io.h

#ifndef _ASM_IO_H
#define _ASM_IO_H

/*
 * This file contains the definitions for the x86 IO instructions
 * inb/inw/inl/outb/outw/outl and the "string versions" of the same
 * (insb/insw/insl/outsb/outsw/outsl). You can also use "pausing"
 * versions of the single-IO instructions (inb_p/inw_p/..).
 *
 * This file is not meant to be obfuscating: it's just complicated
 * to (a) handle it all in a way that makes gcc able to optimize it
 * as well as possible and (b) trying to avoid writing the same thing
 * over and over again with slight variations and possibly making a
 * mistake somewhere.
 */

#ifdef SLOW_IO_BY_JUMPING
#define __SLOW_DOWN_IO __asm__ __volatile__("jmp 1f\n1:\tjmp 1f\n1:")
#else
#define __SLOW_DOWN_IO __asm__ __volatile__("outb %al,$0x80")
#endif

#ifdef REALLY_SLOW_IO
#define SLOW_DOWN_IO { __SLOW_DOWN_IO; __SLOW_DOWN_IO; __SLOW_DOWN_IO; __SLOW_DOWN_IO; }
#else
#define SLOW_DOWN_IO __SLOW_DOWN_IO
#endif

/*
 * Talk about misusing macros..
 */

#define __OUT1(s,x) \
static inline void __out##s(unsigned x value, unsigned short port) {

#define __OUT2(s,s1,s2) \
__asm__ __volatile__ ("out" #s " %" s1 "0,%" s2 "1"

#define __OUT(s,s1,x) \
__OUT1(s,x) __OUT2(s,s1,"w") : : "a" (value), "d" (port)); } \
__OUT1(s##c,x) __OUT2(s,s1,"") : : "a" (value), "id" (port)); } \
__OUT1(s##_p,x) __OUT2(s,s1,"w") : : "a" (value), "d" (port)); SLOW_DOWN_IO; } \
__OUT1(s##c_p,x) __OUT2(s,s1,"") : : "a" (value), "id" (port)); SLOW_DOWN_IO; }

#define __IN1(s) \
static inline RETURN_TYPE __in##s(unsigned short port) { RETURN_TYPE _v;

#define __IN2(s,s1,s2) \
__asm__ __volatile__ ("in" #s " %" s2 "1,%" s1 "0"

#define __IN(s,s1,i...) \
__IN1(s) __IN2(s,s1,"w") : "=a" (_v) : "d" (port) ,##i ); return _v; } \
__IN1(s##c) __IN2(s,s1,"") : "=a" (_v) : "id" (port) ,##i ); return _v; } \
__IN1(s##_p) __IN2(s,s1,"w") : "=a" (_v) : "d" (port) ,##i ); SLOW_DOWN_IO; return _v; } \
__IN1(s##c_p) __IN2(s,s1,"") : "=a" (_v) : "id" (port) ,##i ); SLOW_DOWN_IO; return _v; }

#define __OUTS(s) \
extern inline void outs##s(unsigned short port, const void * addr, unsigned long count) \
{ __asm__ __volatile__ ("cld ; rep ; outs" #s \
: "=S" (addr), "=c" (count) : "d" (port),"0" (addr),"1" (count)); }

#define RETURN_TYPE unsigned char
/* __IN(b,"b","0" (0)) */
__IN(b,"")
#undef RETURN_TYPE
#define RETURN_TYPE unsigned short
/* __IN(w,"w","0" (0)) */
__IN(w,"")
#undef RETURN_TYPE
#define RETURN_TYPE unsigned int
__IN(l,"")
#undef RETURN_TYPE

__OUT(b,"b",char)
__OUT(w,"w",short)
__OUT(l,,int)

__OUTS(b)
__OUTS(w)
__OUTS(l)

/*
 * Note that due to the way __builtin_constant_p() works, you
 *  - can't use it inside a inline function (it will never be true)
 *  - you don't have to worry about side effects within the __builtin..
 */
#define outb(val,port) \
((__builtin_constant_p((port)) && (port) < 256) ? \
	__outbc((val),(port)) : \
	__outb((val),(port)))

#define inb(port) \
((__builtin_constant_p((port)) && (port) < 256) ? \
	__inbc(port) : \
	__inb(port))


#define outw(val,port) \
((__builtin_constant_p((port)) && (port) < 256) ? \
	__outwc((val),(port)) : \
	__outw((val),(port)))

#define inw(port) \
((__builtin_constant_p((port)) && (port) < 256) ? \
	__inwc(port) : \
	__inw(port))


#define outl(val,port) \
((__builtin_constant_p((port)) && (port) < 256) ? \
	__outlc((val),(port)) : \
	__outl((val),(port)))

#define inl(port) \
((__builtin_constant_p((port)) && (port) < 256) ? \
	__inlc(port) : \
	__inl(port))

static __inline unsigned char
inb_p (unsigned short int __port)
{
	  unsigned char _v;

	    __asm__ __volatile__ ("inb %w1,%0\noutb %%al,$0x80":"=a" (_v):"Nd" (__port));
	      return _v;
}

static __inline void
outb_p (unsigned char __value, unsigned short int __port)
{
	  __asm__ __volatile__ ("outb %b0,%w1\noutb %%al,$0x80": :"a" (__value),
			                          "Nd" (__port));
}

#endif