source types. Since the HNM may not know the form of those sources in advance, it exposes a plugin framework to allow new event sources to be added.

Plugins are DLLs (shared objects) that must register with the HNM subsystem via the hnm_register_module() function. Plugins are loaded via the policy.cfg file (see "Configuration" for details.)

You'll find the following plugins on your system under the /lib/dll/hmi-notification/ directory:
Plugin Filename Description
Generic Provides a generic PPS interface that allows applications to use the HNM policy-management facilities without implementing a custom plugin. This plugin can also be used for automated testing.
HandsFreePhone Generates display events to notify subscribing HMI applications so they can handle incoming handsfree phone calls.
VirtualMechanic Notifies the HNM of caution and alert conditions for relevant vehicle systems.

The following sections in this chapter cover each of these plugins.