rm device identification

device_id.cpp

using namespace std;
#include <fcntl.h>
#include <linux/input.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

// from evtest.c
#define BITS_PER_LONG (sizeof(long) * 8)
#define NBITS(x) ((((x)-1) / BITS_PER_LONG) + 1)
#define OFF(x) ((x) % BITS_PER_LONG)
#define BIT(x) (1UL << OFF(x))
#define LONG(x) ((x) / BITS_PER_LONG)
#define test_bit(bit, array) ((array[LONG(bit)] >> OFF(bit)) & 1)

namespace input {
enum EV_TYPE { TOUCH, STYLUS, BUTTONS, UNKNOWN, INVALID };
auto check_bit_set(int fd, int type, int i) {
  unsigned long bit[NBITS(KEY_MAX)];
  ioctl(fd, EVIOCGBIT(type, KEY_MAX), bit);
  return test_bit(i, bit);
}

EV_TYPE id_by_capabilities(int fd) {
  int version;

  if (ioctl(fd, EVIOCGVERSION, &version)) {
    return INVALID;
  }

  unsigned long bit[EV_MAX];
  ioctl(fd, EVIOCGBIT(0, EV_MAX), bit);

  if (test_bit(EV_KEY, bit)) {
    if (check_bit_set(fd, EV_KEY, BTN_STYLUS) && test_bit(EV_ABS, bit)) {
      return STYLUS;
    }
    if (check_bit_set(fd, EV_KEY, KEY_POWER)) {
      return BUTTONS;
    }
  }
  if (test_bit(EV_REL, bit)) {
    if (check_bit_set(fd, EV_ABS, ABS_MT_SLOT)) {
      return TOUCH;
    }
  }

  return UNKNOWN;
}

EV_TYPE id_by_name(int fd) {
  char name[256];
  ioctl(fd, EVIOCGNAME(sizeof(name)), name);
  auto s = std::string(name);
  if (s.find("I2C Digitizer") != -1) {
    return STYLUS;
  }
  if (s.find("_mt") != -1) {
    return TOUCH;
  }
  if (s.find("keys") != -1) {
    return BUTTONS;
  }

  return UNKNOWN;
}
}; // namespace input

int main(int argc, char *argv[]) {
  for (auto s : {"/dev/input/event0", "/dev/input/event1", "/dev/input/event2",
                 "/dev/input/mice"}) {
    auto fd = open(s, O_RDWR);
    std::cout << s << ' ' << input::id_by_capabilities(fd) << ' '
              << input::id_by_name(fd) << std::endl;
    close(fd);
  };
};