HID Descriptor dump

/*
 * Dump Hidraw Descriptor
 *
 * adapted from:
 * Hidraw Userspace Example
 *
 */

/* Linux */
#include <linux/types.h>
#include <linux/input.h>
#include <linux/hidraw.h>

/*
 * Ugly hack to work around failing compilation on systems that don't
 * yet populate new version of hidraw.h to userspace.
 */
#ifndef HIDIOCSFEATURE
#warning Please have your distro update the userspace kernel headers
#define HIDIOCSFEATURE(len)    _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x06, len)
#define HIDIOCGFEATURE(len)    _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x07, len)
#endif

/* Unix */
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

/* C */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>

const char *
bus_str(int bus)
{
  switch (bus) {
  case BUS_USB:
    return "USB";
    break;
  case BUS_HIL:
    return "HIL";
    break;
  case BUS_BLUETOOTH:
    return "Bluetooth";
    break;
  case BUS_VIRTUAL:
    return "Virtual";
    break;
  default:
    return "Other";
    break;
  }
}

/*

Usage: hid-desc /dev/hidraw1 etc.

 */

int main(int argc, char **argv)
{
  int fd;
  int i, res, desc_size = 0;
  char buf[256];
  struct hidraw_report_descriptor rpt_desc;
  struct hidraw_devinfo info;
  char *device = "/dev/hidraw0";

  if (argc > 1)
    device = argv[1];

  /* Open the Device with non-blocking reads. In real life,
     don't use a hard coded path; use libudev instead. */
  fd = open(device, O_RDWR|O_NONBLOCK);

  if (fd < 0) {
    perror("Unable to open device");
    return 1;
  }

  memset(&rpt_desc, 0x0, sizeof(rpt_desc));
  memset(&info, 0x0, sizeof(info));
  memset(buf, 0x0, sizeof(buf));

  /* Get Report Descriptor Size */
  res = ioctl(fd, HIDIOCGRDESCSIZE, &desc_size);
  if (res < 0)
    perror("HIDIOCGRDESCSIZE");
  else
    printf("Report Descriptor Size: %d\n", desc_size);

  /* Get Report Descriptor */
  rpt_desc.size = desc_size;
  res = ioctl(fd, HIDIOCGRDESC, &rpt_desc);
  if (res < 0) {
    perror("HIDIOCGRDESC");
  } else {
    printf("Report Descriptor:\n");
    for (i = 0; i < rpt_desc.size; i++)
      printf("%02hhx ", rpt_desc.value[i]);
    puts("\n");
  }

  /* Get Raw Name */
  res = ioctl(fd, HIDIOCGRAWNAME(256), buf);
  if (res < 0)
    perror("HIDIOCGRAWNAME");
  else
    printf("Raw Name: %s\n", buf);

  /* Get Physical Location */
  res = ioctl(fd, HIDIOCGRAWPHYS(256), buf);
  if (res < 0)
    perror("HIDIOCGRAWPHYS");
  else
    printf("Raw Phys: %s\n", buf);

  /* Get Raw Info */
  res = ioctl(fd, HIDIOCGRAWINFO, &info);
  if (res < 0) {
    perror("HIDIOCGRAWINFO");
  } else {
    printf("Raw Info:\n");
    printf("\tbustype: %d (%s)\n",
      info.bustype, bus_str(info.bustype));
    printf("\tvendor: 0x%04hx\n", info.vendor);
    printf("\tproduct: 0x%04hx\n", info.product);
  }

#if 0
  /* Get a report from the device */
  res = read(fd, buf, 16);
  if (res < 0) {
    perror("read");
  } else {
    printf("read() read %d bytes:\n\t", res);
    for (i = 0; i < res; i++)
      printf("%hhx ", buf[i]);
    puts("\n");
  }
#endif

  close(fd);
  return 0;
}