Date: Tue, 23 Apr 1996 01:01:43 +0000 From: "Franz Hollerer" <eeg@telecom.at> To: kuku@gilberto.physik.rwth-aachen.de, Gabor Zahemszky <zgabor@CoDe.hu> Cc: freebsd-questions@freebsd.org Subject: Re: How can I read/write from/to an I/O-port? Message-ID: <199604222308.BAA123184@pina1.telecom.at>
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> > > I have a little problem. So I hope someone can help
> > > me:
> > >
> > > Under Linux a /dev/port exits to write/read to/from an I/O-port.
> > > Does a similar /dev/??? exits under FreeBSD or must I write
> > > a little device driver for this?
> >
> > Under FreeBSD there is /dev/io.
> >
> > Do an open("/dev/io",flags,mode) on it and you can access i/o
> > ports using in/out instructions.
>
> OK. How? What does flags mean? How can I use the fd, I get from open?
> (A little example please....)
Hi,
I did not exactly understand why it works, but it works!
I have looked at the code too.
It really seams that port-io will change (Linux like).
So I give you the example for Linux and SCO too.
For SCO I wrote a little device driver which behaves like /dev/port
under Linux.
Please notice that the example is a fragment of a library.
Franz
/* ============================================================ */
/*
read /write from/to an io-port: inp(), outp()
22.04.96 Franz Hollerer
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#if defined FreeBSD
# include <machine/cpufunc.h>
#endif
#include <fcntl.h>
#include "decl.h"
/* ============================================================ */
int prnterr PARAMS((const char *fmt, ...));
char *getprgname PARAMS(());
void outp PARAMS((int addr, u_char b));
u_char inp PARAMS(());
/* ============================================================ */
#if defined LINUX || defined SCO
/*
output byte from port
*/
void outp(addr, b) /* Linux || SCO */
int addr;
u_char b;
{
static int fd=-1;
if (fd==-1 && (fd=open("/dev/port", O_WRONLY))==-1)
{
prnterr("%s: cannot open '/dev/port'\n", getprgname());
exit(1);
}
lseek(fd, addr, SEEK_SET);
write(fd, &b, 1);
} /* eof outp */
#endif /* LINUX */
#if defined FreeBSD
/*
output byte from port
*/
void outp(addr, b) /* FreeBSD */
int addr;
u_char b;
{
static int fd=-1;
if (fd==-1 && (fd=open("/dev/io", O_WRONLY))==-1)
{
prnterr("%s: cannot open '/dev/io'\n", getprgname());
exit(1);
}
outbv(addr, b);
} /* eof outp */
#endif /* FreeBSD */
#if !defined LINUX && !defined FreeBSD && !defined SCO
# warning "outp() not implemented!"
#endif /* !LINUX && !FreeBSD */
/* ============================================================ */
#if defined LINUX || SCO
/*
input byte from port
*/
u_char inp(addr) /* Linux || SCO */
int addr;
{
static int fd=-1;
u_char b;
if (fd==-1 && (fd=open("/dev/port", O_RDONLY))==-1)
{
prnterr("%s: cannot open '/dev/port'\n", getprgname());
exit(1);
}
lseek(fd, addr, SEEK_SET);
read(fd, &b, 1);
return(b);
} /* eof inp */
#endif /* LINUX */
#if defined FreeBSD
/*
input byte from port
*/
u_char inp(addr) /* FreeBSD */
int addr;
{
static int fd=-1;
u_char b;
if (fd==-1 && (fd=open("/dev/io", O_RDONLY))==-1)
{
prnterr("%s: cannot open '/dev/io'\n", getprgname());
exit(1);
}
b=inbv(addr);
return(b);
} /* eof inp */
#endif /* FreeBSD */
#if !defined LINUX && !defined FreeBSD && !defined SCO
# warning: "inp() not implemented!"
#endif /* !LINUX && !FreeBSD */
EEG, Hard&Software Development
Austria
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