audio: added support for dual mic capture.

Added support for simultaneous capture from front and back
mics.

Change-Id: Ica1b75fe432f419272ae92e8ab04b1d34524c189
diff --git a/audio/audio_hw.c b/audio/audio_hw.c
index 66a6da7..c5f1867 100644
--- a/audio/audio_hw.c
+++ b/audio/audio_hw.c
@@ -1341,7 +1341,8 @@
         /* Select front end */
 
 
-        if ((adev->active_input != 0) && (adev->active_input->aux_channels)) {
+        if ((adev->active_input != 0) && (adev->active_input->aux_channels ||
+                adev->active_input->main_channels == AUDIO_CHANNEL_IN_FRONT_BACK)) {
             ALOGV("select input device(): multi-mic configuration main mic %s sub mic %s",
                   main_mic_on ? "ON" : "OFF", sub_mic_on ? "ON" : "OFF");
             if (main_mic_on) {
diff --git a/audio/audio_policy.conf b/audio/audio_policy.conf
index 1012c26..bf387a2 100644
--- a/audio/audio_policy.conf
+++ b/audio/audio_policy.conf
@@ -47,7 +47,7 @@
     inputs {
       primary {
         sampling_rates 8000|11025|16000|22050|24000|32000|44100|48000
-        channel_masks AUDIO_CHANNEL_IN_MONO|AUDIO_CHANNEL_IN_STEREO
+        channel_masks AUDIO_CHANNEL_IN_MONO|AUDIO_CHANNEL_IN_STEREO|AUDIO_CHANNEL_IN_FRONT_BACK
         formats AUDIO_FORMAT_PCM_16_BIT
         devices AUDIO_DEVICE_IN_BUILTIN_MIC|AUDIO_DEVICE_IN_BLUETOOTH_SCO_HEADSET|AUDIO_DEVICE_IN_WIRED_HEADSET|AUDIO_DEVICE_IN_BACK_MIC
       }