FASTIO

Hal_parport has a note about FASTIO

/* If FASTIO is defined, uses outb() and inb() from <asm.io>,
instead of rtapi_outb() and rtapi_inb() - the <asm.io> ones
are inlined, and save a microsecond or two (on my 233MHz box)
*/

I searched around and saw this FASTIO mentioned and enabled in several drivers.
it is NOT in a file name asm.io ( doesnt exist)
there IS an asm/io.h
BUT the macros (inline) seem to be in rtapi_parport.h
the CODE between the triple quotes could be inserted into hal_parport to try
(my intenet is to rewrite hal_pi_gpio to allow invert and reset pins,
so I study all the current techniques to enumrate and store pins & states)

"""
This FASTIO could allow faster threads or reduce UXRTdelays
(UnexpectedRealtimeDelays)

"""
If FASTIO is defined, uses outb() and inb() from <asm.io>,
instead of rtapi_outb() and rtapi_inb() - the <asm.io> ones
are inlined, and save a microsecond or two (on my 233MHz box)
(JMKasunich)

(usage)
#define FASTIO

#ifdef FASTIO
#define rtapi_inb inb
#define rtapi_outb outb
#include <asm/io.h>
#endif
"""
This 'usage' seems to contradict the original notes.

Has anyone tried FASTIO ( used an assembler macro to speed up byte sized reads and writes? )
and
There is no <asm.io> so where are these macros?

Thanks
TomP