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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Thu, 7 May 2020 13:58:17 -0700
Message-ID: <CABBYNZJ=gUUOGY8BAnt0EU+q3H2SyWXE3nxG1aS7NX1WdJY=MA@mail.gmail.com>
Subject: Re: avrcp: Cannot connect Sennheiser Momentum True Wireless 2
To:     Andrey Semashev <andrey.semashev@gmail.com>
Cc:     "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
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Hi Andrey,

On Thu, May 7, 2020 at 1:29 PM Luiz Augusto von Dentz
<luiz.dentz@gmail.com> wrote:
>
> Hi Andrey,
>
> On Wed, May 6, 2020 at 10:32 AM Andrey Semashev
> <andrey.semashev@gmail.com> wrote:
> >
> > On 2020-05-06 19:56, Andrey Semashev wrote:
> > > Hello!
> > >
> > > I have a problem connecting Sennheiser Momentum True Wireless 2
> > > headphones over Bluetooth. The headphones say "Connected" and then
> > > reboot immediately after. After reboot the headphones say "Power on" and
> > > try connecting again, and fail the same way, and so on.
> > >
> > >  From the Bluetooth packet dump it looks like the problem happens after
> > > bluetoothd sends AVRCP ListPlayerApplicationSettingAttributes message to
> > > the headphones. The headphones send Not Implemented response and then
> > > reboot. Both in the request and the response Wireshark shows warnings
> > > about encoding issues.
> > >
> > > I'm attaching a packet dump captured from one of the connection
> > > attempts. The ListPlayerApplicationSettingAttributes message is in
> > > packet 262 and the response is in packet 264.
> > >
> > > This is on Kubuntu 20.04. I tried bluez 5.53 from Kubuntu and revision
> > > 3146b7a0785758be2d4e894d44e99d29c0db983e from git master - the behavior
> > > is the same.
> > >
> > > I've also verified that the headphones do work on Windows 10. On that
> > > system, ListPlayerApplicationSettingAttributes is not present in the
> > > packet exchange. I can provide the packet dump from Windows, if needed.
> > >
> > > I hope this is the right place to report problems like this one. If not
> > > - sorry, and please point me to the right place.
> > >
> > > Thank you.
> >
> > I'll add that I can connect the headphones if I disable AVRCP by adding
> > --noplugin=avrcp to bluetoothd command line.
>
> Weird the ListPlayerApplicationSettingAttributes should only really be
> used when the remote device claims to be have target role but I doubt
> the headsets would be implementing that so perhaps we are not
> detecting this properly, do you have the HCI traces in btsnoop format?
> You can collect that with use of btmon.

Looks like the device is setting the bit for Category 1:
Player/Recorder which is why we are sending player related command,
other stacks might not do that because they are not dual-role, cannot
act as controllers, even if Player Application Settings is optional
for category 1 it still means that we could perhaps list them. It
looks like we are not parsing properly the ctype since it appears that
it returns AVC_CTYPE_NOT_IMPLEMENTED instead of AVC_CTYPE_REJECTED, is
that perhaps causing a crash on bluetoothd?


>
> --
> Luiz Augusto von Dentz


-- 
Luiz Augusto von Dentz