[Bluetooth] Add support for TIOCOUTQ and TIOCINQ ioctls

Almost every protocol family supports the TIOCOUTQ and TIOCINQ ioctls
and even Bluetooth could make use of them. When implementing audio
streaming and integration with GStreamer or PulseAudio they will allow
a better timing and synchronization.
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

net/bluetooth/af_bluetooth.c

@@ -335,11 +335,34 @@ EXPORT_SYMBOL(bt_sock_poll);
 int bt_sock_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 {
 	struct sock *sk = sock->sk;
+	struct sk_buff *skb;
+	long amount;
 	int err;
 
 	BT_DBG("sk %p cmd %x arg %lx", sk, cmd, arg);
 
 	switch (cmd) {
+	case TIOCOUTQ:
+		if (sk->sk_state == BT_LISTEN)
+			return -EINVAL;
+
+		amount = sk->sk_sndbuf - atomic_read(&sk->sk_wmem_alloc);
+		if (amount < 0)
+			amount = 0;
+		err = put_user(amount, (int __user *) arg);
+		break;
+
+	case TIOCINQ:
+		if (sk->sk_state == BT_LISTEN)
+			return -EINVAL;
+
+		lock_sock(sk);
+		skb = skb_peek(&sk->sk_receive_queue);
+		amount = skb ? skb->len : 0;
+		release_sock(sk);
+		err = put_user(amount, (int __user *) arg);
+		break;
+
 	case SIOCGSTAMP:
 		err = sock_get_timestamp(sk, (struct timeval __user *) arg);
 		break;