ALSA project - the C library reference
The hook extension in the ALSA library allows expansion of configuration nodes at run-time. The existence of a hook is determined by the presence of a @hooks compound node.
This example defines a hook which loads two configuration files at the beginning:
snd_config_hook_load()- loads and parses the given configuration files.
snd_config_hook_load_for_all_cards()- loads and parses the given configuration files for each installed sound card. The driver name (the type of the sound card) is passed in the private configuration node.