Control XMMS with parallel port

paraxmms.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>

#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kd.h>

#include "parapin.h"

void xmms_command(int command);
void gom_volume(int delta);
void run_command(char* commandLine, char** argList);

#define XMMS_FWD 1
#define XMMS_REW 2
#define XMMS_PLAY 3
#define XMMS_PAUSE 4
#define XMMS_STOP 5
#define XMMS_VOL_P 6
#define XMMS_VOL_M 7

#define VOLUME_DELTA 5

int main(int argc, char *argv[])
{
  struct timespec t_check;
  struct timespec t_refrac;
  int value;
  int r_pin = LP_PIN02;
  int min_nrefrac = 200000000;
  int max_nrefrac = 500000000;
  int refrac_delta = 50000000;
  int fd = open("/dev/tty0", O_RDONLY);

  t_check.tv_sec = 0;
  t_check.tv_nsec = 100000000;
  t_refrac.tv_sec = 0;
  t_refrac.tv_nsec = max_nrefrac;
  
  if (pin_init_user(LPT1) < 0) {
    exit(0);
  }

  pin_output_mode(LP_DATA_PINS);
  pin_input_mode(LP_PIN10 | LP_PIN11 | LP_PIN12 | LP_PIN13 | LP_PIN15);
  
  printf("\nstarting\n");
  clear_pin(r_pin);
  set_pin(r_pin);
  while (1) {
    value = pin_is_set(LP_PIN10 | LP_PIN11 | LP_PIN12 | LP_PIN13 | LP_PIN15);
    //printf("Pin 10: %s Pin 11: %s\n", value_10 ? "HIGH":"LOW", value_11 ? "HIGH":"LOW");
    printf("Value: %i\n", value);
    if (value) {
      ioctl(fd,KDMKTONE,(10<<16)+(1193180/1000));
      if (value & LP_PIN10) {
        printf("Pin 10 is high\n");
        xmms_command(XMMS_REW);
      }
      if (value & LP_PIN11) {
        printf("Pin 11 is high\n");
        gom_volume(VOLUME_DELTA);
      }
      if (value & LP_PIN12) {
        printf("Pin 12 is high\n");
        xmms_command(XMMS_PLAY);
      }
      if (value & LP_PIN13) {
        printf("Pin 13 is high\n");
        xmms_command(XMMS_FWD);
      }
      if (value & LP_PIN15) {
        printf("Pin 15 is high\n");
        gom_volume(-VOLUME_DELTA);
      }
      clear_pin(r_pin);
      nanosleep(&t_refrac, NULL);
      t_refrac.tv_nsec -= refrac_delta;
      if (t_refrac.tv_nsec < min_nrefrac) t_refrac.tv_nsec = min_nrefrac;
    } else {
      t_refrac.tv_nsec = max_nrefrac;
      nanosleep(&t_check, NULL);
    }
    set_pin(r_pin);
  }
  printf("\n\n");
  return 0;
}

void xmms_command(int command) {

    int cmd_length = 30;
    char commandLine[cmd_length];
    char* argList[6];

    snprintf(commandLine, cmd_length, "./xmms-cmd.sh");
    argList[0] = "./xmms-cmd.sh";
    if (command == XMMS_FWD) {
        argList[1] = "--fwd";
    } else if (command == XMMS_REW) {
        argList[1] = "--rew";
    } else if (command == XMMS_PLAY) {
        argList[1] = "--play-pause";
    } else if (command == XMMS_PAUSE) {
        argList[1] = "--pause";
    } else if (command == XMMS_STOP) {
        argList[1] = "--stop";
    } else if (command == XMMS_VOL_P) {
        argList[1] = "-v"; // not yet supported
    } else if (command == XMMS_VOL_M) {
        argList[1] = "-v"; // not yet supported
    } else {
        printf("xmms_command: Unknown command: %i\n", command);
        exit;
    }
    argList[2] = NULL;
    
    run_command(commandLine, argList);
}

void gom_volume(int delta) {

    int cmd_length = 30;
    char commandLine[cmd_length];
    char* argList[6];

    fprintf(stderr, "[gom_volume] Delta: %i\n", delta);

    snprintf(commandLine, cmd_length, "gom");
    argList[0] = "gom";
    argList[1] = "--volume";
    if (delta > 0) {
        snprintf(argList[2], 10, "+%i", delta);
    } else {
        snprintf(argList[2], 10, "%i", delta);
    }
    argList[3] = NULL;

    run_command(commandLine, argList);
}

void run_command(char* commandLine, char** argList) {
    int returnValue = fork();
    switch (returnValue) {
        case 0:
            returnValue = execvp(commandLine, argList); // should never return
            perror("[child] Can't execute\n");
            exit(1); // Causes the child process to become zombie until the parent process exits
            break;
        case -1:
            fprintf(stderr, "Can't fork!");
            break;
        default:
            //fprintf(stderr, "Child process ID: %i\n", returnValue);
            break;
    }
}