SOLVED

static int s3c24xx_serial_ioctl(struct uart_port *port, unsigned int cmd,
unsigned long arg)
{

  if(cmd==0x22)
  {
    switch (arg) //
    {
      case 0://rs232
      {
        mode=0;
        usart_mode(port->line,mode);
        break;
      }
      case 1://rs485-2w
      {
        mode=1;
        usart_mode(port->line,mode);
        break;

      }
      case 2://rs422
      case 3://rs485-4w
      {
        mode=2;
        usart_mode(port->line,mode);
        break;
      }

      default:
      {
        printk(KERN_ERR "%s:no existe modo \n",__func__);
        break;
      }
    }
  }
  return -ENOIOCTLCMD;
}