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 12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) {
    	std::string vid_str = str.substr(pos-4, 4);
    	std::string pid_str = str.substr(pos+1, 4);
    	std::istringstream(vid_str) >> std::hex >> vid_value;
    	std::istringstream(pid_str) >> std::hex >> pid_value;
    	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) {
    	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))
    	fprintf(stderr, "  fail to read modalias\n");
    if (modalias.size() < 14 || modalias.substr(0,5) != "usb:v" || modalias[9] != 'p')
    	fprintf(stderr, "  not a usb format modalias\n");
    if (!(std::istringstream(modalias.substr(5,4)) >> std::hex >> vid_value))
    	fprintf(stderr, "  fail to read vid\n");
    if (!(std::istringstream(modalias.substr(10,4)) >> std::hex >> pid_value))
    	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) {
    	std::string str = bus_line.substr(pos+7, 4);
    	std::istringstream(str) >> std::hex >> vid;
    } else {
    	fprintf(stderr, "not found vid\n");
    	return -1;
    }
    
    pos = bus_line.find("Product");
    if (pos != std::string::npos) {
    	std::string str = bus_line.substr(pos+8, 4);
    	std::istringstream(str) >> std::hex >> pid;
    } else {
    	fprintf(stderr, "not found pid\n");
    	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) {
    	std::string str = event_line.substr(pos, std::string::npos);
    	str.erase(std::remove_if(str.begin(), str.end(), isspace), str.end());
    	std::string vid_str, pid_str;
    	std::string prefix = "/sys/class/input/" + str + "/device/id/";
    	if (!(std::ifstream(prefix +"vendor") >> vid_str)) {
    		  fprintf(stderr, "not found /device/id/vendor\n");
    		  return -1;
    	}
    	if (!(std::ifstream(prefix + "product") >> pid_str)) {
    		  fprintf(stderr, "not found /device/id/product\n");
    		  return -1;
    	}
    		
    	std::istringstream(vid_str) >> std::hex >> vid;
    	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][]

8. 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：

#include "funset.hpp"
    #include <map>
    #include <string>
    #include <sstream>
    #include <fstream>
    #include <algorithm>
    #ifndef _MSC_VER
    #include <dirent.h>
    #include <fcntl.h>
    #include <unistd.h>
    #include <errno.h>
    #include <sys/stat.h>
    #include <sys/types.h>
    #include <sys/time.h>
    #include <sys/mman.h>
    #include <sys/ioctl.h>
    #include <linux/videodev2.h>
    #else
    #endif
    
    #ifndef _MSC_VER
    namespace {
    
    int v4l2_is_v4l_dev(const char *name)
    {
    	return !strncmp(name, "video", 5) ||
    		!strncmp(name, "radio", 5) ||
    		!strncmp(name, "vbi", 3) ||
    		!strncmp(name, "v4l-subdev", 10);
    }
    
    int test_v4l2_get_device_list(std::map<std::string, std::string>& device_list)
    {
    	device_list.clear();
    
    	const char* dir_name = "/dev";
    	DIR* dir = opendir(dir_name);
    	if (!dir) {
    		fprintf(stderr, "Error: couldn't open the directory: %s\n", dir_name);
    		return -1;
    	}
    
    	struct dirent* entry = nullptr;
    	int fd;
    
    	while ((entry = readdir(dir))) {
    		char device_name[256];
    		if (!v4l2_is_v4l_dev(entry->d_name))
    			continue;
    		
    		snprintf(device_name, sizeof(device_name), "/dev/%s", entry->d_name);
    		if ((fd = device_open(device_name)) < 0)
    			continue;
    
    		struct v4l2_capability cap;
    		if (ioctl(fd, VIDIOC_QUERYCAP, &cap) < 0) {
    			fprintf(stderr, "Error: cam_info: can't open device: %s\n", device_name);
    			goto fail;
    		}
    
    		device_list[device_name] = reinterpret_cast<char*>(cap.card);
    
    		close(fd);
    		continue;
    
    		fail:
    			if (fd >= 0) close(fd);
    			break;
    	}
    
    	closedir(dir);
    	return 0;
    }
    
    int parse_input_devices(const std::string& name, unsigned int& vid, unsigned int& pid)
    {
    	const std::string device_list_file = "/proc/bus/input/devices";
    	std::ifstream file_input(device_list_file.c_str());
    	if (!file_input.is_open()) {
    		fprintf(stderr, "fail to open file: %s\n", device_list_file.c_str());
    		return -1;
    	}
    
    	std::string current_line, bus_line, search_name_line = name, search_bus_line = "Bus=";
    	while (getline(file_input, current_line)) {
    		auto pos = current_line.find(search_bus_line);
    		if (pos != std::string::npos)
    		      bus_line = current_line;
    
    		pos = current_line.find(search_name_line);
    		if (pos != std::string::npos)
    		      break;
    	}
    	file_input.close();
    
    	auto pos = bus_line.find("Vendor");
    	if (pos != std::string::npos) {
    		std::string str = bus_line.substr(pos+7, 4);
    		std::istringstream(str) >> std::hex >> vid;
    	} else {
    		fprintf(stderr, "not found vid\n");
    		return -1;
    	}
    
    	pos = bus_line.find("Product");
    	if (pos != std::string::npos) {
    		std::string str = bus_line.substr(pos+8, 4);
    		std::istringstream(str) >> std::hex >> pid;
    	} else {
    		fprintf(stderr, "not found pid\n");
    		return -1;
    	}
    
    	return 0;
    }
    
    int parse_input_devices2(const std::string& name, unsigned int& vid, unsigned int& pid)
    {
    	const std::string device_list_file = "/proc/bus/input/devices";
    	std::ifstream file_input(device_list_file.c_str());
    	if (!file_input.is_open()) {
    		fprintf(stderr, "fail to open file: %s\n", device_list_file.c_str());
    		return -1;
    	}
    
    	std::string current_line, event_line, search_name_line = name, search_event_line = "event";
    	bool flag = false;
    	while (getline(file_input, current_line)) {
    		auto pos = current_line.find(search_name_line);
    		if (pos != std::string::npos)
    		      flag = true;
    		else if (!flag)
    			continue;
    
    		if (flag) {
    			pos = current_line.find(search_event_line);
    			if (pos != std::string::npos) {
    				event_line = current_line;
    				break;
    			}
    		}
    	}
    	file_input.close();
    
    	if (!flag) {
    		fprintf(stderr, "not found event\n");
    		return -1;
    	}
    
    	auto pos = event_line.find(search_event_line);
    	if (pos != std::string::npos) {
    		std::string str = event_line.substr(pos, std::string::npos);
    		str.erase(std::remove_if(str.begin(), str.end(), isspace), str.end());
    		std::string vid_str, pid_str;
    		std::string prefix = "/sys/class/input/" + str + "/device/id/";
    		if (!(std::ifstream(prefix +"vendor") >> vid_str)) {
    		      fprintf(stderr, "not found /device/id/vendor\n");
    		      return -1;
    		}
    		if (!(std::ifstream(prefix + "product") >> pid_str)) {
    		      fprintf(stderr, "not found /device/id/product\n");
    		      return -1;
    		}
    			
    		std::istringstream(vid_str) >> std::hex >> vid;
    		std::istringstream(pid_str) >> std::hex >> pid;
    	}
    
    	return 0;
    }
    
    } // namespace
    
    int test_get_usb_camera_vid_pid()
    {
    	// get usb video device list
    	std::map<std::string, std::string> device_list;
    	if (test_v4l2_get_device_list(device_list) !=0) {
    		fprintf(stderr, "fail to get usb video device list\n");
    		return -1;
    	}
    
    	int count = 1;
    	fprintf(stdout, "device count: %d\n", device_list.size());
    	for (auto it = device_list.cbegin(); it != device_list.cend(); ++it) {
    		fprintf(stdout, "%d. device address: %s, description(name): %s\n", count++,  (*it).first.c_str(), (*it).second.c_str());
    
    		unsigned int vid_value, pid_value;
    		fprintf(stdout, " method1. get vid and pid through v4l2:\n");
    		std::string str = (*it).second;
    		auto pos = str.find(":");
    		if (pos != std::string::npos) {
    			std::string vid_str = str.substr(pos-4, 4);
    			std::string pid_str = str.substr(pos+1, 4);
    			std::istringstream(vid_str) >> std::hex >> vid_value;
    			std::istringstream(pid_str) >> std::hex >> pid_value;
    			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);
    		} else {
    			fprintf(stderr, "  fail to get vid and pid\n");	
    		}
    
    		fprintf(stdout, " method2. get vid and pid through device/modalias:\n");
    		str = (*it).first;
    		pos = str.find_last_of("/");
    		if (pos == std::string::npos) {
    			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))
    			fprintf(stderr, "  fail to read modalias\n");
    		if (modalias.size() < 14 || modalias.substr(0,5) != "usb:v" || modalias[9] != 'p')
    			fprintf(stderr, "  not a usb format modalias\n");
    		if (!(std::istringstream(modalias.substr(5,4)) >> std::hex >> vid_value))
    			fprintf(stderr, "  fail to read vid\n");
    		if (!(std::istringstream(modalias.substr(10,4)) >> std::hex >> pid_value))
    			fprintf(stderr, "  fail to read pid\n");
    		fprintf(stdout, "  vid value: %d, pid value: %d\n", vid_value, pid_value);
    
    		fprintf(stdout, " method3. get vid and pid through /proc/bus/input/devices:\n");
    		vid_value = 0; pid_value = 0;
    		parse_input_devices((*it).second, vid_value, pid_value);
    		fprintf(stdout, "  vid value: %d, pid value: %d\n", vid_value, pid_value);
    
    		fprintf(stderr, " method4. get vid and pid through /sys/class/input/eventXXX:\n");
    		vid_value = 0; pid_value = 0;
    		parse_input_devices2((*it).second, vid_value, pid_value);
    		fprintf(stdout, "  vid value: %d, pid value: %d\n", vid_value, pid_value);
    	}	
    
    	return  0;
    }
    #else
    int test_get_usb_camera_vid_pid()
    {
    	fprintf(stderr, "only support linux platform\n");
    	return -1;
    }
    #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。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZlbmdiaW5nY2h1bg_size_16_color_FFFFFF_t_70][]

**GitHub**：[https://github.com//fengbingchun/OpenCV\_Test][https_github.com_fengbingchun_OpenCV_Test]

[20191212140933219.png]: https://img-blog.csdnimg.cn/20191212140933219.png
[20191212141124864.png]: https://img-blog.csdnimg.cn/20191212141124864.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZlbmdiaW5nY2h1bg_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20191212141756705.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZlbmdiaW5nY2h1bg==,size_16,color_FFFFFF,t_70
[https_github.com_fengbingchun_OpenCV_Test]: https://github.com//fengbingchun/OpenCV_Test