This crate is a provides the vendor-specific Bluetooth HCI for STMicro's BlueNRG family of Bluetooth RF modules. It extends bluetooth-hci with vendor-specific commands and events (and associated errors).
This crate supports both the older BlueNRG version of the HCI, and the newer BlueNRG-MS version. By default, the crate implements BlueNRG-MS.
As you will notice, documentation is woefully lacking. This is still (as of April 2018) actively developed, so more is on the way!