Do not use libv4l if no plugin is registered.

content/common/gpu/media/generic_v4l2_device.cc

 // Copyright 2014 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 <fcntl.h>
 #include <libdrm/drm_fourcc.h>
 #include <linux/videodev2.h>
 #include <poll.h>
 #include <sys/eventfd.h>
@@ skipping 11 matching lines @@
 // Auto-generated for dlopen libv4l2 libraries
 #include "content/common/gpu/media/v4l2_stubs.h"
 #include "third_party/v4l-utils/lib/include/libv4l2.h"
 
 using content_common_gpu_media::kModuleV4l2;
 using content_common_gpu_media::InitializeStubs;
 using content_common_gpu_media::StubPathMap;
 
 static const base::FilePath::CharType kV4l2Lib[] =
     FILE_PATH_LITERAL("/usr/lib/libv4l2.so");
-#else
-#define v4l2_close close
-#define v4l2_ioctl ioctl
 #endif
 
 namespace content {
 
 namespace {
 const char kDecoderDevice[] = "/dev/video-dec";
 const char kEncoderDevice[] = "/dev/video-enc";
 const char kImageProcessorDevice[] = "/dev/gsc0";
 }
 
 GenericV4L2Device::GenericV4L2Device(Type type)
     : type_(type),
       device_fd_(-1),
-      device_poll_interrupt_fd_(-1) {}
+      device_poll_interrupt_fd_(-1),
+      use_libv4l2_(false) {}
 
 GenericV4L2Device::~GenericV4L2Device() {
   if (device_poll_interrupt_fd_ != -1) {
     close(device_poll_interrupt_fd_);
     device_poll_interrupt_fd_ = -1;
   }
   if (device_fd_ != -1) {
-    v4l2_close(device_fd_);
+    Close();
     device_fd_ = -1;
   }
 }
 
+void GenericV4L2Device::Close() {
+#if defined(USE_LIBV4L2)
+  if (use_libv4l2_) {
+    v4l2_close(device_fd_);
+    return;
+  }
+#endif
+  close(device_fd_);

[Pawel Osciak, 2015/04/21 05:02:42]

Perhaps this would be a good time to start using base::ScopedFd for both fds?

[wuchengli, 2015/04/21 06:12:10]

Good idea. Done.

+}
+
 int GenericV4L2Device::Ioctl(int request, void* arg) {
-  return HANDLE_EINTR(v4l2_ioctl(device_fd_, request, arg));
+#if defined(USE_LIBV4L2)
+  if (use_libv4l2_)
+    return HANDLE_EINTR(v4l2_ioctl(device_fd_, request, arg));
+#endif
+  return HANDLE_EINTR(ioctl(device_fd_, request, arg));
 }
 
 bool GenericV4L2Device::Poll(bool poll_device, bool* event_pending) {
   struct pollfd pollfds[2];
   nfds_t nfds;
   int pollfd = -1;
 
   pollfds[0].fd = device_poll_interrupt_fd_;
   pollfds[0].events = POLLIN | POLLERR;
   nfds = 1;
@@ skipping 73 matching lines @@
       break;
   }
 
   DVLOG(2) << "Initialize(): opening device: " << device_path;
   // Open the video device.
   device_fd_ = HANDLE_EINTR(open(device_path, O_RDWR | O_NONBLOCK | O_CLOEXEC));
   if (device_fd_ == -1) {
     return false;
   }
 #if defined(USE_LIBV4L2)
-  if (HANDLE_EINTR(v4l2_fd_open(device_fd_, V4L2_DISABLE_CONVERSION)) == -1) {
-    v4l2_close(device_fd_);
-    return false;
+  if (HANDLE_EINTR(v4l2_fd_open(device_fd_, V4L2_DISABLE_CONVERSION)) >= 0) {

[Pawel Osciak, 2015/04/21 05:02:42]

I'd prefer != -1.

[wuchengli, 2015/04/21 06:12:10]

Done. I was confused when I discussed with you. != -1 is correct.

+    DVLOG(2) << "Found a libv4l2 plugin for " << device_path;

[Pawel Osciak, 2015/04/21 05:02:42]

v4l2_fd_open succeeding is not exactly equivalent of finding a plugin. I know
right now it is, but I'd prefer not calling this out explicitly. Could we
instead say "using libvl42 for " or something like that?

[wuchengli, 2015/04/21 06:12:10]

Done.

+    use_libv4l2_ = true;
   }
 #endif
 
   device_poll_interrupt_fd_ = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
   if (device_poll_interrupt_fd_ == -1) {
     return false;
   }
   return true;
 }
 
@@ skipping 120 matching lines @@
   StubPathMap paths;
   paths[kModuleV4l2].push_back(kV4l2Lib);
 
   return InitializeStubs(paths);
 #else
   return true;
 #endif
 }
 
 }  //  namespace content