Fix Bluetooth on RTL8761B (Kernel 6+)

Properties1
tagsops, linux, bluetooth, drivers

1 min read

Some Bluetooth 5.0 adapters using the RTL8761B chipset fail to load their driver on Ubuntu 20.04/22.04 (and other distros) — not because the firmware is missing, but because the kernel asks for the wrong filename.

Diagnose

Plug in the adapter and check dmesg for a firmware load failure:

sudo dmesg | grep bluetooth

A failing device shows something like:

bluetooth hci0: loading /lib/firmware/rtl_bt/rtl8761bu_config.bin failed with error -40
bluetooth hci0: Direct firmware load for rtl_bt/rtl8761bu_config.bin failed with error -40

The driver requests the rtl8761bu (USB) firmware files, but the system only ships the rtl8761b (non-u) ones — so the load fails even though a compatible firmware is already present.

Fix

Symlink the missing rtl8761bu filenames to the rtl8761b files that already exist in /lib/firmware/rtl_bt. No package install or download needed. After creating the links, unplug and replug the adapter — no reboot required.

Reference: fosspost.org — Fix Bluetooth RTL8761B on Ubuntu 22.04

Cheatsheet

Diagnose

sudo dmesg | grep bluetooth

Fix

cd /lib/firmware/rtl_bt
sudo ln -s rtl8761b_config.bin rtl8761bu_config.bin
sudo ln -s rtl8761b_fw.bin rtl8761bu_fw.bin

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