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

[+cc stable@vger.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:

quoted

Hi Trent,

quoted

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.

quoted

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 [off-list ref]

Tested on Intel AX200 Bluetooth (8087:0029):

Tested-by: Sebastian Reichel <sre@kernel.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