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

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Message-ID: <YB68RUVLRGQKS+yH@dawn.lan>
Date:   Sat, 6 Feb 2021 16:56:53 +0100
From:   Sjoerd Simons <sjoerd@...labora.com>
To:     Marcel Holtmann <marcel@...tmann.org>
Cc:     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
Subject: Re: [PATCH] Bluetooth: btusb: Always fallback to alt 1 for WBS

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>

Regards,
  Sjoerd