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

[<hildawu@realtek.com>]

From: hildawu <hildawu@realtek.com>

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.

Signed-off-by: hildawu <hildawu@realtek.com>
---
 drivers/bluetooth/btusb.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index 6f253378e893..872034e7a232 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -1752,6 +1752,13 @@ static void btusb_work(struct work_struct *work)
 			 * which work with WBS at all.
 			 */
 			new_alts = btusb_find_altsetting(data, 6) ? 6 : 1;
+			/* 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.
+			 */
+			if ((new_alts == 1) && (btusb_find_altsetting(data, 3)))
+				new_alts = 3;
 		}
 
 		if (btusb_switch_alt_setting(hdev, new_alts) < 0)
-- 
2.17.1