Update comments

We no longer put the filename at start of file.

Change-Id: Ic435b159a23105681e3d4a6cb1ac097bc853302e

6 files changed, 65 insertions, 30 deletions

diff --git a/include/media/AudioSystem.h b/include/media/AudioSystem.h
index da99620..1916ac5 100644
--- a/include/media/AudioSystem.h
+++ b/include/media/AudioSystem.h
@@ -131,7 +131,7 @@ public:
         NUM_CONFIG_EVENTS
     };
 
-    // audio output descritor used to cache output configurations in client process to avoid frequent calls
+    // audio output descriptor used to cache output configurations in client process to avoid frequent calls
     // through IAudioFlinger
     class OutputDescriptor {
     public:
diff --git a/include/media/AudioTrack.h b/include/media/AudioTrack.h
index 11db81b..0f2c323 100644
--- a/include/media/AudioTrack.h
+++ b/include/media/AudioTrack.h
@@ -58,8 +58,8 @@ public:
         EVENT_BUFFER_END = 5        // Playback head is at the end of the buffer.
     };
 
-    /* Create Buffer on the stack and pass it to obtainBuffer()
-     * and releaseBuffer().
+    /* Client should declare Buffer on the stack and pass address to obtainBuffer()
+     * and releaseBuffer().  See also callback_t for EVENT_MORE_DATA.
      */
 
     class Buffer
@@ -68,12 +68,16 @@ public:
         enum {
             MUTE    = 0x00000001
         };
-        uint32_t    flags;
+        uint32_t    flags;        // 0 or MUTE
         audio_format_t format; // but AUDIO_FORMAT_PCM_8_BIT -> AUDIO_FORMAT_PCM_16_BIT
         // accessed directly by WebKit ANP callback
         int         channelCount; // will be removed in the future, do not use
-        size_t      frameCount;
-        size_t      size;
+
+        size_t      frameCount;   // number of sample frames corresponding to size;
+                                  // on input it is the number of frames desired,
+                                  // on output is the number of frames actually filled
+
+        size_t      size;         // input/output in byte units
         union {
             void*       raw;
             short*      i16;    // signed 16-bit
@@ -84,15 +88,15 @@ public:
 
     /* As a convenience, if a callback is supplied, a handler thread
      * is automatically created with the appropriate priority. This thread
-     * invokes the callback when a new buffer becomes available or an underrun condition occurs.
+     * invokes the callback when a new buffer becomes available or various conditions occur.
      * Parameters:
      *
      * event:   type of event notified (see enum AudioTrack::event_type).
      * user:    Pointer to context for use by the callback receiver.
      * info:    Pointer to optional parameter according to event type:
      *          - EVENT_MORE_DATA: pointer to AudioTrack::Buffer struct. The callback must not write
-     *          more bytes than indicated by 'size' field and update 'size' if less bytes are
-     *          written.
+     *            more bytes than indicated by 'size' field and update 'size' if fewer bytes are
+     *            written.
      *          - EVENT_UNDERRUN: unused.
      *          - EVENT_LOOP_END: pointer to an int indicating the number of loops remaining.
      *          - EVENT_MARKER: pointer to an uint32_t containing the marker position in frames.
@@ -225,7 +229,7 @@ public:
      */
             uint32_t     latency() const;
 
-    /* getters, see constructor */
+    /* getters, see constructors and set() */
 
             audio_stream_type_t streamType() const;
             audio_format_t format() const;
@@ -401,13 +405,19 @@ public:
             status_t    attachAuxEffect(int effectId);
 
     /* Obtains a buffer of "frameCount" frames. The buffer must be
-     * filled entirely. If the track is stopped, obtainBuffer() returns
+     * filled entirely, and then released with releaseBuffer().
+     * If the track is stopped, obtainBuffer() returns
      * STOPPED instead of NO_ERROR as long as there are buffers available,
      * at which point NO_MORE_BUFFERS is returned.
      * Buffers will be returned until the pool (buffercount())
      * is exhausted, at which point obtainBuffer() will either block
      * or return WOULD_BLOCK depending on the value of the "blocking"
      * parameter.
+     *
+     * Interpretation of waitCount:
+     *  +n  limits wait time to n * WAIT_PERIOD_MS,
+     *  -1  causes an (almost) infinite wait time,
+     *   0  non-blocking.
      */
 
         enum {
@@ -416,12 +426,19 @@ public:
         };
 
             status_t    obtainBuffer(Buffer* audioBuffer, int32_t waitCount);
+
+    /* Release a filled buffer of "frameCount" frames for AudioFlinger to process. */
             void        releaseBuffer(Buffer* audioBuffer);
 
     /* As a convenience we provide a write() interface to the audio buffer.
-     * This is implemented on top of lockBuffer/unlockBuffer. For best
-     * performance use callbacks. Return actual number of bytes written.
-     *
+     * This is implemented on top of obtainBuffer/releaseBuffer. For best
+     * performance use callbacks. Returns actual number of bytes written >= 0,
+     * or one of the following negative status codes:
+     *      INVALID_OPERATION   AudioTrack is configured for shared buffer mode
+     *      BAD_VALUE           size is invalid
+     *      STOPPED             AudioTrack was stopped during the write
+     *      NO_MORE_BUFFERS     when obtainBuffer() returns same
+     *      or any other error code returned by IAudioTrack::start() or restoreTrack_l().
      */
             ssize_t     write(const void* buffer, size_t size);
 
@@ -448,6 +465,7 @@ private:
         AudioTrack& mReceiver;
     };
 
+            // body of AudioTrackThread::threadLoop()
             bool processAudioBuffer(const sp<AudioTrackThread>& thread);
             status_t createTrack_l(audio_stream_type_t streamType,
                                  uint32_t sampleRate,
@@ -484,7 +502,7 @@ private:
 
     bool                    mActive;                // protected by mLock
 
-    callback_t              mCbf;
+    callback_t              mCbf;                   // callback handler for events, or NULL
     void*                   mUserData;
     uint32_t                mNotificationFramesReq; // requested number of frames between each notification callback
     uint32_t                mNotificationFramesAct; // actual number of frames between each notification callback
diff --git a/include/media/EffectsFactoryApi.h b/include/media/EffectsFactoryApi.h
index df83995..65c26f4 100644
--- a/include/media/EffectsFactoryApi.h
+++ b/include/media/EffectsFactoryApi.h
@@ -87,7 +87,7 @@ int EffectQueryEffect(uint32_t index, effect_descriptor_t *pDescriptor);
 //    Description:    Creates an effect engine of the specified type and returns an
 //          effect control interface on this engine. The function will allocate the
 //          resources for an instance of the requested effect engine and return
-//          a handler on the effect control interface.
+//          a handle on the effect control interface.
 //
 //    Input:
 //          pEffectUuid:    pointer to the effect uuid.
@@ -115,17 +115,17 @@ int EffectCreate(const effect_uuid_t *pEffectUuid, int32_t sessionId, int32_t io
 //
 //    Function:       EffectRelease
 //
-//    Description:    Releases the effect engine whose handler is given as argument.
+//    Description:    Releases the effect engine whose handle is given as argument.
 //          All resources allocated to this particular instance of the effect are
 //          released.
 //
 //    Input:
-//          handle:    handler on the effect interface to be released.
+//          handle:    handle on the effect interface to be released.
 //
 //    Output:
 //        returned value:    0          successful operation.
 //                          -ENODEV     factory failed to initialize
-//                          -EINVAL     invalid interface handler
+//                          -EINVAL     invalid interface handle
 //
 ////////////////////////////////////////////////////////////////////////////////
 int EffectRelease(effect_handle_t handle);
diff --git a/include/media/IAudioTrack.h b/include/media/IAudioTrack.h
index b346722..e4772a1 100644
--- a/include/media/IAudioTrack.h
+++ b/include/media/IAudioTrack.h
@@ -46,12 +46,12 @@ public:
 
     /* Stop a track. If set, the callback will cease being called and
      * obtainBuffer will return an error. Buffers that are already released 
-     * will be processed, unless flush() is called.
+     * will continue to be processed, unless/until flush() is called.
      */
     virtual void        stop() = 0;
 
-    /* Flush a stopped track. All pending buffers are discarded.
-     * This function has no effect if the track is not stopped.
+    /* Flush a stopped or paused track. All pending/released buffers are discarded.
+     * This function has no effect if the track is not stopped or paused.
      */
     virtual void        flush() = 0;
 
@@ -62,7 +62,7 @@ public:
     
     /* Pause a track. If set, the callback will cease being called and
      * obtainBuffer will return an error. Buffers that are already released 
-     * will be processed, unless flush() is called.
+     * will continue to be processed, unless/until flush() is called.
      */
     virtual void        pause() = 0;
 
diff --git a/include/media/MemoryLeakTrackUtil.h b/include/media/MemoryLeakTrackUtil.h
index 290b748..ac0f6b2 100644
--- a/include/media/MemoryLeakTrackUtil.h
+++ b/include/media/MemoryLeakTrackUtil.h
@@ -19,7 +19,7 @@
 
 namespace android {
 /*
- * Dump the memory adddress of the calling process to the given fd.
+ * Dump the memory address of the calling process to the given fd.
  */
 extern void dumpMemoryAddresses(int fd);
 
diff --git a/include/private/media/AudioTrackShared.h b/include/private/media/AudioTrackShared.h
index 23226c0..af2db93 100644
--- a/include/private/media/AudioTrackShared.h
+++ b/include/private/media/AudioTrackShared.h
@@ -62,16 +62,23 @@ struct audio_track_cblk_t
     // are in the same line of data cache.
                 Mutex       lock;           // sizeof(int)
                 Condition   cv;             // sizeof(int)
+
+                // next 4 are offsets within "buffers"
     volatile    uint32_t    user;
     volatile    uint32_t    server;
                 uint32_t    userBase;
                 uint32_t    serverBase;
+
+                // if there is a shared buffer, "buffers" is the value of pointer() for the shared
+                // buffer, otherwise "buffers" points immediately after the control block
                 void*       buffers;
                 uint32_t    frameCount;
+
                 // Cache line boundary
+
                 uint32_t    loopStart;
-                uint32_t    loopEnd;
-                int         loopCount;
+                uint32_t    loopEnd;        // read-only for server, read/write for client
+                int         loopCount;      // read/write for client
 
                 // Channel volumes are fixed point U4.12, so 0x1000 means 1.0.
                 // Left channel is in [0:15], right channel is in [16:31].
@@ -82,29 +89,39 @@ private:
 public:
 
                 uint32_t    sampleRate;
+
                 // NOTE: audio_track_cblk_t::frameSize is not equal to AudioTrack::frameSize() for
                 // 8 bit PCM data: in this case,  mCblk->frameSize is based on a sample size of
                 // 16 bit because data is converted to 16 bit before being stored in buffer
 
+                // read-only for client, server writes once at initialization and is then read-only
                 uint8_t     frameSize;       // would normally be size_t, but 8 bits is plenty
+
+                // never used
                 uint8_t     pad1;
+
+                // used by client only
                 uint16_t    bufferTimeoutMs; // Maximum cumulated timeout before restarting audioflinger
 
-                uint16_t    waitTimeMs;      // Cumulated wait time
+                uint16_t    waitTimeMs;      // Cumulated wait time, used by client only
 private:
+                // client write-only, server read-only
                 uint16_t    mSendLevel;      // Fixed point U4.12 so 0x1000 means 1.0
 public:
     volatile    int32_t     flags;
 
                 // Cache line boundary (32 bytes)
 
+                // Since the control block is always located in shared memory, this constructor
+                // is only used for placement new().  It is never used for regular new() or stack.
                             audio_track_cblk_t();
-                uint32_t    stepUser(uint32_t frameCount);
-                bool        stepServer(uint32_t frameCount);
+                uint32_t    stepUser(uint32_t frameCount);      // called by client only, where
+                // client includes regular AudioTrack and AudioFlinger::PlaybackThread::OutputTrack
+                bool        stepServer(uint32_t frameCount);    // called by server only
                 void*       buffer(uint32_t offset) const;
                 uint32_t    framesAvailable();
                 uint32_t    framesAvailable_l();
-                uint32_t    framesReady();
+                uint32_t    framesReady();                      // called by server only
                 bool        tryLock();
 
                 // No barriers on the following operations, so the ordering of loads/stores