Some USB BT adapters don't satisfy the MTU requirement mentioned in
commit e848dbd364ac ("Bluetooth: btusb: Add support USB ALT 3 for WBS")
and have ALT 3 setting that produces no/garbled audio. Check that the MTU
condition is satisfied, and fall back to ALT 1 if not.
Tested with USB adapters (mtu<72, produce sound only with ALT1)
BCM20702A1 0b05:17cb, CSR8510A10 0a12:0001, and (mtu>=72, ALT3)
RTL8761BU 0bda:8771, Intel AX200 8087:0029 (after disabling ALT6).
Signed-off-by: Pauli Virtanen <pav@xxxxxx>
---
drivers/bluetooth/btusb.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index a9855a2dd561..3ee66e415c4d 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -1763,9 +1763,11 @@ static void btusb_work(struct work_struct *work)
/* Because mSBC frames do not need to be aligned to the
* SCO packet boundary. If support the Alt 3, use the
* Alt 3 for HCI payload >= 60 Bytes let air packet
- * data satisfy 60 bytes.
+ * data satisfy 60 bytes. USB Alt 3 support also needs
+ * HFP transparent MTU >= 72 Bytes.
*/
- if (new_alts == 1 && btusb_find_altsetting(data, 3))
+ if (new_alts == 1 && hdev->sco_mtu >= 72 &&
+ btusb_find_altsetting(data, 3))
new_alts = 3;
}
--
2.31.1
