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Commit 211ef98d authored by Daniel Norman's avatar Daniel Norman
Browse files

Ensure that the BD's HID descriptor includes the BD usage page (0x41). 

Bug: 316036493
Test: (CTS)      atest BrailleDisplayTest
Test: (Internal) atest BrailleDisplayConnectionTest
Change-Id: I191d1df8391d5b803f7fba0d2ee3f21c540abea5
parent a82202a5

services/accessibility/java/com/android/server/accessibility/BrailleDisplayConnection.java

+57 −3
Original line number Diff line number Diff line
@@ -232,9 +232,63 @@ class BrailleDisplayConnection extends IBrailleDisplayConnection.Stub { 
    }



    /** Returns true if this descriptor includes usages for the Braille display usage page 0x41. */

    private static boolean isBrailleDisplay(byte[] descriptor) {

        // TODO: b/316036493 - Check that descriptor includes 0x41 reports.

        return true;

    @VisibleForTesting

    static boolean isBrailleDisplay(byte[] descriptor) {

        boolean foundMatch = false;

        for (int i = 0; i < descriptor.length; i++) {

            // HID Spec "6.2.2.2 Short Items" defines that the report descriptor is a collection of

            // items: each item is a collection of bytes where the first byte defines info about

            // the type of item and the following 0, 1, 2, or 4 bytes are data bytes for that item.

            // All items in the HID descriptor are expected to be Short Items.

            final byte itemInfo = descriptor[i];

            if (!isHidItemShort(itemInfo)) {

                Slog.w(LOG_TAG, "Item " + itemInfo + " declares unsupported long type");

                return false;

            }

            final int dataSize = getHidItemDataSize(itemInfo);

            if (i + dataSize >= descriptor.length) {

                Slog.w(LOG_TAG, "Item " + itemInfo + " specifies size past the remaining bytes");

                return false;

            }

            // The item we're looking for (usage page declaration) should have size 1.

            if (dataSize == 1) {

                final byte itemData = descriptor[i + 1];

                if (isHidItemBrailleDisplayUsagePage(itemInfo, itemData)) {

                    foundMatch = true;

                }

            }

            // Move to the next item by skipping past all data bytes in this item.

            i += dataSize;

        }

        return foundMatch;

    }



    private static boolean isHidItemShort(byte itemInfo) {

        // Info bits 7-4 describe the item type, and HID Spec "6.2.2.3 Long Items" says that long

        // items always have type bits 1111. Otherwise, the item is a short item.

        return (itemInfo & 0b1111_0000) != 0b1111_0000;

    }



    private static int getHidItemDataSize(byte itemInfo) {

        // HID Spec "6.2.2.2 Short Items" says that info bits 0-1 specify the optional data size:

        // 0, 1, 2, or 4 bytes.

        return switch (itemInfo & 0b0000_0011) {

            case 0b00 -> 0;

            case 0b01 -> 1;

            case 0b10 -> 2;

            default -> 4;

        };

    }



    private static boolean isHidItemBrailleDisplayUsagePage(byte itemInfo, byte itemData) {

        // From HID Spec "6.2.2.7 Global Items"

        final byte usagePageType = 0b0000_0100;

        // From HID Usage Tables version 1.2.

        final byte brailleDisplayUsagePage = 0x41;

        // HID Spec "6.2.2.2 Short Items" says item info bits 2-7 describe the type and

        // function of the item.

        final byte itemType = (byte) (itemInfo & 0b1111_1100);

        return itemType == usagePageType && itemData == brailleDisplayUsagePage;

    }



    /**

services/tests/servicestests/src/com/android/server/accessibility/BrailleDisplayConnectionTest.java

+235 −146
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
package com.android.server.accessibility;



import static com.google.common.truth.Truth.assertThat;

import static com.google.common.truth.Truth.assertWithMessage;



import static org.junit.Assert.assertThrows;

import static org.mockito.ArgumentMatchers.anyInt;
@@ -33,17 +34,24 @@ import android.testing.DexmakerShareClassLoaderRule; 


import androidx.test.platform.app.InstrumentationRegistry;



import com.android.internal.util.HexDump;



import com.google.common.truth.Expect;



import org.junit.Before;

import org.junit.Rule;

import org.junit.Test;

import org.junit.experimental.runners.Enclosed;

import org.junit.runner.RunWith;

import org.junit.runners.Parameterized;

import org.mockito.Mock;

import org.mockito.Mockito;

import org.mockito.MockitoAnnotations;



import java.io.File;

import java.nio.file.Path;

import java.util.Arrays;

import java.util.Collection;

import java.util.List;



/**
@@ -51,7 +59,10 @@ import java.util.List; 
 *

 * <p>Prefer adding new tests in CTS where possible.

 */

@RunWith(Enclosed.class)

public class BrailleDisplayConnectionTest {



    public static class ScannerTest {

        private static final Path NULL_PATH = Path.of("/dev/null");



        private BrailleDisplayConnection mBrailleDisplayConnection;
@@ -108,7 +119,8 @@ public class BrailleDisplayConnectionTest { 
            int descriptorSize = 4;

            byte[] descriptor = {0xB, 0xE, 0xE, 0xF};

            when(mNativeInterface.getHidrawDescSize(anyInt())).thenReturn(descriptorSize);

        when(mNativeInterface.getHidrawDesc(anyInt(), eq(descriptorSize))).thenReturn(descriptor);

            when(mNativeInterface.getHidrawDesc(anyInt(), eq(descriptorSize))).thenReturn(

                    descriptor);



            BrailleDisplayConnection.BrailleDisplayScanner scanner =

                    mBrailleDisplayConnection.getDefaultNativeScanner(mNativeInterface);
@@ -198,15 +210,18 @@ public class BrailleDisplayConnectionTest { 
            Bundle bd1 = new Bundle(), bd2 = new Bundle();



            Path path1 = Path.of("/dev/path1"), path2 = Path.of("/dev/path2");

        bd1.putString(BrailleDisplayController.TEST_BRAILLE_DISPLAY_HIDRAW_PATH, path1.toString());

        bd2.putString(BrailleDisplayController.TEST_BRAILLE_DISPLAY_HIDRAW_PATH, path2.toString());

            bd1.putString(BrailleDisplayController.TEST_BRAILLE_DISPLAY_HIDRAW_PATH,

                    path1.toString());

            bd2.putString(BrailleDisplayController.TEST_BRAILLE_DISPLAY_HIDRAW_PATH,

                    path2.toString());

            byte[] desc1 = {0xB, 0xE}, desc2 = {0xE, 0xF};

            bd1.putByteArray(BrailleDisplayController.TEST_BRAILLE_DISPLAY_DESCRIPTOR, desc1);

            bd2.putByteArray(BrailleDisplayController.TEST_BRAILLE_DISPLAY_DESCRIPTOR, desc2);

            String uniq1 = "uniq1", uniq2 = "uniq2";

            bd1.putString(BrailleDisplayController.TEST_BRAILLE_DISPLAY_UNIQUE_ID, uniq1);

            bd2.putString(BrailleDisplayController.TEST_BRAILLE_DISPLAY_UNIQUE_ID, uniq2);

        int bus1 = BrailleDisplayConnection.BUS_USB, bus2 = BrailleDisplayConnection.BUS_BLUETOOTH;

            int bus1 = BrailleDisplayConnection.BUS_USB, bus2 =

                    BrailleDisplayConnection.BUS_BLUETOOTH;

            bd1.putBoolean(BrailleDisplayController.TEST_BRAILLE_DISPLAY_BUS_BLUETOOTH,

                    bus1 == BrailleDisplayConnection.BUS_BLUETOOTH);

            bd2.putBoolean(BrailleDisplayController.TEST_BRAILLE_DISPLAY_BUS_BLUETOOTH,
@@ -232,3 +247,77 @@ public class BrailleDisplayConnectionTest { 
            expect.that(scanner.getHidrawNodePaths(Path.of("/dev"))).isNull();

        }

    }



    @RunWith(Parameterized.class)

    public static class BrailleDisplayDescriptorTest {

        @Parameterized.Parameters(name = "{0}")

        public static Collection<Object[]> data() {

            return Arrays.asList(new Object[][]{

                    {"match_BdPage", new byte[]{

                            // Just one item, defines the BD page

                            0x05, 0x41}},

                    {"match_BdPageAfterAnotherPage", new byte[]{

                            // One item defines another page

                            0x05, 0x01,

                            // Next item defines BD page

                            0x05, 0x41}},

                    {"match_BdPageAfterSizeZeroItem", new byte[]{

                            // Size-zero item (last 2 bits are 00)

                            0x00,

                            // Next item defines BD page

                            0x05, 0x41}},

                    {"match_BdPageAfterSizeOneItem", new byte[]{

                            // Size-one item (last 2 bits are 01)

                            0x01, 0x7F,

                            // Next item defines BD page

                            0x05, 0x41}},

                    {"match_BdPageAfterSizeTwoItem", new byte[]{

                            // Size-two item (last 2 bits are 10)

                            0x02, 0x7F, 0x7F,

                            0x05, 0x41}},

                    {"match_BdPageAfterSizeFourItem", new byte[]{

                            // Size-four item (last 2 bits are 11)

                            0x03, 0x7F, 0x7F, 0x7F, 0x7F,

                            0x05, 0x41}},

                    {"match_BdPageInBetweenOtherPages", new byte[]{

                            // One item defines another page

                            0x05, 0x01,

                            // Next item defines BD page

                            0x05, 0x41,

                            // Next item defines another page

                            0x05, 0x02}},

                    {"fail_OtherPage", new byte[]{

                            // Just one item, defines another page

                            0x05, 0x01}},

                    {"fail_BdPageBeforeMissingData", new byte[]{

                            // This item defines BD page

                            0x05, 0x41,

                            // Next item specifies size-one item (last 2 bits are 01) but

                            // that one data byte is missing; this descriptor is malformed.

                            0x01}},

                    {"fail_BdPageWithWrongDataSize", new byte[]{

                            // This item defines a page with two-byte ID 0x41 0x7F, not 0x41.

                            0x06, 0x41, 0x7F}},

                    {"fail_LongItem", new byte[]{

                            // Item has type bits 1111, indicating Long Item.

                            (byte) 0xF0}},

            });

        }





        @Parameterized.Parameter(0)

        public String mTestName;

        @Parameterized.Parameter(1)

        public byte[] mDescriptor;



        @Test

        public void isBrailleDisplay() {

            final boolean expectedMatch = mTestName.startsWith("match_");

            assertWithMessage(

                    "Expected isBrailleDisplay==" + expectedMatch

                            + " for descriptor " + HexDump.toHexString(mDescriptor))

                    .that(BrailleDisplayConnection.isBrailleDisplay(mDescriptor))

                    .isEqualTo(expectedMatch);

        }

    }

}