gnss/1.0/IGnssBatching.hal

/*
 * Copyright (C) 2016 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@1.0;

import IGnssBatchingCallback;

/*
 * Extended interface for GNSS Batching support.
 *
 * If this interface is supported, this batching request must be able to run in
 * parallel with, or without, non-batched location requested by the
 * IGnss start() & stop() - i.e. both requests must be handled independently,
 * and not interfere with each other.
 *
 * For example, if a 1Hz continuous output is underway on the IGnssCallback,
 * due to an IGnss start() operation,
 * and then a IGnssBatching start() is called for a location every 10
 * seconds, the newly added batching request must not disrupt the 1Hz
 * continuous location output on the IGnssCallback.
 *
 * As with GNSS Location outputs, source of location must be GNSS satellite
 * measurements, optionally using interial and baro sensors to improve
 * relative motion filtering. No additional absolute positioning information,
 * such as WiFi derived location, may be mixed with the GNSS information.
 */

interface IGnssBatching {
    /*
     * Enum which holds the bit masks for batching control.
     */
    enum Flag : uint8_t {
        /*
         * If this flag is set, the hardware implementation
         * must wake up the application processor when the FIFO is full, and
         * call IGnssBatchingCallback to return the locations.
         *
         * If the flag is not set, the hardware implementation must drop
         * the oldest data when the FIFO is full.
         */
        WAKEUP_ON_FIFO_FULL = 0x01
    };

    struct Options {
        /*
         * Time interval between samples in the location batch, in nano
         * seconds.
         */
        int64_t periodNanos;

        /*
         * Flags controlling how batching should behave.
         */
        bitfield<Flag> flags;
    };

    /*
     * Opens the interface and provides the callback routines
     * to the implementation of this interface.
     *
     * @param callback Callback interface for IGnssBatching.
     *
     * @return success Returns true on success.
     */
    init(IGnssBatchingCallback callback) generates (bool success);

    /*
     * Return the batch size (in number of GnssLocation objects)
     * available in this hardware implementation.
     *
     * If the available size is variable, for example, based on other operations
     * consuming memory, this is the minimum size guaranteed to be available
     * for batching operations.
     *
     * This may, for example, be used by the upper layer, to decide on the
     * batching interval and whether the AP should be woken up or not.
     *
     * @return batchSize number of location objects supported per batch
     */
    getBatchSize() generates (uint16_t batchSize);

    /*
     * Start batching locations. This API is primarily used when the AP is
     * asleep and the device can batch locations in the hardware.
     *
     * IGnssBatchingCallback is used to return the locations.
     *
     * When the buffer is full and WAKEUP_ON_FIFO_FULL is used,
     * IGnssBatchingCallback must be called to return the locations.
     *
     * When the buffer is full and WAKEUP_ON_FIFO_FULL is not set,
     * the oldest location object is dropped. In this case the AP must not be
     * woken up. The AP would then generally be responsible for using
     * flushBatchedLocation to explicitly ask for the location as needed,
     * to avoid it being dropped.
     *
     * @param options See struct Options definition.
     *
     * @return success Returns true on success.
     */
    start(Options options) generates (bool success);

    /**
     * Retrieve all batched locations currently stored.
     *
     * IGnssBatchingCallback is used to return the location.
     *
     * IGnssBatchingCallback must be called in response, even if there are
     * no locations to flush (in which case the Location vector must be empty).
     *
     * Subsequent calls to flushBatchedLocation
     * must not return any of the locations returned in this call.
     */
    flush();

    /**
     * Stop batching.
     *
     * @return success Returns true on success.
     */
    stop() generates (bool success);

    /**
     * Closes the interface. If any batch operations are in progress,
     * they should be stopped.
     *
     * init() may be called again, after this, if the interface is to be restored
     */
    cleanup();

};