Re: Direct access to parport

[Eric Lammerts <eric@lammerts.org>]

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