Add v4l2 on linux

src/uvc/uvc-v4l2.cc

@@ -0,0 +1,152 @@
+#include "uvc.h"  // NOLINT
+
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <glog/logging.h>
+
+#include <fstream>
+#include <string>
+
+MYNTEYE_BEGIN_NAMESPACE
+
+namespace uvc {
+
+struct context {
+  context() {
+    VLOG(2) << __func__;
+  }
+
+  ~context() {
+    VLOG(2) << __func__;
+  }
+};
+
+struct device {
+  const std::shared_ptr<context> parent;
+
+  std::string dev_name;  // Device name (typically of the form /dev/video*)
+  int busnum, devnum, parent_devnum;  // USB device bus number and device number
+
+  int vid, pid, mi;  // Vendor ID, product ID, and multiple interface index
+  int fd = -1;       // File descriptor for this device
+
+  device(std::shared_ptr<context> parent, const std::string &name)
+      : parent(parent), dev_name("/dev/" + name) {
+    VLOG(2) << __func__ << ": " << dev_name;
+
+    struct stat st;
+    if (stat(dev_name.c_str(), &st) < 0) {  // file status
+      LOG(FATAL) << "Cannot identify '" << dev_name << "': " << errno << ", "
+                 << strerror(errno);
+    }
+    if (!S_ISCHR(st.st_mode)) {  // character device?
+      LOG(FATAL) << dev_name << " is no device";
+    }
+
+    // Search directory and up to three parent directories to find busnum/devnum
+    std::ostringstream ss;
+    ss << "/sys/dev/char/" << major(st.st_rdev) << ":" << minor(st.st_rdev)
+       << "/device/";
+    auto path = ss.str();
+
+    bool good = false;
+    for (int i = 0; i <= 3; ++i) {
+      if (std::ifstream(path + "busnum") >> busnum) {
+        if (std::ifstream(path + "devnum") >> devnum) {
+          if (std::ifstream(path + "../devnum") >> parent_devnum) {
+            good = true;
+            break;
+          }
+        }
+      }
+      path += "../";
+    }
+    if (!good)
+      LOG(FATAL) << "Failed to read busnum/devnum";
+
+    std::string modalias;
+    if (!(std::ifstream(
+              "/sys/class/video4linux/" + name + "/device/modalias") >>
+          modalias))
+      LOG(FATAL) << "Failed to read modalias";
+    if (modalias.size() < 14 || modalias.substr(0, 5) != "usb:v" ||
+        modalias[9] != 'p')
+      LOG(FATAL) << "Not a usb format modalias";
+    if (!(std::istringstream(modalias.substr(5, 4)) >> std::hex >> vid))
+      LOG(FATAL) << "Failed to read vendor ID";
+    if (!(std::istringstream(modalias.substr(10, 4)) >> std::hex >> pid))
+      LOG(FATAL) << "Failed to read product ID";
+    if (!(std::ifstream(
+              "/sys/class/video4linux/" + name + "/device/bInterfaceNumber") >>
+          std::hex >> mi))
+      LOG(FATAL) << "Failed to read interface number";
+
+    fd = open(dev_name.c_str(), O_RDWR | O_NONBLOCK, 0);
+    if (fd < 0) {
+      LOG(FATAL) << "Cannot open '" << dev_name << "': " << errno << ", "
+                 << strerror(errno);
+    }
+  }
+
+  ~device() {
+    VLOG(2) << __func__;
+    if (fd != -1) {
+      LOG_IF(WARNING, close(fd) < 0) << "close error " << errno << ", "
+                                     << strerror(errno);
+    }
+  }
+};
+
+std::shared_ptr<context> create_context() {
+  return std::make_shared<context>();
+}
+
+std::vector<std::shared_ptr<device>> query_devices(
+    std::shared_ptr<context> context) {
+  std::vector<std::shared_ptr<device>> devices;
+
+  DIR *dir = opendir("/sys/class/video4linux");
+  if (!dir)
+    LOG(FATAL) << "Cannot access /sys/class/video4linux";
+  while (dirent *entry = readdir(dir)) {
+    std::string name = entry->d_name;
+    if (name == "." || name == "..")
+      continue;
+
+    // Resolve a pathname to ignore virtual video devices
+    std::string path = "/sys/class/video4linux/" + name;
+    char buff[PATH_MAX];
+    ssize_t len = ::readlink(path.c_str(), buff, sizeof(buff) - 1);
+    if (len != -1) {
+      buff[len] = '\0';
+      std::string real_path = std::string(buff);
+      if (real_path.find("virtual") != std::string::npos)
+        continue;
+    }
+
+    try {
+      devices.push_back(std::make_shared<device>(context, name));
+    } catch (const std::exception &e) {
+      LOG(INFO) << "Not a USB video device: " << e.what();
+    }
+  }
+  closedir(dir);
+
+  return devices;
+}
+
+int get_vendor_id(const device &device) {
+  return device.vid;
+}
+
+int get_product_id(const device &device) {
+  return device.pid;
+}
+
+}  // namespace uvc
+
+MYNTEYE_END_NAMESPACE