[RFC PATCH 2/2] Bluetooth: btrtl: drop the blanket RTL8761B extended scan quirk

[Kamil Serwus]

Commit 5ead2063611ae5 ("Bluetooth: btrtl: fix RTL8761B/BU broken LE
extended scan") sets HCI_QUIRK_BROKEN_EXT_SCAN for every CHIP_ID_8761B.
It was validated on one dongle, USB 0bda:a728, and it regresses others
that share the chip id but not the firmware bug.

On USB 0bda:8771 (fw 0xdfc6d922) extended scan works flawlessly, while
the legacy scan-disable command the quirk forces makes the controller
stop answering entirely:

  Bluetooth: hci0: command 0x200c tx timeout
  Bluetooth: hci0: Opcode 0x200c failed: -110
  Bluetooth: hci0: Unable to disable scanning: -110
  Bluetooth: hci0: Resetting usb device.

btusb then resets the device, it re-enumerates (hci0 -> hci1 -> hci2)
and every connected BLE device is dropped - here a Kensington SlimBlade
Pro trackball and a Keychron Q8 Max keyboard. Linux 7.1.x, without the
quirk, drives the same dongle with the same firmware for hours without a
single scan error.

Nothing in btrtl can tell the two apart: same project_id, same
ic_id_table entry, same rtl8761bu_fw.bin. They differ only by USB id,
which btrtl_set_quirks() cannot see, and both take their driver_info
from the same generic Realtek entry in btusb's quirks_table, so
driver_info cannot separate them either.

With the previous patch the 0bda:a728 dongle recognises itself on its
first rejected extended scan, so the static guess is no longer needed.

Fixes: 5ead2063611ae ("Bluetooth: btrtl: fix RTL8761B/BU broken LE extended scan")
Signed-off-by: Kamil Serwus <kserwus@xxxxxxxxx>
---
 drivers/bluetooth/btrtl.c | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/drivers/bluetooth/btrtl.c b/drivers/bluetooth/btrtl.c
index 7f54d2d2d..03fa9409e 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,
-- 
2.55.0