Date: Mon, 22 Apr 1996 09:21:17 +0200 (MET DST) From: "Christoph P. Kukulies" <kuku@gilberto.physik.rwth-aachen.de> To: zgabor@CoDe.hu (Gabor Zahemszky) Cc: kuku@gilberto.physik.rwth-aachen.de, freebsd-questions@freebsd.org Subject: Re: How can I read/write from/to an I/O-port? Message-ID: <199604220721.JAA24177@gilberto.physik.rwth-aachen.de> In-Reply-To: <199604191211.MAA03635@CoDe.CoDe.hu>
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>
> >
> > >
> > > Hi,
> > >
> > > 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....)
/usr/include/fcntl.h:
#define O_RDONLY 0x0000 /* open for reading only */
#define O_WRONLY 0x0001 /* open for writing only */
#define O_RDWR 0x0002 /* open for reading and writing */
#define O_ACCMODE 0x0003 /* mask for above modes */
If you want to read & write to a specific port, use O_RDWR.
Once you have opened the io space (device), you can read/write
(be cautious!) to any location in the io space. That can be
done by in/out (inline assembler - gcc) or by functions, doing that.
Look at the driver code in /sys/i386/isa. It's full of example code.
>
> --
> Gabor Zahemszky <zgabor@CoDe.hu>
>
> -:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-
> Earth is the cradle of human sense, but you can't stay in the cradle forever.
> Tsiolkovsky
>
--Chris Christoph P. U. Kukulies kuku@gil.physik.rwth-aachen.de
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