diff --git a/services/surfaceflinger/DisplayHardware/FramebufferSurface.cpp b/services/surfaceflinger/DisplayHardware/FramebufferSurface.cpp
index 4c3b3e5..14b54cd 100644
--- a/services/surfaceflinger/DisplayHardware/FramebufferSurface.cpp
+++ b/services/surfaceflinger/DisplayHardware/FramebufferSurface.cpp
@@ -56,7 +56,7 @@
  *
  */
 
-FramebufferSurface::FramebufferSurface(HWComposer& hwc, DisplayId displayId,
+FramebufferSurface::FramebufferSurface(HWComposer& hwc, PhysicalDisplayId displayId,
                                        const sp<IGraphicBufferConsumer>& consumer,
                                        uint32_t maxWidth, uint32_t maxHeight)
       : ConsumerBase(consumer),
diff --git a/services/surfaceflinger/DisplayHardware/FramebufferSurface.h b/services/surfaceflinger/DisplayHardware/FramebufferSurface.h
index a1859f3..759943a 100644
--- a/services/surfaceflinger/DisplayHardware/FramebufferSurface.h
+++ b/services/surfaceflinger/DisplayHardware/FramebufferSurface.h
@@ -23,6 +23,7 @@
 #include <compositionengine/DisplaySurface.h>
 #include <compositionengine/impl/HwcBufferCache.h>
 #include <gui/ConsumerBase.h>
+#include <ui/DisplayId.h>
 #include <ui/Size.h>
 
 #include "DisplayIdentification.h"
@@ -39,7 +40,7 @@
 
 class FramebufferSurface : public ConsumerBase, public compositionengine::DisplaySurface {
 public:
-    FramebufferSurface(HWComposer& hwc, DisplayId displayId,
+    FramebufferSurface(HWComposer& hwc, PhysicalDisplayId displayId,
                        const sp<IGraphicBufferConsumer>& consumer, uint32_t maxWidth,
                        uint32_t maxHeight);
 
@@ -69,7 +70,7 @@
     status_t nextBuffer(uint32_t& outSlot, sp<GraphicBuffer>& outBuffer,
             sp<Fence>& outFence, ui::Dataspace& outDataspace);
 
-    const DisplayId mDisplayId;
+    const PhysicalDisplayId mDisplayId;
 
     // Framebuffer size has a dimension limitation in pixels based on the graphics capabilities of
     // the device.
diff --git a/services/surfaceflinger/DisplayHardware/HWC2.h b/services/surfaceflinger/DisplayHardware/HWC2.h
index 1f03787..89df84b 100644
--- a/services/surfaceflinger/DisplayHardware/HWC2.h
+++ b/services/surfaceflinger/DisplayHardware/HWC2.h
@@ -240,15 +240,14 @@
 
 class Display : public HWC2::Display {
 public:
-    Display(android::Hwc2::Composer& composer,
-            const std::unordered_set<hal::Capability>& capabilities, hal::HWDisplayId id,
-            hal::DisplayType type);
+    Display(android::Hwc2::Composer&, const std::unordered_set<hal::Capability>&, hal::HWDisplayId,
+            hal::DisplayType);
     ~Display() override;
 
     // Required by HWC2
     hal::Error acceptChanges() override;
     hal::Error createLayer(Layer** outLayer) override;
-    hal::Error destroyLayer(Layer* layer) override;
+    hal::Error destroyLayer(Layer*) override;
     hal::Error getActiveConfig(std::shared_ptr<const Config>* outConfig) const override;
     hal::Error getActiveConfigIndex(int* outIndex) const override;
     hal::Error getChangedCompositionTypes(
@@ -258,8 +257,7 @@
     int32_t getSupportedPerFrameMetadata() const override;
     hal::Error getRenderIntents(hal::ColorMode colorMode,
                                 std::vector<hal::RenderIntent>* outRenderIntents) const override;
-    hal::Error getDataspaceSaturationMatrix(hal::Dataspace dataspace,
-                                            android::mat4* outMatrix) override;
+    hal::Error getDataspaceSaturationMatrix(hal::Dataspace, android::mat4* outMatrix) override;
 
     // Doesn't call into the HWC2 device, so no errors are possible
     std::vector<std::shared_ptr<const Config>> getConfigs() const override;
@@ -285,11 +283,11 @@
     hal::Error setClientTarget(uint32_t slot, const android::sp<android::GraphicBuffer>& target,
                                const android::sp<android::Fence>& acquireFence,
                                hal::Dataspace dataspace) override;
-    hal::Error setColorMode(hal::ColorMode mode, hal::RenderIntent renderIntent) override;
+    hal::Error setColorMode(hal::ColorMode, hal::RenderIntent) override;
     hal::Error setColorTransform(const android::mat4& matrix, hal::ColorTransform hint) override;
-    hal::Error setOutputBuffer(const android::sp<android::GraphicBuffer>& buffer,
+    hal::Error setOutputBuffer(const android::sp<android::GraphicBuffer>&,
                                const android::sp<android::Fence>& releaseFence) override;
-    hal::Error setPowerMode(hal::PowerMode mode) override;
+    hal::Error setPowerMode(hal::PowerMode) override;
     hal::Error setVsyncEnabled(hal::Vsync enabled) override;
     hal::Error validate(uint32_t* outNumTypes, uint32_t* outNumRequests) override;
     hal::Error presentOrValidate(uint32_t* outNumTypes, uint32_t* outNumRequests,
@@ -317,13 +315,13 @@
     virtual bool isVsyncPeriodSwitchSupported() const override;
 
 private:
-    int32_t getAttribute(hal::HWConfigId configId, hal::Attribute attribute);
-    void loadConfig(hal::HWConfigId configId);
+    int32_t getAttribute(hal::HWConfigId, hal::Attribute);
+    void loadConfig(hal::HWConfigId);
     void loadConfigs();
 
     // This may fail (and return a null pointer) if no layer with this ID exists
     // on this display
-    Layer* getLayerById(hal::HWLayerId id) const;
+    Layer* getLayerById(hal::HWLayerId) const;
 
     friend android::TestableSurfaceFlinger;
 
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.cpp b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
index 195182a..2379e6e 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
@@ -186,7 +186,7 @@
     return mCapabilities.count(capability) > 0;
 }
 
-bool HWComposer::hasDisplayCapability(DisplayId displayId,
+bool HWComposer::hasDisplayCapability(HalDisplayId displayId,
                                       hal::DisplayCapability capability) const {
     RETURN_IF_INVALID_DISPLAY(displayId, false);
     return mDisplayData.at(displayId).hwcDisplay->getCapabilities().count(capability) > 0;
@@ -214,10 +214,8 @@
     RETURN_IF_INVALID_DISPLAY(*displayId, false);
 
     auto& displayData = mDisplayData[*displayId];
-    if (displayData.isVirtual) {
-        LOG_DISPLAY_ERROR(*displayId, "Invalid operation on virtual display");
-        return false;
-    }
+    LOG_FATAL_IF(displayData.isVirtual, "%s: Invalid operation on virtual display with ID %s",
+                 __FUNCTION__, to_string(*displayId));
 
     {
         std::lock_guard lock(displayData.lastHwVsyncLock);
@@ -244,11 +242,6 @@
 
 std::optional<DisplayId> HWComposer::allocateVirtualDisplay(uint32_t width, uint32_t height,
                                                             ui::PixelFormat* format) {
-    if (mRemainingHwcVirtualDisplays == 0) {
-        ALOGE("%s: No remaining virtual displays", __FUNCTION__);
-        return {};
-    }
-
     if (SurfaceFlinger::maxVirtualDisplaySize != 0 &&
         (width > SurfaceFlinger::maxVirtualDisplaySize ||
          height > SurfaceFlinger::maxVirtualDisplaySize)) {
@@ -256,31 +249,28 @@
               height, SurfaceFlinger::maxVirtualDisplaySize);
         return {};
     }
+
+    const auto displayId = mVirtualIdGenerator.nextId();
+    if (!displayId) {
+        ALOGE("%s: No remaining virtual displays", __FUNCTION__);
+        return {};
+    }
+
     hal::HWDisplayId hwcDisplayId = 0;
     const auto error = static_cast<hal::Error>(
             mComposer->createVirtualDisplay(width, height, format, &hwcDisplayId));
     if (error != hal::Error::NONE) {
         ALOGE("%s: Failed to create HWC virtual display", __FUNCTION__);
+        mVirtualIdGenerator.markUnused(*displayId);
         return {};
     }
 
     auto display = std::make_unique<HWC2::impl::Display>(*mComposer.get(), mCapabilities,
                                                          hwcDisplayId, hal::DisplayType::VIRTUAL);
     display->setConnected(true);
-
-    DisplayId displayId;
-    if (mFreeVirtualDisplayIds.empty()) {
-        displayId = getVirtualDisplayId(mNextVirtualDisplayId++);
-    } else {
-        displayId = *mFreeVirtualDisplayIds.begin();
-        mFreeVirtualDisplayIds.erase(displayId);
-    }
-
-    auto& displayData = mDisplayData[displayId];
+    auto& displayData = mDisplayData[*displayId];
     displayData.hwcDisplay = std::move(display);
     displayData.isVirtual = true;
-
-    --mRemainingHwcVirtualDisplays;
     return displayId;
 }
 
@@ -301,7 +291,7 @@
     mPhysicalDisplayIdMap[hwcDisplayId] = displayId;
 }
 
-HWC2::Layer* HWComposer::createLayer(DisplayId displayId) {
+HWC2::Layer* HWComposer::createLayer(HalDisplayId displayId) {
     RETURN_IF_INVALID_DISPLAY(displayId, nullptr);
 
     HWC2::Layer* layer;
@@ -310,14 +300,14 @@
     return layer;
 }
 
-void HWComposer::destroyLayer(DisplayId displayId, HWC2::Layer* layer) {
+void HWComposer::destroyLayer(HalDisplayId displayId, HWC2::Layer* layer) {
     RETURN_IF_INVALID_DISPLAY(displayId);
 
     auto error = mDisplayData[displayId].hwcDisplay->destroyLayer(layer);
     RETURN_IF_HWC_ERROR(error, displayId);
 }
 
-nsecs_t HWComposer::getRefreshTimestamp(DisplayId displayId) const {
+nsecs_t HWComposer::getRefreshTimestamp(PhysicalDisplayId displayId) const {
     RETURN_IF_INVALID_DISPLAY(displayId, 0);
     const auto& displayData = mDisplayData.at(displayId);
     // this returns the last refresh timestamp.
@@ -329,13 +319,13 @@
     return now - ((now - displayData.lastHwVsync) % vsyncPeriodNanos);
 }
 
-bool HWComposer::isConnected(DisplayId displayId) const {
+bool HWComposer::isConnected(PhysicalDisplayId displayId) const {
     RETURN_IF_INVALID_DISPLAY(displayId, false);
     return mDisplayData.at(displayId).hwcDisplay->isConnected();
 }
 
 std::vector<std::shared_ptr<const HWC2::Display::Config>> HWComposer::getConfigs(
-        DisplayId displayId) const {
+        PhysicalDisplayId displayId) const {
     RETURN_IF_INVALID_DISPLAY(displayId, {});
 
     const auto& displayData = mDisplayData.at(displayId);
@@ -349,7 +339,7 @@
 }
 
 std::shared_ptr<const HWC2::Display::Config> HWComposer::getActiveConfig(
-        DisplayId displayId) const {
+        PhysicalDisplayId displayId) const {
     RETURN_IF_INVALID_DISPLAY(displayId, nullptr);
 
     std::shared_ptr<const HWC2::Display::Config> config;
@@ -371,7 +361,7 @@
 
 // Composer 2.4
 
-DisplayConnectionType HWComposer::getDisplayConnectionType(DisplayId displayId) const {
+DisplayConnectionType HWComposer::getDisplayConnectionType(PhysicalDisplayId displayId) const {
     RETURN_IF_INVALID_DISPLAY(displayId, DisplayConnectionType::Internal);
     const auto& hwcDisplay = mDisplayData.at(displayId).hwcDisplay;
 
@@ -386,12 +376,12 @@
     return type;
 }
 
-bool HWComposer::isVsyncPeriodSwitchSupported(DisplayId displayId) const {
+bool HWComposer::isVsyncPeriodSwitchSupported(PhysicalDisplayId displayId) const {
     RETURN_IF_INVALID_DISPLAY(displayId, false);
     return mDisplayData.at(displayId).hwcDisplay->isVsyncPeriodSwitchSupported();
 }
 
-nsecs_t HWComposer::getDisplayVsyncPeriod(DisplayId displayId) const {
+nsecs_t HWComposer::getDisplayVsyncPeriod(PhysicalDisplayId displayId) const {
     RETURN_IF_INVALID_DISPLAY(displayId, 0);
 
     nsecs_t vsyncPeriodNanos;
@@ -400,7 +390,7 @@
     return vsyncPeriodNanos;
 }
 
-int HWComposer::getActiveConfigIndex(DisplayId displayId) const {
+int HWComposer::getActiveConfigIndex(PhysicalDisplayId displayId) const {
     RETURN_IF_INVALID_DISPLAY(displayId, -1);
 
     int index;
@@ -420,7 +410,7 @@
     return index;
 }
 
-std::vector<ui::ColorMode> HWComposer::getColorModes(DisplayId displayId) const {
+std::vector<ui::ColorMode> HWComposer::getColorModes(PhysicalDisplayId displayId) const {
     RETURN_IF_INVALID_DISPLAY(displayId, {});
 
     std::vector<ui::ColorMode> modes;
@@ -429,7 +419,7 @@
     return modes;
 }
 
-status_t HWComposer::setActiveColorMode(DisplayId displayId, ui::ColorMode mode,
+status_t HWComposer::setActiveColorMode(PhysicalDisplayId displayId, ui::ColorMode mode,
                                         ui::RenderIntent renderIntent) {
     RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
 
@@ -443,14 +433,12 @@
     return NO_ERROR;
 }
 
-void HWComposer::setVsyncEnabled(DisplayId displayId, hal::Vsync enabled) {
+void HWComposer::setVsyncEnabled(PhysicalDisplayId displayId, hal::Vsync enabled) {
     RETURN_IF_INVALID_DISPLAY(displayId);
     auto& displayData = mDisplayData[displayId];
 
-    if (displayData.isVirtual) {
-        LOG_DISPLAY_ERROR(displayId, "Invalid operation on virtual display");
-        return;
-    }
+    LOG_FATAL_IF(displayData.isVirtual, "%s: Invalid operation on virtual display with ID %s",
+                 __FUNCTION__, to_string(*displayId));
 
     // NOTE: we use our own internal lock here because we have to call
     // into the HWC with the lock held, and we want to make sure
@@ -471,7 +459,7 @@
     ATRACE_INT(tag.c_str(), enabled == hal::Vsync::ENABLE ? 1 : 0);
 }
 
-status_t HWComposer::setClientTarget(DisplayId displayId, uint32_t slot,
+status_t HWComposer::setClientTarget(HalDisplayId displayId, uint32_t slot,
                                      const sp<Fence>& acquireFence, const sp<GraphicBuffer>& target,
                                      ui::Dataspace dataspace) {
     RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
@@ -484,7 +472,7 @@
 }
 
 status_t HWComposer::getDeviceCompositionChanges(
-        DisplayId displayId, bool frameUsesClientComposition,
+        HalDisplayId displayId, bool frameUsesClientComposition,
         std::optional<android::HWComposer::DeviceRequestedChanges>* outChanges) {
     ATRACE_CALL();
 
@@ -554,12 +542,12 @@
     return NO_ERROR;
 }
 
-sp<Fence> HWComposer::getPresentFence(DisplayId displayId) const {
+sp<Fence> HWComposer::getPresentFence(HalDisplayId displayId) const {
     RETURN_IF_INVALID_DISPLAY(displayId, Fence::NO_FENCE);
     return mDisplayData.at(displayId).lastPresentFence;
 }
 
-sp<Fence> HWComposer::getLayerReleaseFence(DisplayId displayId, HWC2::Layer* layer) const {
+sp<Fence> HWComposer::getLayerReleaseFence(HalDisplayId displayId, HWC2::Layer* layer) const {
     RETURN_IF_INVALID_DISPLAY(displayId, Fence::NO_FENCE);
     const auto& displayFences = mDisplayData.at(displayId).releaseFences;
     auto fence = displayFences.find(layer);
@@ -570,7 +558,7 @@
     return fence->second;
 }
 
-status_t HWComposer::presentAndGetReleaseFences(DisplayId displayId) {
+status_t HWComposer::presentAndGetReleaseFences(HalDisplayId displayId) {
     ATRACE_CALL();
 
     RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
@@ -598,14 +586,12 @@
     return NO_ERROR;
 }
 
-status_t HWComposer::setPowerMode(DisplayId displayId, hal::PowerMode mode) {
+status_t HWComposer::setPowerMode(PhysicalDisplayId displayId, hal::PowerMode mode) {
     RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
 
     const auto& displayData = mDisplayData[displayId];
-    if (displayData.isVirtual) {
-        LOG_DISPLAY_ERROR(displayId, "Invalid operation on virtual display");
-        return INVALID_OPERATION;
-    }
+    LOG_FATAL_IF(displayData.isVirtual, "%s: Invalid operation on virtual display with ID %s",
+                 __FUNCTION__, to_string(*displayId));
 
     if (mode == hal::PowerMode::OFF) {
         setVsyncEnabled(displayId, hal::Vsync::DISABLE);
@@ -654,7 +640,8 @@
 }
 
 status_t HWComposer::setActiveConfigWithConstraints(
-        DisplayId displayId, size_t configId, const hal::VsyncPeriodChangeConstraints& constraints,
+        PhysicalDisplayId displayId, size_t configId,
+        const hal::VsyncPeriodChangeConstraints& constraints,
         hal::VsyncPeriodChangeTimeline* outTimeline) {
     RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
 
@@ -671,7 +658,7 @@
     return NO_ERROR;
 }
 
-status_t HWComposer::setColorTransform(DisplayId displayId, const mat4& transform) {
+status_t HWComposer::setColorTransform(HalDisplayId displayId, const mat4& transform) {
     RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
 
     auto& displayData = mDisplayData[displayId];
@@ -684,15 +671,14 @@
     return NO_ERROR;
 }
 
-void HWComposer::disconnectDisplay(DisplayId displayId) {
+void HWComposer::disconnectDisplay(HalDisplayId displayId) {
     RETURN_IF_INVALID_DISPLAY(displayId);
     auto& displayData = mDisplayData[displayId];
 
     // If this was a virtual display, add its slot back for reuse by future
     // virtual displays
     if (displayData.isVirtual) {
-        mFreeVirtualDisplayIds.insert(displayId);
-        ++mRemainingHwcVirtualDisplays;
+        mVirtualIdGenerator.markUnused(*HalVirtualDisplayId::tryCast(displayId));
     }
 
     const auto hwcDisplayId = displayData.hwcDisplay->getId();
@@ -707,27 +693,25 @@
     mDisplayData.erase(displayId);
 }
 
-status_t HWComposer::setOutputBuffer(DisplayId displayId, const sp<Fence>& acquireFence,
+status_t HWComposer::setOutputBuffer(HalVirtualDisplayId displayId, const sp<Fence>& acquireFence,
                                      const sp<GraphicBuffer>& buffer) {
     RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
     const auto& displayData = mDisplayData[displayId];
 
-    if (!displayData.isVirtual) {
-        LOG_DISPLAY_ERROR(displayId, "Invalid operation on physical display");
-        return INVALID_OPERATION;
-    }
+    LOG_FATAL_IF(!displayData.isVirtual, "%s: Invalid operation on physical display with ID %s",
+                 __FUNCTION__, to_string(*displayId));
 
     auto error = displayData.hwcDisplay->setOutputBuffer(buffer, acquireFence);
     RETURN_IF_HWC_ERROR(error, displayId, UNKNOWN_ERROR);
     return NO_ERROR;
 }
 
-void HWComposer::clearReleaseFences(DisplayId displayId) {
+void HWComposer::clearReleaseFences(HalDisplayId displayId) {
     RETURN_IF_INVALID_DISPLAY(displayId);
     mDisplayData[displayId].releaseFences.clear();
 }
 
-status_t HWComposer::getHdrCapabilities(DisplayId displayId, HdrCapabilities* outCapabilities) {
+status_t HWComposer::getHdrCapabilities(HalDisplayId displayId, HdrCapabilities* outCapabilities) {
     RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
 
     auto& hwcDisplay = mDisplayData[displayId].hwcDisplay;
@@ -736,12 +720,12 @@
     return NO_ERROR;
 }
 
-int32_t HWComposer::getSupportedPerFrameMetadata(DisplayId displayId) const {
+int32_t HWComposer::getSupportedPerFrameMetadata(HalDisplayId displayId) const {
     RETURN_IF_INVALID_DISPLAY(displayId, 0);
     return mDisplayData.at(displayId).hwcDisplay->getSupportedPerFrameMetadata();
 }
 
-std::vector<ui::RenderIntent> HWComposer::getRenderIntents(DisplayId displayId,
+std::vector<ui::RenderIntent> HWComposer::getRenderIntents(HalDisplayId displayId,
                                                            ui::ColorMode colorMode) const {
     RETURN_IF_INVALID_DISPLAY(displayId, {});
 
@@ -751,7 +735,7 @@
     return renderIntents;
 }
 
-mat4 HWComposer::getDataspaceSaturationMatrix(DisplayId displayId, ui::Dataspace dataspace) {
+mat4 HWComposer::getDataspaceSaturationMatrix(HalDisplayId displayId, ui::Dataspace dataspace) {
     RETURN_IF_INVALID_DISPLAY(displayId, {});
 
     mat4 matrix;
@@ -761,7 +745,7 @@
     return matrix;
 }
 
-status_t HWComposer::getDisplayedContentSamplingAttributes(DisplayId displayId,
+status_t HWComposer::getDisplayedContentSamplingAttributes(HalDisplayId displayId,
                                                            ui::PixelFormat* outFormat,
                                                            ui::Dataspace* outDataspace,
                                                            uint8_t* outComponentMask) {
@@ -775,7 +759,7 @@
     return NO_ERROR;
 }
 
-status_t HWComposer::setDisplayContentSamplingEnabled(DisplayId displayId, bool enabled,
+status_t HWComposer::setDisplayContentSamplingEnabled(HalDisplayId displayId, bool enabled,
                                                       uint8_t componentMask, uint64_t maxFrames) {
     RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
     const auto error =
@@ -789,7 +773,7 @@
     return NO_ERROR;
 }
 
-status_t HWComposer::getDisplayedContentSample(DisplayId displayId, uint64_t maxFrames,
+status_t HWComposer::getDisplayedContentSample(HalDisplayId displayId, uint64_t maxFrames,
                                                uint64_t timestamp, DisplayedFrameStats* outStats) {
     RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
     const auto error =
@@ -799,7 +783,8 @@
     return NO_ERROR;
 }
 
-std::future<status_t> HWComposer::setDisplayBrightness(DisplayId displayId, float brightness) {
+std::future<status_t> HWComposer::setDisplayBrightness(PhysicalDisplayId displayId,
+                                                       float brightness) {
     RETURN_IF_INVALID_DISPLAY(displayId, promise::yield<status_t>(BAD_INDEX));
     auto& display = mDisplayData[displayId].hwcDisplay;
 
@@ -816,7 +801,7 @@
             });
 }
 
-status_t HWComposer::setAutoLowLatencyMode(DisplayId displayId, bool on) {
+status_t HWComposer::setAutoLowLatencyMode(PhysicalDisplayId displayId, bool on) {
     RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
     const auto error = mDisplayData[displayId].hwcDisplay->setAutoLowLatencyMode(on);
     if (error == hal::Error::UNSUPPORTED) {
@@ -830,7 +815,7 @@
 }
 
 status_t HWComposer::getSupportedContentTypes(
-        DisplayId displayId, std::vector<hal::ContentType>* outSupportedContentTypes) {
+        PhysicalDisplayId displayId, std::vector<hal::ContentType>* outSupportedContentTypes) {
     RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
     const auto error =
             mDisplayData[displayId].hwcDisplay->getSupportedContentTypes(outSupportedContentTypes);
@@ -840,7 +825,7 @@
     return NO_ERROR;
 }
 
-status_t HWComposer::setContentType(DisplayId displayId, hal::ContentType contentType) {
+status_t HWComposer::setContentType(PhysicalDisplayId displayId, hal::ContentType contentType) {
     RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
     const auto error = mDisplayData[displayId].hwcDisplay->setContentType(contentType);
     if (error == hal::Error::UNSUPPORTED) {
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.h b/services/surfaceflinger/DisplayHardware/HWComposer.h
index 488cdc5..028a9a4 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.h
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.h
@@ -38,6 +38,7 @@
 #include <utils/StrongPointer.h>
 #include <utils/Timers.h>
 
+#include "DisplayIdGenerator.h"
 #include "DisplayIdentification.h"
 #include "HWC2.h"
 #include "Hal.h"
@@ -88,7 +89,7 @@
                                               DisplayIdentificationData* outData) const = 0;
 
     virtual bool hasCapability(hal::Capability) const = 0;
-    virtual bool hasDisplayCapability(DisplayId, hal::DisplayCapability) const = 0;
+    virtual bool hasDisplayCapability(HalDisplayId, hal::DisplayCapability) const = 0;
 
     // Attempts to allocate a virtual display and returns its ID if created on the HWC device.
     virtual std::optional<DisplayId> allocateVirtualDisplay(uint32_t width, uint32_t height,
@@ -97,9 +98,9 @@
     virtual void allocatePhysicalDisplay(hal::HWDisplayId, PhysicalDisplayId) = 0;
 
     // Attempts to create a new layer on this display
-    virtual HWC2::Layer* createLayer(DisplayId) = 0;
+    virtual HWC2::Layer* createLayer(HalDisplayId) = 0;
     // Destroy a previously created layer
-    virtual void destroyLayer(DisplayId, HWC2::Layer*) = 0;
+    virtual void destroyLayer(HalDisplayId, HWC2::Layer*) = 0;
 
     // Gets any required composition change requests from the HWC device.
     //
@@ -109,61 +110,60 @@
     // with fewer handshakes, but this does not work if client composition is
     // expected.
     virtual status_t getDeviceCompositionChanges(
-            DisplayId, bool frameUsesClientComposition,
+            HalDisplayId, bool frameUsesClientComposition,
             std::optional<DeviceRequestedChanges>* outChanges) = 0;
 
-    virtual status_t setClientTarget(DisplayId, uint32_t slot, const sp<Fence>& acquireFence,
+    virtual status_t setClientTarget(HalDisplayId, uint32_t slot, const sp<Fence>& acquireFence,
                                      const sp<GraphicBuffer>& target, ui::Dataspace) = 0;
 
     // Present layers to the display and read releaseFences.
-    virtual status_t presentAndGetReleaseFences(DisplayId) = 0;
+    virtual status_t presentAndGetReleaseFences(HalDisplayId) = 0;
 
     // set power mode
-    virtual status_t setPowerMode(DisplayId, hal::PowerMode) = 0;
+    virtual status_t setPowerMode(PhysicalDisplayId, hal::PowerMode) = 0;
 
     // Sets a color transform to be applied to the result of composition
-    virtual status_t setColorTransform(DisplayId, const mat4& transform) = 0;
+    virtual status_t setColorTransform(HalDisplayId, const mat4& transform) = 0;
 
-    // reset state when an external, non-virtual display is disconnected
-    virtual void disconnectDisplay(DisplayId) = 0;
+    // reset state when a display is disconnected
+    virtual void disconnectDisplay(HalDisplayId) = 0;
 
     // get the present fence received from the last call to present.
-    virtual sp<Fence> getPresentFence(DisplayId) const = 0;
+    virtual sp<Fence> getPresentFence(HalDisplayId) const = 0;
 
     // Get last release fence for the given layer
-    virtual sp<Fence> getLayerReleaseFence(DisplayId, HWC2::Layer*) const = 0;
+    virtual sp<Fence> getLayerReleaseFence(HalDisplayId, HWC2::Layer*) const = 0;
 
     // Set the output buffer and acquire fence for a virtual display.
-    // Returns INVALID_OPERATION if displayId is not a virtual display.
-    virtual status_t setOutputBuffer(DisplayId, const sp<Fence>& acquireFence,
+    virtual status_t setOutputBuffer(HalVirtualDisplayId, const sp<Fence>& acquireFence,
                                      const sp<GraphicBuffer>& buffer) = 0;
 
     // After SurfaceFlinger has retrieved the release fences for all the frames,
     // it can call this to clear the shared pointers in the release fence map
-    virtual void clearReleaseFences(DisplayId) = 0;
+    virtual void clearReleaseFences(HalDisplayId) = 0;
 
     // Fetches the HDR capabilities of the given display
-    virtual status_t getHdrCapabilities(DisplayId, HdrCapabilities* outCapabilities) = 0;
+    virtual status_t getHdrCapabilities(HalDisplayId, HdrCapabilities* outCapabilities) = 0;
 
-    virtual int32_t getSupportedPerFrameMetadata(DisplayId) const = 0;
+    virtual int32_t getSupportedPerFrameMetadata(HalDisplayId) const = 0;
 
     // Returns the available RenderIntent of the given display.
-    virtual std::vector<ui::RenderIntent> getRenderIntents(DisplayId, ui::ColorMode) const = 0;
+    virtual std::vector<ui::RenderIntent> getRenderIntents(HalDisplayId, ui::ColorMode) const = 0;
 
-    virtual mat4 getDataspaceSaturationMatrix(DisplayId, ui::Dataspace) = 0;
+    virtual mat4 getDataspaceSaturationMatrix(HalDisplayId, ui::Dataspace) = 0;
 
     // Returns the attributes of the color sampling engine.
-    virtual status_t getDisplayedContentSamplingAttributes(DisplayId, ui::PixelFormat* outFormat,
+    virtual status_t getDisplayedContentSamplingAttributes(HalDisplayId, ui::PixelFormat* outFormat,
                                                            ui::Dataspace* outDataspace,
                                                            uint8_t* outComponentMask) = 0;
-    virtual status_t setDisplayContentSamplingEnabled(DisplayId, bool enabled,
+    virtual status_t setDisplayContentSamplingEnabled(HalDisplayId, bool enabled,
                                                       uint8_t componentMask,
                                                       uint64_t maxFrames) = 0;
-    virtual status_t getDisplayedContentSample(DisplayId, uint64_t maxFrames, uint64_t timestamp,
+    virtual status_t getDisplayedContentSample(HalDisplayId, uint64_t maxFrames, uint64_t timestamp,
                                                DisplayedFrameStats* outStats) = 0;
 
     // Sets the brightness of a display.
-    virtual std::future<status_t> setDisplayBrightness(DisplayId, float brightness) = 0;
+    virtual std::future<status_t> setDisplayBrightness(PhysicalDisplayId, float brightness) = 0;
 
     // Events handling ---------------------------------------------------------
 
@@ -174,33 +174,35 @@
                                                                hal::Connection) = 0;
 
     virtual bool onVsync(hal::HWDisplayId, int64_t timestamp) = 0;
-    virtual void setVsyncEnabled(DisplayId, hal::Vsync enabled) = 0;
+    virtual void setVsyncEnabled(PhysicalDisplayId, hal::Vsync enabled) = 0;
 
-    virtual nsecs_t getRefreshTimestamp(DisplayId) const = 0;
-    virtual bool isConnected(DisplayId) const = 0;
+    virtual nsecs_t getRefreshTimestamp(PhysicalDisplayId) const = 0;
+    virtual bool isConnected(PhysicalDisplayId) const = 0;
 
     // Non-const because it can update configMap inside of mDisplayData
     virtual std::vector<std::shared_ptr<const HWC2::Display::Config>> getConfigs(
-            DisplayId) const = 0;
+            PhysicalDisplayId) const = 0;
 
-    virtual std::shared_ptr<const HWC2::Display::Config> getActiveConfig(DisplayId) const = 0;
-    virtual int getActiveConfigIndex(DisplayId) const = 0;
+    virtual std::shared_ptr<const HWC2::Display::Config> getActiveConfig(
+            PhysicalDisplayId) const = 0;
+    virtual int getActiveConfigIndex(PhysicalDisplayId) const = 0;
 
-    virtual std::vector<ui::ColorMode> getColorModes(DisplayId) const = 0;
+    virtual std::vector<ui::ColorMode> getColorModes(PhysicalDisplayId) const = 0;
 
-    virtual status_t setActiveColorMode(DisplayId, ui::ColorMode mode, ui::RenderIntent) = 0;
+    virtual status_t setActiveColorMode(PhysicalDisplayId, ui::ColorMode mode,
+                                        ui::RenderIntent) = 0;
 
     // Composer 2.4
-    virtual DisplayConnectionType getDisplayConnectionType(DisplayId) const = 0;
-    virtual bool isVsyncPeriodSwitchSupported(DisplayId) const = 0;
-    virtual nsecs_t getDisplayVsyncPeriod(DisplayId) const = 0;
+    virtual DisplayConnectionType getDisplayConnectionType(PhysicalDisplayId) const = 0;
+    virtual bool isVsyncPeriodSwitchSupported(PhysicalDisplayId) const = 0;
+    virtual nsecs_t getDisplayVsyncPeriod(PhysicalDisplayId) const = 0;
     virtual status_t setActiveConfigWithConstraints(
-            DisplayId, size_t configId, const hal::VsyncPeriodChangeConstraints&,
+            PhysicalDisplayId, size_t configId, const hal::VsyncPeriodChangeConstraints&,
             hal::VsyncPeriodChangeTimeline* outTimeline) = 0;
-    virtual status_t setAutoLowLatencyMode(DisplayId, bool on) = 0;
+    virtual status_t setAutoLowLatencyMode(PhysicalDisplayId, bool on) = 0;
     virtual status_t getSupportedContentTypes(
-            DisplayId, std::vector<hal::ContentType>* outSupportedContentTypes) = 0;
-    virtual status_t setContentType(DisplayId, hal::ContentType) = 0;
+            PhysicalDisplayId, std::vector<hal::ContentType>* outSupportedContentTypes) = 0;
+    virtual status_t setContentType(PhysicalDisplayId, hal::ContentType) = 0;
     virtual const std::unordered_map<std::string, bool>& getSupportedLayerGenericMetadata()
             const = 0;
 
@@ -232,7 +234,7 @@
                                       DisplayIdentificationData* outData) const override;
 
     bool hasCapability(hal::Capability) const override;
-    bool hasDisplayCapability(DisplayId, hal::DisplayCapability) const override;
+    bool hasDisplayCapability(HalDisplayId, hal::DisplayCapability) const override;
 
     // Attempts to allocate a virtual display and returns its ID if created on the HWC device.
     std::optional<DisplayId> allocateVirtualDisplay(uint32_t width, uint32_t height,
@@ -242,63 +244,62 @@
     void allocatePhysicalDisplay(hal::HWDisplayId, PhysicalDisplayId) override;
 
     // Attempts to create a new layer on this display
-    HWC2::Layer* createLayer(DisplayId) override;
+    HWC2::Layer* createLayer(HalDisplayId) override;
     // Destroy a previously created layer
-    void destroyLayer(DisplayId, HWC2::Layer*) override;
+    void destroyLayer(HalDisplayId, HWC2::Layer*) override;
 
     status_t getDeviceCompositionChanges(
-            DisplayId, bool frameUsesClientComposition,
+            HalDisplayId, bool frameUsesClientComposition,
             std::optional<DeviceRequestedChanges>* outChanges) override;
 
-    status_t setClientTarget(DisplayId, uint32_t slot, const sp<Fence>& acquireFence,
+    status_t setClientTarget(HalDisplayId, uint32_t slot, const sp<Fence>& acquireFence,
                              const sp<GraphicBuffer>& target, ui::Dataspace) override;
 
     // Present layers to the display and read releaseFences.
-    status_t presentAndGetReleaseFences(DisplayId) override;
+    status_t presentAndGetReleaseFences(HalDisplayId) override;
 
     // set power mode
-    status_t setPowerMode(DisplayId, hal::PowerMode mode) override;
+    status_t setPowerMode(PhysicalDisplayId, hal::PowerMode mode) override;
 
     // Sets a color transform to be applied to the result of composition
-    status_t setColorTransform(DisplayId, const mat4& transform) override;
+    status_t setColorTransform(HalDisplayId, const mat4& transform) override;
 
-    // reset state when an external, non-virtual display is disconnected
-    void disconnectDisplay(DisplayId) override;
+    // reset state when a display is disconnected
+    void disconnectDisplay(HalDisplayId) override;
 
     // get the present fence received from the last call to present.
-    sp<Fence> getPresentFence(DisplayId) const override;
+    sp<Fence> getPresentFence(HalDisplayId) const override;
 
     // Get last release fence for the given layer
-    sp<Fence> getLayerReleaseFence(DisplayId, HWC2::Layer*) const override;
+    sp<Fence> getLayerReleaseFence(HalDisplayId, HWC2::Layer*) const override;
 
     // Set the output buffer and acquire fence for a virtual display.
-    // Returns INVALID_OPERATION if displayId is not a virtual display.
-    status_t setOutputBuffer(DisplayId, const sp<Fence>& acquireFence,
+    status_t setOutputBuffer(HalVirtualDisplayId, const sp<Fence>& acquireFence,
                              const sp<GraphicBuffer>& buffer) override;
 
     // After SurfaceFlinger has retrieved the release fences for all the frames,
     // it can call this to clear the shared pointers in the release fence map
-    void clearReleaseFences(DisplayId) override;
+    void clearReleaseFences(HalDisplayId) override;
 
     // Fetches the HDR capabilities of the given display
-    status_t getHdrCapabilities(DisplayId, HdrCapabilities* outCapabilities) override;
+    status_t getHdrCapabilities(HalDisplayId, HdrCapabilities* outCapabilities) override;
 
-    int32_t getSupportedPerFrameMetadata(DisplayId) const override;
+    int32_t getSupportedPerFrameMetadata(HalDisplayId) const override;
 
     // Returns the available RenderIntent of the given display.
-    std::vector<ui::RenderIntent> getRenderIntents(DisplayId, ui::ColorMode) const override;
+    std::vector<ui::RenderIntent> getRenderIntents(HalDisplayId, ui::ColorMode) const override;
 
-    mat4 getDataspaceSaturationMatrix(DisplayId, ui::Dataspace) override;
+    mat4 getDataspaceSaturationMatrix(HalDisplayId, ui::Dataspace) override;
 
     // Returns the attributes of the color sampling engine.
-    status_t getDisplayedContentSamplingAttributes(DisplayId, ui::PixelFormat* outFormat,
+    status_t getDisplayedContentSamplingAttributes(HalDisplayId, ui::PixelFormat* outFormat,
                                                    ui::Dataspace* outDataspace,
                                                    uint8_t* outComponentMask) override;
-    status_t setDisplayContentSamplingEnabled(DisplayId, bool enabled, uint8_t componentMask,
+    status_t setDisplayContentSamplingEnabled(HalDisplayId, bool enabled, uint8_t componentMask,
                                               uint64_t maxFrames) override;
-    status_t getDisplayedContentSample(DisplayId, uint64_t maxFrames, uint64_t timestamp,
+    status_t getDisplayedContentSample(HalDisplayId, uint64_t maxFrames, uint64_t timestamp,
                                        DisplayedFrameStats* outStats) override;
-    std::future<status_t> setDisplayBrightness(DisplayId, float brightness) override;
+    std::future<status_t> setDisplayBrightness(PhysicalDisplayId, float brightness) override;
 
     // Events handling ---------------------------------------------------------
 
@@ -307,31 +308,32 @@
     std::optional<DisplayIdentificationInfo> onHotplug(hal::HWDisplayId, hal::Connection) override;
 
     bool onVsync(hal::HWDisplayId, int64_t timestamp) override;
-    void setVsyncEnabled(DisplayId, hal::Vsync enabled) override;
+    void setVsyncEnabled(PhysicalDisplayId, hal::Vsync enabled) override;
 
-    nsecs_t getRefreshTimestamp(DisplayId) const override;
-    bool isConnected(DisplayId) const override;
+    nsecs_t getRefreshTimestamp(PhysicalDisplayId) const override;
+    bool isConnected(PhysicalDisplayId) const override;
 
     // Non-const because it can update configMap inside of mDisplayData
-    std::vector<std::shared_ptr<const HWC2::Display::Config>> getConfigs(DisplayId) const override;
+    std::vector<std::shared_ptr<const HWC2::Display::Config>> getConfigs(
+            PhysicalDisplayId) const override;
 
-    std::shared_ptr<const HWC2::Display::Config> getActiveConfig(DisplayId) const override;
-    int getActiveConfigIndex(DisplayId) const override;
+    std::shared_ptr<const HWC2::Display::Config> getActiveConfig(PhysicalDisplayId) const override;
+    int getActiveConfigIndex(PhysicalDisplayId) const override;
 
-    std::vector<ui::ColorMode> getColorModes(DisplayId) const override;
+    std::vector<ui::ColorMode> getColorModes(PhysicalDisplayId) const override;
 
-    status_t setActiveColorMode(DisplayId, ui::ColorMode, ui::RenderIntent) override;
+    status_t setActiveColorMode(PhysicalDisplayId, ui::ColorMode, ui::RenderIntent) override;
 
     // Composer 2.4
-    DisplayConnectionType getDisplayConnectionType(DisplayId) const override;
-    bool isVsyncPeriodSwitchSupported(DisplayId) const override;
-    nsecs_t getDisplayVsyncPeriod(DisplayId) const override;
-    status_t setActiveConfigWithConstraints(DisplayId, size_t configId,
+    DisplayConnectionType getDisplayConnectionType(PhysicalDisplayId) const override;
+    bool isVsyncPeriodSwitchSupported(PhysicalDisplayId) const override;
+    nsecs_t getDisplayVsyncPeriod(PhysicalDisplayId) const override;
+    status_t setActiveConfigWithConstraints(PhysicalDisplayId, size_t configId,
                                             const hal::VsyncPeriodChangeConstraints&,
                                             hal::VsyncPeriodChangeTimeline* outTimeline) override;
-    status_t setAutoLowLatencyMode(DisplayId, bool) override;
-    status_t getSupportedContentTypes(DisplayId, std::vector<hal::ContentType>*) override;
-    status_t setContentType(DisplayId, hal::ContentType) override;
+    status_t setAutoLowLatencyMode(PhysicalDisplayId, bool) override;
+    status_t getSupportedContentTypes(PhysicalDisplayId, std::vector<hal::ContentType>*) override;
+    status_t setContentType(PhysicalDisplayId, hal::ContentType) override;
 
     const std::unordered_map<std::string, bool>& getSupportedLayerGenericMetadata() const override;
 
@@ -385,7 +387,7 @@
         nsecs_t lastHwVsync GUARDED_BY(lastHwVsyncLock) = 0;
     };
 
-    std::unordered_map<DisplayId, DisplayData> mDisplayData;
+    std::unordered_map<HalDisplayId, DisplayData> mDisplayData;
 
     std::unique_ptr<android::Hwc2::Composer> mComposer;
     std::unordered_set<hal::Capability> mCapabilities;
@@ -397,9 +399,7 @@
     std::optional<hal::HWDisplayId> mExternalHwcDisplayId;
     bool mHasMultiDisplaySupport = false;
 
-    std::unordered_set<DisplayId> mFreeVirtualDisplayIds;
-    uint32_t mNextVirtualDisplayId = 0;
-    uint32_t mRemainingHwcVirtualDisplays{getMaxVirtualDisplayCount()};
+    RandomDisplayIdGenerator<HalVirtualDisplayId> mVirtualIdGenerator{getMaxVirtualDisplayCount()};
 };
 
 } // namespace impl
diff --git a/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.cpp b/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.cpp
index fba3261..247ee23 100644
--- a/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.cpp
+++ b/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.cpp
@@ -57,8 +57,7 @@
     }
 }
 
-VirtualDisplaySurface::VirtualDisplaySurface(HWComposer& hwc,
-                                             const std::optional<DisplayId>& displayId,
+VirtualDisplaySurface::VirtualDisplaySurface(HWComposer& hwc, VirtualDisplayId displayId,
                                              const sp<IGraphicBufferProducer>& sink,
                                              const sp<IGraphicBufferProducer>& bqProducer,
                                              const sp<IGraphicBufferConsumer>& bqConsumer,
@@ -125,7 +124,7 @@
 }
 
 status_t VirtualDisplaySurface::beginFrame(bool mustRecompose) {
-    if (!mDisplayId) {
+    if (GpuVirtualDisplayId::tryCast(mDisplayId)) {
         return NO_ERROR;
     }
 
@@ -139,7 +138,7 @@
 }
 
 status_t VirtualDisplaySurface::prepareFrame(CompositionType compositionType) {
-    if (!mDisplayId) {
+    if (GpuVirtualDisplayId::tryCast(mDisplayId)) {
         return NO_ERROR;
     }
 
@@ -187,7 +186,7 @@
 }
 
 status_t VirtualDisplaySurface::advanceFrame() {
-    if (!mDisplayId) {
+    if (GpuVirtualDisplayId::tryCast(mDisplayId)) {
         return NO_ERROR;
     }
 
@@ -219,9 +218,11 @@
             mFbProducerSlot, fbBuffer.get(),
             mOutputProducerSlot, outBuffer.get());
 
+    const auto halDisplayId = HalVirtualDisplayId::tryCast(mDisplayId);
+    LOG_FATAL_IF(!halDisplayId);
     // At this point we know the output buffer acquire fence,
     // so update HWC state with it.
-    mHwc.setOutputBuffer(*mDisplayId, mOutputFence, outBuffer);
+    mHwc.setOutputBuffer(*halDisplayId, mOutputFence, outBuffer);
 
     status_t result = NO_ERROR;
     if (fbBuffer != nullptr) {
@@ -230,7 +231,7 @@
         mHwcBufferCache.getHwcBuffer(mFbProducerSlot, fbBuffer, &hwcSlot, &hwcBuffer);
 
         // TODO: Correctly propagate the dataspace from GL composition
-        result = mHwc.setClientTarget(*mDisplayId, hwcSlot, mFbFence, hwcBuffer,
+        result = mHwc.setClientTarget(*halDisplayId, hwcSlot, mFbFence, hwcBuffer,
                                       ui::Dataspace::UNKNOWN);
     }
 
@@ -238,7 +239,8 @@
 }
 
 void VirtualDisplaySurface::onFrameCommitted() {
-    if (!mDisplayId) {
+    const auto halDisplayId = HalVirtualDisplayId::tryCast(mDisplayId);
+    if (!halDisplayId) {
         return;
     }
 
@@ -246,7 +248,7 @@
             "Unexpected onFrameCommitted() in %s state", dbgStateStr());
     mDbgState = DBG_STATE_IDLE;
 
-    sp<Fence> retireFence = mHwc.getPresentFence(*mDisplayId);
+    sp<Fence> retireFence = mHwc.getPresentFence(*halDisplayId);
     if (mCompositionType == COMPOSITION_MIXED && mFbProducerSlot >= 0) {
         // release the scratch buffer back to the pool
         Mutex::Autolock lock(mMutex);
@@ -301,7 +303,7 @@
 
 status_t VirtualDisplaySurface::requestBuffer(int pslot,
         sp<GraphicBuffer>* outBuf) {
-    if (!mDisplayId) {
+    if (GpuVirtualDisplayId::tryCast(mDisplayId)) {
         return mSource[SOURCE_SINK]->requestBuffer(pslot, outBuf);
     }
 
@@ -323,7 +325,7 @@
 
 status_t VirtualDisplaySurface::dequeueBuffer(Source source,
         PixelFormat format, uint64_t usage, int* sslot, sp<Fence>* fence) {
-    LOG_FATAL_IF(!mDisplayId);
+    LOG_FATAL_IF(GpuVirtualDisplayId::tryCast(mDisplayId));
 
     status_t result =
             mSource[source]->dequeueBuffer(sslot, fence, mSinkBufferWidth, mSinkBufferHeight,
@@ -369,7 +371,7 @@
                                               PixelFormat format, uint64_t usage,
                                               uint64_t* outBufferAge,
                                               FrameEventHistoryDelta* outTimestamps) {
-    if (!mDisplayId) {
+    if (GpuVirtualDisplayId::tryCast(mDisplayId)) {
         return mSource[SOURCE_SINK]->dequeueBuffer(pslot, fence, w, h, format, usage, outBufferAge,
                                                    outTimestamps);
     }
@@ -456,7 +458,7 @@
 
 status_t VirtualDisplaySurface::queueBuffer(int pslot,
         const QueueBufferInput& input, QueueBufferOutput* output) {
-    if (!mDisplayId) {
+    if (GpuVirtualDisplayId::tryCast(mDisplayId)) {
         return mSource[SOURCE_SINK]->queueBuffer(pslot, input, output);
     }
 
@@ -514,7 +516,7 @@
 
 status_t VirtualDisplaySurface::cancelBuffer(int pslot,
         const sp<Fence>& fence) {
-    if (!mDisplayId) {
+    if (GpuVirtualDisplayId::tryCast(mDisplayId)) {
         return mSource[SOURCE_SINK]->cancelBuffer(mapProducer2SourceSlot(SOURCE_SINK, pslot), fence);
     }
 
@@ -626,7 +628,7 @@
 }
 
 status_t VirtualDisplaySurface::refreshOutputBuffer() {
-    LOG_FATAL_IF(!mDisplayId);
+    LOG_FATAL_IF(GpuVirtualDisplayId::tryCast(mDisplayId));
 
     if (mOutputProducerSlot >= 0) {
         mSource[SOURCE_SINK]->cancelBuffer(
@@ -645,7 +647,9 @@
     // until after GPU calls queueBuffer(). So here we just set the buffer
     // (for use in HWC prepare) but not the fence; we'll call this again with
     // the proper fence once we have it.
-    result = mHwc.setOutputBuffer(*mDisplayId, Fence::NO_FENCE,
+    const auto halDisplayId = HalVirtualDisplayId::tryCast(mDisplayId);
+    LOG_FATAL_IF(!halDisplayId);
+    result = mHwc.setOutputBuffer(*halDisplayId, Fence::NO_FENCE,
                                   mProducerBuffers[mOutputProducerSlot]);
 
     return result;
diff --git a/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.h b/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.h
index 3cbad8f..1974625 100644
--- a/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.h
+++ b/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.h
@@ -24,6 +24,7 @@
 #include <compositionengine/impl/HwcBufferCache.h>
 #include <gui/ConsumerBase.h>
 #include <gui/IGraphicBufferProducer.h>
+#include <ui/DisplayId.h>
 
 #include "DisplayIdentification.h"
 
@@ -77,8 +78,7 @@
                               public BnGraphicBufferProducer,
                               private ConsumerBase {
 public:
-    VirtualDisplaySurface(HWComposer& hwc, const std::optional<DisplayId>& displayId,
-                          const sp<IGraphicBufferProducer>& sink,
+    VirtualDisplaySurface(HWComposer&, VirtualDisplayId, const sp<IGraphicBufferProducer>& sink,
                           const sp<IGraphicBufferProducer>& bqProducer,
                           const sp<IGraphicBufferConsumer>& bqConsumer, const std::string& name);
 
@@ -86,7 +86,7 @@
     // DisplaySurface interface
     //
     virtual status_t beginFrame(bool mustRecompose);
-    virtual status_t prepareFrame(CompositionType compositionType);
+    virtual status_t prepareFrame(CompositionType);
     virtual status_t advanceFrame();
     virtual void onFrameCommitted();
     virtual void dumpAsString(String8& result) const;
@@ -104,25 +104,22 @@
     virtual status_t requestBuffer(int pslot, sp<GraphicBuffer>* outBuf);
     virtual status_t setMaxDequeuedBufferCount(int maxDequeuedBuffers);
     virtual status_t setAsyncMode(bool async);
-    virtual status_t dequeueBuffer(int* pslot, sp<Fence>* fence, uint32_t w, uint32_t h,
-                                   PixelFormat format, uint64_t usage, uint64_t* outBufferAge,
+    virtual status_t dequeueBuffer(int* pslot, sp<Fence>*, uint32_t w, uint32_t h, PixelFormat,
+                                   uint64_t usage, uint64_t* outBufferAge,
                                    FrameEventHistoryDelta* outTimestamps);
     virtual status_t detachBuffer(int slot);
-    virtual status_t detachNextBuffer(sp<GraphicBuffer>* outBuffer,
-            sp<Fence>* outFence);
-    virtual status_t attachBuffer(int* slot, const sp<GraphicBuffer>& buffer);
-    virtual status_t queueBuffer(int pslot,
-            const QueueBufferInput& input, QueueBufferOutput* output);
-    virtual status_t cancelBuffer(int pslot, const sp<Fence>& fence);
+    virtual status_t detachNextBuffer(sp<GraphicBuffer>* outBuffer, sp<Fence>* outFence);
+    virtual status_t attachBuffer(int* slot, const sp<GraphicBuffer>&);
+    virtual status_t queueBuffer(int pslot, const QueueBufferInput&, QueueBufferOutput*);
+    virtual status_t cancelBuffer(int pslot, const sp<Fence>&);
     virtual int query(int what, int* value);
-    virtual status_t connect(const sp<IProducerListener>& listener,
-            int api, bool producerControlledByApp, QueueBufferOutput* output);
-    virtual status_t disconnect(int api, DisconnectMode mode);
+    virtual status_t connect(const sp<IProducerListener>&, int api, bool producerControlledByApp,
+                             QueueBufferOutput*);
+    virtual status_t disconnect(int api, DisconnectMode);
     virtual status_t setSidebandStream(const sp<NativeHandle>& stream);
-    virtual void allocateBuffers(uint32_t width, uint32_t height,
-            PixelFormat format, uint64_t usage);
+    virtual void allocateBuffers(uint32_t width, uint32_t height, PixelFormat, uint64_t usage);
     virtual status_t allowAllocation(bool allow);
-    virtual status_t setGenerationNumber(uint32_t generationNumber);
+    virtual status_t setGenerationNumber(uint32_t);
     virtual String8 getConsumerName() const override;
     virtual status_t setSharedBufferMode(bool sharedBufferMode) override;
     virtual status_t setAutoRefresh(bool autoRefresh) override;
@@ -135,10 +132,9 @@
     //
     // Utility methods
     //
-    static Source fbSourceForCompositionType(CompositionType type);
-    status_t dequeueBuffer(Source source, PixelFormat format, uint64_t usage,
-            int* sslot, sp<Fence>* fence);
-    void updateQueueBufferOutput(QueueBufferOutput&& qbo);
+    static Source fbSourceForCompositionType(CompositionType);
+    status_t dequeueBuffer(Source, PixelFormat, uint64_t usage, int* sslot, sp<Fence>*);
+    void updateQueueBufferOutput(QueueBufferOutput&&);
     void resetPerFrameState();
     status_t refreshOutputBuffer();
 
@@ -148,14 +144,14 @@
     // internally in the VirtualDisplaySurface. To minimize the number of times
     // a producer slot switches which source it comes from, we map source slot
     // numbers to producer slot numbers differently for each source.
-    static int mapSource2ProducerSlot(Source source, int sslot);
-    static int mapProducer2SourceSlot(Source source, int pslot);
+    static int mapSource2ProducerSlot(Source, int sslot);
+    static int mapProducer2SourceSlot(Source, int pslot);
 
     //
     // Immutable after construction
     //
     HWComposer& mHwc;
-    const std::optional<DisplayId> mDisplayId;
+    const VirtualDisplayId mDisplayId;
     const std::string mDisplayName;
     sp<IGraphicBufferProducer> mSource[2]; // indexed by SOURCE_*
     uint32_t mDefaultOutputFormat;