Accessing I/O ports

• Functions to read/write bytes (b), word (w) and longs (l) to I/O ports: unsigned in[bwl](unsigned long *addr); void out[bwl](unsigned port, unsigned long *addr);

• And the strings variants: often more efficient than the corresponding C loop, if the processor supports such operations! void ins[bwl](unsigned port, void *addr, unsigned long count); void outs[bwl](unsigned port, void *addr, unsigned long count);

• Examples

• read 8 bits oldlcr = inb(baseio + UART_LCR);
• write 8 bits outb(MOXA_MUST_ENTER_ENCHANCE, baseio + UART_LCR);