Use a sysprop so connect APIs fail fast if HIDRAW is not supported.

Bug: 311783331
Test: atest BrailleDisplayControllerImplTest
Test: Manually set sysprop on my device, observe API returns failure
Change-Id: I12106e620fbf84d48673e3d113343c2a0954e744

core/java/android/accessibilityservice/BrailleDisplayControllerImpl.java

@@ -25,9 +25,11 @@ import android.hardware.usb.UsbDevice;
 import android.os.Binder;
 import android.os.IBinder;
 import android.os.RemoteException;
+import android.os.SystemProperties;
 import android.view.accessibility.AccessibilityInteractionClient;
 import android.view.accessibility.Flags;
 
+import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.util.FunctionalUtils;
 
 import java.io.IOException;
@@ -36,24 +38,46 @@ import java.util.concurrent.Executor;
 
 /**
  * Default implementation of {@link BrailleDisplayController}.
+ *
+ * @hide
  */
 // BrailleDisplayControllerImpl is not an API, but it implements BrailleDisplayController APIs.
 // This @FlaggedApi annotation tells the linter that this method delegates API checks to its
 // callers.
 @FlaggedApi(Flags.FLAG_BRAILLE_DISPLAY_HID)
-final class BrailleDisplayControllerImpl implements BrailleDisplayController {
+@VisibleForTesting(visibility = VisibleForTesting.Visibility.PACKAGE)
+public final class BrailleDisplayControllerImpl implements BrailleDisplayController {
 
     private final AccessibilityService mAccessibilityService;
     private final Object mLock;
+    private final boolean mIsHidrawSupported;
 
     private IBrailleDisplayConnection mBrailleDisplayConnection;
     private Executor mCallbackExecutor;
     private BrailleDisplayCallback mCallback;
 
+    /**
+     * Read-only property that returns whether HIDRAW access is supported on this device.
+     *
+     * <p>Defaults to true.
+     *
+     * <p>Device manufacturers without HIDRAW kernel support can set this to false in
+     * the device's product makefile.
+     */
+    private static final boolean IS_HIDRAW_SUPPORTED = SystemProperties.getBoolean(
+            "ro.accessibility.support_hidraw", true);
+
     BrailleDisplayControllerImpl(AccessibilityService accessibilityService,
             Object lock) {
+        this(accessibilityService, lock, IS_HIDRAW_SUPPORTED);
+    }
+
+    @VisibleForTesting
+    public BrailleDisplayControllerImpl(AccessibilityService accessibilityService,
+            Object lock, boolean isHidrawSupported) {
         mAccessibilityService = accessibilityService;
         mLock = lock;
+        mIsHidrawSupported = isHidrawSupported;
     }
 
     @Override
@@ -113,6 +137,11 @@ final class BrailleDisplayControllerImpl implements BrailleDisplayController {
                     createConnection,
             @NonNull Executor callbackExecutor, @NonNull BrailleDisplayCallback callback) {
         BrailleDisplayController.checkApiFlagIsEnabled();
+        if (!mIsHidrawSupported) {
+            callbackExecutor.execute(() -> callback.onConnectionFailed(
+                    BrailleDisplayCallback.FLAG_ERROR_CANNOT_ACCESS));
+            return;
+        }
         if (isConnected()) {
             throw new IllegalStateException(
                     "This service already has a connected Braille display");

core/tests/coretests/src/android/accessibilityservice/BrailleDisplayControllerImplTest.java

@@ -22,6 +22,7 @@ import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyZeroInteractions;
 
 import android.hardware.usb.UsbDevice;
 import android.platform.test.annotations.RequiresFlagsEnabled;
@@ -58,6 +59,7 @@ public class BrailleDisplayControllerImplTest {
     @Rule
     public final CheckFlagsRule mCheckFlagsRule = DeviceFlagsValueProvider.createCheckFlagsRule();
 
+    private AccessibilityService mAccessibilityService;
     private BrailleDisplayController mBrailleDisplayController;
 
     @Mock
@@ -76,12 +78,13 @@ public class BrailleDisplayControllerImplTest {
     @Before
     public void test() {
         MockitoAnnotations.initMocks(this);
-        AccessibilityService accessibilityService = spy(new TestAccessibilityService());
-        doReturn((Executor) Runnable::run).when(accessibilityService).getMainExecutor();
-        doReturn(TEST_SERVICE_CONNECTION_ID).when(accessibilityService).getConnectionId();
+        mAccessibilityService = spy(new TestAccessibilityService());
+        doReturn((Executor) Runnable::run).when(mAccessibilityService).getMainExecutor();
+        doReturn(TEST_SERVICE_CONNECTION_ID).when(mAccessibilityService).getConnectionId();
         AccessibilityInteractionClient.addConnection(TEST_SERVICE_CONNECTION_ID,
                 mAccessibilityServiceConnection, /*initializeCache=*/false);
-        mBrailleDisplayController = accessibilityService.getBrailleDisplayController();
+        mBrailleDisplayController = new BrailleDisplayControllerImpl(
+                mAccessibilityService, new Object(), /*isHidrawSupported=*/true);
     }
 
     // Automated CTS tests only use the BluetoothDevice version of BrailleDisplayController#connect
@@ -104,4 +107,17 @@ public class BrailleDisplayControllerImplTest {
         assertThrows(IllegalStateException.class,
                 () -> mBrailleDisplayController.connect(usbDevice, mBrailleDisplayCallback));
     }
+
+    @Test
+    public void connect_HidrawNotSupported_callsOnConnectionFailed() {
+        BrailleDisplayController controller = new BrailleDisplayControllerImpl(
+                mAccessibilityService, new Object(), /*isHidrawSupported=*/false);
+        UsbDevice usbDevice = Mockito.mock(UsbDevice.class);
+
+        controller.connect(usbDevice, mBrailleDisplayCallback);
+
+        verify(mBrailleDisplayCallback).onConnectionFailed(
+                BrailleDisplayController.BrailleDisplayCallback.FLAG_ERROR_CANNOT_ACCESS);
+        verifyZeroInteractions(mAccessibilityServiceConnection);
+    }
 }