chrome/browser/chromeos/camera_detector.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chrome/browser/chromeos/camera_detector.h"
   6
   7 #include "base/bind.h"
   8 #include "base/files/file_enumerator.h"
   9 #include "base/files/file_util.h"
  10 #include "base/location.h"
  11 #include "base/strings/string_split.h"
  12 #include "base/strings/string_util.h"
  13 #include "base/task_runner_util.h"
  14 #include "base/threading/sequenced_worker_pool.h"
  15 #include "components/storage_monitor/udev_util_linux.h"
  16 #include "content/public/browser/browser_thread.h"
  17
  18 namespace chromeos {
  19
  20 namespace {
  21
  22 // Sysfs directory containing V4L devices.
  23 const char kV4LSubsystemDir[] = "/sys/class/video4linux/";
  24 // Name of the udev property with V4L capabilities.
  25 const char kV4LCapabilities[] = "ID_V4L_CAPABILITIES";
  26 // Delimiter character for udev V4L capabilities.
  27 const char kV4LCapabilitiesDelim = ':';
  28 // V4L capability that denotes a capture-enabled device.
  29 const char kV4LCaptureCapability[] = "capture";
  30
  31 }  // namespace
  32
  33 using content::BrowserThread;
  34
  35 // static
  36 CameraDetector::CameraPresence CameraDetector::camera_presence_ =
  37     CameraDetector::kCameraPresenceUnknown;
  38
  39 // static
  40 bool CameraDetector::presence_check_in_progress_ = false;
  41
  42 // static
  43 void CameraDetector::StartPresenceCheck(const base::Closure& callback) {
  44   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  45   if (presence_check_in_progress_)
  46     return;
  47   DVLOG(1) << "Starting camera presence check";
  48   presence_check_in_progress_ = true;
  49   base::PostTaskAndReplyWithResult(
  50       BrowserThread::GetBlockingPool()->GetTaskRunnerWithShutdownBehavior(
  51           base::SequencedWorkerPool::SKIP_ON_SHUTDOWN).get(),
  52       FROM_HERE,
  53       base::Bind(&CameraDetector::CheckPresence),
  54       base::Bind(&CameraDetector::OnPresenceCheckDone, callback));
  55 }
  56
  57 // static
  58 void CameraDetector::OnPresenceCheckDone(const base::Closure& callback,
  59                                          bool present) {
  60   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  61   camera_presence_ = present ? kCameraPresent : kCameraAbsent;
  62   presence_check_in_progress_ = false;
  63   callback.Run();
  64 }
  65
  66 // static
  67 bool CameraDetector::CheckPresence() {
  68   // We do a quick check using udev database because opening each /dev/videoX
  69   // device may trigger costly device initialization.
  70   base::FileEnumerator file_enum(
  71       base::FilePath(kV4LSubsystemDir), false /* not recursive */,
  72       base::FileEnumerator::FILES | base::FileEnumerator::SHOW_SYM_LINKS);
  73   for (base::FilePath path = file_enum.Next(); !path.empty();
  74        path = file_enum.Next()) {
  75     std::string v4l_capabilities;
  76     if (storage_monitor::GetUdevDevicePropertyValueByPath(
  77             path, kV4LCapabilities, &v4l_capabilities)) {
  78       std::vector<std::string> caps = base::SplitString(
  79           v4l_capabilities, std::string(1, kV4LCapabilitiesDelim),
  80           base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
  81       if (find(caps.begin(), caps.end(), kV4LCaptureCapability) != caps.end()) {
  82         return true;
  83       }
  84     }
  85   }
  86   return false;
  87 }
  88
  89 }  // namespace chromeos