Add flag to mark key usage code as a fallback mapping

We don't yet have a way to determine if a device can actually report a
usage code. Adding a flag to mark usage code as fallback only mapping.

Bug: 297094448
Test: atest inputflinger_tests
Change-Id: I137113d0dc9a1c8abf523b96942486be176d0240

5 files changed, 80 insertions, 2 deletions

diff --git a/include/input/Input.h b/include/input/Input.h
index 64ee47342d..567361d679 100644
--- a/include/input/Input.h
+++ b/include/input/Input.h
@@ -285,6 +285,16 @@ enum {
     // This policy flag prevents key events from changing touch mode state.
     POLICY_FLAG_GESTURE = 0x00000008,
 
+    // Indicates that key usage mapping represents a fallback mapping.
+    // Fallback mappings cannot be used to definitively determine whether a device
+    // supports a key code. For example, a HID device can report a key press
+    // as a HID usage code if it is not mapped to any linux key code in the kernel.
+    // However, we cannot know which HID usage codes that device supports from
+    // userspace through the evdev. We can use fallback mappings to convert HID
+    // usage codes to Android key codes without needing to know if a device can
+    // actually report the usage code.
+    POLICY_FLAG_FALLBACK_USAGE_MAPPING = 0x00000010,
+
     POLICY_FLAG_RAW_MASK = 0x0000ffff,
 
 #ifdef __linux__
diff --git a/libs/input/InputEventLabels.cpp b/libs/input/InputEventLabels.cpp
index c218e1e858..0e627e56fd 100644
--- a/libs/input/InputEventLabels.cpp
+++ b/libs/input/InputEventLabels.cpp
@@ -430,7 +430,8 @@ namespace android {
     DEFINE_FLAG(VIRTUAL), \
     DEFINE_FLAG(FUNCTION), \
     DEFINE_FLAG(GESTURE), \
-    DEFINE_FLAG(WAKE)
+    DEFINE_FLAG(WAKE), \
+    DEFINE_FLAG(FALLBACK_USAGE_MAPPING)
 
 // clang-format on
 
diff --git a/libs/input/KeyLayoutMap.cpp b/libs/input/KeyLayoutMap.cpp
index ddc9ea457e..3c1ae3e41b 100644
--- a/libs/input/KeyLayoutMap.cpp
+++ b/libs/input/KeyLayoutMap.cpp
@@ -250,7 +250,7 @@ std::vector<int32_t> KeyLayoutMap::findScanCodesForKey(int32_t keyCode) const {
 std::vector<int32_t> KeyLayoutMap::findUsageCodesForKey(int32_t keyCode) const {
     std::vector<int32_t> usageCodes;
     for (const auto& [usageCode, key] : mKeysByUsageCode) {
-        if (keyCode == key.keyCode) {
+        if (keyCode == key.keyCode && !(key.flags & POLICY_FLAG_FALLBACK_USAGE_MAPPING)) {
             usageCodes.push_back(usageCode);
         }
     }
diff --git a/libs/input/tests/InputDevice_test.cpp b/libs/input/tests/InputDevice_test.cpp
index a0ec6adc65..fe5490caf5 100644
--- a/libs/input/tests/InputDevice_test.cpp
+++ b/libs/input/tests/InputDevice_test.cpp
@@ -167,6 +167,41 @@ TEST_F(InputDeviceKeyMapTest, keyCharacterMapBadLedLabel) {
     ASSERT_FALSE(ret.ok()) << "Should not be able to load KeyLayout at " << klPath;
 }
 
+TEST(InputDeviceKeyLayoutTest, HidUsageCodesFallbackMapping) {
+    std::string klPath = base::GetExecutableDirectory() + "/data/hid_fallback_mapping.kl";
+    base::Result<std::shared_ptr<KeyLayoutMap>> ret = KeyLayoutMap::load(klPath);
+    ASSERT_TRUE(ret.ok()) << "Unable to load KeyLayout at " << klPath;
+    const std::shared_ptr<KeyLayoutMap>& keyLayoutMap = *ret;
+
+    static constexpr std::array<int32_t, 5> hidUsageCodesWithoutFallback = {0x0c0067, 0x0c0070,
+                                                                            0x0c006F, 0x0c0079,
+                                                                            0x0c007A};
+    for (int32_t hidUsageCode : hidUsageCodesWithoutFallback) {
+        int32_t outKeyCode;
+        uint32_t outFlags;
+        keyLayoutMap->mapKey(0, hidUsageCode, &outKeyCode, &outFlags);
+        ASSERT_FALSE(outFlags & POLICY_FLAG_FALLBACK_USAGE_MAPPING)
+                << "HID usage code should not be marked as fallback";
+        std::vector<int32_t> usageCodes = keyLayoutMap->findUsageCodesForKey(outKeyCode);
+        ASSERT_NE(std::find(usageCodes.begin(), usageCodes.end(), hidUsageCode), usageCodes.end())
+                << "Fallback usage code should be mapped to key";
+    }
+
+    static constexpr std::array<int32_t, 6> hidUsageCodesWithFallback = {0x0c007C, 0x0c0173,
+                                                                         0x0c019C, 0x0c01A2,
+                                                                         0x0d0044, 0x0d005a};
+    for (int32_t hidUsageCode : hidUsageCodesWithFallback) {
+        int32_t outKeyCode;
+        uint32_t outFlags;
+        keyLayoutMap->mapKey(0, hidUsageCode, &outKeyCode, &outFlags);
+        ASSERT_TRUE(outFlags & POLICY_FLAG_FALLBACK_USAGE_MAPPING)
+                << "HID usage code should be marked as fallback";
+        std::vector<int32_t> usageCodes = keyLayoutMap->findUsageCodesForKey(outKeyCode);
+        ASSERT_EQ(std::find(usageCodes.begin(), usageCodes.end(), hidUsageCode), usageCodes.end())
+                << "Fallback usage code should not be mapped to key";
+    }
+}
+
 TEST(InputDeviceKeyLayoutTest, DoesNotLoadWhenRequiredKernelConfigIsMissing) {
 #if !defined(__ANDROID__)
     GTEST_SKIP() << "Can't check kernel configs on host";
diff --git a/libs/input/tests/data/hid_fallback_mapping.kl b/libs/input/tests/data/hid_fallback_mapping.kl
new file mode 100644
index 0000000000..b4ca9ef355
--- /dev/null
+++ b/libs/input/tests/data/hid_fallback_mapping.kl
@@ -0,0 +1,32 @@
+# Copyright 2023 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.
+
+#
+# test key layout file for InputDeviceKeyMapTest#HidUsageCodesUseFallbackMapping
+#
+
+# Keys defined by HID usages without fallback mapping flag
+key usage 0x0c0067 WINDOW
+key usage 0x0c006F BRIGHTNESS_UP
+key usage 0x0c0070 BRIGHTNESS_DOWN
+key usage 0x0c0079 KEYBOARD_BACKLIGHT_UP
+key usage 0x0c007A KEYBOARD_BACKLIGHT_DOWN
+
+# Keys defined by HID usages with fallback mapping flag
+key usage 0x0c007C KEYBOARD_BACKLIGHT_TOGGLE FALLBACK_USAGE_MAPPING
+key usage 0x0c0173 MEDIA_AUDIO_TRACK         FALLBACK_USAGE_MAPPING
+key usage 0x0c019C PROFILE_SWITCH            FALLBACK_USAGE_MAPPING
+key usage 0x0c01A2 ALL_APPS                  FALLBACK_USAGE_MAPPING
+key usage 0x0d0044 STYLUS_BUTTON_PRIMARY     FALLBACK_USAGE_MAPPING
+key usage 0x0d005a STYLUS_BUTTON_SECONDARY   FALLBACK_USAGE_MAPPING
\ No newline at end of file