WifiDisplay扫描流程

上一篇说完了WifiDisplay的开启流程，开启以后就直接进入扫描状态。
/frameworks/base/services/core/java/com/android/server/display/WifiDisplayController.java

    private void updateScanState() {
        if (mScanRequested && mWfdEnabled && mDesiredDevice == null) {
            if (!mDiscoverPeersInProgress) {
                Slog.i(TAG, "Starting Wifi display scan.");
                mDiscoverPeersInProgress = true;
                handleScanStarted();
                tryDiscoverPeers();
            }
        } else {
            if (mDiscoverPeersInProgress) {
                // Cancel automatic retry right away.
                mHandler.removeCallbacks(mDiscoverPeers);

                // Defer actually stopping discovery if we have a connection attempt in progress.
                // The wifi display connection attempt often fails if we are not in discovery
                // mode.  So we allow discovery to continue until we give up trying to connect.
                if (mDesiredDevice == null || mDesiredDevice == mConnectedDevice) {
                    Slog.i(TAG, "Stopping Wifi display scan.");
                    mDiscoverPeersInProgress = false;
                    stopPeerDiscovery();
                    handleScanFinished();
                }
            }
        }
    }

handleScanStarted主要就是开启了一个监听器。

    private void handleScanStarted() {
        mHandler.post(new Runnable() {
            @Override
            public void run() {
                mListener.onScanStarted();
            }
        });
    }

尝试开始发现同等设备，然后返回success，就requestPeers，请求这一步把扫描流程走完再返回来梳理。

    private void tryDiscoverPeers() {
        mWifiP2pManager.discoverPeers(mWifiP2pChannel, new ActionListener() {
            @Override
            public void onSuccess() {
                if (DEBUG) {
                    Slog.d(TAG, "Discover peers succeeded.  Requesting peers now.");
                }

                if (mDiscoverPeersInProgress) {
                    requestPeers();
                }
        // Retry discover peers periodically until stopped.
        mHandler.postDelayed(mDiscoverPeers, DISCOVER_PEERS_INTERVAL_MILLIS);
    }

然后下面就是一路函数调用了，和wifi的差不多，一直到supplicant。
/frameworks/base/wifi/java/android/net/wifi/p2p/WifiP2pManager.java

    public void discoverPeers(Channel c, ActionListener listener) {
        checkChannel(c);
        c.mAsyncChannel.sendMessage(DISCOVER_PEERS, 0, c.putListener(listener));
    }

/frameworks/opt/net/wifi/service/java/com/android/server/wifi/p2p/WifiP2pServiceImpl.java

                    case WifiP2pManager.DISCOVER_PEERS:
                        if (mDiscoveryBlocked) {
                            replyToMessage(message, WifiP2pManager.DISCOVER_PEERS_FAILED,
                                    WifiP2pManager.BUSY);
                            break;
                        }
                        // do not send service discovery request while normal find operation.
                        clearSupplicantServiceRequest();
                        if (mWifiNative.p2pFind(DISCOVER_TIMEOUT_S)) {
                            replyToMessage(message, WifiP2pManager.DISCOVER_PEERS_SUCCEEDED);
                            sendP2pDiscoveryChangedBroadcast(true);
                        } else {
                            replyToMessage(message, WifiP2pManager.DISCOVER_PEERS_FAILED,
                                    WifiP2pManager.ERROR);
                        }
                        break;

/frameworks/opt/net/wifi/service/java/com/android/server/wifi/p2p/WifiP2pNative.java

    public boolean p2pFind(int timeout) {
        return mSupplicantP2pIfaceHal.find(timeout);
    }

/frameworks/opt/net/wifi/service/java/com/android/server/wifi/p2p/SupplicantP2pIfaceHal.java

    public boolean find(int timeout) {
        synchronized (mLock) {
            if (!checkSupplicantP2pIfaceAndLogFailure("find")) return false;

            if (timeout < 0) {
                Log.e(TAG, "Invalid timeout value: " + timeout);
                return false;
            }
            SupplicantResult result = new SupplicantResult("find(" + timeout + ")");
            try {
                result.setResult(mISupplicantP2pIface.find(timeout));
            } catch (RemoteException e) {
                Log.e(TAG, "ISupplicantP2pIface exception: " + e);
                supplicantServiceDiedHandler();
            }
            return result.isSuccess();
        }
    }

/hardware/interfaces/wifi/supplicant/1.0/ISupplicantP2pIface.hal

  find(uint32_t timeoutInSec) generates (SupplicantStatus status);

/external/wpa_supplicant_8/wpa_supplicant/hidl/1.0/p2p_iface.cpp

Return P2pIface::find(uint32_t timeout_in_sec, find_cb _hidl_cb)
{
	return validateAndCall(
	    this, SupplicantStatusCode::FAILURE_IFACE_INVALID,
	    &P2pIface::findInternal, _hidl_cb, timeout_in_sec);
}

SupplicantStatus P2pIface::findInternal(uint32_t timeout_in_sec)
{
	struct wpa_supplicant* wpa_s = retrieveIfacePtr();
	if (wpa_s->wpa_state == WPA_INTERFACE_DISABLED) {
		return {SupplicantStatusCode::FAILURE_IFACE_DISABLED, ""};
	}
	uint32_t search_delay = wpas_p2p_search_delay(wpa_s);
	if (wpas_p2p_find(
		wpa_s, timeout_in_sec, P2P_FIND_START_WITH_FULL, 0, nullptr,
		nullptr, search_delay, 0, nullptr, 0)) {
		return {SupplicantStatusCode::FAILURE_UNKNOWN, ""};
	}
	return {SupplicantStatusCode::SUCCESS, ""};
}

/external/wpa_supplicant_8/wpa_supplicant/p2p_supplicant.c

int wpas_p2p_find(struct wpa_supplicant *wpa_s, unsigned int timeout,
		  enum p2p_discovery_type type,
		  unsigned int num_req_dev_types, const u8 *req_dev_types,
		  const u8 *dev_id, unsigned int search_delay,
		  u8 seek_cnt, const char **seek_string, int freq)
{
	wpas_p2p_clear_pending_action_tx(wpa_s);
	wpa_s->p2p_long_listen = 0;

	if (wpa_s->global->p2p_disabled || wpa_s->global->p2p == NULL ||
	    wpa_s->p2p_in_provisioning) {
		wpa_dbg(wpa_s, MSG_DEBUG, "P2P: Reject p2p_find operation%s%s",
			(wpa_s->global->p2p_disabled || !wpa_s->global->p2p) ?
			" (P2P disabled)" : "",
			wpa_s->p2p_in_provisioning ?
			" (p2p_in_provisioning)" : "");
		return -1;
	}

	wpa_supplicant_cancel_sched_scan(wpa_s);

	return p2p_find(wpa_s->global->p2p, timeout, type,
			num_req_dev_types, req_dev_types, dev_id,
			search_delay, seek_cnt, seek_string, freq);
}

扫描结果出来以后，如果返回success可以看到执行requestPeers函数,也就是向对端设备发起请求了。
/frameworks/base/services/core/java/com/android/server/display/WifiDisplayController.java

    private void tryDiscoverPeers() {
        mWifiP2pManager.discoverPeers(mWifiP2pChannel, new ActionListener() {
            @Override
            public void onSuccess() {
                if (DEBUG) {
                    Slog.d(TAG, "Discover peers succeeded.  Requesting peers now.");
                }

                if (mDiscoverPeersInProgress) {
                    requestPeers();
                }

    private void requestPeers() {
        mWifiP2pManager.requestPeers(mWifiP2pChannel, new PeerListListener() {
            @Override
            public void onPeersAvailable(WifiP2pDeviceList peers) {
                if (DEBUG) {
                    Slog.d(TAG, "Received list of peers.");
                }

                mAvailableWifiDisplayPeers.clear();
                for (WifiP2pDevice device : peers.getDeviceList()) {
                    if (DEBUG) {
                        Slog.d(TAG, "  " + describeWifiP2pDevice(device));
                    }

                    if (isWifiDisplay(device)) {
                        mAvailableWifiDisplayPeers.add(device);
                    }
                }

                if (mDiscoverPeersInProgress) {
                    handleScanResults();
                }
            }
        });
    }

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