diff --git a/gnss/2.1/IGnssAntennaInfoCallback.hal b/gnss/2.1/IGnssAntennaInfoCallback.hal
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+/*
+ * 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.gnss@2.1;
+
+/**
+ * The callback interface to report GNSS antenna information from the HAL.
+ */
+interface IGnssAntennaInfoCallback {
+    /**
+     * A row of doubles. This is used to represent a row in a 2D array, which are used to
+     * characterize the phase center variation corrections and signal gain corrections.
+     */
+    struct Row {
+        vec<double> row;
+    };
+
+    /**
+     * A point in 3D space, with associated uncertainty.
+     */
+    struct Coord {
+        double x;
+
+        double xUncertainty;
+
+        double y;
+
+        double yUncertainty;
+
+        double z;
+
+        double zUncertainty;
+    };
+
+    struct GnssAntennaInfo {
+        /**
+         * The carrier frequency in MHz.
+         */
+        double carrierFrequencyMHz;
+
+        /**
+         * Phase center offset (PCO) with associated 1-sigma uncertainty. PCO is defined with
+         * respect to the origin of the Android sensor coordinate system, e.g., center of primary
+         * screen for mobiles - see sensor or form factor documents for details.
+         */
+        Coord phaseCenterOffsetCoordinateMillimeters;
+
+        /**
+         * 2D vectors representing the phase center variation (PCV) corrections, in
+         * millimeters, at regularly spaced azimuthal angle (theta) and zenith angle
+         * (phi). The PCV correction is added to the phase measurement to obtain the
+         * corrected value.
+         *
+         * The azimuthal angle, theta, is defined with respect to the X axis of the
+         * Android sensor coordinate system, increasing toward the Y axis. The zenith
+         * angle, phi, is defined with respect to the Z axis of the Android Sensor
+         * coordinate system, increasing toward the X-Y plane.
+         *
+         * Each row vector (outer vectors) represents a fixed theta. The first row
+         * corresponds to a theta angle of 0 degrees. The last row corresponds to a
+         * theta angle of (360 - deltaTheta) degrees, where deltaTheta is the regular
+         * spacing between azimuthal angles, i.e., deltaTheta = 360 / (number of rows).
+         *
+         * The columns (inner vectors) represent fixed zenith angles, beginning at 0
+         * degrees and ending at 180 degrees. They are separated by deltaPhi, the regular
+         * spacing between zenith angles, i.e., deltaPhi = 180 / (number of columns - 1).
+         *
+         * This field is optional, i.e., an empty vector.
+         */
+        vec<Row> phaseCenterVariationCorrectionMillimeters;
+
+        /**
+         * 2D vectors of 1-sigma uncertainty in millimeters associated with the PCV
+         * correction values.
+         *
+         * This field is optional, i.e., an empty vector.
+         */
+        vec<Row> phaseCenterVariationCorrectionUncertaintyMillimeters;
+
+        /**
+         * 2D vectors representing the signal gain corrections at regularly spaced
+         * azimuthal angle (theta) and zenith angle (phi). The values are calculated or
+         * measured at the antenna feed point without considering the radio and receiver
+         * noise figure and path loss contribution, in dBi, i.e., decibel over isotropic
+         * antenna with the same total power. The signal gain correction is added the
+         * signal gain measurement to obtain the corrected value.
+         *
+         * The azimuthal angle, theta, is defined with respect to the X axis of the
+         * Android sensor coordinate system, increasing toward the Y axis. The zenith
+         * angle, phi, is defined with respect to the Z axis of the Android Sensor
+         * coordinate system, increasing toward the X-Y plane.
+         *
+         * Each row vector (outer vectors) represents a fixed theta. The first row
+         * corresponds to a theta angle of 0 degrees. The last row corresponds to a
+         * theta angle of (360 - deltaTheta) degrees, where deltaTheta is the regular
+         * spacing between azimuthal angles, i.e., deltaTheta = 360 / (number of rows).
+         *
+         * The columns (inner vectors) represent fixed zenith angles, beginning at 0
+         * degrees and ending at 180 degrees. They are separated by deltaPhi, the regular
+         * spacing between zenith angles, i.e., deltaPhi = 180 / (number of columns - 1).
+         *
+         * This field is optional, i.e., an empty vector.
+         */
+        vec<Row> signalGainCorrectionDbi;
+
+        /**
+         * 2D vectors of 1-sigma uncertainty in dBi associated with the signal
+         * gain correction values.
+         *
+         * This field is optional, i.e., an empty vector.
+         */
+        vec<Row> signalGainCorrectionUncertaintyDbi;
+    };
+
+    /**
+     * Called when on connection, and on known-change to these values, such as upon a known
+     * GNSS RF antenna tuning change, or a foldable device state change.
+     *
+     * This is optional. It can never be called if the GNSS antenna information is not
+     * available.
+     */
+    gnssAntennaInfoCb(vec<GnssAntennaInfo> gnssAntennaInfos);
+};