Detect what driver is loaded for a UART connected chip?

Question

I'm trying to detect what driver is responsible for providing the HCI interface for the Raspberry Pi 3 Bluetooth module.

Here is an equivalent of what I'd like to achieve but for a USB dongle.

user@lime:~$ hciconfig 
hci0:   Type: BR/EDR  Bus: USB
    BD Address: 00:1A:7D:DA:71:13  ACL MTU: 310:10  SCO MTU: 64:8
    UP RUNNING 
    RX bytes:616 acl:0 sco:0 events:37 errors:0
    TX bytes:977 acl:0 sco:0 commands:37 errors:0

Because of Bus: USB i know it's a usb device.

user@lime:~$ lsusb 
Bus 004 Device 002: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

The dongle is: Bus 004 Device 002: ID 0a12:0001 Cambridge Silicon Radio...

user@lime:~$ lsusb -t
/:  Bus 05.Port 1: Dev 1, Class=root_hub, Driver=musb-hdrc/1p, 480M
/:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=ohci-platform/1p, 12M
    |__ Port 1: Dev 2, If 0, Class=Wireless, Driver=btusb, 12M
    |__ Port 1: Dev 2, If 1, Class=Wireless, Driver=btusb, 12M

Based on the port (4) and device (2) I see that the driver used is btusb.

Applying the same procedure for the UART connected chip on the RPi3.

Running hciconfig results in:

$ hciconfig 
hci0:   Type: BR/EDR  Bus: UART
    BD Address: B8:27:EB:E7:80:CE  ACL MTU: 1021:8  SCO MTU: 64:1
    UP RUNNING 
    RX bytes:717 acl:0 sco:0 events:42 errors:0
    TX bytes:1532 acl:0 sco:0 commands:42 errors:0

The Bus: UART confirms it's a UART connected device.

How do I find the driver in use?

Answer 1

You might get some clues from lsmod:

$ lsmod
Module                  Size  Used by
bnep                   12310  2 
hci_uart               22713  1 
btbcm                   8478  1 hci_uart
bluetooth             425568  22 bnep,btbcm,hci_uart
...

In this example, on a raspberry pi 3, perhaps you want btbcm?

Answer 2

usb-devices | egrep '0a12' -A7 | grep -i driver