297 lines
12 KiB
Java
297 lines
12 KiB
Java
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/*
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* Copyright (C) 2024 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.accessibilityservice;
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import android.annotation.CallbackExecutor;
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import android.annotation.FlaggedApi;
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import android.annotation.NonNull;
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import android.annotation.RequiresPermission;
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import android.bluetooth.BluetoothDevice;
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import android.hardware.usb.UsbDevice;
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import android.os.Binder;
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import android.os.IBinder;
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import android.os.RemoteException;
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import android.os.SystemProperties;
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import android.view.accessibility.AccessibilityInteractionClient;
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import android.view.accessibility.Flags;
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import com.android.internal.annotations.VisibleForTesting;
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import com.android.internal.util.FunctionalUtils;
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import java.io.IOException;
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import java.util.Objects;
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import java.util.concurrent.Executor;
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/**
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* Default implementation of {@link BrailleDisplayController}.
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*
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* @hide
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*/
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// BrailleDisplayControllerImpl is not an API, but it implements BrailleDisplayController APIs.
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// This @FlaggedApi annotation tells the linter that this method delegates API checks to its
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// callers.
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@FlaggedApi(Flags.FLAG_BRAILLE_DISPLAY_HID)
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@VisibleForTesting(visibility = VisibleForTesting.Visibility.PACKAGE)
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public final class BrailleDisplayControllerImpl implements BrailleDisplayController {
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private final AccessibilityService mAccessibilityService;
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private final Object mLock;
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private final boolean mIsHidrawSupported;
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private IBrailleDisplayConnection mBrailleDisplayConnection;
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private Executor mCallbackExecutor;
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private BrailleDisplayCallback mCallback;
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/**
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* Read-only property that returns whether HIDRAW access is supported on this device.
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*
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* <p>Defaults to true.
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*
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* <p>Device manufacturers without HIDRAW kernel support can set this to false in
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* the device's product makefile.
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*/
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private static final boolean IS_HIDRAW_SUPPORTED = SystemProperties.getBoolean(
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"ro.accessibility.support_hidraw", true);
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BrailleDisplayControllerImpl(AccessibilityService accessibilityService,
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Object lock) {
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this(accessibilityService, lock, IS_HIDRAW_SUPPORTED);
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}
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@VisibleForTesting
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public BrailleDisplayControllerImpl(AccessibilityService accessibilityService,
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Object lock, boolean isHidrawSupported) {
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mAccessibilityService = accessibilityService;
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mLock = lock;
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mIsHidrawSupported = isHidrawSupported;
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}
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@Override
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@RequiresPermission(android.Manifest.permission.BLUETOOTH_CONNECT)
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public void connect(@NonNull BluetoothDevice bluetoothDevice,
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@NonNull BrailleDisplayCallback callback) {
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connect(bluetoothDevice, mAccessibilityService.getMainExecutor(), callback);
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}
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@Override
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@RequiresPermission(android.Manifest.permission.BLUETOOTH_CONNECT)
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public void connect(@NonNull BluetoothDevice bluetoothDevice,
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@NonNull @CallbackExecutor Executor callbackExecutor,
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@NonNull BrailleDisplayCallback callback) {
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Objects.requireNonNull(bluetoothDevice);
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Objects.requireNonNull(callbackExecutor);
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Objects.requireNonNull(callback);
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connect(serviceConnection -> serviceConnection.connectBluetoothBrailleDisplay(
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bluetoothDevice.getAddress(), new IBrailleDisplayControllerWrapper()),
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callbackExecutor, callback);
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}
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@Override
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public void connect(@NonNull UsbDevice usbDevice,
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@NonNull BrailleDisplayCallback callback) {
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connect(usbDevice, mAccessibilityService.getMainExecutor(), callback);
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}
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@Override
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public void connect(@NonNull UsbDevice usbDevice,
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@NonNull @CallbackExecutor Executor callbackExecutor,
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@NonNull BrailleDisplayCallback callback) {
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Objects.requireNonNull(usbDevice);
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Objects.requireNonNull(callbackExecutor);
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Objects.requireNonNull(callback);
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connect(serviceConnection -> serviceConnection.connectUsbBrailleDisplay(
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usbDevice, new IBrailleDisplayControllerWrapper()),
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callbackExecutor, callback);
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}
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/**
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* Shared implementation for the {@code connect()} API methods.
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*
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* <p>Performs a blocking call to system_server to create the connection. Success is
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* returned through {@link BrailleDisplayCallback#onConnected} while normal connection
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* errors are returned through {@link BrailleDisplayCallback#onConnectionFailed}. This
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* connection is implemented using cached data from the HIDRAW driver so it returns
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* quickly without needing to perform any I/O with the Braille display.
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*
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* <p>The AIDL call to system_server is blocking (not posted to a handler thread) so
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* that runtime exceptions signaling abnormal connection errors from API misuse
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* (e.g. lacking permissions, providing an invalid BluetoothDevice, calling connect
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* while already connected) are propagated to the API caller.
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*/
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private void connect(
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FunctionalUtils.RemoteExceptionIgnoringConsumer<IAccessibilityServiceConnection>
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createConnection,
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@NonNull Executor callbackExecutor, @NonNull BrailleDisplayCallback callback) {
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BrailleDisplayController.checkApiFlagIsEnabled();
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if (!mIsHidrawSupported) {
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callbackExecutor.execute(() -> callback.onConnectionFailed(
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BrailleDisplayCallback.FLAG_ERROR_CANNOT_ACCESS));
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return;
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}
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if (isConnected()) {
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throw new IllegalStateException(
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"This service already has a connected Braille display");
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}
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final IAccessibilityServiceConnection serviceConnection =
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AccessibilityInteractionClient.getConnection(
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mAccessibilityService.getConnectionId());
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if (serviceConnection == null) {
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throw new IllegalStateException("Accessibility service is not connected");
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}
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synchronized (mLock) {
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mCallbackExecutor = callbackExecutor;
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mCallback = callback;
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}
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try {
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createConnection.acceptOrThrow(serviceConnection);
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} catch (RemoteException e) {
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throw e.rethrowFromSystemServer();
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}
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}
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@Override
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public boolean isConnected() {
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BrailleDisplayController.checkApiFlagIsEnabled();
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return mBrailleDisplayConnection != null;
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}
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@Override
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public void write(@NonNull byte[] buffer) throws IOException {
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BrailleDisplayController.checkApiFlagIsEnabled();
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Objects.requireNonNull(buffer);
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if (buffer.length > IBinder.getSuggestedMaxIpcSizeBytes()) {
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// This same check must be performed in the system to prevent reflection misuse,
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// but perform it here too to prevent unnecessary IPCs from non-reflection callers.
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throw new IllegalArgumentException("Invalid write buffer size " + buffer.length);
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}
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synchronized (mLock) {
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if (mBrailleDisplayConnection == null) {
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throw new IOException("Braille display is not connected");
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}
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try {
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mBrailleDisplayConnection.write(buffer);
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} catch (RemoteException e) {
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throw e.rethrowFromSystemServer();
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}
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}
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}
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@Override
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public void disconnect() {
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BrailleDisplayController.checkApiFlagIsEnabled();
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synchronized (mLock) {
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try {
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if (mBrailleDisplayConnection != null) {
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mBrailleDisplayConnection.disconnect();
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}
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} catch (RemoteException e) {
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throw e.rethrowFromSystemServer();
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} finally {
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clearConnectionLocked();
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}
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}
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}
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/**
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* Implementation of the {@code IBrailleDisplayController} AIDL interface provided to
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* system_server, which system_server uses to pass messages back to this
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* {@code BrailleDisplayController}.
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*
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* <p>Messages from system_server are routed to the {@link BrailleDisplayCallback} callbacks
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* implemented by the accessibility service.
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*
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* <p>Note: Per API Guidelines 7.5 the Binder identity must be cleared before invoking the
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* callback executor so that Binder identity checks in the callbacks are performed using the
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* app's identity.
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*/
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private final class IBrailleDisplayControllerWrapper extends IBrailleDisplayController.Stub {
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/**
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* Called when the system successfully connects to a Braille display.
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*/
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@Override
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public void onConnected(IBrailleDisplayConnection connection, byte[] hidDescriptor) {
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BrailleDisplayController.checkApiFlagIsEnabled();
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final long identity = Binder.clearCallingIdentity();
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try {
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synchronized (mLock) {
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mBrailleDisplayConnection = connection;
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mCallbackExecutor.execute(() -> mCallback.onConnected(hidDescriptor));
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}
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} finally {
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Binder.restoreCallingIdentity(identity);
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}
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}
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/**
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* Called when the system is unable to connect to a Braille display.
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*/
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@Override
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public void onConnectionFailed(@BrailleDisplayCallback.ErrorCode int errorCode) {
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BrailleDisplayController.checkApiFlagIsEnabled();
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final long identity = Binder.clearCallingIdentity();
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try {
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synchronized (mLock) {
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mCallbackExecutor.execute(() -> mCallback.onConnectionFailed(errorCode));
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}
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} finally {
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Binder.restoreCallingIdentity(identity);
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}
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}
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/**
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* Called when input is received from the currently connected Braille display.
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*/
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@Override
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public void onInput(byte[] input) {
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BrailleDisplayController.checkApiFlagIsEnabled();
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final long identity = Binder.clearCallingIdentity();
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try {
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synchronized (mLock) {
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// Ignore input that arrives after disconnection.
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if (mBrailleDisplayConnection != null) {
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mCallbackExecutor.execute(() -> mCallback.onInput(input));
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}
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}
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} finally {
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Binder.restoreCallingIdentity(identity);
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}
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}
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/**
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* Called when the currently connected Braille display is disconnected.
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*/
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@Override
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public void onDisconnected() {
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BrailleDisplayController.checkApiFlagIsEnabled();
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final long identity = Binder.clearCallingIdentity();
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try {
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synchronized (mLock) {
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mCallbackExecutor.execute(mCallback::onDisconnected);
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clearConnectionLocked();
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}
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} finally {
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Binder.restoreCallingIdentity(identity);
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}
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}
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}
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private void clearConnectionLocked() {
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mBrailleDisplayConnection = null;
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}
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}
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