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

[Thorsten Leemhuis]

On 9/18/26 15:37, Thorsten Leemhuis wrote:
> 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

Hmm, seems nobody cares, so we need to go the next step: can you please
test if latest mainline (7.3-rc4 or later) is affected to rule out that
it's something specific to the stable series in question?

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@xxxxxxxxx/
>>
>>    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.
>>
>