RCAR_CAN_RX_FIFO_MBX
data = readl(&priv->regs->mb[RCAR_CAN_RX_FIFO_MBX].id);
dlc = readb(&priv->regs->mb[RCAR_CAN_RX_FIFO_MBX].dlc);
readb(&priv->regs->mb[RCAR_CAN_RX_FIFO_MBX].data[dlc]);