Dear Maintainer,

#   * What led up to the situation?
I upgraded to the kernel 6.12.111 on my desktop computer. After the upgrade, bluetooth no longer worked.
#   * What exactly did you do (or not do) that was effective (or
#     ineffective)?

I rebooted the computer and selected the old kernel, 6.12.107, from the boot menu. After booting the old kernel, bluetooth worked again.
#   * What outcome did you expect instead?

I would expect bluetooth to work with the current kernel.

Hi Erik

Yes understandable. It would be great if you could bisect the problem. That would involve
compiling and testing a few kernels

    git clone --single-branch -b linux-6.12.y https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
    cd linux-stable
    git checkout v6.12.107
    cp /boot/config-$(uname -r) .config
    yes '' | make localmodconfig
    make savedefconfig
    mv defconfig arch/x86/configs/my_defconfig

    # test 6.12.107 to ensure this is "good"
    make my_defconfig
    make -j $(nproc) bindeb-pkg
    ... install the resulting .deb package and confirm problem does not exist

    # test 6.12.111 to ensure this is "bad"
    git checkout v6.12.111
    make my_defconfig
    make -j $(nproc) bindeb-pkg
    ... install the resulting .deb package and confirm problem exists

With that confirmed, the bisection can start:

    git bisect start
    git bisect good v6.12.107
    git bisect bad v6.12.111

In each bisection step git checks out a state between the oldest
known-bad and the newest known-good commit. In each step test using:

    make my_defconfig
    make -j $(nproc) bindeb-pkg
    ... install, verify if problem exists

and if the problem is hit run:

    git bisect bad

and if the problem doesn't trigger run:

    git bisect good

. Please pay attention to always select the just built kernel for
booting, it won't always be the default kernel picked up by grub.

Iterate until git announces to have identified the first bad commit.

Then provide the output of

    git bisect log

In the course of the bisection you might have to uninstall previous
kernels again to not exhaust the disk space in /boot. Also in the end
uninstall all self-built kernels again.

Regards,
Salvatore

Hi,

the output of git bisect log is

git bisect start
# status: waiting for both good and bad commits
# bad: [e2acc2211022246c77740d5df08265cc27eedcc5] Linux 6.12.111
git bisect bad e2acc2211022246c77740d5df08265cc27eedcc5
# status: waiting for good commit(s), bad commit known
# good: [f717995cb7dcd8998ab15516b8006aea09cfde0d] Linux 6.12.107
git bisect good f717995cb7dcd8998ab15516b8006aea09cfde0d
# bad: [2e3d827cd56865c14f6ca118bbccd7801091fb21] Bluetooth: hci_sync: free the advertising instance on the failure and cancel paths
git bisect bad 2e3d827cd56865c14f6ca118bbccd7801091fb21
# bad: [ebc41dfc59d190956e0113e8bd90c28f6f21e8b9] scsi: qla2xxx: Bound rsp_info_len to avoid OOB sense-data read
git bisect bad ebc41dfc59d190956e0113e8bd90c28f6f21e8b9
# bad: [af3ce383ba0d0d48957a22ac7058ff5698775898] power: supply: charger-manager: register regulators before exposing sysfs
git bisect bad af3ce383ba0d0d48957a22ac7058ff5698775898
# good: [58bcdfb2b2e412088839ae740b1a95154dc0b8d0] nfsd: clear opcnt on compound arg release to prevent OOB read
git bisect good 58bcdfb2b2e412088839ae740b1a95154dc0b8d0
# bad: [f4fde735a813705875e836e1dea41a93e994c779] Bluetooth: hci_conn: re-enable advertising only for peripheral role
git bisect bad f4fde735a813705875e836e1dea41a93e994c779
# good: [b11a78646c104df205e7eb5903bcce7590396dea] eCryptfs: bound the packet-length peek to the user buffer
git bisect good b11a78646c104df205e7eb5903bcce7590396dea
# good: [2ae970ad5adc254360b25d153956009a7d9ee8a2] ARM: 9477/1: Disable broken eBPF JIT on the Risc PC
git bisect good 2ae970ad5adc254360b25d153956009a7d9ee8a2
# bad: [d66ceeefb87ddb097b0546bafc581380b816b048] dm-era: fix shadowed superblock leak on take-snap failure
git bisect bad d66ceeefb87ddb097b0546bafc581380b816b048
# bad: [32412aff8d11d00672053cb10750869f2de94a1f] Bluetooth: btusb: Add ASUS USB-BT600 for Realtek 8761CU
git bisect bad 32412aff8d11d00672053cb10750869f2de94a1f
# good: [fe7ba73dde94c5f413b1588cd444b49105015dda] auxdisplay: charlcd: cancel backlight work on registration failure
git bisect good fe7ba73dde94c5f413b1588cd444b49105015dda
# bad: [f05baf6e0680d8c10d2fbbc5953848fc3e3db957] Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU
git bisect bad f05baf6e0680d8c10d2fbbc5953848fc3e3db957
# good: [48ca2b8c8a6ba5c26269120c8092db0b617a18a7] block: set QUEUE_FLAG_DYING unconditionally in blk_mark_disk_dead()
git bisect good 48ca2b8c8a6ba5c26269120c8092db0b617a18a7
# first bad commit: [f05baf6e0680d8c10d2fbbc5953848fc3e3db957] Bluetooth: btusb: Add ASUS USB-BT540 for Realtek 8761CU

Hi Erik
https://lore.kernel.org/regressions/9ac1c05b-e9f2-49e9-af63-9cd0e42115fc@gmail.com/
.

Upstrema has queued 4a23ce935f74 ("Bluetooth: btrtl: Add the support
for RTL8761CUV") for the next 6.12.y, can you verify in advance if
that fixes your issue and pick the patch on top?

Regards,
Salvatore

Hi,

4a23ce935f74 does not apply cleanly to v6.12.111

diff --cc drivers/bluetooth/btrtl.c
index 6bb068dee6d2,5603b282f9bc..000000000000
--- a/drivers/bluetooth/btrtl.c
+++ b/drivers/bluetooth/btrtl.c
@@@ -1317,7 -1317,7 +1317,11 @@@ void btrtl_set_quirks(struct hci_dev *h
         case CHIP_ID_8922A:
         case CHIP_ID_8852BT:
         case CHIP_ID_8761C:
++<<<<<<< HEAD
  +              set_bit(HCI_QUIRK_WIDEBAND_SPEECH_SUPPORTED, &hdev->quirks);
++=======
+               hci_set_quirk(hdev, HCI_QUIRK_WIDEBAND_SPEECH_SUPPORTED);
++>>>>>>> 4a23ce935f74 (Bluetooth: btrtl: Add the support for RTL8761CUV)

                 /* RTL8852C needs to transmit mSBC data continuously without
                  * the zero length of USB packets for the ALT 6 supported chips


or to the first bad commit f05baf6e0680d8c10d2fbbc5953848fc3e3db957

diff --cc drivers/bluetooth/btrtl.c
index 49b74827344c,5603b282f9bc..000000000000
--- a/drivers/bluetooth/btrtl.c
+++ b/drivers/bluetooth/btrtl.c
@@@ -1306,7 -1316,8 +1317,12 @@@ void btrtl_set_quirks(struct hci_dev *h
         case CHIP_ID_8851B:
         case CHIP_ID_8922A:
         case CHIP_ID_8852BT:
++<<<<<<< HEAD
  +              set_bit(HCI_QUIRK_WIDEBAND_SPEECH_SUPPORTED, &hdev->quirks);
++=======
+       case CHIP_ID_8761C:
+               hci_set_quirk(hdev, HCI_QUIRK_WIDEBAND_SPEECH_SUPPORTED);
++>>>>>>> 4a23ce935f74 (Bluetooth: btrtl: Add the support for RTL8761CUV)

                 /* RTL8852C needs to transmit mSBC data continuously without
                  * the zero length of USB packets for the ALT 6 supported chips

Hi Erik,

Apologies, this is my error. The mentioned commit 4a23ce935f74 *is*
already part of 6.12.111 upstream, so we have here a different issue
to report upstream caused by the
f05baf6e0680d8c10d2fbbc5953848fc3e3db957 commit.

I'm looping in Ben, who said yesterday in the kernel-team meeting to
look into this issue as well.

but I think we should bring this new problem to upstream regressions
list as wel.

Regards,
Salvatore

Hi

In Debian Erik Brangs reported that after the update from 6.12.107 to
6.12.111, specifically with the backport of 980084de4d9b ("Bluetooth:
btusb: Add ASUS USB-BT540 for Realtek 8761CU") Bluetooth is not
anymore working, the full report is found at
https://bugs.debian.org/1149377 .

| [   38.135482] Bluetooth: hci0: RTL: btrtl_initialize: key id 0
| [   38.135486] Bluetooth: hci0: RTL: loading rtl_bt/rtl8761cu_fw.bin
| [   38.135751] snd_hda_intel 0000:08:00.1: bound 0000:08:00.0 (ops amdgpu_dm_audio_component_bind_ops [amdgpu])
| [   38.138313] input: HDA ATI HDMI HDMI/DP,pcm=3 as /devices/pci0000:00/0000:00:03.1/0000:06:00.0/0000:07:00.0/0000:08:00.1/sound/card1/input11
| [   38.138410] input: HDA ATI HDMI HDMI/DP,pcm=7 as /devices/pci0000:00/0000:00:03.1/0000:06:00.0/0000:07:00.0/0000:08:00.1/sound/card1/input12
| [   38.138478] input: HDA ATI HDMI HDMI/DP,pcm=8 as /devices/pci0000:00/0000:00:03.1/0000:06:00.0/0000:07:00.0/0000:08:00.1/sound/card1/input13
| [   38.138534] input: HDA ATI HDMI HDMI/DP,pcm=9 as /devices/pci0000:00/0000:00:03.1/0000:06:00.0/0000:07:00.0/0000:08:00.1/sound/card1/input14
| [   38.138657] bluetooth hci0: firmware: failed to load rtl_bt/rtl8761cu_fw.bin (-2)
| [   38.138860] bluetooth hci0: firmware: failed to load rtl_bt/rtl8761cu_fw.bin (-2)
| [   38.138874] bluetooth hci0: firmware: failed to load rtl_bt/rtl8761cu_fw.bin (-2)
| [   38.138877] bluetooth hci0: Direct firmware load for rtl_bt/rtl8761cu_fw.bin failed with error -2
| [   38.138881] Bluetooth: hci0: RTL: firmware file rtl_bt/rtl8761cu_fw not found
| [   38.194794] snd_hda_codec_realtek hdaudioC2D0: autoconfig for ALC887-VD: line_outs=1 (0x14/0x0/0x0/0x0/0x0) type:line
| [   38.194806] snd_hda_codec_realtek hdaudioC2D0:    speaker_outs=0 (0x0/0x0/0x0/0x0/0x0)
| [   38.194809] snd_hda_codec_realtek hdaudioC2D0:    hp_outs=1 (0x1b/0x0/0x0/0x0/0x0)
| [   38.194812] snd_hda_codec_realtek hdaudioC2D0:    mono: mono_out=0x0
| [   38.194815] snd_hda_codec_realtek hdaudioC2D0:    inputs:
| [   38.194817] snd_hda_codec_realtek hdaudioC2D0:      Rear Mic=0x18
| [   38.194820] snd_hda_codec_realtek hdaudioC2D0:      Front Mic=0x19
| [   38.194822] snd_hda_codec_realtek hdaudioC2D0:      Line=0x1a
| [   38.208365] snd_hda_codec_realtek hdaudioC0D1: autoconfig for ALC898: line_outs=3 (0x14/0x15/0x16/0x0/0x0) type:line
| [   38.208384] snd_hda_codec_realtek hdaudioC0D1:    speaker_outs=0 (0x0/0x0/0x0/0x0/0x0)
| [   38.208387] snd_hda_codec_realtek hdaudioC0D1:    hp_outs=1 (0x1b/0x0/0x0/0x0/0x0)
| [   38.208390] snd_hda_codec_realtek hdaudioC0D1:    mono: mono_out=0x0
| [   38.208392] snd_hda_codec_realtek hdaudioC0D1:    inputs:
| [   38.208394] snd_hda_codec_realtek hdaudioC0D1:      Rear Mic=0x18
| [   38.208396] snd_hda_codec_realtek hdaudioC0D1:      Front Mic=0x19
| [   38.208398] snd_hda_codec_realtek hdaudioC0D1:      Line=0x1a
| [   38.237349] input: HD-Audio Generic Rear Mic as /devices/pci0000:00/0000:00:08.1/0000:0a:00.4/sound/card2/input15
| [   38.237414] input: HD-Audio Generic Front Mic as /devices/pci0000:00/0000:00:08.1/0000:0a:00.4/sound/card2/input16
| [   38.237517] input: HD-Audio Generic Line as /devices/pci0000:00/0000:00:08.1/0000:0a:00.4/sound/card2/input17
| [   38.237541] input: HDA Digital PCBeep as /devices/pci0000:00/0000:00:01.3/0000:01:00.2/0000:02:04.0/0000:03:00.0/sound/card0/input20
| [   38.237619] input: HDA Creative Rear Mic as /devices/pci0000:00/0000:00:01.3/0000:01:00.2/0000:02:04.0/0000:03:00.0/sound/card0/input21
| [   38.237651] input: HD-Audio Generic Line Out as /devices/pci0000:00/0000:00:08.1/0000:0a:00.4/sound/card2/input18
| [   38.237712] input: HD-Audio Generic Front Headphone as /devices/pci0000:00/0000:00:08.1/0000:0a:00.4/sound/card2/input19
| [   38.237778] input: HDA Creative Front Mic as /devices/pci0000:00/0000:00:01.3/0000:01:00.2/0000:02:04.0/0000:03:00.0/sound/card0/input22
| [   38.239278] input: HDA Creative Line as /devices/pci0000:00/0000:00:01.3/0000:01:00.2/0000:02:04.0/0000:03:00.0/sound/card0/input23
| [   38.239482] input: HDA Creative Line Out Front as /devices/pci0000:00/0000:00:01.3/0000:01:00.2/0000:02:04.0/0000:03:00.0/sound/card0/input24
| [   38.239593] input: HDA Creative Line Out Surround as /devices/pci0000:00/0000:00:01.3/0000:01:00.2/0000:02:04.0/0000:03:00.0/sound/card0/input25
| [   38.239799] input: HDA Creative Line Out CLFE as /devices/pci0000:00/0000:00:01.3/0000:01:00.2/0000:02:04.0/0000:03:00.0/sound/card0/input26
| [   38.241509] input: HDA Creative Front Headphone as /devices/pci0000:00/0000:00:01.3/0000:01:00.2/0000:02:04.0/0000:03:00.0/sound/card0/input27
| [   38.252148] intel_rapl_common: Found RAPL domain package
| [   38.252153] intel_rapl_common: Found RAPL domain core
| [   38.285591] usbcore: registered new interface driver ath9k_htc
| [   38.287837] usb 1-9: firmware: failed to load ath9k_htc/htc_9271-1.dev.0.fw (-2)
| [   38.287850] usb 1-9: firmware: failed to load ath9k_htc/htc_9271-1.dev.0.fw (-2)
| [   38.287860] usb 1-9: firmware: failed to load ath9k_htc/htc_9271-1.dev.0.fw (-2)
| [   38.287863] usb 1-9: Direct firmware load for ath9k_htc/htc_9271-1.dev.0.fw failed with error -2
| [   38.368469] Adding 33487868k swap on /dev/sda6.  Priority:-2 extents:1 across:33487868k SS
| [   38.748227] audit: type=1400 audit(1790704634.157:2): apparmor="STATUS" operation="profile_load" profile="unconfined" name="brave" pid=1418 comm="apparmor_parser"
| [   38.748260] audit: type=1400 audit(1790704634.157:3): apparmor="STATUS" operation="profile_load" profile="unconfined" name="Discord" pid=1413 comm="apparmor_parser"
| [   38.748306] audit: type=1400 audit(1790704634.157:4): apparmor="STATUS" operation="profile_load" profile="unconfined" name="vscode" pid=1426 comm="apparmor_parser"
| [   38.748347] audit: type=1400 audit(1790704634.157:5): apparmor="STATUS" operation="profile_load" profile="unconfined" name="balena-etcher" pid=1417 comm="apparmor_parser"
| [   38.748381] audit: type=1400 audit(1790704634.157:6): apparmor="STATUS" operation="profile_load" profile="unconfined" name="crun" pid=1427 comm="apparmor_parser"
| [   38.748419] audit: type=1400 audit(1790704634.157:7): apparmor="STATUS" operation="profile_load" profile="unconfined" name="busybox" pid=1420 comm="apparmor_parser"
| [   38.748470] audit: type=1400 audit(1790704634.157:8): apparmor="STATUS" operation="profile_load" profile="unconfined" name="chrome" pid=1424 comm="apparmor_parser"
| [   38.748511] audit: type=1400 audit(1790704634.157:9): apparmor="STATUS" operation="profile_load" profile="unconfined" name="buildah" pid=1419 comm="apparmor_parser"
| [   38.748556] audit: type=1400 audit(1790704634.157:10): apparmor="STATUS" operation="profile_load" profile="unconfined" name="cam" pid=1421 comm="apparmor_parser"
| [   38.748595] audit: type=1400 audit(1790704634.157:11): apparmor="STATUS" operation="profile_load" profile="unconfined" name="chromium" pid=1425 comm="apparmor_parser"
| [   39.218164] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
| [   39.218168] Bluetooth: BNEP filters: protocol multicast
| [   39.218175] Bluetooth: BNEP socket layer initialized
| [   39.363652] usb 1-9: ath9k_htc: Transferred FW: ath9k_htc/htc_9271-1.4.0.fw, size: 51008
| [   39.440211] Generic FE-GE Realtek PHY r8169-0-400:00: attached PHY driver (mii_bus:phy_addr=r8169-0-400:00, irq=MAC)
| [   39.442083] NET: Registered PF_QIPCRTR protocol family
| [   39.614314] ath9k_htc 1-9:1.0: ath9k_htc: HTC initialized with 33 credits
| [   39.640566] r8169 0000:04:00.0 enp4s0: Link is Down
| [   39.845845] ath9k_htc 1-9:1.0: ath9k_htc: FW Version: 1.4
| [   39.845849] ath9k_htc 1-9:1.0: FW RMW support: On
| [   39.845851] ath: EEPROM regdomain: 0x809c
| [   39.845853] ath: EEPROM indicates we should expect a country code
| [   39.845855] ath: doing EEPROM country->regdmn map search
| [   39.845856] ath: country maps to regdmn code: 0x52
| [   39.845857] ath: Country alpha2 being used: CN
| [   39.845859] ath: Regpair used: 0x52
| [   39.849223] ieee80211 phy0: Atheros AR9271 Rev:1
| [   39.854386] ath9k_htc 1-9:1.0 wlx30b5c211d175: renamed from wlan0
| [   41.745845] wlx30b5c211d175: authenticate with 1c:ed:6f:bb:ed:4c (local address=30:b5:c2:11:d1:75)
| [   41.745849] wlx30b5c211d175: send auth to 1c:ed:6f:bb:ed:4c (try 1/3)
| [   41.807272] wlx30b5c211d175: authenticate with 1c:ed:6f:bb:ed:4c (local address=30:b5:c2:11:d1:75)
| [   41.807275] wlx30b5c211d175: send auth to 1c:ed:6f:bb:ed:4c (try 1/3)
| [   41.813896] wlx30b5c211d175: authenticated
| [   41.816186] wlx30b5c211d175: associate with 1c:ed:6f:bb:ed:4c (try 1/3)
| [   41.821911] wlx30b5c211d175: RX AssocResp from 1c:ed:6f:bb:ed:4c (capab=0x1431 status=0 aid=5)
| [   41.828348] wlx30b5c211d175: associated
| [   41.948210] wlx30b5c211d175: Limiting TX power to 20 (20 - 0) dBm as advertised by 1c:ed:6f:bb:ed:4c
| [   42.675206] r8169 0000:04:00.0 enp4s0: Link is Up - 1Gbps/Full - flow control rx/tx
| [   45.079778] kauditd_printk_skb: 119 callbacks suppressed
| [   45.079783] audit: type=1400 audit(1790704640.485:131): apparmor="ALLOWED" operation="capable" class="cap" profile="Xorg" pid=1955 comm="Xorg" capability=12  capname="net_admin"
| [   45.272603] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
| [   46.036834] audit: type=1400 audit(1790704641.445:132): apparmor="STATUS" operation="profile_load" profile="unconfined" name="docker-default" pid=2246 comm="apparmor_parser"
| [   46.186122] evm: overlay not supported
| [   46.358551] Bridge firewalling registered
| [   46.408480] Initializing XFRM netlink socket
| [   46.552168] audit: type=1400 audit(1790704641.957:133): apparmor="ALLOWED" operation="capable" class="cap" profile="Xorg" pid=1955 comm="Xorg" capability=12  capname="net_admin"
| [   67.792012] Guest personality initialized and is inactive
| [   67.792063] VMCI host device registered (name=vmci, major=10, minor=260)
| [   67.792065] Initialized host personality
| [   67.799049] NET: Registered PF_VSOCK protocol family
| [   68.979467] systemd-journald[544]: Time jumped backwards, rotating.

the device now requests rtl_bt/rtl8761cu_fw.bin firwmare (assumtion the device
had previously working firwmare but with adding support for ASUS USB-BT540 for
Realtek 8761CU, tries to load the not avaialble firmware and get not
functional? I'm looping in Ben Hutchings which has much more experience on that
on our end.

#regzbot introduced: f05baf6e0680d8c10d2fbbc5953848fc3e3db957
#regzbot link: https://bugs.debian.org/1149377

Maybe the answer is simply here, Debian needs to provide the firmware from now
on in the firmware-realtek in stable?

Regards,
Salvatore

rtl_bt/rtl8761cu_fw.bin has been in linux-firmware only since 20251111,
and Debian trixie's firmware-realtek 20250410-2 does not have it.

Marcel, Luiz: could you, or Christoph Zwerschke as the author of the ID
commit, send an upstream revert, or a fallback to ROM firmware when
rtl8761cu_fw.bin is missing? Stable will take it for 7.2, 6.18 and 6.12
through the normal Cc: stable route once it is in mainline.

Anyone working on this?

If not: Should we revert 980084de4d9b and its backports? Or only the
backports to older stable series?

Strictly speaking it should be the former due to our policies wrt to
firmware -- but I guess most users of a more recent kernels also have a
newer firmware, so I wonder if reverting the change might do more harm
then good now.

Ciao, Thorsten

Ciao Thorsten,

Thanks for looking into this regression as well.

If my understanding is correct from a earlier fixed regression in the
ariea, aka
https://lore.kernel.org/regressions/0fd8c1c9-7f56-4bcb-a727-e4386d8ef094@online.de/
should then not only 980084de4d9b ("Bluetooth: btusb: Add ASUS
USB-BT540 for Realtek 8761CU") be reverted, but as well along
6f0624b4427e ("Bluetooth: btusb: Add ASUS USB-BT600 for Realtek
8761CU") and as well 4a23ce935f74 ("Bluetooth: btrtl: Add the support
for RTL8761CUV")?

Regards,
Salvatore

Maybe, I didn't look closer, but that's why reverting in mainline likely
really is a bad idea: it might cause a regression for users that depend
on those changes (one of which is from 6.19).

So I guess reverting some or all of those backports in "older stable
series", as Sasha suggested, might be the best -- but I guess it would
be good if someone with more knowledge in this area could provide an
opinion.

Ciao, Thorsten