Hi Larry,
>>> In 'commit a2698a9bf9b0 ("Bluetooth: btusb: Add Realtek
>>> 8723A/8723B/8761A/8821A support"), support of some Realtek
>>> devices was added to the Generic Bluetooth USB driver in kernel.
>>> However, these devices are not in the module device table of
>>> btusb.ko, so the kernel wouldn't probe them at all.
>>>
>>> To fix this, add four entries in the device table btusb_table,
>>> based on code from <https://github.com/lwfinger/rtl8723au_bt>
>>> ('new' branch).
>>>
>>> This enables bluetooth support in the Lenovo Ideapad Yoga 13
>>> which has RTL8723AU USB device, with product ID 0bda:1724.
>>>
>>> Signed-off-by: Xi Ruoyao <xry111@xxxxxxxxxxx>
>>> ---
>>> drivers/bluetooth/btusb.c | 6 ++++++
>>> 1 file changed, 6 insertions(+)
>>>
>>> diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
>>> index 3c10d4d..dd87623 100644
>>> --- a/drivers/bluetooth/btusb.c
>>> +++ b/drivers/bluetooth/btusb.c
>>> @@ -148,6 +148,12 @@ static const struct usb_device_id btusb_table[] = {
>>> { USB_DEVICE(0x8087, 0x0a5a),
>>> .driver_info = BTUSB_INTEL_BOOT | BTUSB_BROKEN_ISOC },
>>>
>>> + /* Realtek Bluetooth */
>>> + { USB_VENDOR_AND_INTERFACE_INFO(0x0bda, 0xe0, 0x01, 0x01) },
>>> + { USB_VENDOR_AND_INTERFACE_INFO(0x0bd5, 0xe0, 0x01, 0x01) },
>>> + { USB_VENDOR_AND_INTERFACE_INFO(0x13d3, 0xe0, 0x01, 0x01) },
>>> + { USB_VENDOR_AND_INTERFACE_INFO(0x0489, 0xe0, 0x01, 0x01) },
>>> +
>>
>> I highly doubt these are needed. There is a generic entry for an USB transport that is already covering these.
>
> Something changed in recent kernels, and the generic USB transport entries do not seem to be recognized in the case where a wifi and BT device share a single USB ID. As the OP's tablet has such a case, I suggest that 0bda line be accepted, but not the others. If I had a computer with an RTL8723AU, I would have a chance at debugging what changed, but sadly, that is not the case.
these Realtek devices are causing the most messy setup in a generic driver. And Bluetooth USB support has been really clean and simple for the last 10 years. I really wonder how many ways this gets done wrong before someone gets a clue and gets this right. At the end of the day this USB transport is 15 years old.
Anyway, for obvious reasons the content of /sys/kernel/debug/usb/devices should be included here so that someone can actually look at how the USB endpoints are configured.
Regards
Marcel
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