matos/core/io.h
2018-07-20 15:42:51 +02:00

22 lines
798 B
C

#pragma once
#include "types.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;
}