Linux下获取usb视频设备vendor id和product id的8种方法

谁借莪１个温暖的怀抱￠ 2023-06-21 10:25 115阅读 0赞

在使用usb摄像头获取视频时，有时需要获取此摄像头供应商ID(vendor id, vid)和产品ID(product id, pid)，这里在Linux下提供获取vid和pid的8种方法：

  1. 通过v4l2中结构体v4l2_capability的成员变量card：此变量中会包含设备名、vid、pid信息，其内容例如为“UVC Camera (046d:081b)”，其中”:”前四个字符为vid，”:”后四个字符为pid，代码段如下：其中str存放card的值

    std::string str = (*it).second;
    auto pos = str.find(“:”);
    if (pos != std::string::npos) {

    1.  std::string vid_str = str.substr(pos-4, 4);
    2.  std::string pid_str = str.substr(pos+1, 4);
    3.  std::istringstream(vid_str) >> std::hex >> vid_value;
    4.  std::istringstream(pid_str) >> std::hex >> pid_value;
    5.  fprintf(stdout, "  vid: str: %s, value: %d; pid: str: %s, value: %d\n", vid_str.c_str(), vid_value, pid_str.c_str(), pid_value);

    }

  2. 通过解析/sys/class/video4linux/xxxx/device/modalias文件，其中xxxx为video0或video1等，当有usb camera插入到Linux上时，则会有此文件，其内容例如为” usb:v046Dp081Bd0012dcEFdsc02dp01ic0Eisc01ip00in00”，其中”usb:v”后四个字符为vid，”usb:v046Dp”后四个字符为pid，代码段如下：其中str为设备地址，如”/dev/video0”

    str = (*it).first;
    pos = str.find_last_of(“/“);
    if (pos == std::string::npos) {

    1.  fprintf(stderr, "  fail to get vid and pid\n");

    }
    std::string name = str.substr(pos+1);
    std::string modalias;
    vid_value = 0; pid_value = 0;
    if (!(std::ifstream(“/sys/class/video4linux/“ + name + “/device/modalias”) >> modalias))

    1.  fprintf(stderr, "  fail to read modalias\n");

    if (modalias.size() < 14 || modalias.substr(0,5) != “usb:v” || modalias[9] != ‘p’)

    1.  fprintf(stderr, "  not a usb format modalias\n");

    if (!(std::istringstream(modalias.substr(5,4)) >> std::hex >> vid_value))

    1.  fprintf(stderr, "  fail to read vid\n");

    if (!(std::istringstream(modalias.substr(10,4)) >> std::hex >> pid_value))

    1.  fprintf(stderr, "  fail to read pid\n");

    fprintf(stdout, “ vid value: %d, pid value: %d\n”, vid_value, pid_value);

  3. 通过解析/proc/bus/input/devices文件，输入设备名可以获取对应的vid和pid，代码段如下：其中bus_line为”I: Bus=0003 Vendor=046d Product=081b Version=0012”

    auto pos = bus_line.find(“Vendor”);
    if (pos != std::string::npos) {

    1.  std::string str = bus_line.substr(pos+7, 4);
    2.  std::istringstream(str) >> std::hex >> vid;

    } else {

    1.  fprintf(stderr, "not found vid\n");
    2.  return -1;

    }

    pos = bus_line.find(“Product”);
    if (pos != std::string::npos) {

    1.  std::string str = bus_line.substr(pos+8, 4);
    2.  std::istringstream(str) >> std::hex >> pid;

    } else {

    1.  fprintf(stderr, "not found pid\n");
    2.  return -1;

    }

  4. 通过设备的event可以直接读取vid和pid，如event为event6，则为/sys/class/input/event6/device/id/vendor和/sys/class/input/event6/device/id/product，可通过解析/proc/bus/input/devices得到指定设备的event，代码段为：其中event_line为”H: Handlers=kbd event6”

    auto pos = event_line.find(search_event_line);
    if (pos != std::string::npos) {

    1.  std::string str = event_line.substr(pos, std::string::npos);
    2.  str.erase(std::remove_if(str.begin(), str.end(), isspace), str.end());
    3.  std::string vid_str, pid_str;
    4.  std::string prefix = "/sys/class/input/" + str + "/device/id/";
    5.  if (!(std::ifstream(prefix +"vendor") >> vid_str)) {
    6.        fprintf(stderr, "not found /device/id/vendor\n");
    7.        return -1;
    8.  }
    9.  if (!(std::ifstream(prefix + "product") >> pid_str)) {
    10.        fprintf(stderr, "not found /device/id/product\n");
    11.        return -1;
    12.  }
    14.  std::istringstream(vid_str) >> std::hex >> vid;
    15.  std::istringstream(pid_str) >> std::hex >> pid;

    }

  5. 通过解析/sys/kernel/debug/usb/devices可获取vid和pid，但是好像需要root权限。

  6. 通过在Linux上安装libusb，然后调用其库提供的相应接口来获取vid和pid。

  7. 可以通过执行lsusb命令获取vid和pid，执行结果如下：其中红框标注的为真实usb摄像头信息

20191212140933219.png

  1. 可以通过执行v4l2-ctl —list-devices命令获取vid和pid，执行结果如下：

20191212141124864.png

以下是上面1—4种方法实现的完整C++代码：

  1. #include "funset.hpp"
  2. #include <map>
  3. #include <string>
  4. #include <sstream>
  5. #include <fstream>
  6. #include <algorithm>
  7. #ifndef _MSC_VER
  8. #include <dirent.h>
  9. #include <fcntl.h>
  10. #include <unistd.h>
  11. #include <errno.h>
  12. #include <sys/stat.h>
  13. #include <sys/types.h>
  14. #include <sys/time.h>
  15. #include <sys/mman.h>
  16. #include <sys/ioctl.h>
  17. #include <linux/videodev2.h>
  18. #else
  19. #endif
  21. #ifndef _MSC_VER
  22. namespace {
  24. int v4l2_is_v4l_dev(const char *name)
  25. {
  26.     return !strncmp(name, "video", 5) ||
  27.         !strncmp(name, "radio", 5) ||
  28.         !strncmp(name, "vbi", 3) ||
  29.         !strncmp(name, "v4l-subdev", 10);
  30. }
  32. int test_v4l2_get_device_list(std::map<std::string, std::string>& device_list)
  33. {
  34.     device_list.clear();
  36.     const char* dir_name = "/dev";
  37.     DIR* dir = opendir(dir_name);
  38.     if (!dir) {
  39.         fprintf(stderr, "Error: couldn't open the directory: %s\n", dir_name);
  40.         return -1;
  41.     }
  43.     struct dirent* entry = nullptr;
  44.     int fd;
  46.     while ((entry = readdir(dir))) {
  47.         char device_name[256];
  48.         if (!v4l2_is_v4l_dev(entry->d_name))
  49.             continue;
  51.         snprintf(device_name, sizeof(device_name), "/dev/%s", entry->d_name);
  52.         if ((fd = device_open(device_name)) < 0)
  53.             continue;
  55.         struct v4l2_capability cap;
  56.         if (ioctl(fd, VIDIOC_QUERYCAP, &cap) < 0) {
  57.             fprintf(stderr, "Error: cam_info: can't open device: %s\n", device_name);
  58.             goto fail;
  59.         }
  61.         device_list[device_name] = reinterpret_cast<char*>(cap.card);
  63.         close(fd);
  64.         continue;
  66.         fail:
  67.             if (fd >= 0) close(fd);
  68.             break;
  69.     }
  71.     closedir(dir);
  72.     return 0;
  73. }
  75. int parse_input_devices(const std::string& name, unsigned int& vid, unsigned int& pid)
  76. {
  77.     const std::string device_list_file = "/proc/bus/input/devices";
  78.     std::ifstream file_input(device_list_file.c_str());
  79.     if (!file_input.is_open()) {
  80.         fprintf(stderr, "fail to open file: %s\n", device_list_file.c_str());
  81.         return -1;
  82.     }
  84.     std::string current_line, bus_line, search_name_line = name, search_bus_line = "Bus=";
  85.     while (getline(file_input, current_line)) {
  86.         auto pos = current_line.find(search_bus_line);
  87.         if (pos != std::string::npos)
  88.               bus_line = current_line;
  90.         pos = current_line.find(search_name_line);
  91.         if (pos != std::string::npos)
  92.               break;
  93.     }
  94.     file_input.close();
  96.     auto pos = bus_line.find("Vendor");
  97.     if (pos != std::string::npos) {
  98.         std::string str = bus_line.substr(pos+7, 4);
  99.         std::istringstream(str) >> std::hex >> vid;
  100.     } else {
  101.         fprintf(stderr, "not found vid\n");
  102.         return -1;
  103.     }
  105.     pos = bus_line.find("Product");
  106.     if (pos != std::string::npos) {
  107.         std::string str = bus_line.substr(pos+8, 4);
  108.         std::istringstream(str) >> std::hex >> pid;
  109.     } else {
  110.         fprintf(stderr, "not found pid\n");
  111.         return -1;
  112.     }
  114.     return 0;
  115. }
  117. int parse_input_devices2(const std::string& name, unsigned int& vid, unsigned int& pid)
  118. {
  119.     const std::string device_list_file = "/proc/bus/input/devices";
  120.     std::ifstream file_input(device_list_file.c_str());
  121.     if (!file_input.is_open()) {
  122.         fprintf(stderr, "fail to open file: %s\n", device_list_file.c_str());
  123.         return -1;
  124.     }
  126.     std::string current_line, event_line, search_name_line = name, search_event_line = "event";
  127.     bool flag = false;
  128.     while (getline(file_input, current_line)) {
  129.         auto pos = current_line.find(search_name_line);
  130.         if (pos != std::string::npos)
  131.               flag = true;
  132.         else if (!flag)
  133.             continue;
  135.         if (flag) {
  136.             pos = current_line.find(search_event_line);
  137.             if (pos != std::string::npos) {
  138.                 event_line = current_line;
  139.                 break;
  140.             }
  141.         }
  142.     }
  143.     file_input.close();
  145.     if (!flag) {
  146.         fprintf(stderr, "not found event\n");
  147.         return -1;
  148.     }
  150.     auto pos = event_line.find(search_event_line);
  151.     if (pos != std::string::npos) {
  152.         std::string str = event_line.substr(pos, std::string::npos);
  153.         str.erase(std::remove_if(str.begin(), str.end(), isspace), str.end());
  154.         std::string vid_str, pid_str;
  155.         std::string prefix = "/sys/class/input/" + str + "/device/id/";
  156.         if (!(std::ifstream(prefix +"vendor") >> vid_str)) {
  157.               fprintf(stderr, "not found /device/id/vendor\n");
  158.               return -1;
  159.         }
  160.         if (!(std::ifstream(prefix + "product") >> pid_str)) {
  161.               fprintf(stderr, "not found /device/id/product\n");
  162.               return -1;
  163.         }
  165.         std::istringstream(vid_str) >> std::hex >> vid;
  166.         std::istringstream(pid_str) >> std::hex >> pid;
  167.     }
  169.     return 0;
  170. }
  172. } // namespace
  174. int test_get_usb_camera_vid_pid()
  175. {
  176.     // get usb video device list
  177.     std::map<std::string, std::string> device_list;
  178.     if (test_v4l2_get_device_list(device_list) !=0) {
  179.         fprintf(stderr, "fail to get usb video device list\n");
  180.         return -1;
  181.     }
  183.     int count = 1;
  184.     fprintf(stdout, "device count: %d\n", device_list.size());
  185.     for (auto it = device_list.cbegin(); it != device_list.cend(); ++it) {
  186.         fprintf(stdout, "%d. device address: %s, description(name): %s\n", count++,  (*it).first.c_str(), (*it).second.c_str());
  188.         unsigned int vid_value, pid_value;
  189.         fprintf(stdout, " method1. get vid and pid through v4l2:\n");
  190.         std::string str = (*it).second;
  191.         auto pos = str.find(":");
  192.         if (pos != std::string::npos) {
  193.             std::string vid_str = str.substr(pos-4, 4);
  194.             std::string pid_str = str.substr(pos+1, 4);
  195.             std::istringstream(vid_str) >> std::hex >> vid_value;
  196.             std::istringstream(pid_str) >> std::hex >> pid_value;
  197.             fprintf(stdout, "  vid: str: %s, value: %d; pid: str: %s, value: %d\n", vid_str.c_str(), vid_value, pid_str.c_str(), pid_value);
  198.         } else {
  199.             fprintf(stderr, "  fail to get vid and pid\n");    
  200.         }
  202.         fprintf(stdout, " method2. get vid and pid through device/modalias:\n");
  203.         str = (*it).first;
  204.         pos = str.find_last_of("/");
  205.         if (pos == std::string::npos) {
  206.             fprintf(stderr, "  fail to get vid and pid\n");
  207.         }
  208.         std::string name = str.substr(pos+1);
  209.         std::string modalias;
  210.         vid_value = 0; pid_value = 0;
  211.         if (!(std::ifstream("/sys/class/video4linux/" + name + "/device/modalias") >> modalias))
  212.             fprintf(stderr, "  fail to read modalias\n");
  213.         if (modalias.size() < 14 || modalias.substr(0,5) != "usb:v" || modalias[9] != 'p')
  214.             fprintf(stderr, "  not a usb format modalias\n");
  215.         if (!(std::istringstream(modalias.substr(5,4)) >> std::hex >> vid_value))
  216.             fprintf(stderr, "  fail to read vid\n");
  217.         if (!(std::istringstream(modalias.substr(10,4)) >> std::hex >> pid_value))
  218.             fprintf(stderr, "  fail to read pid\n");
  219.         fprintf(stdout, "  vid value: %d, pid value: %d\n", vid_value, pid_value);
  221.         fprintf(stdout, " method3. get vid and pid through /proc/bus/input/devices:\n");
  222.         vid_value = 0; pid_value = 0;
  223.         parse_input_devices((*it).second, vid_value, pid_value);
  224.         fprintf(stdout, "  vid value: %d, pid value: %d\n", vid_value, pid_value);
  226.         fprintf(stderr, " method4. get vid and pid through /sys/class/input/eventXXX:\n");
  227.         vid_value = 0; pid_value = 0;
  228.         parse_input_devices2((*it).second, vid_value, pid_value);
  229.         fprintf(stdout, "  vid value: %d, pid value: %d\n", vid_value, pid_value);
  230.     }    
  232.     return  0;
  233. }
  234. #else
  235. int test_get_usb_camera_vid_pid()
  236. {
  237.     fprintf(stderr, "only support linux platform\n");
  238.     return -1;
  239. }
  240. #endif

执行结果如下：从结果可知，这四种方法与通过命令行获取到的pid和vid是一致的。

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GitHub：https://github.com//fengbingchun/OpenCV_Test

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