sxmo-utils/programs/sxmo_vibratepine.c

/* Based on: https://xnux.eu/devices/feature/vibrator.html#toc-example-program-to-control-the-vibration-motor */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <stdbool.h>
#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/input.h>


void syscall_error(int is_err, const char* fmt, ...)
{
  va_list ap;

  if (!is_err)
          return;

  printf("ERROR: ");
  va_start(ap, fmt);
  vprintf(fmt, ap);
  va_end(ap);
  printf(": %s\n", strerror(errno));

  exit(1);
}

int open_event_dev(const char* name_needle, int flags)
{
  char path[256];
  char name[256];
  int fd, ret;

  // find the right device and open it
  for (int i = 0; i < 10; i++) {
          snprintf(path, sizeof path, "/dev/input/event%d", i);
          fd = open(path, flags);
          if (fd < 0)
                  continue;

          ret = ioctl(fd, EVIOCGNAME(256), name);
          if (ret < 0)
                  continue;
          
          if (strstr(name, name_needle))
                  return fd;
          
          close(fd);
  }
  
  errno = ENOENT;
  return -1;
}

void usage() {
  fprintf(stderr, "Usage: sxmo_vibratepine duration_ms\n");
  fprintf(stderr, "       sxmo_vibratepine duration_ms strength_number\n");
}

int main(int argc, char* argv[])
{
  int fd, ret;
  struct pollfd pfds[1];
  int effects;

  int durationMs, strength;

  if (argc < 2) {
    usage();
    return 1;
  }
  argc--;

  if (argc > 1) {
    strength = atoi(argv[argc--]);
  } else {
    strength = 4000;
  }

  durationMs = atoi(argv[argc--]);

  fd = open_event_dev("vibrator", O_RDWR | O_CLOEXEC);
  syscall_error(fd < 0, "Can't open vibrator event device");
  ret = ioctl(fd, EVIOCGEFFECTS, &effects);
  syscall_error(ret < 0, "EVIOCGEFFECTS failed");

  struct ff_effect e = {
          .type = FF_RUMBLE,
          .id = -1,
          .u.rumble = { .strong_magnitude = strength },
  };

  ret = ioctl(fd, EVIOCSFF, &e);
  syscall_error(ret < 0, "EVIOCSFF failed");

  struct input_event play = { .type = EV_FF, .code = e.id, .value = 3 };
  ret = write(fd, &play, sizeof play);
  syscall_error(ret < 0, "write failed");

  usleep(durationMs * 1000);

  ret = ioctl(fd, EVIOCRMFF, e.id);
  syscall_error(ret < 0, "EVIOCRMFF failed");

  close(fd);
  return 0;
}