Adding GetAudioInputDeviceNames to AudioManager, this function is supposed to do device enumerati...

media/audio/linux/audio_manager_linux.cc

Index: media/audio/linux/audio_manager_linux.cc
===================================================================
--- media/audio/linux/audio_manager_linux.cc	(revision 86276)
+++ media/audio/linux/audio_manager_linux.cc	(working copy)
@@ -30,8 +30,31 @@
 }
 
 bool AudioManagerLinux::HasAudioInputDevices() {
-  // TODO(satish): Make this actually query audio devices.
-  return true;
+  if (!initialized()) {
+    return false;
+  }
+
+  // Constants specified by the ALSA API for device hints.
+  static const int kGetAllDevices = -1;
+  static const char kPcmInterfaceName[] = "pcm";
+  bool has_device = false;
+  void** hints = NULL;
+
+  // Use the same approach to find the devices as in
+  // AlsaPcmOutputStream::FindDeviceForChannels
+  // Get Alsa device hints.
+  int error = wrapper_->DeviceNameHint(kGetAllDevices,
+                                       kPcmInterfaceName,
+                                       &hints);
+  if (error == 0) {
+    has_device = HasAnyValidAudioInputDevice(hints);
+  } else {
+    LOG(ERROR) << "Unable to get device hints: " << wrapper_->StrError(error);
+  }
+
+  // Destroy the hint now that we're done with it.
+  wrapper_->DeviceNameFreeHint(hints);
+  return has_device;
 }
 
 AudioOutputStream* AudioManagerLinux::MakeAudioOutputStream(
@@ -96,8 +119,8 @@
 }
 
 AudioManagerLinux::~AudioManagerLinux() {
-  // Make sure we stop the thread first. If we let the default destructor to
-  // destruct the members, we may destroy audio streams before stopping the
+  // Make sure we stop the thread first. If we allow the default destructor to
+  // destroy the members, we may destroy audio streams before stopping the
   // thread, resulting an unexpected behavior.
   // This way we make sure activities of the audio streams are all stopped
   // before we destroy them.
@@ -147,6 +170,73 @@
   base::LaunchApp(CommandLine(FilePath(command)), false, false, NULL);
 }
 
+void AudioManagerLinux::GetAudioInputDeviceNames(
+    media::AudioDeviceNames* device_names) {
+  // TODO(xians): query a full list of valid devices.
+  if (HasAudioInputDevices()) {
+    // Add the default device to the list.
+    // We use index 0 to make up the unique_id to identify the
+    // default devices.
+    media::AudioDeviceName name;
+    name.device_name = AudioManagerBase::kDefaultDeviceName;
+    name.unique_id = "0";
+    device_names->push_back(name);
+  }
+}
+
+bool AudioManagerLinux::HasAnyValidAudioInputDevice(void** hints) {
+  static const char kIoHintName[] = "IOID";
+  static const char kNameHintName[] = "NAME";
+
+  // Since "default", "pulse" and "dmix" devices are virtual devices mapped to
+  // real devices, we remove them from the list to avoiding duplicate counting.
+  // In addition, note that we support no more than 2 channels for recording,
+  // hence surround devices are not stored in the list. Finally, output and
+  // null devices are not considered as valid devices for recording.
+  static const char kOutputDevice[] = "Output";
+  static const char kNotWantedDefaultDevice[] = "default";
+  static const char kNotWantedNullDevice[] = "null";
+  static const char kNotWantedPulseDevice[] = "pulse";
+  static const char kNotWantedDmixDevice[] = "dmix";
+  static const char kNotWantedSurroundDevice[] = "surround";
+
+  for (void** hint_iter = hints; *hint_iter != NULL; hint_iter++) {
+    // Only examine devices that are input capable..  Valid values are
+    // "Input", "Output", and NULL which means both input and output.
+    scoped_ptr_malloc<char> io(wrapper_->DeviceNameGetHint(*hint_iter,
+                                                           kIoHintName));
+    // Wrong device type, skip it.
+    if (io != NULL &&
+        strncmp(kOutputDevice, io.get(), strlen(kOutputDevice)) == 0)
+      continue;
+
+    scoped_ptr_malloc<char> hint_device_name(
+        wrapper_->DeviceNameGetHint(*hint_iter, kNameHintName));
+    // Now check if if it is a valid device.
+    if (hint_device_name != NULL &&
+        strncmp(kNotWantedDefaultDevice,
+                hint_device_name.get(),
+                strlen(kNotWantedDefaultDevice)) != 0 &&
+        strncmp(kNotWantedNullDevice,
+                hint_device_name.get(),
+                strlen(kNotWantedNullDevice)) != 0 &&
+        strncmp(kNotWantedPulseDevice,
+                hint_device_name.get(),
+                strlen(kNotWantedPulseDevice)) != 0 &&
+        strncmp(kNotWantedDmixDevice,
+                hint_device_name.get(),
+                strlen(kNotWantedDmixDevice)) != 0 &&
+        strncmp(kNotWantedSurroundDevice,
+                hint_device_name.get(),
+                strlen(kNotWantedSurroundDevice)) != 0) {
+      return true;
+    }
+  }
+
+  // Did not find a valid device.
+  return false;
+}
+
 // static
 AudioManager* AudioManager::CreateAudioManager() {
   return new AudioManagerLinux();