This preserves the existing behavior of the method but changes the implementation to use #read_storage_controllers. The caps that call a mix of #get_port_and_device and #read_storage_controllers may be a candidate for further refactoring, but this makes sure that we're fetching storage attachments consistently.
Vagrant Core Plugins
These are plugins that ship with Vagrant. Vagrant core uses its own plugin system to power a lot of the core pieces that ship with Vagrant. Each plugin will have its own README which explains its specific role.