RCANFD_FIFO_DEPTH
sent = priv->tx_tail % RCANFD_FIFO_DEPTH;
if (unsent != RCANFD_FIFO_DEPTH)
can_put_echo_skb(skb, ndev, priv->tx_head % RCANFD_FIFO_DEPTH, 0);
if (priv->tx_head - priv->tx_tail >= RCANFD_FIFO_DEPTH)
ndev = alloc_candev(sizeof(*priv), RCANFD_FIFO_DEPTH);
for (i = 0; i < RCANFD_FIFO_DEPTH; i++)