Re: [PATCH v2] Bluetooth: btusb: Add support USB ALT 3 for WBS

On Sunday, July 11, 2021 8:33:57 AM PDT Pauli Virtanen wrote:

pe, 2021-05-14 kello 11:19 +0800, hildawu@realtek.com kirjoitti:

quoted

Because mSBC frames do not need to be aligned to the SCO packet
boundary. Using USB ALT 3 let HCI payload >= 60 bytes, let mSBC
data satisfy 60 Bytes avoid payload unaligned situation and fixed
some headset no voise issue.

USB Alt 3 supported also need HFP support transparent MTU in 72
Bytes.

This change seemed to break msbc audio on some non-realtek adapters I
have. Tested Pipewire on BCM20702A1 (0b05:17cb), CSR8510A10 (0a12:0001)
-> no sound output and input appears garbled. Reverting this patch
makes it work again. Indeed these adapters report SCO mtu=64 which is
less than 72. On the other hand, with RTL8761BU (0bda:8771) msbc audio
works fine with this patch out of the box, indeed reading/writing 72
byte packets to/from the sco socket

When I fixed WBS when previous patches from Intel and Realtek broke it for 
most adapters, I also tested alt 3.  I also found it didn't work for many 
adapters.

It is annoying that a chipset vendor can not be bothered to do the basic 
testing I am able to do by buying random bt adapters from amazon.  Nor 
respond when their patches, once accepted, cause problems.