So this is now handled with the new bluetoothctl tool. A gatt table can be set up using this tool as follows:-
#bluetoothctl
[bluetoothctl] menu gatt
[bluetoothctl] register-service 0xFFFF # (Choose yes when asked if primary service)
[bluetoothctl] register-characteristic 0xAAAA read # (Select a value of 1 when prompted)
[bluetoothctl] register-characteristic 0xBBBB read,write # (Select a value of 0 when prompted)
[bluetoothctl] register-characteristic 0xCCCC read # (Select a value of 2 when prompted)
[bluetoothctl] register-application # (This commits the services/characteristics and registers the profile)
[bluetoothctl] back
[bluetoothctl] advertise on
I’ve tried this with a few service/characteristic combinations and was able to get it to work. The GAP (0x1800) and GATT (0x1801) services are available by default and will be part of the GATT table when you advertise. You can also use the following command to see the available services:-
[bluetoothctl] show
Controller 00:AA:BB:CC:DD:EE (public)
Name: MyMachine
Alias: MyMachine
Class: 0x000c0000
Powered: yes
Discoverable: no
Pairable: yes
UUID: Headset AG (00001112-0000-1000-8000-00805f9b34fb)
UUID: Generic Attribute Profile (00001801-0000-1000-8000-00805f9b34fb)
UUID: A/V Remote Control (0000110e-0000-1000-8000-00805f9b34fb)
UUID: Generic Access Profile (00001800-0000-1000-8000-00805f9b34fb)
UUID: PnP Information (00001200-0000-1000-8000-00805f9b34fb)
UUID: A/V Remote Control Target (0000110c-0000-1000-8000-00805f9b34fb)
UUID: Audio Source (0000110a-0000-1000-8000-00805f9b34fb)
UUID: Audio Sink (0000110b-0000-1000-8000-00805f9b34fb)
**UUID: Unknown (0000ffff-0000-1000-8000-00805f9b34fb)**
UUID: Headset (00001108-0000-1000-8000-00805f9b34fb)
Modalias: usb:v1D6Bp0246d0532
Discovering: no