Re: [REGRESSION] RTL8761BU 0bda:a728: removing BROKEN_EXT_SCAN fixes 0x200c timeout

[Thorsten Leemhuis <regressions@leemhuis.info>]

Lo!

On 9/18/26 11:21, Andy Tsvetinskiy wrote:
> 
>    This report concerns USB ID 0bda:a728, not 0bda:8771.
> 
>    I have a Realtek RTL8761BUV USB Bluetooth adapter:
> 
>    - USB ID: 0bda:a728
>    - Product: Bluetooth 5.4 Radio
>    - Firmware: rtl_bt/rtl8761bu_fw.bin
>    - Firmware version: 0xdfc6d922
>    - Running kernel: 6.18.51-1-lts
>    - Distribution: Arch Linux
> 
>    With the stock btusb driver, Bluetooth repeatedly failed with:
> 
>        Bluetooth: hci0: command 0x200c tx timeout
>        Bluetooth: hci0: Opcode 0x200c failed: -110
>        Bluetooth: hci0: Unable to disable scanning: -110
>        Bluetooth: hci0: Resetting usb device.
>        usb 1-2.2: reset full-speed USB device
>        Bluetooth: hci0: unexpected event for opcode 0x200c

Thx for the report. Just replying to bring a few people into the loop
that can help handling this: the Blutooth maintainers and developers
which were involved in ca0583c2466174 ("Bluetooth: btusb: limit RTL8761B
BROKEN_EXT_SCAN quirk to 0bda:a728") [v7.3-rc1] and 5ead2063611ae5
("Bluetooth: btrtl: fix RTL8761B/BU broken LE extended scan")
[v7.2-rc1]. Ciao, Thorsten

>    The firmware was loaded successfully:
> 
>        Bluetooth: hci0: RTL: loading rtl_bt/rtl8761bu_fw.bin
>        Bluetooth: hci0: RTL: loading rtl_bt/rtl8761bu_config.bin
>        Bluetooth: hci0: RTL: fw version 0xdfc6d922
> 
>    The USB autosuspend setting was not the cause:
> 
>        /sys/bus/usb/devices/1-2.2/power/autosuspend: -1
> 
>    The current upstream fix ca0583c24661
>    ("Bluetooth: btusb: limit RTL8761B BROKEN_EXT_SCAN quirk to 0bda:a728")
>    is already present in my kernel. It sets BTUSB_BROKEN_EXT_SCAN for 0bda:a728.
> 
>    I tested the opposite change locally in drivers/bluetooth/btusb.c:
> 
>        - { USB_DEVICE(0x0bda, 0xa728), .driver_info = BTUSB_REALTEK |
>        -                    BTUSB_BROKEN_EXT_SCAN },
>        + { USB_DEVICE(0x0bda, 0xa728), .driver_info = BTUSB_REALTEK },
> 
>    After rebuilding and reloading the btusb module:
> 
>        systemctl stop bluetooth
>        modprobe -r btusb
>        modprobe btusb
>        systemctl start bluetooth
> 
>    Bluetooth scanning worked normally. A 20-second scan completed with:
> 
>        Discovery started
>        Discovering: yes
> 
>    After loading the patched module, no new occurrences of the
> following messages appeared:
> 
>        Opcode 0x200c failed: -110
>        Opcode 0x2042 failed
>        command tx timeout
>        Unable to disable scanning
>        Resetting usb device
> 
>    The patched driver is currently loaded and Bluetooth remains operational.
> 
>    This suggests that different RTL8761BUV devices or firmware
> revisions using USB ID 0bda:a728 may require different scan quirks. On
> my device, keeping BTUSB_BROKEN_EXT_SCAN causes the legacy 0x200c
> command to
>  time out, while removing the quirk fixes the issue.
> 
>    Relevant upstream reports:
> 
>    https://linux-regtracking.leemhuis.info/regzbot/regression/lore/20260822141115.58815-1-kserwus@gmail.com/
> 
>    https://bugzilla.redhat.com/show_bug.cgi?id=2521504
> 
>    https://lkml.iu.edu/2608.2/12212.html
> 
>    Please let me know if more logs, a full patch, or additional
> testing is needed.
>