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Date: Tue, 4 Mar 2003 23:31:52 +0100 (CET)
From: Eric Lammerts <eric@lammerts.org>
To: Uwe Reimann <linux-kernel@pulsar.homelinux.net>
cc: linux-kernel@vger.kernel.org
Subject: Re: Direct access to parport
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On Tue, 4 Mar 2003, Uwe Reimann wrote:
> I'd like to connect some self made hardware to the parallel port and
> read the values of the dataline using linux. Can this be done in
> userspace or do I have to write kernel code to do so? I'm currently
> thinking of writing a device like lp, which in turn uses the parport
> device. Does this sound like a good idea?

>From userspace it's quite simple:

#include <stdio.h>
#include <sys/io.h>

int main(int argc, char **argv)
{
	int addr = 0x378;

	if(ioperm(addr, 3, 1) == -1) {
		perror("ioperm");
		exit(1);
	}
	printf("0x%02x\n", inb(addr + 1));
}

The ioperm() only works if you're root.

Eric
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