/* pario.c
 * Dient zum Auslesen der Standard-Parallelport-Register und kann z. B.
 * verwendet werden um zu sehen, welche Werte in das Status-Register
 * geschrieben wurden.
 *
 * This Program won't work on the sparc, where there's no concept of I/O space
 * Tested with Linux 2.2 on the x86.
 *
 * important: this program won't work without the compiler-option -O or -02 ...
 * and this program can only be run by a superuser (or another user after
 * "chown root.root pario; chmod 4755 pario").
 *
 * It takes approx. 1,5us for one Parallel Port I/O (with an onboard Parallel Port).
 *
 *  dd if=/dev/port bs=1 count=1 skip=889

Rolf Freitag
Lizenz: GPL

 */

#include <stdio.h>
#include <errno.h>                                /* error codes */
#include <sys/io.h>                               /* or <asm/io.h> */
#include <stdlib.h>                               // exit, atoi
#include <unistd.h>                               // getuid(), usleep

#ifndef BIT0                                      /* ifdef to avoid redefinition; existing definitions should be ok */
#   define BIT0                (0x1)              // 2^0
#endif
#ifndef BIT1
#   define BIT1                (0x2)
#endif
#ifndef BIT2
#   define BIT2                (0x4)
#endif
#ifndef BIT3
#   define BIT3                (0x8)
#endif
#ifndef BIT4
#   define BIT4                (0x10)             // 16
#endif
#ifndef BIT5
#   define BIT5                (0x20)             // 32
#endif
#ifndef BIT6
#   define BIT6                (0x40)             // 64
#endif
#ifndef BIT7
#   define BIT7                (0x80)             // 128
#endif

int
main (int argc, char *argv[])
{
  unsigned int b;                                 /* parallel port base (e. g. 0x3bc, 0x378=888 or 0x278=632), a wrong value may cause serious damage */
  unsigned char b0;

  if (2 != argc)
  {
    printf ("Usage: %s <parallel port base>\n", argv[0]);
    exit (-1);
  }
  b = strtol (argv[1],  (char **)NULL, 0);
  if (geteuid () != 0)
  {
    printf ("\a\n\nError: $EUID==%d!=0 (you are not a superuser).\n\n", getuid ());
    exit (-EPERM);
  }
  iopl (3);                                       /* allows access to all I/O-Ports, ioperm doesen't work above the 0x3ff-Limit e. g. at PCI-Cards */
  b0 = inb (b + 2);
  printf ("Der Wert, der von Port 0x%hx (Kontroll-Register des Parallelports) soeben gelesen wurde ist: 0x%hx\n", b + 2, b0);
  printf
    ("BIT0: /STROBE (out, Pin 1), BIT1: /AUTOFD (out, Pin 14), BIT2: /INIT (not inverting, out, Pin 16), BIT3: /SELECT (out, Pin 17), BIT4: Interrupt enable, Bit5: data read /write\n");
  b0 |= BIT5;                                     // read mode
  outb (b0, b + 2);
  // outb (0xff, b);
  b0 = inb (b + 1);
  printf ("Der Wert, der von Port 0x%hx (Status-Register des Parallelports) soeben gelesen wurde ist: 0x%hx\n", b + 1, b0);
  printf ("BIT3: /ERROR (in, Pin 15), BIT4: SELECTING (in, Pin 13), BIT5: PAPEREND (in, Pin 12), BIT6: /ACK (in, l->h irq, Pin 10), BIT7: BUSY (in, Pin 11)\n");
  b0 = inb (b);
  printf ("Der Wert, der von Port 0x%hx (Daten-Register des Parallelports) soeben gelesen wurde ist: 0x%hx\n", b, b0);
  printf ("BIT0 - BIT7: Data0 - Data7 (out (mayby in), Pin 2 - 9)\n");
  iopl (0);                                       /* release region */
  exit (0);
}