diff --git a/audio/4.0/IDevice.hal b/audio/4.0/IDevice.hal
index e3f36f6..23cf9fb 100644
--- a/audio/4.0/IDevice.hal
+++ b/audio/4.0/IDevice.hal
@@ -200,14 +200,17 @@
     /**
      * Gets the HW synchronization source of the device. Calling this method is
      * equivalent to getting AUDIO_PARAMETER_HW_AV_SYNC on the legacy HAL.
+     * Optional method
      *
+     * @return retval operation completion status: OK or NOT_SUPPORTED.
      * @return hwAvSync HW synchronization source
      */
-    getHwAvSync() generates (AudioHwSync hwAvSync);
+    getHwAvSync() generates (Result retval, AudioHwSync hwAvSync);
 
     /**
      * Sets whether the screen is on. Calling this method is equivalent to
      * setting AUDIO_PARAMETER_KEY_SCREEN_STATE on the legacy HAL.
+     * Optional method
      *
      * @param turnedOn whether the screen is turned on.
      * @return retval operation completion status.
@@ -219,11 +222,19 @@
      * The framework does not interpret the parameters, they are passed
      * in an opaque manner between a vendor application and HAL.
      *
-     * @param keys parameter keys.
+     * Multiple parameters can be retrieved at the same time.
+     * The implementation should return as many requested parameters
+     * as possible, even if one or more is not supported
+     *
+     * @param context provides more information about the request
+     * @param keys keys of the requested parameters
      * @return retval operation completion status.
+     *         OK must be returned if keys is empty.
+     *         NOT_SUPPORTED must be returned if at least one key is unknown.
      * @return parameters parameter key value pairs.
+     *         Must contain the value of all requested keys if retval == OK
      */
-    getParameters(vec<string> keys)
+    getParameters(vec<ParameterValue> context, vec<string> keys)
             generates (Result retval, vec<ParameterValue> parameters);
 
     /**
@@ -231,16 +242,28 @@
      * The framework does not interpret the parameters, they are passed
      * in an opaque manner between a vendor application and HAL.
      *
+     * Multiple parameters can be set at the same time though this is
+     * discouraged as it make failure analysis harder.
+     *
+     * If possible, a failed setParameters should not impact the platform state.
+     *
+     * @param context provides more information about the request
      * @param parameters parameter key value pairs.
      * @return retval operation completion status.
+     *         All parameters must be successfully set for OK to be returned
      */
-    setParameters(vec<ParameterValue> parameters) generates (Result retval);
+    setParameters(vec<ParameterValue> context, vec<ParameterValue> parameters)
+            generates (Result retval);
 
     /**
-     * Dumps information about the stream into the provided file descriptor.
+     * Dumps information about the device into the provided file descriptor.
      * This is used for the dumpsys facility.
+     * The implementation should not block as the caller might have time
+     * constraint on the dump.
+     * A back to back dump of all HAL Device and Stream should take under 100ms.
      *
      * @param fd dump file descriptor.
+     * @return retval operation completion status: OK or NOT_SUPPORTED.
      */
-    debugDump(handle fd);
+    debugDump(handle fd) generates (Result retval);
 };
diff --git a/audio/4.0/IPrimaryDevice.hal b/audio/4.0/IPrimaryDevice.hal
index 60330fb..4eafdbb 100644
--- a/audio/4.0/IPrimaryDevice.hal
+++ b/audio/4.0/IPrimaryDevice.hal
@@ -52,6 +52,7 @@
      * Sets whether BT SCO Noise Reduction and Echo Cancellation are enabled.
      * Calling this method is equivalent to setting AUDIO_PARAMETER_KEY_BT_NREC
      * on the legacy HAL.
+     * Optional method
      *
      * @param enabled whether BT SCO NR + EC are enabled.
      * @return retval operation completion status.
@@ -70,6 +71,7 @@
     /**
      * Sets whether BT SCO Wideband mode is enabled. Calling this method is
      * equivalent to setting AUDIO_PARAMETER_KEY_BT_SCO_WB on the legacy HAL.
+     * Optional method
      *
      * @param enabled whether BT Wideband is enabled.
      * @return retval operation completion status.
@@ -115,6 +117,7 @@
      * Sets whether Hearing Aid Compatibility - Telecoil (HAC-T) mode is
      * enabled. Calling this method is equivalent to setting
      * AUDIO_PARAMETER_KEY_HAC on the legacy HAL.
+     * Optional method
      *
      * @param enabled whether HAC mode is enabled.
      * @return retval operation completion status.
diff --git a/audio/4.0/IStream.hal b/audio/4.0/IStream.hal
index 162e0fd..62b8d03 100644
--- a/audio/4.0/IStream.hal
+++ b/audio/4.0/IStream.hal
@@ -53,17 +53,30 @@
     getSampleRate() generates (uint32_t sampleRateHz);
 
     /**
-     * Return supported sampling rates of the stream. Calling this method is
-     * equivalent to getting AUDIO_PARAMETER_STREAM_SUP_SAMPLING_RATES on the
-     * legacy HAL.
+     * Return supported native sampling rates of the stream for a given format.
+     * A supported native sample rate is a sample rate that can be efficiently
+     * played by the hardware (typically without sample-rate conversions).
      *
+     * This function is only called for dynamic profile. If called for
+     * non-dynamic profile is should return NOT_SUPPORTED or the same list
+     * as in audio_policy_configuration.xml.
+     *
+     * Calling this method is equivalent to getting
+     * AUDIO_PARAMETER_STREAM_SUP_SAMPLING_RATES on the legacy HAL.
+     *
+     *
+     * @param format audio format for which the sample rates are supported.
+     * @return retval operation completion status.
+     *                Must be OK if the format is supported.
      * @return sampleRateHz supported sample rates.
      */
-    getSupportedSampleRates() generates (vec<uint32_t> sampleRates);
+    getSupportedSampleRates(AudioFormat format)
+            generates (Result retval, vec<uint32_t> sampleRates);
 
     /**
      * Sets the sampling rate of the stream. Calling this method is equivalent
      * to setting AUDIO_PARAMETER_STREAM_SAMPLING_RATE on the legacy HAL.
+     * Optional method. If implemented, only called on a stopped stream.
      *
      * @param sampleRateHz sample rate in Hz.
      * @return retval operation completion status.
@@ -82,13 +95,18 @@
      * equivalent to getting AUDIO_PARAMETER_STREAM_SUP_CHANNELS on the legacy
      * HAL.
      *
+     * @param format audio format for which the channel masks are supported.
+     * @return retval operation completion status.
+     *                Must be OK if the format is supported.
      * @return masks supported audio masks.
      */
-    getSupportedChannelMasks() generates (vec<AudioChannelMask> masks);
+    getSupportedChannelMasks(AudioFormat format)
+            generates (Result retval, vec<AudioChannelMask> masks);
 
     /**
      * Sets the channel mask of the stream. Calling this method is equivalent to
      * setting AUDIO_PARAMETER_STREAM_CHANNELS on the legacy HAL.
+     * Optional method
      *
      * @param format audio format.
      * @return retval operation completion status.
@@ -114,6 +132,7 @@
     /**
      * Sets the audio format of the stream. Calling this method is equivalent to
      * setting AUDIO_PARAMETER_STREAM_FORMAT on the legacy HAL.
+     * Optional method
      *
      * @param format audio format.
      * @return retval operation completion status.
@@ -159,10 +178,12 @@
 
     /**
      * Return the set of device(s) which this stream is connected to.
+     * Optional method
      *
+     * @return retval operation completion status: OK or NOT_SUPPORTED.
      * @return device set of device(s) which this stream is connected to.
      */
-    getDevice() generates (AudioDevice device);
+    getDevice() generates (Result retval, AudioDevice device);
 
     /**
      * Connects the stream to the device.
@@ -192,6 +213,7 @@
     /**
      * Sets the HW synchronization source. Calling this method is equivalent to
      * setting AUDIO_PARAMETER_STREAM_HW_AV_SYNC on the legacy HAL.
+     * Optional method
      *
      * @param hwAvSync HW synchronization source
      * @return retval operation completion status.
@@ -203,11 +225,19 @@
      * The framework does not interpret the parameters, they are passed
      * in an opaque manner between a vendor application and HAL.
      *
-     * @param keys parameter keys.
+     * Multiple parameters can be retrieved at the same time.
+     * The implementation should return as many requested parameters
+     * as possible, even if one or more is not supported
+     *
+     * @param context provides more information about the request
+     * @param keys keys of the requested parameters
      * @return retval operation completion status.
+     *         OK must be returned if keys is empty.
+     *         NOT_SUPPORTED must be returned if at least one key is unknown.
      * @return parameters parameter key value pairs.
+     *         Must contain the value of all requested keys if retval == OK
      */
-    getParameters(vec<string> keys)
+    getParameters(vec<ParameterValue> context, vec<string> keys)
             generates (Result retval, vec<ParameterValue> parameters);
 
     /**
@@ -215,18 +245,30 @@
      * The framework does not interpret the parameters, they are passed
      * in an opaque manner between a vendor application and HAL.
      *
+     * Multiple parameters can be set at the same time though this is
+     * discouraged as it make failure analysis harder.
+     *
+     * If possible, a failed setParameters should not impact the platform state.
+     *
+     * @param context provides more information about the request
      * @param parameters parameter key value pairs.
      * @return retval operation completion status.
+     *         All parameters must be successfully set for OK to be returned
      */
-    setParameters(vec<ParameterValue> parameters) generates (Result retval);
+    setParameters(vec<ParameterValue> context, vec<ParameterValue> parameters)
+            generates (Result retval);
 
     /**
      * Dumps information about the stream into the provided file descriptor.
      * This is used for the dumpsys facility.
+     * The implementation should not block as the caller might have time
+     * constraint on the dump.
+     * A back to back dump of all HAL Device and Stream should take under 100ms.
      *
      * @param fd dump file descriptor.
+     * @return retval operation completion status: OK or NOT_SUPPORTED.
      */
-    debugDump(handle fd);
+    debugDump(handle fd) generates (Result retval);
 
     /**
      * Called by the framework to start a stream operating in mmap mode.
diff --git a/audio/4.0/IStreamIn.hal b/audio/4.0/IStreamIn.hal
index 306aeb1..ea2826e 100644
--- a/audio/4.0/IStreamIn.hal
+++ b/audio/4.0/IStreamIn.hal
@@ -26,6 +26,7 @@
      * Returns the source descriptor of the input stream. Calling this method is
      * equivalent to getting AUDIO_PARAMETER_STREAM_INPUT_SOURCE on the legacy
      * HAL.
+     * Optional method
      *
      * @return retval operation completion status.
      * @return source audio source.
@@ -34,6 +35,7 @@
 
     /**
      * Set the input gain for the audio driver.
+     * Optional method
      *
      * @param gain 1.0f is unity, 0.0f is zero.
      * @result retval operation completion status.
diff --git a/audio/4.0/IStreamOut.hal b/audio/4.0/IStreamOut.hal
index 22b91f0..02f1697 100644
--- a/audio/4.0/IStreamOut.hal
+++ b/audio/4.0/IStreamOut.hal
@@ -36,10 +36,12 @@
      * allowing to directly set the volume as apposed to via the framework.
      * This method might produce multiple PCM outputs or hardware accelerated
      * codecs, such as MP3 or AAC.
+     * Optional method
      *
      * @param left left channel attenuation, 1.0f is unity, 0.0f is zero.
      * @param right right channel attenuation, 1.0f is unity, 0.0f is zero.
      * @return retval operation completion status.
+     *        If a volume is outside [0,1], return INVALID_ARGUMENTS
      */
     setVolume(float left, float right) generates (Result retval);
 
@@ -115,6 +117,7 @@
     /**
      * Return the number of audio frames written by the audio DSP to DAC since
      * the output has exited standby.
+     * Optional method
      *
      * @return retval operation completion status.
      * @return dspFrames number of audio frames written.
@@ -125,6 +128,7 @@
      * Get the local time at which the next write to the audio driver will be
      * presented. The units are microseconds, where the epoch is decided by the
      * local audio HAL.
+     * Optional method
      *
      * @return retval operation completion status.
      * @return timestampUs time of the next write.
@@ -152,6 +156,9 @@
      * Warning: failure to call this method results in callback implementation
      * on the client side being held until the HAL server termination.
      *
+     * If no callback was previously set, the method should be a no-op
+     * and return OK.
+     *
      * @return retval operation completion status: OK or NOT_SUPPORTED.
      */
     clearCallback() generates (Result retval);
@@ -223,6 +230,7 @@
     /**
      * Notifies to the audio driver to flush the queued data. Stream must
      * already be paused before calling 'flush'.
+     * Optional method
      *
      * Implementation of this function is mandatory for offloaded playback.
      *
@@ -244,6 +252,8 @@
      * timestamp must correspond to N rather than N+M. The terms 'recent' and
      * 'small' are not defined. They reflect the quality of the implementation.
      *
+     * Optional method
+     *
      * @return retval operation completion status.
      * @return frames count of presented audio frames.
      * @return timeStamp associated clock time.
diff --git a/audio/common/4.0/types.hal b/audio/common/4.0/types.hal
index d0e99fc..eaff69d 100644
--- a/audio/common/4.0/types.hal
+++ b/audio/common/4.0/types.hal
@@ -83,7 +83,7 @@
  */
 
 /**
- * Audio stream type describing the intented use case of a stream.
+ * Audio stream type describing the intended use case of a stream.
  */
 @export(name="audio_stream_type_t", value_prefix="AUDIO_STREAM_")
 enum AudioStreamType : int32_t {
diff --git a/audio/effect/4.0/IEffectsFactory.hal b/audio/effect/4.0/IEffectsFactory.hal
index 0e1c0d2..84efb74 100644
--- a/audio/effect/4.0/IEffectsFactory.hal
+++ b/audio/effect/4.0/IEffectsFactory.hal
@@ -59,8 +59,12 @@
     /**
      * Dumps information about effects into the provided file descriptor.
      * This is used for the dumpsys facility.
+     * The implementation should not block as the caller might have time
+     * constraint on the dump.
+     * A back to back dump of all HAL Device and Stream should take under 100ms.
      *
      * @param fd dump file descriptor.
+     * @return retval operation completion status: OK or NOT_SUPPORTED.
      */
-    debugDump(handle fd);
+    debugDump(handle fd) generates (Result retval);
 };