Re: [PATCH] Bluetooth: btusb: limit RTL8761B BROKEN_EXT_SCAN quirk to 0bda:a728

Hi Kamil,

On Mon, Aug 24, 2026 at 2:03 AM Thorsten Leemhuis
<[email protected]> wrote:
>
> On 8/24/26 07:32, Junjie Cao wrote:
> > Commit 5ead2063611a ("Bluetooth: btrtl: fix RTL8761B/BU broken LE
> > extended scan") set HCI_QUIRK_BROKEN_EXT_SCAN for every CHIP_ID_8761B
> > device to cure repeated 0x2042 failures on an 0bda:a728 dongle. The
> > brokenness is per-dongle, not per-chip: on a TP-Link UB500 (2357:0604,
> > RTL8761BU, fw 0xdfc6d922) extended scan works, and the legacy scan
> > path the quirk forces is what is broken -- LE Set Scan Enable (0x200c)
> > times out with -110 about 30 s after firmware load, btusb resets the
> > device, and the adapter re-enumerates in an endless loop (382 firmware
> > reloads in one boot). 7.1.8, which predates the stable backport, runs
> > clean on this unit; 7.1.9 loops.
> >
> > Move the quirk from btrtl's chip-wide switch to a btusb device-table
> > flag on the USB id the original fix was verified against. Other 8761B
> > dongles return to their earlier long-standing behaviour.
> > > Link: https://bugzilla.redhat.com/show_bug.cgi?id=2521504
> > Fixes: 5ead2063611a ("Bluetooth: btrtl: fix RTL8761B/BU broken LE extended scan")
>
> Thx. Just to make sure everyone is aware of it: Kamil (now CCed)
> reported problems due to the commit yesterday and provided patches, too:
> https://lore.kernel.org/all/[email protected]/
>
> I suggested that a quick revert might be the best approach for now,
> which Kamil submitted:
> https://lore.kernel.org/all/[email protected]/
>
> No comment yet from the BT folks yet.
>
> Ciao, Thorsten
>
> > Cc: [email protected]
> > Signed-off-by: Junjie Cao <[email protected]>
> > ---
> > #regzbot introduced: 5ead2063611a
> > #regzbot link: https://bugzilla.redhat.com/show_bug.cgi?id=2521504
> >
> >  drivers/bluetooth/btrtl.c | 13 -------------
> >  drivers/bluetooth/btusb.c |  8 ++++++++
> >  2 files changed, 8 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/bluetooth/btrtl.c b/drivers/bluetooth/btrtl.c
> > index 7f54d2d2d13a..03fa9409e3ee 100644
> > --- a/drivers/bluetooth/btrtl.c
> > +++ b/drivers/bluetooth/btrtl.c
> > @@ -1343,19 +1343,6 @@ void btrtl_set_quirks(struct hci_dev *hdev, struct btrtl_device_info *btrtl_dev)
> >       if (!btrtl_dev->ic_info)
> >               return;
> >
> > -     switch (btrtl_dev->project_id) {
> > -     case CHIP_ID_8761B:
> > -             /* RTL8761B/BU reports HCI version 5.1 but does not support
> > -              * the LE Extended Scan commands (Opcode 0x2042), causing
> > -              * repeated -EBUSY failures when BlueZ attempts extended
> > -              * scanning while a connection is active.
> > -              */
> > -             hci_set_quirk(hdev, HCI_QUIRK_BROKEN_EXT_SCAN);
> > -             break;
> > -     default:
> > -             break;
> > -     }
> > -
> >       switch (btrtl_dev->ic_info->lmp_subver) {
> >       case RTL_ROM_LMP_8703B:
> >               /* 8723CS reports two pages for local ext features,
> > diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
> > index 2bae85b0016c..84614e60d142 100644
> > --- a/drivers/bluetooth/btusb.c
> > +++ b/drivers/bluetooth/btusb.c
> > @@ -67,6 +67,7 @@ static struct usb_driver btusb_driver;
> >  #define BTUSB_INTEL_NO_WBS_SUPPORT   BIT(26)
> >  #define BTUSB_ACTIONS_SEMI           BIT(27)
> >  #define BTUSB_BARROT                 BIT(28)
> > +#define BTUSB_BROKEN_EXT_SCAN                BIT(29)
> >
> >  static const struct usb_device_id btusb_table[] = {
> >       /* Generic Bluetooth USB device */
> > @@ -619,6 +620,10 @@ static const struct usb_device_id quirks_table[] = {
> >       { USB_DEVICE(0x0489, 0xe130), .driver_info = BTUSB_REALTEK |
> >                                                    BTUSB_WIDEBAND_SPEECH },
> >
> > +     /* Realtek 8761BU Bluetooth devices */
> > +     { USB_DEVICE(0x0bda, 0xa728), .driver_info = BTUSB_REALTEK |
> > +                                                  BTUSB_BROKEN_EXT_SCAN },
> > +
> >       /* Realtek Bluetooth devices */
> >       { USB_VENDOR_AND_INTERFACE_INFO(0x0bda, 0xe0, 0x01, 0x01),
> >         .driver_info = BTUSB_REALTEK },
> > @@ -4403,6 +4408,9 @@ static int btusb_probe(struct usb_interface *intf,
> >       if (id->driver_info & BTUSB_INVALID_LE_STATES)
> >               hci_set_quirk(hdev, HCI_QUIRK_BROKEN_LE_STATES);
> >
> > +     if (id->driver_info & BTUSB_BROKEN_EXT_SCAN)
> > +             hci_set_quirk(hdev, HCI_QUIRK_BROKEN_EXT_SCAN);
> > +
> >       if (id->driver_info & BTUSB_DIGIANSWER) {
> >               data->cmdreq_type = USB_TYPE_VENDOR;
> >               hci_set_quirk(hdev, HCI_QUIRK_RESET_ON_CLOSE);

Any chance to test this change? It looks better since it does remove
the original workaround for the specific USB ID while also fixing the
regression.

-- 
Luiz Augusto von Dentz