Bluetooth: Add debugfs controls for LE CoC MPS and Credits

This patch adds entries to debugfs to control the values used for the
MPS and Credits for LE Flow Control Mode.
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/l2cap_core.c

@@ -49,6 +49,9 @@ static u8 l2cap_fixed_chan[8] = { L2CAP_FC_L2CAP | L2CAP_FC_CONNLESS, };
 static LIST_HEAD(chan_list);
 static DEFINE_RWLOCK(chan_list_lock);
 
+static u16 le_max_credits = L2CAP_LE_MAX_CREDITS;
+static u16 le_default_mps = L2CAP_LE_DEFAULT_MPS;
+
 static struct sk_buff *l2cap_build_cmd(struct l2cap_conn *conn,
 				       u8 code, u8 ident, u16 dlen, void *data);
 static void l2cap_send_cmd(struct l2cap_conn *conn, u8 ident, u8 code, u16 len,
@@ -501,7 +504,7 @@ void l2cap_le_flowctl_init(struct l2cap_chan *chan)
 	chan->omtu = L2CAP_LE_MIN_MTU;
 	chan->mode = L2CAP_MODE_LE_FLOWCTL;
 	chan->tx_credits = 0;
-	chan->rx_credits = L2CAP_LE_MAX_CREDITS;
+	chan->rx_credits = le_max_credits;
 
 	if (chan->imtu < L2CAP_LE_DEFAULT_MPS)
 		chan->mps = chan->imtu;
@@ -1214,7 +1217,7 @@ static void l2cap_le_flowctl_start(struct l2cap_chan *chan)
 	if (chan->imtu < L2CAP_LE_DEFAULT_MPS)
 		chan->mps = chan->imtu;
 	else
-		chan->mps = L2CAP_LE_DEFAULT_MPS;
+		chan->mps = le_default_mps;
 
 	skb_queue_head_init(&chan->tx_q);
 
@@ -6831,10 +6834,10 @@ static void l2cap_chan_le_send_credits(struct l2cap_chan *chan)
 	/* We return more credits to the sender only after the amount of
 	 * credits falls below half of the initial amount.
 	 */
-	if (chan->rx_credits >= (L2CAP_LE_MAX_CREDITS + 1) / 2)
+	if (chan->rx_credits >= (le_max_credits + 1) / 2)
 		return;
 
-	return_credits = L2CAP_LE_MAX_CREDITS - chan->rx_credits;
+	return_credits = le_max_credits - chan->rx_credits;
 
 	BT_DBG("chan %p returning %u credits to sender", chan, return_credits);
 
@@ -7448,6 +7451,11 @@ int __init l2cap_init(void)
 	l2cap_debugfs = debugfs_create_file("l2cap", 0444, bt_debugfs,
 					    NULL, &l2cap_debugfs_fops);
 
+	debugfs_create_u16("l2cap_le_max_credits", 0466, bt_debugfs,
+			   &le_max_credits);
+	debugfs_create_u16("l2cap_le_default_mps", 0466, bt_debugfs,
+			   &le_default_mps);
+
 	return 0;
 }