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)
@@ -9,6 +9,7 @@
 #include "base/logging.h"
 #include "base/nix/xdg_util.h"
 #include "base/process_util.h"
+#include "base/stringprintf.h"
 #include "media/audio/audio_output_dispatcher.h"
 #include "media/audio/fake_audio_input_stream.h"
 #include "media/audio/fake_audio_output_stream.h"
@@ -30,8 +31,79 @@
 }
 
 bool AudioManagerLinux::HasAudioInputDevices() {

[awong, 2011/05/23 17:36:15]

It's slightly confusing to me that you don't populate the AudioInputDevices list
here if you're iterating and rejecting devices.

If you're only pass back the device named "default", shouldn't you only search
for the device named default?

[xians, 2011/05/24 13:50:27]

Sorry that I forgot to reply this.
We cant do this because the default device isnnt always listed by
snd_device_name_hint() (depending on ALSA configuration in the userspace)

-  // 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";
+  static const char kIoHintName[] = "IOID";
+  static const char kNameHintName[] = "NAME";
+  // Since "default", "pulse" and "dmix" devices are virtual devices mapped to

[awong, 2011/05/23 17:36:15]

Newline before comment.

[xians, 2011/05/23 20:15:59]

Done.

+  // 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";
+  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) {
+    // NOTE: Do not early return from inside this if statement.  The

[awong, 2011/05/23 17:36:15]

This function is long anyways. Throw the whole body of this if statement into
another function that just returns has_device() and then you can keep the memory
management safe from early returns.

[xians, 2011/05/23 20:15:59]

I made a helper function to do this. But I am actually not sure if the name I
made fits the design style in chrome. Please give me suggestion if it doesnt
look good to you.

+    // hints above need to be freed.
+    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) {
+        // Found a real and valid device.
+        has_device = true;
+        break;
+      }
+    }
+  } else {
+    LOG(ERROR) << "Unable to get device hints: " << wrapper_->StrError(error);
+  }
+  // Destory the hint now that we're done with it.

[awong, 2011/05/23 17:36:15]

Newline before comment.

[xians, 2011/05/23 20:15:59]

Done.

+  wrapper_->DeviceNameFreeHint(hints);
+  hints = NULL;
+  return has_device;
 }
 
 AudioOutputStream* AudioManagerLinux::MakeAudioOutputStream(
@@ -147,6 +219,21 @@
   base::LaunchApp(CommandLine(FilePath(command)), false, false, NULL);
 }
 
+void AudioManagerLinux::GetAudioInputDeviceNames(
+    AudioInputDeviceNames* device_names) {
+  // TODO(xians): query a full list of valid devices.
+  if (HasAudioInputDevices()) {
+    // Add the default device to the list.
+    // We use (device_name)_(index) to make up the unique_ids to identify the
+    // devices. For default device, the index is 0, so its unique_id is
+    // Default_0.
+    AudioInputDeviceName name;
+    name.device_name = AudioManagerBase::kDefaultDeviceName;
+    name.unique_id = StringPrintf("%s_0", AudioManagerBase::kDefaultDeviceName);
+    device_names->push_back(name);
+  }
+}
+
 // static
 AudioManager* AudioManager::CreateAudioManager() {
   return new AudioManagerLinux();