Implement audio device callback

Add class AudioSystem::AudioDeviceCallback notifying
AudioSystem clients upon device selection change on a given
input or output thread.
Maintain a list of installed callback per I/O handle in AudioSystem
and call registered callbacks when an OPEN of CONFIG_CHANGED event
is received on IAudioFlingerClient::ioConfigChanged().
Add methods to AudioTrack and AudioRecord to add and remove device
change callbacks.
Add methods to AudioTrack and AudioRecord to query currently selected
device.
ioConfigChanged() events now convey the audio patch describing
the input or output thread routing.

Fix AudioRecord failure to start when invalidation is
handled by start().

Change-Id: I9e938adf025fa712337c63b1e02a8c18f2a20d39
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index 8b8dd78..2c4d801 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -500,6 +500,7 @@
         // mName will be set by concrete (non-virtual) subclass
         mDeathRecipient(new PMDeathRecipient(this))
 {
+    memset(&mPatch, 0, sizeof(struct audio_patch));
 }
 
 AudioFlinger::ThreadBase::~ThreadBase()
@@ -1930,6 +1931,7 @@
     switch (event) {
     case AUDIO_OUTPUT_OPENED:
     case AUDIO_OUTPUT_CONFIG_CHANGED:
+        desc->mPatch = mPatch;
         desc->mChannelMask = mChannelMask;
         desc->mSamplingRate = mSampleRate;
         desc->mFormat = mFormat;
@@ -3002,6 +3004,7 @@
         mEffectChains[i]->setDevice_l(type);
     }
     mOutDevice = type;
+    mPatch = *patch;
 
     if (mOutput->audioHwDev->version() >= AUDIO_DEVICE_API_VERSION_3_0) {
         audio_hw_device_t *hwDevice = mOutput->audioHwDev->hwDevice();
@@ -3028,6 +3031,7 @@
                 param.toString().string());
         *handle = AUDIO_PATCH_HANDLE_NONE;
     }
+    sendIoConfigEvent_l(AUDIO_OUTPUT_CONFIG_CHANGED);
     return status;
 }
 
@@ -6727,6 +6731,7 @@
     switch (event) {
     case AUDIO_INPUT_OPENED:
     case AUDIO_INPUT_CONFIG_CHANGED:
+        desc->mPatch = mPatch;
         desc->mChannelMask = mChannelMask;
         desc->mSamplingRate = mSampleRate;
         desc->mFormat = mFormat;
@@ -6884,6 +6889,7 @@
 
     // store new device and send to effects
     mInDevice = patch->sources[0].ext.device.type;
+    mPatch = *patch;
     for (size_t i = 0; i < mEffectChains.size(); i++) {
         mEffectChains[i]->setDevice_l(mInDevice);
     }
@@ -6936,6 +6942,8 @@
         *handle = AUDIO_PATCH_HANDLE_NONE;
     }
 
+    sendIoConfigEvent_l(AUDIO_INPUT_CONFIG_CHANGED);
+
     return status;
 }