#pragma once #include "stdarg.h" // NIH http://wiki.osdev.org/Inline_Assembly/Examples#I.2FO_access static inline void outb(uint16_t port, uint8_t val) { asm volatile ( "outb %0, %1" : : "a"(val), "Nd"(port) ); /* There's an outb %al, $imm8 encoding, for compile-time constant port numbers that fit in 8b. (N constraint). * Wider immediate constants would be truncated at assemble-time (e.g. "i" constraint). * The outb %al, %dx encoding is the only option for all other cases. * %1 expands to %dx because port is a uint16_t. %w1 could be used if we had the port number a wider C type */ } static inline uint8_t inb(uint16_t port) { uint8_t ret; asm volatile ( "inb %1, %0" : "=a"(ret) : "Nd"(port) ); return ret; }