2 files changed, 44 insertions, 26 deletions

diff --git a/services/inputflinger/reader/EventHub.cpp b/services/inputflinger/reader/EventHub.cpp
index cc105bdf24..3c8b6f54c1 100644
--- a/services/inputflinger/reader/EventHub.cpp
+++ b/services/inputflinger/reader/EventHub.cpp
@@ -1654,10 +1654,6 @@ EventHub::AssociatedDevice::AssociatedDevice(const std::filesystem::path& sysfsR
         lightInfos(readLightsConfiguration(sysfsRootPath)),
         layoutInfo(readLayoutConfiguration(sysfsRootPath)) {}
 
-bool EventHub::AssociatedDevice::isChanged() const {
-    return AssociatedDevice(sysfsRootPath) != *this;
-}
-
 std::string EventHub::AssociatedDevice::dump() const {
     return StringPrintf("path=%s, numBatteries=%zu, numLight=%zu", sysfsRootPath.c_str(),
                         batteryInfos.size(), lightInfos.size());
@@ -2652,33 +2648,56 @@ status_t EventHub::disableDevice(int32_t deviceId) {
 void EventHub::sysfsNodeChanged(const std::string& sysfsNodePath) {
     std::scoped_lock _l(mLock);
 
-    // Check in opening devices
-    for (auto it = mOpeningDevices.begin(); it != mOpeningDevices.end(); it++) {
-        std::unique_ptr<Device>& device = *it;
-        if (device->associatedDevice &&
-            sysfsNodePath.find(device->associatedDevice->sysfsRootPath.string()) !=
-                    std::string::npos &&
-            device->associatedDevice->isChanged()) {
-            it = mOpeningDevices.erase(it);
-            openDeviceLocked(device->path);
+    // Testing whether a sysfs node changed involves several syscalls, so use a cache to avoid
+    // testing the same node multiple times.
+    std::map<std::shared_ptr<const AssociatedDevice>, bool /*changed*/> testedDevices;
+    auto isAssociatedDeviceChanged = [&testedDevices, &sysfsNodePath](const Device& dev) {
+        if (!dev.associatedDevice) {
+            return false;
         }
-    }
+        if (auto testedIt = testedDevices.find(dev.associatedDevice);
+            testedIt != testedDevices.end()) {
+            return testedIt->second;
+        }
+        // Cache miss
+        if (sysfsNodePath.find(dev.associatedDevice->sysfsRootPath.string()) == std::string::npos) {
+            testedDevices.emplace(dev.associatedDevice, false);
+            return false;
+        }
+        auto reloadedDevice = AssociatedDevice(dev.associatedDevice->sysfsRootPath);
+        const bool changed = *dev.associatedDevice != reloadedDevice;
+        testedDevices.emplace(dev.associatedDevice, changed);
+        return changed;
+    };
 
-    // Check in already added device
-    std::vector<Device*> devicesToReopen;
-    for (const auto& [id, device] : mDevices) {
-        if (device->associatedDevice &&
-            sysfsNodePath.find(device->associatedDevice->sysfsRootPath.string()) !=
-                    std::string::npos &&
-            device->associatedDevice->isChanged()) {
-            devicesToReopen.push_back(device.get());
+    std::set<Device*> devicesToClose;
+    std::set<std::string /*path*/> devicesToOpen;
+
+    // Check in opening devices. If its associated device changed,
+    // the device should be removed from mOpeningDevices and needs to be opened again.
+    std::erase_if(mOpeningDevices, [&](const auto& dev) {
+        if (isAssociatedDeviceChanged(*dev)) {
+            devicesToOpen.emplace(dev->path);
+            return true;
+        }
+        return false;
+    });
+
+    // Check in already added device. If its associated device changed,
+    // the device needs to be re-opened.
+    for (const auto& [id, dev] : mDevices) {
+        if (isAssociatedDeviceChanged(*dev)) {
+            devicesToOpen.emplace(dev->path);
+            devicesToClose.emplace(dev.get());
         }
     }
-    for (const auto& device : devicesToReopen) {
+
+    for (auto* device : devicesToClose) {
         closeDeviceLocked(*device);
-        openDeviceLocked(device->path);
     }
-    devicesToReopen.clear();
+    for (const auto& path : devicesToOpen) {
+        openDeviceLocked(path);
+    }
 }
 
 void EventHub::createVirtualKeyboardLocked() {
diff --git a/services/inputflinger/reader/include/EventHub.h b/services/inputflinger/reader/include/EventHub.h
index 8109dae715..31ac63f31e 100644
--- a/services/inputflinger/reader/include/EventHub.h
+++ b/services/inputflinger/reader/include/EventHub.h
@@ -626,7 +626,6 @@ private:
         std::unordered_map<int32_t /*lightId*/, RawLightInfo> lightInfos;
         std::optional<RawLayoutInfo> layoutInfo;
 
-        bool isChanged() const;
         bool operator==(const AssociatedDevice&) const = default;
         bool operator!=(const AssociatedDevice&) const = default;
         std::string dump() const;