linux-kernel - Re: "Bluetooth: hci0: HCI_REQ-0xfcf0" errors in dmesg

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Date:   Mon, 31 Oct 2022 21:08:55 +0000
From:   "Gix, Brian" <brian.gix@...el.com>
To:     "luiz.dentz@...il.com" <luiz.dentz@...il.com>,
        "mat.jonczyk@...pl" <mat.jonczyk@...pl>
CC:     "Von Dentz, Luiz" <luiz.von.dentz@...el.com>,
        "johan.hedberg@...il.com" <johan.hedberg@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
        "marcel@...tmann.org" <marcel@...tmann.org>
Subject: Re: "Bluetooth: hci0: HCI_REQ-0xfcf0" errors in dmesg

On Mon, 2022-10-31 at 13:37 -0700, Luiz Augusto von Dentz wrote:
> On Mon, Oct 31, 2022 at 1:15 PM Mateusz Jończyk <mat.jonczyk@...pl>
> wrote:
> > 
> > On 6.1.0-rc3, I have been seeing this error message in dmesg:
> > 
> >         Bluetooth: hci0: HCI_REQ-0xfcf0
> > 
> > It is printed on every boot, resume from suspend and rfkill unblock
> > of the Bluetooth device.
> > The device seems to be functioning normally though (but I have done
> > limited testing only).
> > 
> > After some investigation, it turned out to be caused by
> >         commit dd50a864ffae ("Bluetooth: Delete unreferenced
> > hci_request code")
> > which modified hci_req_add() in net/bluetooth/hci_request.c to
> > always print an error message
> > when that function is executed.
> > 
> > I have added dump_stack() to hci_req_add() and got the following
> > backtraces:
> > 
> > On boot:
> > 
> > [   18.487766] Bluetooth: hci0: RTL: fw version 0xab6b705c
> > [   18.548951] Bluetooth: hci0: HCI_REQ-0xfcf0
> > [   18.548961] CPU: 3 PID: 108 Comm: kworker/u9:0 Not tainted
> > 6.1.0-rc3unif4-00001-gb33a0948e932 #86
> > 
...
> > on rfkill unblock:
> > 
> > [ 1671.040970] Bluetooth: hci0: HCI_REQ-0xfcf0
> > [ 1671.040992] CPU: 3 PID: 5006 Comm: kworker/u9:2 Not tainted
... 
> > My hardware: HP laptop 17-by0001nw, device is a Realtek combo card:
> > 
> > "Realtek RTL8822BE 802.11 ac 2×2 WiFi + Bluetooth 4.2 Combo Adapter
> > (MU-MIMO supported)"
> > 
> > I am ready to provide additional information and testing, if need
> > be.
> 
> @Gix, Brian Can you give a look, we should probably convert the
> msft_set_filter_enable to use the cmd_sync instead.

This, I suspect, will be an ongoing issue, particularily with Vender
Opcodes, which we don't have much direct visability and testing
capabilities.  The error gets logged because it is using a deprecated
(but still working) mechanism to issue HCI opcodes.

If I can get the source code path of the call as it is being
contructed, I can try making you a patch Mateusz...  But you will
probably need to do the testing/verification for me.


> 
> > Greetings,
> > 
> > Mateusz Jończyk

--Brian