diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index aab8331..04fee50 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -637,6 +637,17 @@
     return displayIds;
 }
 
+status_t SurfaceFlinger::getPrimaryPhysicalDisplayId(PhysicalDisplayId* id) const {
+    Mutex::Autolock lock(mStateLock);
+    const auto display = getInternalDisplayIdLocked();
+    if (!display) {
+        return NAME_NOT_FOUND;
+    }
+
+    *id = *display;
+    return NO_ERROR;
+}
+
 sp<IBinder> SurfaceFlinger::getPhysicalDisplayToken(PhysicalDisplayId displayId) const {
     Mutex::Autolock lock(mStateLock);
     return getPhysicalDisplayTokenLocked(displayId);
@@ -5242,6 +5253,7 @@
         case REMOVE_TUNNEL_MODE_ENABLED_LISTENER:
         case NOTIFY_POWER_BOOST:
         case SET_GLOBAL_SHADOW_SETTINGS:
+        case GET_PRIMARY_PHYSICAL_DISPLAY_ID:
         case ACQUIRE_FRAME_RATE_FLEXIBILITY_TOKEN: {
             // ACQUIRE_FRAME_RATE_FLEXIBILITY_TOKEN and OVERRIDE_HDR_TYPES are used by CTS tests,
             // which acquire the necessary permission dynamically. Don't use the permission cache
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index ace806f..89c1d50 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -611,6 +611,8 @@
         Mutex::Autolock lock(mStateLock);
         return getPhysicalDisplayIdsLocked();
     }
+    status_t getPrimaryPhysicalDisplayId(PhysicalDisplayId*) const override EXCLUDES(mStateLock);
+
     sp<IBinder> getPhysicalDisplayToken(PhysicalDisplayId displayId) const override;
     status_t setTransactionState(const FrameTimelineInfo& frameTimelineInfo,
                                  const Vector<ComposerState>& state,
diff --git a/services/surfaceflinger/SurfaceFlingerProperties.cpp b/services/surfaceflinger/SurfaceFlingerProperties.cpp
index 4a69c8f..e15eae8 100644
--- a/services/surfaceflinger/SurfaceFlingerProperties.cpp
+++ b/services/surfaceflinger/SurfaceFlingerProperties.cpp
@@ -34,6 +34,8 @@
 using android::hardware::graphics::common::V1_2::PixelFormat;
 using android::ui::DisplayPrimaries;
 
+// Keep logic in sync with WindowManagerService functions that query SurfaceFlinger properties.
+// Consider exposing properties via ISurfaceComposer instead.
 int64_t vsync_event_phase_offset_ns(int64_t defaultValue) {
     auto temp = SurfaceFlingerProperties::vsync_event_phase_offset_ns();
     if (temp.has_value()) {