Bug#1149377: [regression 6.12.y] After backport of 980084de4d9b ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller (requests firmware)

From	Thorsten Leemhuis <regressions@leemhuis.info>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#1149377: [regression 6.12.y] After backport of 980084de4d9b ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller (requests firmware)
Date	2026-10-25 19:10 +0100
Message-ID	<NSaPr-7PzO-177@gated-at.bofh.it> (permalink)
References	<NRnOF-7p0a-9@gated-at.bofh.it> <NRQxj-7ES5-3@gated-at.bofh.it> <NSaPr-7PzO-175@gated-at.bofh.it> <NIKr7-2zfo-7@gated-at.bofh.it> <NSaPr-7PzO-175@gated-at.bofh.it>
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On 10/25/26 07:16, Greg Kroah-Hartman wrote:
> On Sat, Oct 24, 2026 at 04:10:59PM -0400, Sasha Levin wrote:
>>> I did meanwhile and agree, the backports of these should be reverted
>>> from 6.18.y and 6.12.y:
>>>
>>> * 980084de4d9b25 ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek
>>> 8761CU") [v7.3-rc1]
>>> * 6f0624b4427e38 ("Bluetooth: btusb: Add ASUS USB-BT600 for Realtek
>>> 8761CU") [v7.3-rc1]
>>> * 4a23ce935f74d1 ("Bluetooth: btrtl: Add the support for RTL8761CUV")
>>> [v6.19-rc1]
>>
>> The stable trees match mainline here, so nothing is going into stable for
>> this. The fix has to come from the Bluetooth maintainers or Christoph: an
>> upstream revert of the ID commits, or a fallback to the ROM firmware when
>> rtl8761cu_fw.bin is missing. Stable will take either one for 7.2, 6.18 and
>> 6.12 through the normal Cc: stable route once it is in mainline.
>>
>> The other way out is on the distro side. rtl_bt/rtl8761cu_fw.bin has been in
>> linux-firmware since 20251111, so a newer firmware-realtek package fixes this
>> without any kernel change.
> 
> That's the simplest solution, any users hitting this should also upgrade
> that package as it's been out for almost a year now.
Feels wrong to me, as
Documentation/driver-api/firmware/firmware-usage-guidelines.rst says
"Users switching to a newer kernel should *not* have to install newer
firmware files to keep their hardware working.". So what those three
commits did in mainline even there could be considered a
mistake/regression. No worries, mistakes happen. And reverting it now in
mainline would do more damage than good. But overall it feels wrong to
bring that mistake over to older stable series.

Ciao, Thorsten

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Bug#1149377: [regression 6.12.y] After backport of 980084de4d9b ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller (requests firmware) Salvatore Bonaccorso <carnil@debian.org> - 2026-10-03 17:20 +0200
  Processed: [regression 6.12.y] After backport of 980084de4d9b  ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not  anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller  (requests firmware) "Debian Bug Tracking System" <owner@bugs.debian.org> - 2026-10-03 17:20 +0200
  Bug#1149377: [regression 6.12.y] After backport of 980084de4d9b ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller (requests firmware) Sasha Levin <sashal@kernel.org> - 2026-10-04 18:40 +0200
    Bug#1149377: [regression 6.12.y] After backport of 980084de4d9b ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller (requests firmware) Thorsten Leemhuis <regressions@leemhuis.info> - 2026-10-12 17:40 +0200
      Bug#1149377: [regression 6.12.y] After backport of 980084de4d9b ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller (requests firmware) Thorsten Leemhuis <regressions@leemhuis.info> - 2026-10-13 11:10 +0200
        Bug#1149377: [regression 6.12.y] After backport of 980084de4d9b ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller (requests firmware) Thorsten Leemhuis <regressions@leemhuis.info> - 2026-10-23 15:50 +0200
          Bug#1149377: [regression 6.12.y] After backport of 980084de4d9b ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller (requests firmware) Sasha Levin <sashal@kernel.org> - 2026-10-24 22:30 +0200
            Bug#1149377: [regression 6.12.y] After backport of 980084de4d9b ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller (requests firmware) Thorsten Leemhuis <regressions@leemhuis.info> - 2026-10-25 19:10 +0100
              Bug#1149377: [regression 6.12.y] After backport of 980084de4d9b ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller (requests firmware) Sasha Levin <sashal@kernel.org> - 2026-10-26 00:40 +0100
                Bug#1149377: [regression 6.12.y] After backport of 980084de4d9b ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller (requests firmware) Thorsten Leemhuis <regressions@leemhuis.info> - 2026-11-02 12:20 +0100
                Bug#1149377: [regression 6.12.y] After backport of 980084de4d9b ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller (requests firmware) Thorsten Leemhuis <regressions@leemhuis.info> - 2026-11-02 12:20 +0100
            Bug#1149377: [regression 6.12.y] After backport of 980084de4d9b ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller (requests firmware) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2026-10-25 19:10 +0100
              Bug#1149377: [regression 6.12.y] After backport of 980084de4d9b ("Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU") bluethooth not anymore working on 0b05:1bef ASUSTek Computer, Inc. Bluetooth Controller (requests firmware) Thorsten Leemhuis <regressions@leemhuis.info> - 2026-10-25 19:10 +0100

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