fix detection of video capture device on linux

media/video/capture/linux/video_capture_device_linux.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/video/capture/linux/video_capture_device_linux.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #if defined(OS_OPENBSD)
 #include <sys/videoio.h>
@@ skipping 67 matching lines @@
   while (!enumerator.Next().empty()) {
     file_util::FileEnumerator::FindInfo info;
     enumerator.GetFindInfo(&info);
 
     Name name;
     name.unique_id = path.value() + info.filename;
     if ((fd = open(name.unique_id.c_str() , O_RDONLY)) < 0) {
       // Failed to open this device.
       continue;
     }
-    // Test if this is a V4L2 device.
+    // Test if this is a V4L2 capture device.
     v4l2_capability cap;
     if ((ioctl(fd, VIDIOC_QUERYCAP, &cap) == 0) &&
-        (cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
+        (cap.capabilities & V4L2_CAP_VIDEO_CAPTURE) &&
+        !(cap.capabilities & V4L2_CAP_VIDEO_OUTPUT)) {
       // This is a V4L2 video capture device
       name.device_name = StringPrintf("%s", cap.card);
       device_names->push_back(name);
     }
     close(fd);
   }
 }
 
 VideoCaptureDevice* VideoCaptureDevice::Create(const Name& device_name) {
   VideoCaptureDeviceLinux* self = new VideoCaptureDeviceLinux(device_name);
@@ skipping 94 matching lines @@
   DCHECK_EQ(v4l2_thread_.message_loop(), MessageLoop::current());
 
   observer_ = observer;
 
   // Need to open camera with O_RDWR after Linux kernel 3.3.
   if ((device_fd_ = open(device_name_.unique_id.c_str(), O_RDWR)) < 0) {
     SetErrorState("Failed to open V4L2 device driver.");
     return;
   }
 
-  // Test if this is a V4L2 device.
+  // Test if this is a V4L2 capture device.
   v4l2_capability cap;
   if (!((ioctl(device_fd_, VIDIOC_QUERYCAP, &cap) == 0) &&
-      (cap.capabilities & V4L2_CAP_VIDEO_CAPTURE))) {
+      (cap.capabilities & V4L2_CAP_VIDEO_CAPTURE) &&
+      !(cap.capabilities & V4L2_CAP_VIDEO_OUTPUT))) {
     // This is not a V4L2 video capture device.
     close(device_fd_);
     device_fd_ = -1;
     SetErrorState("This is not a V4L2 video capture device");
     return;
   }
 
   v4l2_format video_fmt;
   memset(&video_fmt, 0, sizeof(video_fmt));
   video_fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
@@ skipping 231 matching lines @@
   buffer_pool_size_ = 0;
 }
 
 void VideoCaptureDeviceLinux::SetErrorState(const std::string& reason) {
   DVLOG(1) << reason;
   state_ = kError;
   observer_->OnError();
 }
 
 }  // namespace media