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Sender: Larry Finger <larry.finger@gmail.com>
Subject: Re: Strange problem with USB device
To:     Alan Stern <stern@rowland.harvard.edu>
Cc:     linux-usb@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        ierturk@ieee.org
References: <cfc37ce0-823e-0d19-f5d7-fcd571a94943@lwfinger.net>
 <20210608182038.GA1812516@rowland.harvard.edu>
From:   Larry Finger <Larry.Finger@lwfinger.net>
Message-ID: <a7c7ba62-a74f-d7db-bfd9-4f6c8e25e0b8@lwfinger.net>
Date:   Tue, 8 Jun 2021 13:37:07 -0500
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On 6/8/21 1:20 PM, Alan Stern wrote:
> On Tue, Jun 08, 2021 at 12:41:23PM -0500, Larry Finger wrote:
>> Hi,
>>
>> In https://bugzilla.suse.com/show_bug.cgi?id=1186889, a user is
>> reporting that his Bluetooth component of a Realtek RTL8822CE is not
> 
> Is that a USB device?  That is, does it connect to the computer
> via a USB cable?  I'll assume it does...
> 
>> being found in openSUSE's kernel 5.3.18. His lsusb scan is as follows:
>>
>> $ lsusb
>> Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
>> Bus 001 Device 003: ID 13d3:56c9 IMC Networks HP TrueVision HD Camera
>> Bus 001 Device 002: ID 045e:07fd Microsoft Corp. Nano Transceiver 1.1
>> Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
>>
>> The Bluetooth device is found and works in Windows 10, where the Device
>> Manager reports hardware ID's of 0bda:b00c. This combination is in
>> driver btusb.
>>
>> Is there a bug in the USB bus scan in kernel 5.3.18 that has since been
>> fixed, or is there still a bug that misses this device?
> 
> Given only the information you have provided, it is impossible to
> answer that question.  Broadly speaking, lots of bugs in the USB
> subsystem have been fixed since kernel 5.3.18, but I don't know
> if any of them would affect detecting new devices on the bus like
> this.
> 
> One thing you might try is to turn on USB debugging before
> plugging in the device:
> 
> echo 'module usbcore =p' >/sys/kernel/debug/dynamic_debug/control
> 
> The additional information this adds to the dmesg log may be
> helpful.

The BT device is part of the same card as the PCIe wifi device, thus there is no 
"plugging" it in a conventional sense. Is there some way to add the usbcore 
debugging statement to the kernel options line at boot time?

As I told GregKH, I am having the person with the problem try a rescue system 
with a 5.12 kernel.

Larry