diff --git a/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISession.aidl b/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISession.aidl
index 87eaf96..9934a76 100644
--- a/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISession.aidl
+++ b/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISession.aidl
@@ -34,17 +34,17 @@
 package android.hardware.biometrics.fingerprint;
 @VintfStability
 interface ISession {
-  void generateChallenge(in int cookie);
-  void revokeChallenge(in int cookie, in long challenge);
-  android.hardware.biometrics.common.ICancellationSignal enroll(in int cookie, in android.hardware.keymaster.HardwareAuthToken hat);
-  android.hardware.biometrics.common.ICancellationSignal authenticate(in int cookie, in long operationId);
-  android.hardware.biometrics.common.ICancellationSignal detectInteraction(in int cookie);
-  void enumerateEnrollments(in int cookie);
-  void removeEnrollments(in int cookie, in int[] enrollmentIds);
-  void getAuthenticatorId(in int cookie);
-  void invalidateAuthenticatorId(in int cookie);
-  void resetLockout(in int cookie, in android.hardware.keymaster.HardwareAuthToken hat);
-  void close(in int cookie);
+  void generateChallenge();
+  void revokeChallenge(in long challenge);
+  android.hardware.biometrics.common.ICancellationSignal enroll(in android.hardware.keymaster.HardwareAuthToken hat);
+  android.hardware.biometrics.common.ICancellationSignal authenticate(in long operationId);
+  android.hardware.biometrics.common.ICancellationSignal detectInteraction();
+  void enumerateEnrollments();
+  void removeEnrollments(in int[] enrollmentIds);
+  void getAuthenticatorId();
+  void invalidateAuthenticatorId();
+  void resetLockout(in android.hardware.keymaster.HardwareAuthToken hat);
+  void close();
   void onPointerDown(in int pointerId, in int x, in int y, in float minor, in float major);
   void onPointerUp(in int pointerId);
   void onUiReady();
diff --git a/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISessionCallback.aidl b/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISessionCallback.aidl
index 3a97717..3c40ad6 100644
--- a/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISessionCallback.aidl
+++ b/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISessionCallback.aidl
@@ -34,7 +34,6 @@
 package android.hardware.biometrics.fingerprint;
 @VintfStability
 interface ISessionCallback {
-  void onStateChanged(in int cookie, in android.hardware.biometrics.fingerprint.SessionState state);
   void onChallengeGenerated(in long challenge);
   void onChallengeRevoked(in long challenge);
   void onAcquired(in android.hardware.biometrics.fingerprint.AcquiredInfo info, in int vendorCode);
diff --git a/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/SessionState.aidl b/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/SessionState.aidl
deleted file mode 100644
index 9b0b6f6..0000000
--- a/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/SessionState.aidl
+++ /dev/null
@@ -1,49 +0,0 @@
-/*
- * Copyright (C) 2020 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.
- */
-///////////////////////////////////////////////////////////////////////////////
-// THIS FILE IS IMMUTABLE. DO NOT EDIT IN ANY CASE.                          //
-///////////////////////////////////////////////////////////////////////////////
-
-// This file is a snapshot of an AIDL file. Do not edit it manually. There are
-// two cases:
-// 1). this is a frozen version file - do not edit this in any case.
-// 2). this is a 'current' file. If you make a backwards compatible change to
-//     the interface (from the latest frozen version), the build system will
-//     prompt you to update this file with `m <name>-update-api`.
-//
-// You must not make a backward incompatible change to any AIDL file built
-// with the aidl_interface module type with versions property set. The module
-// type is used to build AIDL files in a way that they can be used across
-// independently updatable components of the system. If a device is shipped
-// with such a backward incompatible change, it has a high risk of breaking
-// later when a module using the interface is updated, e.g., Mainline modules.
-
-package android.hardware.biometrics.fingerprint;
-@Backing(type="byte") @VintfStability
-enum SessionState {
-  IDLING = 0,
-  CLOSED = 1,
-  GENERATING_CHALLENGE = 2,
-  REVOKING_CHALLENGE = 3,
-  ENROLLING = 4,
-  AUTHENTICATING = 5,
-  DETECTING_INTERACTION = 6,
-  ENUMERATING_ENROLLMENTS = 7,
-  REMOVING_ENROLLMENTS = 8,
-  GETTING_AUTHENTICATOR_ID = 9,
-  INVALIDATING_AUTHENTICATOR_ID = 10,
-  RESETTING_LOCKOUT = 11,
-}
diff --git a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/IFingerprint.aidl b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/IFingerprint.aidl
index 98a4530..271a9bf 100644
--- a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/IFingerprint.aidl
+++ b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/IFingerprint.aidl
@@ -32,27 +32,14 @@
     /**
      * createSession:
      *
-     * Creates a session which can then be used by the framework to perform operations such as
-     * enroll, authenticate, etc for the given sensorId and userId.
+     * Creates a instance of ISession which can be used by the framework to perform operations
+     * such as ISession#enroll, ISession#authenticate, etc. for the given sensorId and userId.
      *
-     * Calling this method while there is an active session is considered an error. If the
-     * framework is in a bad state and for some reason cannot close its session, it should use
-     * the reset method below.
-     *
-     * A physical sensor identified by sensorId typically supports only a single in-flight session
-     * at a time. As such, if a session is currently in a state other than SessionState::IDLING, the
-     * HAL MUST finish or cancel the current operation and return to SessionState::IDLING before the
-     * new session is created. For example:
-     *   1) If a session for sensorId=0, userId=0 is currently in a cancellable state (see
-     *      ICancellationSignal) such as SessionState::AUTHENTICATING and the framework requests a
-     *      new session for sensorId=0, userId=10, the HAL must end the current session with
-     *      Error::CANCELED, invoke ISessionCallback#onStateChanged with SessionState::IDLING, and
-     *      then return a new session for sensorId=0, userId=10.
-     *   2) If a session for sensorId=0, userId=0 is currently in a non-cancellable state such as
-     *      SessionState::REMOVING_ENROLLMENTS, and the framework requests a new session for
-     *      sensorId=0, userId=10, the HAL must finish the current operation before invoking
-     *      ISessionCallback#onStateChanged with SessionState::IDLING, and return a new session for
-     *      sensorId=0, userId=10.
+     * Calling this method while there is an active session is considered an error. If the framework
+     * wants to create a new session when it already has an active session, it must first cancel the
+     * current operation if it's cancellable, or wait until it completes. Then, the framework must
+     * explicitly close the session with ISession#close. Once the framework receives
+     * ISessionCallback#onSessionClosed, a new session can be created.
      *
      * Implementations must store user-specific state or metadata in /data/vendor_de/<user>/fpdata
      * as specified by the SeLinux policy. This directory is created/removed by vold (see
diff --git a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISession.aidl b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISession.aidl
index ef2e6fc..940548b 100644
--- a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISession.aidl
+++ b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISession.aidl
@@ -22,23 +22,28 @@
 /**
  * Operations that can be performed for unique sessions retrieved via IFingerprint#createSession.
  * Methods defined within this interface can be split into the following categories:
- *   1) Methods associated with a state (see the SessionState enum). State-based operations are
- *      handled by the HAL in FIFO order.
- *   1a) Cancellable state-based operations. If a cancellable operation is in-progress and the
- *       framework requests a subsequent state-based operation, the implementation should finish
- *       the operation via ISessionCallback#onError with Error::CANCELED.
- *   1b) Non-cancellable state-based operations. These operations should fully complete before the
- *       next state-based operation can be started.
- *   2) Methods without a state. These methods may be invoked by the framework depending on its
- *      use case. For example on devices with sensors of FingerprintSensorType::UNDER_DISPLAY_*,
- *      ISession#onFingerDown may be invoked while the HAL is in SessionState::ENROLLING,
- *      SessionState::AUTHENTICATING, or SessionState::DETECTING_INTERACTION.
+ *   1) Non-interrupting operations. These operations are handled by the HAL in FIFO order.
+ *   1a) Cancellable operations. These are usually the operations that can execute for several
+ *       minutes. To allow for cancellation, they return an instance of ICancellationSignal that
+ *       lets the framework cancel them by calling ICancellationSignal#cancel. If such an operation
+ *       is cancelled, it must notify the framework by calling ISessionCallback#onError with
+ *       Error::CANCELED.
+ *   1b) Non-cancellable operations. Such operations cannot be cancelled once started.
+ *   2) Interrupting operations. These operations may be invoked by the framework immediately,
+ *      regardless of whether another operation is executing. For example, on devices with sensors
+ *      of FingerprintSensorType::UNDER_DISPLAY_*, ISession#onFingerDown may be invoked while the
+ *      HAL is executing ISession#enroll, ISession#authenticate or ISession#detectInteraction.
  *
- * If the HAL has multiple operations in its queue, it is not required to notify the framework
- * of SessionState::IDLING between each operation. However, it must notify the framework when all
- * work is completed. See ISessionCallback#onStateChanged. For example, the following is a valid
- * sequence of ISessionCallback#onStateChanged invocations: SessionState::IDLING -->
- * SessionState::ENROLLING --> SessionState::ENUMERATING_ENROLLMENTS --> SessionState::IDLING.
+ * The lifecycle of a non-interrupting operation ends when one of its terminal callbacks is called.
+ * For example, ISession#authenticate is considered completed when either of the following callbacks
+ * is called: ISessionCallback#onError or ISessionCallback#onAuthenticationSucceeded.
+ *
+ * The lifecycle of an interrupting operation ends when it returns. Interrupting operations do not
+ * have callbacks.
+ *
+ * ISession only supports execution of one non-interrupting operation at a time, regardless of
+ * whether it's cancellable. The framework must wait for a corresponding callback indicating the end of
+ * the current non-interrupting operation before a new non-interrupting operation can be started.
  */
 @VintfStability
 interface ISession {
@@ -84,9 +89,8 @@
      * | 0        | 10     | <Time4>    | <Random4> |
      * ----------------------------------------------
      *
-     * @param cookie A unique number identifying this operation
      */
-    void generateChallenge(in int cookie);
+    void generateChallenge();
 
     /**
      * revokeChallenge:
@@ -95,23 +99,17 @@
      * parameters is requested, the implementation must still notify the framework using the
      * provided callback.
      *
-     * @param cookie A unique number identifying this operation
      * @param challenge Challenge that should be revoked.
      */
-    void revokeChallenge(in int cookie, in long challenge);
+    void revokeChallenge(in long challenge);
 
     /**
      * enroll:
      *
      * A request to add a fingerprint enrollment.
      *
-     * Once the HAL is able to start processing the enrollment request, it must notify the framework
-     * via ISessionCallback#onStateChanged with SessionState::ENROLLING.
-     *
      * At any point during enrollment, if a non-recoverable error occurs, the HAL must notify the
-     * framework via ISessionCallback#onError with the applicable enrollment-specific error, and
-     * then send ISessionCallback#onStateChanged(cookie, SessionState::IDLING) if no subsequent
-     * operation is in the queue.
+     * framework via ISessionCallback#onError with the applicable enrollment-specific error.
      *
      * Before capturing fingerprint data, the implementation must first verify the authenticity and
      * integrity of the provided HardwareAuthToken. In addition, it must check that the challenge
@@ -132,24 +130,17 @@
      * implementation MUST update and associate this (sensorId, userId) pair with a new new
      * entropy-encoded random identifier. See ISession#getAuthenticatorId for more information.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      * @param hat See above documentation.
      */
-    ICancellationSignal enroll(in int cookie, in HardwareAuthToken hat);
+    ICancellationSignal enroll(in HardwareAuthToken hat);
 
     /**
      * authenticate:
      *
      * A request to start looking for fingerprints to authenticate.
      *
-     * Once the HAL is able to start processing the authentication request, it must notify framework
-     * via ISessionCallback#onStateChanged with SessionState::AUTHENTICATING.
-     *
      * At any point during authentication, if a non-recoverable error occurs, the HAL must notify
-     * the framework via ISessionCallback#onError with the applicable authentication-specific error,
-     * and then send ISessionCallback#onStateChanged(cookie, SessionState::IDLING) if no
-     * subsequent operation is in the queue.
+     * the framework via ISessionCallback#onError with the applicable authentication-specific error.
      *
      * During authentication, the implementation may notify the framework via
      * ISessionCallback#onAcquired with messages that may be used to guide the user. This callback
@@ -171,8 +162,6 @@
      * must be set with the operationId passed in during #authenticate. If the sensor is NOT
      * SensorStrength::STRONG, the HardwareAuthToken MUST be null.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      * @param operationId For sensors configured as SensorStrength::STRONG, this must be used ONLY
      *                    upon successful authentication and wrapped in the HardwareAuthToken's
      *                    "challenge" field and sent to the framework via
@@ -184,7 +173,7 @@
      *                    setUserAuthenticationParameters in KeyGenParameterSpec.Builder and
      *                    KeyProtection.Builder.
      */
-    ICancellationSignal authenticate(in int cookie, in long operationId);
+    ICancellationSignal authenticate(in long operationId);
 
     /**
      * detectInteraction:
@@ -193,17 +182,12 @@
      * if SensorProps#supportsDetectInteraction is true. If invoked on implementations that do not
      * support this functionality, the HAL must respond with ISession#onError(UNABLE_TO_PROCESS, 0).
      *
-     * Once the HAL is able to start processing this request, it must notify the framework via
-     * ISessionCallback#onStateChanged with SessionState::DETECTING_INTERACTION.
-     *
      * The framework will use this method in cases where determing user presence is required, but
      * identifying/authentication is not. For example, when the device is encrypted (first boot) or
      * in lockdown mode.
      *
      * At any point during detectInteraction, if a non-recoverable error occurs, the HAL must notify
-     * the framework via ISessionCallback#onError with the applicable error, and then send
-     * ISessionCallback#onStateChanged(cookie, SessionState::IDLING) if no subsequent operation is
-     * in the queue.
+     * the framework via ISessionCallback#onError with the applicable error.
      *
      * The implementation must only check for a fingerprint-like image was detected (e.g. to
      * minimize interactions due to non-fingerprint objects), and the lockout counter must not
@@ -221,10 +205,8 @@
      * Note that if the operation is canceled, the implementation must notify the framework via
      * ISessionCallback#onError with Error::CANCELED.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path.
-     *               The framework will guarantee that it is unique per ISession.
      */
-    ICancellationSignal detectInteraction(in int cookie);
+    ICancellationSignal detectInteraction();
 
     /*
      * enumerateEnrollments:
@@ -232,32 +214,22 @@
      * A request to enumerate (list) the enrollments for this (sensorId, userId) pair. The
      * framework typically uses this to ensure that its cache is in sync with the HAL.
      *
-     * Once the HAL is able to start processing this request, it must notify the framework via
-     * ISessionCallback#onStateChanged with SessionState::ENUMERATING_ENROLLMENTS.
-     *
      * The implementation must then notify the framework with a list of enrollments applicable
      * for the current session via ISessionCallback#onEnrollmentsEnumerated.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path.
-     *               The framework will guarantee that it is unique per ISession.
      */
-    void enumerateEnrollments(in int cookie);
+    void enumerateEnrollments();
 
     /**
      * removeEnrollments:
      *
      * A request to remove the enrollments for this (sensorId, userId) pair.
      *
-     * Once the HAL is able to start processing this request, it must notify the framework via
-     * ISessionCallback#onStateChanged with SessionState::REMOVING_ENROLLMENTS.
-     *
      * After removing the enrollmentIds from everywhere necessary (filesystem, secure subsystems,
      * etc), the implementation must notify the framework via ISessionCallback#onEnrollmentsRemoved.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path.
-     *               The framework will guarantee that it is unique per ISession.
      */
-    void removeEnrollments(in int cookie, in int[] enrollmentIds);
+    void removeEnrollments(in int[] enrollmentIds);
 
     /**
      * getAuthenticatorId:
@@ -285,10 +257,8 @@
      *   3) MUST not change if a fingerprint is deleted.
      *   4) MUST be an entropy-encoded random number
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      */
-    void getAuthenticatorId(in int cookie);
+    void getAuthenticatorId();
 
     /**
      * invalidateAuthenticatorId:
@@ -312,10 +282,8 @@
      * for more details). As such, the framework would coordinate invalidation across multiple
      * biometric HALs as necessary.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      */
-    void invalidateAuthenticatorId(in int cookie);
+    void invalidateAuthenticatorId();
 
     /**
      * resetLockout:
@@ -326,8 +294,7 @@
      *   2) Verify that the timestamp provided within the HAT is relatively recent (e.g. on the
      *      order of minutes, not hours).
      * If either of the checks fail, the HAL must invoke ISessionCallback#onError with
-     * Error::UNABLE_TO_PROCESS and return to SessionState::IDLING if no subsequent work is in the
-     * queue.
+     * Error::UNABLE_TO_PROCESS and return to the idling state.
      *
      * Upon successful verification, the HAL must clear the lockout counter and notify the framework
      * via ISessionCallback#onLockoutCleared.
@@ -358,29 +325,26 @@
      * See the Android CDD section 7.3.10 for the full set of lockout and rate-limiting
      * requirements.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      * @param hat HardwareAuthToken See above documentation.
      */
-    void resetLockout(in int cookie, in HardwareAuthToken hat);
+    void resetLockout(in HardwareAuthToken hat);
 
     /*
      * Close this session and allow the HAL to release the resources associated with this session.
      *
-     * A session can only be closed when it's in SessionState::IDLING. Closing a session will
-     * result in a ISessionCallback#onStateChanged call with SessionState::CLOSED.
+     * A session can only be closed when the HAL is idling, i.e. not performing any of the
+     * non-interruptable operations. If the HAL is busy performing a cancellable operation, the
+     * operation must be explicitly cancelled with a call to ICancellationSignal#cancel before
+     * the session can be closed.
      *
-     * If a session is unresponsive or stuck in a state other than SessionState::CLOSED,
-     * IFingerprint#reset could be used as a last resort to terminate the session and recover the
-     * HAL from a bad state.
+     * After a session is closed, the HAL must notify the framework by calling
+     * ISessionCallback#onSessionClosed.
      *
      * All sessions must be explicitly closed. Calling IFingerprint#createSession while there is an
      * active session is considered an error.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      */
-    void close(in int cookie);
+    void close();
 
     /**
      * Methods for notifying the under-display fingerprint sensor about external events.
@@ -394,9 +358,8 @@
      * of other types, the HAL must treat this as a no-op and return immediately.
      *
      * For sensors of type FingerprintSensorType::UNDER_DISPLAY_*, this method is used to notify the
-     * HAL of display touches. This method can be invoked when the session is in one of the
-     * following states: SessionState::ENROLLING, SessionState::AUTHENTICATING, or
-     * SessionState::DETECTING_INTERACTION.
+     * HAL of display touches. This method can be invoked when the HAL is performing any one of:
+     * ISession#authenticate, ISession#enroll, ISession#detectInteraction.
      *
      * Note that the framework will only invoke this method if the event occurred on the display on
      * which this sensor is located.
diff --git a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISessionCallback.aidl b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISessionCallback.aidl
index cf3a271..95657b3 100644
--- a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISessionCallback.aidl
+++ b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISessionCallback.aidl
@@ -18,17 +18,11 @@
 
 import android.hardware.biometrics.fingerprint.AcquiredInfo;
 import android.hardware.biometrics.fingerprint.Error;
-import android.hardware.biometrics.fingerprint.SessionState;
 import android.hardware.keymaster.HardwareAuthToken;
 
 @VintfStability
 interface ISessionCallback {
     /**
-     * Used to notify the framework of session state changes. See ISession for more information.
-     */
-    void onStateChanged(in int cookie, in SessionState state);
-
-    /**
      * Notifies the framework when a challenge is successfully generated.
      */
     void onChallengeGenerated(in long challenge);
@@ -39,10 +33,10 @@
     void onChallengeRevoked(in long challenge);
 
     /**
-     * This method must only be used to notify the framework during the following states:
-     *   1) SessionState::ENROLLING
-     *   2) SessionState::AUTHENTICATING
-     *   3) SessionState::DETECTING_INTERACTION
+     * This method must only be used to notify the framework during the following operations:
+     *   1) ISession#enroll
+     *   2) ISession#authenticate
+     *   3) ISession#detectInteraction
      *
      * These messages may be used to provide user guidance multiple times if necessary per
      * operation.
@@ -56,18 +50,18 @@
     void onAcquired(in AcquiredInfo info, in int vendorCode);
 
     /**
-     * This method must only be used to notify the framework during the following states:
-     *   1) SessionState::ENROLLING
-     *   2) SessionState::AUTHENTICATING
-     *   3) SessionState::DETECTING_INTERACTION
-     *   4) SessionState::INVALIDATING_AUTHENTICATOR_ID
-     *   5) SessionState::RESETTING_LOCKOUT
+     * This method must only be used to notify the framework during the following operations:
+     *   1) ISession#enroll
+     *   2) ISession#authenticate
+     *   3) ISession#detectInteraction
+     *   4) ISession#invalidateAuthenticatorId
+     *   5) ISession#resetLockout
      *
      * These messages may be used to notify the framework or user that a non-recoverable error
-     * has occurred. The operation is finished, and the HAL must proceed with the next operation
-     * or return to SessionState::IDLING if the queue is empty.
+     * has occurred. The operation is finished, and the HAL can proceed with the next operation
+     * or return to the idling state.
      *
-     * Note that cancellation (see common::ICancellationSignal) and preemption most be followed with
+     * Note that cancellation (see common::ICancellationSignal) and preemption must be followed with
      * an Error::CANCELED message.
      *
      * @param error See the Error enum.
@@ -79,8 +73,7 @@
     void onError(in Error error, in int vendorCode);
 
     /**
-     * This method must only be used to notify the framework during the following state:
-     *   1) SessionState::ENROLLING
+     * This method must only be used to notify the framework during the ISession#enroll operation.
      *
      * @param enrollmentId Unique stable identifier for the enrollment that's being added by this
      *                     ISession#enroll invocation.
@@ -89,7 +82,7 @@
     void onEnrollmentProgress(in int enrollmentId, int remaining);
 
     /**
-     * This method must only be used to notify the framework during SessionState::AUTHENTICATING.
+     * This method must only be used to notify the framework during ISession#authenticate.
      *
      * Used to notify the framework upon successful authentication. Note that the authentication
      * lifecycle ends when either 1) a fingerprint is accepted, or 2) an error occurred. The
@@ -104,7 +97,7 @@
     void onAuthenticationSucceeded(in int enrollmentId, in HardwareAuthToken hat);
 
     /**
-     * This method must only be used to notify the framework during SessionState::AUTHENTICATING.
+     * This method must only be used to notify the framework during ISession#authenticate.
      *
      * Used to notify the framework upon rejected attempts. Note that the authentication
      * lifecycle ends when either 1) a fingerprint is accepted, or 2) an occurred. The
@@ -113,7 +106,7 @@
     void onAuthenticationFailed();
 
     /**
-     * This method must only be used to notify the framework during SessionState::AUTHENTICATING.
+     * This method must only be used to notify the framework during ISession#authenticate.
      *
      * Authentication is locked out due to too many unsuccessful attempts. This is a rate-limiting
      * lockout, and authentication can be restarted after a period of time. See
@@ -126,7 +119,7 @@
     void onLockoutTimed(in long durationMillis);
 
     /**
-     * This method must only be used to notify the framework during SessionState::AUTHENTICATING.
+     * This method must only be used to notify the framework during ISession#authenticate.
      *
      * Authentication is disabled until the user unlocks with their device credential
      * (PIN/Pattern/Password). See ISession#resetLockout.
@@ -153,7 +146,7 @@
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::DETECTING_INTERACTION
+     * ISession#detectInteraction
      *
      * Notifies the framework that user interaction occurred. See ISession#detectInteraction.
      */
@@ -161,7 +154,7 @@
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::ENUMERATING_ENROLLMENTS.
+     * ISession#enumerateEnrollments.
      *
      * Notifies the framework of the current enrollments. See ISession#enumerateEnrollments.
      *
@@ -171,7 +164,7 @@
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::REMOVING_ENROLLMENTS.
+     * ISession#removeEnrollments.
      *
      * Notifies the framework that the specified enrollments are removed.
      *
@@ -181,7 +174,7 @@
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::GETTING_AUTHENTICATOR_ID.
+     * ISession#getAuthenticatorId.
      *
      * Notifies the framework with the authenticatorId corresponding to this session's
      * (userId, sensorId) pair.
@@ -192,7 +185,7 @@
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::INVALIDATING_AUTHENTICATOR_ID.
+     * ISession#invalidateAuthenticatorId.
      *
      * See ISession#invalidateAuthenticatorId for more information.
      *
diff --git a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/SessionState.aidl b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/SessionState.aidl
deleted file mode 100644
index 19a6ce3..0000000
--- a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/SessionState.aidl
+++ /dev/null
@@ -1,81 +0,0 @@
-/*
- * Copyright (C) 2020 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.biometrics.fingerprint;
-
-@VintfStability
-@Backing(type="byte")
-enum SessionState {
-    /**
-     * The HAL is not processing any session requests.
-     */
-    IDLING,
-
-    /**
-     * The session has been closed by the client.
-     */
-    CLOSED,
-
-    /**
-     * The HAL is processing the ISession#generateChallenge request.
-     */
-    GENERATING_CHALLENGE,
-
-    /**
-     * The HAL is processing the ISession#revokeChallenge request.
-     */
-    REVOKING_CHALLENGE,
-
-    /**
-     * The HAL is processing the ISession#enroll request.
-     */
-    ENROLLING,
-
-    /**
-     * The HAL is processing the ISession#authenticate request.
-     */
-    AUTHENTICATING,
-
-    /**
-     * The HAL is processing the ISession#detectInteraction request.
-     */
-    DETECTING_INTERACTION,
-
-    /**
-     * The HAL is processing the ISession#enumerateEnrollments request.
-     */
-    ENUMERATING_ENROLLMENTS,
-
-    /**
-     * The HAL is processing the ISession#removeEnrollments request.
-     */
-    REMOVING_ENROLLMENTS,
-
-    /**
-     * The HAL is processing the ISession#getAuthenticatorId request.
-     */
-    GETTING_AUTHENTICATOR_ID,
-
-    /**
-     * The HAL is processing the ISession#invalidateAuthenticatorId request.
-     */
-    INVALIDATING_AUTHENTICATOR_ID,
-
-    /**
-     * The HAL is processing the ISession#resetLockout request.
-     */
-    RESETTING_LOCKOUT
-}