kernel/hal/io.c


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#include "kernel.h"

// Write a byte to an I/O port.
void 
out(WORD port, BYTE value )
{
    __asm__ __volatile__ (
	"outb %b0, %w1"
	:
	: "a" (value), "Nd" (port)
    );
}

// Read a byte from an I/O port.
BYTE 
in(WORD port)
{
    BYTE value;

    __asm__ __volatile__ (
	"inb %w1, %b0"
	: "=a" (value)
	: "Nd" (port)
    );

    return value;
}

// Short delay.  May be needed when talking to some
// (slow) I/O devices.
void 
iodelay(void)
{
    BYTE value = 0;
    __asm__ __volatile__ (
	"outb %0, $0x80"
	:
	: "a" (value)
    );
}