diff --git a/audio/4.0/IPrimaryDevice.hal b/audio/4.0/IPrimaryDevice.hal
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+++ b/audio/4.0/IPrimaryDevice.hal
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+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.hardware.audio@4.0;
+
+import android.hardware.audio.common@4.0;
+import IDevice;
+
+interface IPrimaryDevice extends IDevice {
+    typedef android.hardware.audio@4.0::Result Result;
+
+    /**
+     * Sets the audio volume of a voice call.
+     *
+     * @param volume 1.0f means unity, 0.0f is zero.
+     * @return retval operation completion status.
+     */
+    setVoiceVolume(float volume) generates (Result retval);
+
+    /**
+     * This method is used to notify the HAL about audio mode changes.
+     *
+     * @param mode new mode.
+     * @return retval operation completion status.
+     */
+    setMode(AudioMode mode) generates (Result retval);
+
+    /**
+     * Gets whether BT SCO Noise Reduction and Echo Cancellation are enabled.
+     * Calling this method is equivalent to getting AUDIO_PARAMETER_KEY_BT_NREC
+     * on the legacy HAL.
+     *
+     * @return retval operation completion status.
+     * @return enabled whether BT SCO NR + EC are enabled.
+     */
+    getBtScoNrecEnabled() generates (Result retval, bool enabled);
+
+    /**
+     * 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.
+     *
+     * @param enabled whether BT SCO NR + EC are enabled.
+     * @return retval operation completion status.
+     */
+    setBtScoNrecEnabled(bool enabled) generates (Result retval);
+
+    /**
+     * Gets whether BT SCO Wideband mode is enabled. Calling this method is
+     * equivalent to getting AUDIO_PARAMETER_KEY_BT_SCO_WB on the legacy HAL.
+     *
+     * @return retval operation completion status.
+     * @return enabled whether BT Wideband is enabled.
+     */
+    getBtScoWidebandEnabled() generates (Result retval, bool enabled);
+
+    /**
+     * 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.
+     *
+     * @param enabled whether BT Wideband is enabled.
+     * @return retval operation completion status.
+     */
+    setBtScoWidebandEnabled(bool enabled) generates (Result retval);
+
+    enum TtyMode : int32_t {
+        OFF,
+        VCO,
+        HCO,
+        FULL
+    };
+
+    /**
+     * Gets current TTY mode selection. Calling this method is equivalent to
+     * getting AUDIO_PARAMETER_KEY_TTY_MODE on the legacy HAL.
+     *
+     * @return retval operation completion status.
+     * @return mode TTY mode.
+     */
+    getTtyMode() generates (Result retval, TtyMode mode);
+
+    /**
+     * Sets current TTY mode. Calling this method is equivalent to setting
+     * AUDIO_PARAMETER_KEY_TTY_MODE on the legacy HAL.
+     *
+     * @param mode TTY mode.
+     * @return retval operation completion status.
+     */
+    setTtyMode(TtyMode mode) generates (Result retval);
+
+    /**
+     * Gets whether Hearing Aid Compatibility - Telecoil (HAC-T) mode is
+     * enabled. Calling this method is equivalent to getting
+     * AUDIO_PARAMETER_KEY_HAC on the legacy HAL.
+     *
+     * @return retval operation completion status.
+     * @return enabled whether HAC mode is enabled.
+     */
+    getHacEnabled() generates (Result retval, bool enabled);
+
+    /**
+     * 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.
+     *
+     * @param enabled whether HAC mode is enabled.
+     * @return retval operation completion status.
+     */
+    setHacEnabled(bool enabled) generates (Result retval);
+};