linux-kernel - Re: [PATCH] Bluetooth: btusb: Always fallback to alt 1 for WBS

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Date:   Sun, 21 Feb 2021 21:35:57 +0100
From:   Sebastian Reichel <sre@...nel.org>
To:     stable@...r.kernel.org
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        Trent Piepho <tpiepho@...il.com>,
        linux-bluetooth <linux-bluetooth@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Hilda Wu <hildawu@...ltek.com>,
        Sathish Narasimman <sathish.narasimman@...el.com>,
        Chethan T N <chethan.tumkur.narayan@...el.com>,
        Hsin-Yu Chao <hychao@...omium.org>,
        Amit K Bag <amit.k.bag@...el.com>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        kernel@...labora.com, Sjoerd Simons <sjoerd@...labora.com>
Subject: Re: [PATCH] Bluetooth: btusb: Always fallback to alt 1 for WBS

[+cc stable@...r.kernel.org]

Hi,

On Sat, Feb 06, 2021 at 04:56:53PM +0100, Sjoerd Simons wrote:
> On Fri, Dec 18, 2020 at 10:23:08PM +0100, Marcel Holtmann wrote:
> > Hi Trent,
> > 
> > > When alt mode 6 is not available, fallback to the kernel <= 5.7 behavior
> > > of always using alt mode 1.
> > > 
> > > Prior to kernel 5.8, btusb would always use alt mode 1 for WBS (Wide
> > > Band Speech aka mSBC aka transparent SCO).  In commit baac6276c0a9
> > > ("Bluetooth: btusb: handle mSBC audio over USB Endpoints") this
> > > was changed to use alt mode 6, which is the recommended mode in the
> > > Bluetooth spec (Specifications of the Bluetooth System, v5.0, Vol 4.B
> > > §2.2.1).  However, many if not most BT USB adapters do not support alt
> > > mode 6.  In fact, I have been unable to find any which do.
> 
> > patch has been applied to bluetooth-next tree.
> 
> For easier application to the stable tree(s) this should probably get:
>   Fixes: baac6276c0a9 ("Bluetooth: btusb: handle mSBC audio over USB Endpoints")
> 
> In my testing this indeed fixes mSBC audio with both a Belkin (Broadcom
> BCM20702A, 050d:065a) and an Intel Bluetooth (8087:0a2b) adapters.
> 
>   Tested-By: Sjoerd Simons <sjoerd@...labora.com>

Tested on Intel AX200 Bluetooth (8087:0029):

Tested-by: Sebastian Reichel <sre@...nel.org>

The patch has been merged to Linus' tree today and I think it should
be applied to the 5.10 tree, which is used by Debian. This patch is
required to use BT headset with bidirectional-audio in acceptable
quality (That also requires proper userspace software, e.g. pipewire
0.3.22, which Sjoerd uploaded to Debian experimental).

Patch applies cleanly on 5.10.

Thanks,

-- Sebastian

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