pal/include/chre/pal/wifi.h

/*
 * 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.
 */

#ifndef CHRE_PAL_WIFI_H_
#define CHRE_PAL_WIFI_H_

/**
 * @file
 * Defines the interface between the common CHRE core system and the
 * platform-specific WiFi module.
 */

#include <stdbool.h>
#include <stdint.h>

#include "chre/pal/system.h"
#include "chre/pal/version.h"
#include "chre_api/chre/common.h"
#include "chre_api/chre/wifi.h"

#ifdef __cplusplus
extern "C" {
#endif

/**
 * Initial version of the CHRE WiFi PAL, tied to CHRE API v1.1.
 */
#define CHRE_PAL_WIFI_API_V1_0 CHRE_PAL_CREATE_API_VERSION(1, 0)

// v1.1 skipped to avoid confusion with CHRE API v1.1

/**
 * Introduced alongside CHRE API v1.2, adding support for RTT ranging and radio
 * chain preference
 */
#define CHRE_PAL_WIFI_API_V1_2 CHRE_PAL_CREATE_API_VERSION(1, 2)

/**
 * The version of the WiFi GNSS PAL defined in this header file.
 */
#define CHRE_PAL_WIFI_API_CURRENT_VERSION CHRE_PAL_WIFI_API_V1_2

struct chrePalWifiCallbacks {
  /**
   * Callback invoked to inform the CHRE of the result of changes to the scan
   * monitor registration status requested via configureScanMonitor in struct
   * chrePalWifiApi.
   *
   * Unsolicited calls to this function must not be made. In other words,
   * this callback should only be invoked as the direct result of an earlier
   * call to configureScanMonitor. If the scan monitor registration is lost,
   * for example due to a reset of the WiFi subsystem, then the PAL
   * implementation is required to silently re-register the scan monitor when
   * it recovers, as needed.
   *
   * @param enabled true if the scan monitor is currently active and
   *        scanEventCallback will receive unsolicited scan results, false
   *        otherwise
   * @param errorCode An error code from enum chreError
   *
   * @see chrePalWifiApi.configureScanMonitor
   * @see #chreError
   */
  void (*scanMonitorStatusChangeCallback)(bool enabled, uint8_t errorCode);

  /**
   * Callback invoked to inform the CHRE of the result of a request for a
   * scan requested via requestScan in struct chrePalWifiApi.
   *
   * Unsolicited calls to this function must not be made. See
   * scanMonitorStatusChangeCallback() for more information.
   *
   * This function must only be called after the final status of the scan
   * request is known. For example, it must not be called at the point when
   * the scan is initially scheduled if it can still fail prior to delivering
   * a result.
   *
   * @param pending true if the request was successful and the results of the
   *        scan are pending delivery (via scanEventCallback), false otherwise
   * @param errorCode An error code from enum chreError
   */
  void (*scanResponseCallback)(bool pending, uint8_t errorCode);

  /**
   * Callback used to pass scan results from the WiFi module to the core CHRE
   * system, which distributes it to clients (nanoapps).
   *
   * This function call passes ownership of the event memory to the core CHRE
   * system, i.e. the PAL module must not modify the referenced data until the
   * associated API function is called to release the memory.
   *
   * If the results of a given scan are be split across multiple events, and
   * therefore multiple calls to this callback, then the events must be
   * delivered in order, and in one contiguous series of callbacks with no
   * interleaving of events that correspond to any other scan.
   *
   * The PAL module must not deliver the same scan event twice. As a specific
   * example: if an explicit scan request is made via requestScan(), the PAL
   * implementation must not redeliver the result a second time because scan
   * monitoring is enabled.
   *
   * @param event Event data to distribute to clients. The WiFi module
   *        must ensure that this memory remains accessible until it is passed
   *        to the releaseScanEvent() function in struct chrePalWifiApi.
   *
   * @see chrePalWifiApi.configureScanMonitor
   * @see chrePalWifiApi.requestScan
   */
  void (*scanEventCallback)(struct chreWifiScanEvent *event);

  /**
   * Callback used to pass RTT ranging results from the WiFi module to the
   * core CHRE system, which distributes it to clients (nanoapps).
   *
   * Like scanEventCallback, this function call passes ownership of the event
   * memory to the core CHRE system.
   *
   * Only valid if requestedApiVersion given to chrePalWifiGetApi() is greater
   * than or equal to CHRE_PAL_WIFI_API_V1_2.
   *
   * @param errorCode An error code from enum chreError, with CHRE_ERROR_NONE
   *        indicating successful completion of the ranging operation
   * @param event Event data to distribute to clients. Unlike with scan
   *        events, RTT ranging results must be provided for all requested MAC
   *        addresses in a single event. Ignored and may be NULL if errorCode
   *        is not CHRE_ERROR_NONE.
   *
   * @since v1.2
   */
  void (*rangingEventCallback)(uint8_t errorCode,
                               struct chreWifiRangingEvent *event);
};

struct chrePalWifiApi {
  /**
   * Version of the module providing this API. This value should be
   * constructed from CHRE_PAL_CREATE_MODULE_VERSION using the supported
   * API version constant (CHRE_PAL_WIFI_API_*) and the module-specific patch
   * version.
   */
  uint32_t moduleVersion;

  /**
   * Initializes the WiFi module. Initialization must complete synchronously.
   *
   * @param systemApi Structure containing CHRE system function pointers which
   *        the PAL implementation should prefer to use over equivalent
   *        functionality exposed by the underlying platform. The module does
   *        not need to deep-copy this structure; its memory remains
   *        accessible at least until after close() is called.
   * @param callbacks Structure containing entry points to the core CHRE
   *        system. The module does not need to deep-copy this structure; its
   *        memory remains accessible at least until after close() is called.
   *
   * @return true if initialization was successful, false otherwise
   */
  bool (*open)(const struct chrePalSystemApi *systemApi,
               const struct chrePalWifiCallbacks *callbacks);

  /**
   * Performs clean shutdown of the WiFi module, usually done in preparation
   * for stopping the CHRE. The WiFi module must ensure that it will not
   * invoke any callbacks past this point, and complete any relevant teardown
   * activities before returning from this function.
   */
  void (*close)(void);

  //! @see chreWifiGetCapabilities()
  uint32_t (*getCapabilities)(void);

  /**
   * Configures whether the scanEventCallback receives unsolicited scan
   * results, i.e. the results of scans not performed at the request of CHRE.
   *
   * While not expected, a duplicate request, e.g. one that requests to enable
   * scan monitoring when it is already enabled, must follow the successful
   * callback flow.
   *
   * @param enable true to enable listening for all available scan results
   *
   * @return true if the request was accepted for processing, in which case a
   *         subsequent call to scanMonitorStatusChangeCallback will be used
   *         to communicate the result of the operation
   *
   * @see chreWifiConfigureScanMonitorAsync()
   */
  bool (*configureScanMonitor)(bool enable);

  /**
   * Request that the WiFi chipset perform a scan, or deliver results from its
   * cache if the parameters allow for it. If this function returns true, then
   * the scanResponseCallback will be invoked to provide the result of the
   * scan. If that indicates a successful result (the scan data is pending),
   * then scanEventCallback() will be invoked one more more times to deliver
   * the results of the scan. The results for the requested scan are delivered
   * in scanEventCallback() regardless of the most recent setting passed to
   * configureScanMonitor().
   *
   * The asynchronous flow of a scan request made through this API is
   * as follows:
   *
   *  1. requestScan() called, returns true if request accepted, otherwise
   *     false (in which case the request fails at this stage and further
   *     steps do not occur)
   *  2. Scan is performed, or an error is encountered preventing the
   *     successful delivery of the scan result
   *  3. scanResponseCallback() is invoked to indicate whether the scan
   *     succeeded, or the reason for failure (in which case the request fails
   *     at this stage and further steps do not occur)
   *  4. scanEventCallback() is invoked 1 or more times (even if the scan
   *     resulted in no visible APs)
   *
   * Note that the callbacks in steps 3 and 4 must complete in the sequence
   * given, and the call(s) to scanEventCallback() occurring immediately after
   * scanResponseCallback() must be associated with this scan request, and not
   * results delivered pursuant to an active scan monitor registration.
   *
   * This function must follow the CHRE API-defined behavior regarding
   * timeouts. In other words, if a successful scan result is not produced by
   * the lower layers within CHRE_WIFI_SCAN_RESULT_TIMEOUT_NS,
   * scanResponseCallback() must be invoked to indicate the failure, and any
   * late arriving scan result from the lower layers must be dropped.
   *
   * At most 1 scan can be in progress from this API at any given time.
   * In other words, the implementation should return false if another scan
   * initiated via this function has not completed, i.e. it has not failed
   * yet, or the final scan event has not yet been delivered via
   * scanEventCallback(). However, this function must accept and queue a scan
   * request made from this API while a scan requested by another client, such
   * as the applications processor, is in progress.
   *
   * @param params See chreWifiRequestScanAsync(). If requestedApiVersion
   *        supplied to chrePalWifiGetApi is at least CHRE_PAL_WIFI_API_V1_2,
   *        then the new "radioChainPref" parameter will be included.
   *
   * @return true if the request was accepted for further processing, in which
   *         case a subsequent call to scanResponseCallback will be used to
   *         communicate the result of the operation
   *
   * @see #chreWifiScanParams
   * @see chreWifiRequestScanAsync()
   */
  bool (*requestScan)(const struct chreWifiScanParams *params);

  /**
   * Invoked when the core CHRE system no longer needs a WiFi scan event
   * structure that was provided to it via scanEventCallback()
   *
   * @param event Event data to release
   */
  void (*releaseScanEvent)(struct chreWifiScanEvent *event);

  /**
   * Request that the WiFi chipset perform RTT ranging against a set of access
   * points specified in params. If this function returns true, then
   * rangingEventCallback must be invoked once to deliver the final result of
   * the operation, with the accompanying result structure if ranging was
   * performed.
   *
   * RTT functionality in CHRE is based off the Android HAL definitions
   * (hardware/interfaces/wifi/1.0/), but with less parameters. For
   * example, CHRE only supports ranging against access points, and two-sided
   * RTT. When mapping struct chreWifiRangingTarget into the equivalent fields
   * defined in the HAL in struct RttConfig, the following default values
   * should be used to fill the fields not specified in the CHRE structure:
   *
   * <pre>
   *   type = TWO_SIDED
   *   peer = AP
   *   burstPeriod = 0
   *   numBurst = 0
   *   numFramesPerBurst = 8
   *   numRetriesPerRttFrame = 0
   *   numRetriesPerFtmr = 0
   *   mustRequestLci = true
   *   mustRequestLcr = false (can be true, but not exposed by CHRE)
   *   burstDuration = 15
   *   preamble = implementation-dependent**
   *   bw = implementation-dependent**
   * </pre>
   *
   * **These are used to populate the Format And Bandwidth field in the Fine
   *   Timing Measurement Parameters element. Per the specification, proposed
   *   values must fall within the capabilities of the requesting device, and
   *   the configuration used is ultimately negotiated with the responding
   *   STA. Therefore, it is up to the underlying WiFi implementation to pick
   *   suitable values.
   *
   * Like {@link #requestScan}, this function must follow the CHRE API-defined
   * behavior regarding timeouts, indicating failure via rangingEventCallback
   * if the lower layers do not produce a result within
   * CHRE_WIFI_RANGING_RESULT_TIMEOUT_NS.
   *
   * Also like {@link #requestScan}, at most 1 RTT ranging request can be in
   * progress from this API at any given time. Implementations should return
   * false if this condition is not met, but must queue a request made from
   * this API while a request from another client, such as the applications
   * processor, is in progress.
   *
   * @return true if the request was accepted for further processing, in which
   *         case a subsequent call to rangingEventCallback will be used to
   *         communicate the result of the operation
   *
   * @see #chreWifiRangingParams
   * @see chreWifiRequestRangingAsync()
   *
   * @since v1.2
   */
  bool (*requestRanging)(const struct chreWifiRangingParams *params);

  /**
   * Invoked when the core CHRE system no longer needs a WiFi ranging result
   * event structure that was provided to it via rangingEventCallback()
   *
   * @param event Event data to release
   *
   * @since v1.2
   */
  void (*releaseRangingEvent)(struct chreWifiRangingEvent *event);
};

/**
 * Retrieve a handle for the CHRE WiFi PAL.
 *
 * @param requestedApiVersion The implementation of this function must return a
 *        pointer to a structure with the same major version as requested.
 *
 * @return Pointer to API handle, or NULL if a compatible API version is not
 *         supported by the module, or the API as a whole is not implemented. If
 *         non-NULL, the returned API handle must be valid as long as this
 *         module is loaded.
 */
const struct chrePalWifiApi *chrePalWifiGetApi(uint32_t requestedApiVersion);

#ifdef __cplusplus
}
#endif

#endif  // CHRE_PAL_WIFI_H_