Comment 9 for bug 1491988

Please note that the kernel subsystem performs various initialization steps for each HCI controller. Depending on if a controller passes this it gets up in bluetoothd or not. If a HCI controller is still flagged with HCI_SETUP or HCI_CONFIG then something is wrong. Even if the controller turns up in hciconfig that doesn't mean it is usable through the MGMT kernel interface which is used by bluetoothd today.

If you're debugging this in the kernel look at __hci_init in net/bluetooth/hci_core.c and verify all HCI commands are sent correctly and no one gets an error. You can also log those HCI packages send across the wire with hcidump and analyze the output with wireshark.

Could you also please note which types of BT modules you're using?

Also as you changed the summary it's now pretty unclear to a new person reading this what the actual problem is ...