ATMEL_MAX_UART
static struct atmel_uart_port atmel_ports[ATMEL_MAX_UART];
static DECLARE_BITMAP(atmel_ports_in_use, ATMEL_MAX_UART);
.nr = ATMEL_MAX_UART,
ret = find_first_zero_bit(atmel_ports_in_use, ATMEL_MAX_UART);
if (ret >= ATMEL_MAX_UART) {