libaudiohal@aidl: Align position reporting with HIDL

Update comments in StreamHalInterface to align with HIDL HAL
framework contract. Update StreamHalAidl to match the contract.

Bug: 338557486
Test: atest CtsMediaAudioTestCases
Change-Id: I7c21b93c1cc985b7176d2e7ec0207ee0f9abbdb1
diff --git a/media/libaudiohal/impl/StreamHalHidl.h b/media/libaudiohal/impl/StreamHalHidl.h
index 80379d0..433e0a3 100644
--- a/media/libaudiohal/impl/StreamHalHidl.h
+++ b/media/libaudiohal/impl/StreamHalHidl.h
@@ -161,10 +161,14 @@
     // Requests notification when data buffered by the driver/hardware has been played.
     virtual status_t drain(bool earlyNotify);
 
-    // Notifies to the audio driver to flush the queued data.
+    // Notifies to the audio driver to flush (that is, drop) the queued data. Stream must
+    // already be paused before calling 'flush'.
     virtual status_t flush();
 
     // Return a recent count of the number of audio frames presented to an external observer.
+    // This excludes frames which have been written but are still in the pipeline. See the
+    // table at the start of the 'StreamOutHalInterface' for the specification of the frame
+    // count behavior w.r.t. 'flush', 'drain' and 'standby' operations.
     virtual status_t getPresentationPosition(uint64_t *frames, struct timespec *timestamp);
 
     // Notifies the HAL layer that the framework considers the current playback as completed.
@@ -259,6 +263,7 @@
 
     // Return a recent count of the number of audio frames received and
     // the clock time associated with that frame count.
+    // The count must not reset to zero when a PCM input enters standby.
     virtual status_t getCapturePosition(int64_t *frames, int64_t *time);
 
     // Get active microphones