// A simple program to set the 8 data pins of a parallel port to input ports.
// If the first and only argument, the parallel port number, starting with 0, has a negativ sign,
// this flag sets the port to write mode.

// Compile with e. g. gcc -Wall -fbounds-check -O2 -o setpar_bppin setpar_bppin.c -lm
// Dr. Rolf Freitag 2015. License: GPL version 3.

#include <errno.h>              // error codes
#include <stdio.h>              // standard i/o
#include <stdlib.h>             // exit, atoi
#include <string.h>             // strndup,
#include <sys/io.h>             // or <asm/io.h>
#include <unistd.h>             // getuid(), usleep
#include <limits.h>             // INT_MAX,
#include <iso646.h>             // and, or, ...
#include <linux/synclink.h>     // BIT0, BIT1, ...
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>          // ioctl(),
#include <linux/ppdev.h>        // parallel port ioctls
#include <linux/parport.h>      // parallel port modes

// simple version (date)
#define SOFTWARE_VERSION "2015-12-05"

#define MAX_LINE_LENGTH 1024    // maximum line length, e. g. for a device name

/* possible modes:
IEEE1284_MODE_NIBBLE            // similar to the SPP (Standard Parallel Port)
IEEE1284_MODE_BYTE              // bidirectional mode, mode bits (BIT5-BIT7 in the ECR) 001 (binary)
IEEE1284_MODE_COMPAT            // compatibility mode, unidirectional (outbound), SPP, mode bits 000
IEEE1284_MODE_BECP              // Bounded ECP mode 
IEEE1284_MODE_ECP               // ECP mode, mode bits 011
IEEE1284_MODE_ECPRLE            // ECP mode with RLE (Run Length Encoding)
IEEE1284_MODE_ECPSWE            // Software-emulated 
IEEE1284_MODE_EPP               // EPP mode, mode bits 100
IEEE1284_MODE_EPPSL             // EPP 1.7 
IEEE1284_MODE_EPPSWE            // Software-emulated 
IEEE1284_DEVICEID               // This is a flag 
IEEE1284_EXT_LINK               // This flag causes the extensibility link to be requested, using bits 0-6.
*/

int
main (int argc, char *argv[])
{
  long int li = 0;              // local variable
  int i_dir = 0, i_ret = 0;     // direction, return value
  int i_sign = 1;               // sign of the first argument, default 1 for + sign
  int fd = 0;                   // file descriptor for the parallel port
  const int ci_mode = IEEE1284_MODE_BYTE;      // bidirectional parallel port mode aka Byte mode aka PS/2 mode aka Tristate mode, should set 0x20 in the ECR via paused IO
  char ac_filename[MAX_LINE_LENGTH + 1] = { 0 };        // filename to the parallel port addresses
  char ac_tmpstring[MAX_LINE_LENGTH + 1] = { 0 };       // Array of Character, temporary string

  if ((1 >= argc) or (3 <= argc))       // less than two or more than two command line arguments
  {
    (void) fprintf (stderr, "Usage: %s <parallel port number, starting with 0>\n", argv[0]);
    (void) fprintf (stderr, "This program sets the specified parallel port, e. g. parport0, into bidirectional parallel port mode\n");
    (void) fprintf (stderr, "aka Byte mode aka PS/2 mode aka Tristate AND mode read mode, the 8 data pins as inputs.\n");
    (void) fprintf (stderr, "If the first arguments has a negativ sign, this flag sets the port to write mode.\n");
    (void) fprintf (stderr, "In this case you have to use an offset of 1, so you must write -1 for setting partport0 to write mode.\n");
    exit (-1);
  }

  if (geteuid () != 0)
  {
    (void) fprintf (stderr, "\a\n\nError: $EUID==%d!=0 (you are not a superuser).\n\n", getuid ());
    exit (-EPERM);
  }

  li = strtol (argv[1], (char **) NULL, 0);     // convert the first program argument to long int, can be decimal, hex or octal
  if (li < 0)                   // < 0 because -0 is equal +0, so -0 is a crackpot input and treated like +0.
  {
    li = labs (li) - 1;         // remove the sign and offset
    i_sign = -1;                // store the sign flag
  }

  // get the device file name from the argument
  // print the parallel port number (0 or 1 or ...)
  snprintf (ac_tmpstring, sizeof (ac_tmpstring) - 1, "%ld", li);

  // Set the file name, e. g. "/dev/parport1"
  strncat (ac_filename, "/dev/parport", 100);
  strncat (ac_filename, ac_tmpstring, 100);

  // The extended mode direction (0 = write, read else), at most parallel ports BIT5 in the control port
  if (i_sign > 0)
  {
    i_dir = 0xff;               // input mode for the data port
  }
  else
  {
    i_dir = 0;                  // output mode for the data port
  }

  fd = open (ac_filename, O_RDWR);      // open read-write
  if (-1 == fd)                 // if error
  {
    (void) fprintf (stderr, "Could not open the device file %s, exiting!\n", ac_filename);
    exit (1);
  }
  (void) fprintf (stdout, "%s opened with file descriptor %d.\n", ac_filename, fd);
  
  // TODO: Read and display the current (old) mode (PPGETMODE) AND data port direction (PPRCONTROL, BIT5)
  
/* // Exclusive mode: Usually does not work; the kernel complains with "parport0: cannot grant exclusive access for device ppdev0"
  i_ret = ioctl (fd, PPEXCL);   // Register device exclusively (must be before PPCLAIM), 
  if (-1 == i_ret)              // if error
  {
    (void) fprintf (stderr, "ERROR: ioctl(fd(%s), PPEXCL) returned %d, errno: %d, %s\n", ac_filename, i_ret, errno, strerror (errno));
  }
*/
  i_ret = ioctl (fd, PPCLAIM);  // Claim the port to start using it
  if (-1 == i_ret)              // if error
  {
    (void) fprintf (stderr, "ERROR: ioctl(fd(%s), PPCLAIM) returned %d, errno: %d, %s\n", ac_filename, i_ret, errno, strerror (errno));
  }

  //i_ret = ioctl (fd, PPNEGOT, &ci_mode); // Negotiate the particular IEEE 1284 mode
  i_ret = ioctl (fd, PPSETMODE, &ci_mode); // Set the particular IEEE 1284 mode
  if (-1 == i_ret)              // if error
  {
    (void) fprintf (stderr, "ERROR: ioctl(fd(%s), PPNEGOT, ptr_ci_mode) returned %d, errno: %d, %s\n", ac_filename, i_ret, errno, strerror (errno));
  }

  i_ret = ioctl (fd, PPCLRIRQ); // Clear (and return) interrupt count
  if (-1 == i_ret)              // if error
  {
    (void) fprintf (stderr, "ERROR: ioctl(fd(%s), PPCLRIRQ) returned %d, errno: %d, %s\n", ac_filename, i_ret, errno, strerror (errno));
  }

  i_ret = ioctl (fd, PPDATADIR, &i_dir);        // set the data port direction: non-zero for input mode, zero for output
  if (-1 == i_ret)              // if error
  {
    (void) fprintf (stderr, "ERROR: ioctl(fd(%s), PPDATADIR, ptr_i_dir) returned %d, errno: %d, %s\n", ac_filename, i_ret, errno, strerror (errno));
  }

  i_ret = ioctl (fd, PPRELEASE);        // Release the port
  if (-1 == i_ret)              // if error
  {
    (void) fprintf (stderr, "ERROR: ioctl(fd(%s), PPRELEASE) returned %d, errno: %d, %s\n", ac_filename, i_ret, errno, strerror (errno));
  }

  i_ret = close (fd);
  if (-1 == i_ret)              // if error
  {
    (void) fprintf (stderr, "ERROR: close(fd(%s)) returned %d, errno: %d, %s\n", ac_filename, i_ret, errno, strerror (errno));
  }

  (void) fprintf (stdout, "The data pins of the parallelport %s are now configured as %s.\n", ac_filename, (i_sign > 0) ? "inputs" : "outputs");

  return (0);                   // exit with ok
}                               // main