diff --git a/audio/4.0/IDevicesFactory.hal b/audio/4.0/IDevicesFactory.hal
index 987fd68..489294e 100644
--- a/audio/4.0/IDevicesFactory.hal
+++ b/audio/4.0/IDevicesFactory.hal
@@ -18,6 +18,7 @@
 
 import android.hardware.audio.common@4.0;
 import IDevice;
+import IPrimaryDevice;
 
 /** This factory allows a HAL implementation to be split in multiple independent
  *  devices (called module in the pre-treble API).
@@ -28,8 +29,7 @@
  *  Each device name is arbitrary, provided by the vendor's audio_policy_configuration.xml
  *  and only used to identify a device in this factory.
  *  The framework must not interpret the name, treating it as a vendor opaque data
- *  with the following exceptions:
- *  - the "primary" device must always be present and is the device used by the telephony framework.
+ *  with the following exception:
  *  - the "r_submix" device that must be present to support policyMixes (Eg: Android projected).
  *    Note that this Device is included by default in a build derived from AOSP.
  *
@@ -51,4 +51,20 @@
      * @return result the interface for the created device.
      */
     openDevice(string device) generates (Result retval, IDevice result);
+
+    /**
+     * Opens the Primary audio device that must be present.
+     * This function is not optional and must return successfully the primary device.
+     *
+     * This device must have the name "primary".
+     *
+     * The telephony stack uses this device to control the audio during a voice call.
+     *
+     * @return retval operation completion status. Must be SUCCESS.
+     *         For debuging, return INVALID_ARGUMENTS if there is no corresponding
+     *         hardware module found, NOT_INITIALIZED if an error occurred
+     *         while opening the hardware module.
+     * @return result the interface for the created device.
+     */
+    openPrimaryDevice() generates (Result retval, IPrimaryDevice result);
 };