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* Copyright 2009, Google Inc.
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* Author: lexnikitin@google.com (Alexey Nikitin)
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* V4LLookup provides basic functionality to work with V2L2 devices in Linux
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* The functionality is implemented as a class with virtual methods for
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* the purpose of unit testing.
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#include "talk/session/phone/v4llookup.h"
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#include <linux/types.h>
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#include <linux/videodev2.h>
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#include <sys/ioctl.h>
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#include <sys/types.h>
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#include "talk/base/logging.h"
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V4LLookup *V4LLookup::v4l_lookup_ = NULL;
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bool V4LLookup::CheckIsV4L2Device(const std::string& device_path) {
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// check device major/minor numbers are in the range for video devices.
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if (lstat(device_path.c_str(), &s) != 0 || !S_ISCHR(s.st_mode)) return false;
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// check major/minur device numbers are in range for video device
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if (major(s.st_rdev) == 81) {
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dev_t num = minor(s.st_rdev);
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if (num <= 63 && num >= 0) {
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video_fd = ::open(device_path.c_str(), O_RDONLY | O_NONBLOCK);
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if ((video_fd >= 0) || (errno == EBUSY)) {
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::v4l2_capability video_caps;
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memset(&video_caps, 0, sizeof(video_caps));
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if ((errno == EBUSY) ||
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(::ioctl(video_fd, VIDIOC_QUERYCAP, &video_caps) >= 0 &&
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(video_caps.capabilities & V4L2_CAP_VIDEO_CAPTURE))) {
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LOG(LS_INFO) << "Found V4L2 capture device " << device_path;
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LOG(LS_ERROR) << "VIDIOC_QUERYCAP failed for " << device_path;
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LOG(LS_ERROR) << "Failed to open " << device_path;
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}; // namespace cricket