[PATCH v3] Bluetooth: btusb: treat 0bda:0002 rev 7558 as a generic HCI device

[Andrew Bille <andrewbille@gmail.com>]

The internal Bluetooth controller of a Quanta JW6H laptop reports
itself as "CSR BS8510" and exposes a standard Bluetooth USB interface.

Relevant /sys/kernel/debug/usb/devices output is:

    D:  Ver= 2.00 Cls=e0(wlcon) Sub=01 Prot=01 MxPS=64 #Cfgs= 1
    P:  Vendor=0bda ProdID=0002 Rev=75.58
    S:  Product=CSR BS8510
    I:* If#= 0 Alt= 0 #EPs= 3 Cls=e0(wlcon) Sub=01 Prot=01 Driver=btusb

The device currently matches the vendor-wide Realtek quirk and is
therefore initialized through btrtl. It does not respond to the
Realtek-specific register access and initialization fails with:

    Bluetooth: hci0: RTL: RTL: Read reg16 failed (-110)

No Bluetooth controller is then available to userspace.

No external firmware is required when the device is handled through
the generic HCI path.

It is not known whether other devices using USB ID 0bda:0002 are
genuine Realtek controllers. Limit the exception to the observed
bcdDevice revision 0x7558 and log when generic HCI handling is forced,
so other revisions continue to use the existing Realtek path.

With this change the controller registers successfully. Scanning,
pairing and A2DP audio have been tested successfully.

Fixes: a2698a9bf9b0 ("Bluetooth: btusb: Add Realtek 8723A/8723B/8761A/8821A support")
Cc: stable@vger.kernel.org
Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
Assisted-by: ChatGPT:GPT-5.6-Sol
Signed-off-by: Andrew Bille <andrewbille@gmail.com>
---
Changes in v3:
- Rebase onto the current bluetooth-next tree.
- Preserve the updated BTUSB_IGNORE bit test from upstream.
- No functional changes.

Changes in v2:
- Restrict the quirk to the observed bcdDevice revision 0x7558.
- Log when generic HCI handling is forced.
- Add the Quanta JW6H platform and USB descriptor information.
- Document that no external firmware is required.
- Document the possible conflict with other 0bda:0002 devices.

 drivers/bluetooth/btusb.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index 2bae85b0016c..a95e482a501b 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_FORCE_GENERIC		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 },
 
+	/* Device reporting itself as "CSR BS8510" */
+	{ USB_DEVICE_VER(0x0bda, 0x0002, 0x7558, 0x7558),
+	  .driver_info = BTUSB_FORCE_GENERIC },
+
 	/* Realtek Bluetooth devices */
 	{ USB_VENDOR_AND_INTERFACE_INFO(0x0bda, 0xe0, 0x01, 0x01),
 	  .driver_info = BTUSB_REALTEK },
@@ -4122,6 +4127,9 @@ static int btusb_probe(struct usb_interface *intf,
 			id = match;
 	}
 
+	if (id->driver_info & BTUSB_FORCE_GENERIC)
+		dev_info(&intf->dev, "using generic HCI handling\n");
+
 	if (id->driver_info & BTUSB_IGNORE)
 		return -ENODEV;
 
-- 
2.47.3