SF: Add a readonly flag for the hotplug2 hal api feature

Bug: 303460805
Test: adb shell dumpsys SurfaceFlinger | grep hotplug2 -- verify the
flag shows up.

Change-Id: I9abdbec32e8517d82234c2a52d4586d4e6ed12b8
diff --git a/services/surfaceflinger/FlagManager.cpp b/services/surfaceflinger/FlagManager.cpp
index a8f05bb..5bbdfe9 100644
--- a/services/surfaceflinger/FlagManager.cpp
+++ b/services/surfaceflinger/FlagManager.cpp
@@ -102,6 +102,7 @@
     DUMP_FLAG(misc1);
     DUMP_FLAG(late_boot_misc2);
     DUMP_FLAG(vrr_config);
+    DUMP_FLAG(hotplug2);
 
 #undef DUMP_FLAG
 }
@@ -165,6 +166,7 @@
 FLAG_MANAGER_READ_ONLY_FLAG(enable_small_area_detection, "")
 FLAG_MANAGER_READ_ONLY_FLAG(misc1, "")
 FLAG_MANAGER_READ_ONLY_FLAG(vrr_config, "debug.sf.enable_vrr_config")
+FLAG_MANAGER_READ_ONLY_FLAG(hotplug2, "")
 
 /// Trunk stable server flags ///
 FLAG_MANAGER_SERVER_FLAG(late_boot_misc2, "")
diff --git a/services/surfaceflinger/FlagManager.h b/services/surfaceflinger/FlagManager.h
index 5a353bb..9f83b1f 100644
--- a/services/surfaceflinger/FlagManager.h
+++ b/services/surfaceflinger/FlagManager.h
@@ -51,6 +51,7 @@
     bool enable_small_area_detection() const;
     bool misc1() const;
     bool vrr_config() const;
+    bool hotplug2() const;
 
     /// Trunk stable server flags ///
     bool late_boot_misc2() const;
diff --git a/services/surfaceflinger/surfaceflinger_flags.aconfig b/services/surfaceflinger/surfaceflinger_flags.aconfig
index 19d194f..fec450e 100644
--- a/services/surfaceflinger/surfaceflinger_flags.aconfig
+++ b/services/surfaceflinger/surfaceflinger_flags.aconfig
@@ -52,4 +52,12 @@
   description: "Feature flag for SmallAreaDetection"
   bug: "283055450"
   is_fixed_read_only: true
-}
\ No newline at end of file
+}
+
+flag {
+  name: "hotplug2"
+  namespace: "core_graphics"
+  description: "Feature flag for using hotplug2 HAL API"
+  bug: "303460805"
+  is_fixed_read_only: true
+}