Date: Wed, 19 Feb 1997 22:43:26 +0100 From: j@uriah.heep.sax.de (J Wunsch) To: dario@escher.usr.dsi.unimi.it (Dario Maggiorini) Cc: freebsd-hackers@freebsd.org Subject: Re: parallel read Message-ID: <Mutt.19970219224326.j@uriah.heep.sax.de> In-Reply-To: <199702191142.DAA18699@freefall.freebsd.org>; from Dario Maggiorini on Feb 19, 1997 12:37:49 %2B0100 References: <199702191142.DAA18699@freefall.freebsd.org>
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As Dario Maggiorini wrote:
> has anyone of you already
>
> 1 - modified the parallel driver
Dunno.
> 2 - a pointer to some kind of documentation
Add the desired input function as an ioctl into lptioctl. You're
going to read 4 or 5 bits a time only, so you can conveniently pass
them back to the caller within a single `int' value. I wouldn't
bother setting up a lptread() function for this.
> 3 - write asm code to access directly the memory location
> ( i believe it's possible but can't write it by myself, i'm in a hurry
> and has no time to learn asm details )
No need for hairy asm details. They are well-hidden from you, you're
only operating with C or pseudo-C code at the driver level. All you
need is a single inb() call. Have a look into /sys/i386/isa/lpt.c,
and you should figure this out within an hour, provided you've got
reasonable understanding of C coding.
The ioctl command names for lpt(4) are defined in
/sys/i386/include/lpt.h, so they are usable as #include <machine/lpt.h>
from a userland program. Simply add there a:
#define LPT_READSTAT _IOR('p', 2, int) /* get status bits */
Remember that your calling program must pass the _address_ of an int:
#include <sys/ioctl.h>
#include <machine/lpt.h>
...
int status, fd;
if ((fd = open(PATH_LP, O_RDONLY)) == -1) {
err(...);
}
...
if (ioctl(fd, LPT_READSTAT, &status) == -1) {
err(1, "Can't read status");
}
--
cheers, J"org
joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)
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