diff --git a/compatibility_matrices/Android.mk b/compatibility_matrices/Android.mk
index d24d8e9..dd7165d 100644
--- a/compatibility_matrices/Android.mk
+++ b/compatibility_matrices/Android.mk
@@ -21,8 +21,9 @@
 # Clear potential input variables to BUILD_FRAMEWORK_COMPATIBILITY_MATRIX
 LOCAL_ADD_VBMETA_VERSION :=
 LOCAL_ASSEMBLE_VINTF_ENV_VARS :=
+LOCAL_ASSEMBLE_VINTF_ENV_VARS_OVERRIDE :=
+LOCAL_ASSEMBLE_VINTF_ERROR_MESSAGE :=
 LOCAL_ASSEMBLE_VINTF_FLAGS :=
-LOCAL_WARN_REQUIRED_HALS :=
 LOCAL_KERNEL_VERSIONS :=
 LOCAL_GEN_FILE_DEPENDENCIES :=
 
@@ -99,7 +100,8 @@
     PLATFORM_SEPOLICY_VERSION \
     PLATFORM_SEPOLICY_COMPAT_VERSIONS
 
-LOCAL_WARN_REQUIRED_HALS := \
+LOCAL_ASSEMBLE_VINTF_ENV_VARS_OVERRIDE := PRODUCT_ENFORCE_VINTF_MANIFEST=true
+LOCAL_ASSEMBLE_VINTF_ERROR_MESSAGE := \
     "Error: DEVICE_FRAMEWORK_COMPATIBILITY_MATRIX cannot contain required HALs."
 
 include $(BUILD_FRAMEWORK_COMPATIBILITY_MATRIX)
diff --git a/compatibility_matrices/compatibility_matrix.mk b/compatibility_matrices/compatibility_matrix.mk
index 2d6c5d0..6dc2b4f 100644
--- a/compatibility_matrices/compatibility_matrix.mk
+++ b/compatibility_matrices/compatibility_matrix.mk
@@ -25,6 +25,27 @@
 
 # $(warning $(call remove-minor-revision,3.18.0))
 
+##### Input Variables:
+# LOCAL_MODULE: required. Module name for the build system.
+# LOCAL_MODULE_CLASS: optional. Default is ETC.
+# LOCAL_MODULE_PATH: optional. Path of output file. Default is $(TARGET_OUT)/etc/vintf.
+# LOCAL_MODULE_STEM: optional. Name of output file. Default is $(LOCAL_MODULE).
+# LOCAL_SRC_FILES: required. Local source files provided to assemble_vintf
+#       (command line argument -i).
+# LOCAL_GENERATED_SOURCES: optional. Global source files provided to assemble_vintf
+#       (command line argument -i).
+#
+# LOCAL_ADD_VBMETA_VERSION: Use AVBTOOL to add avb version to the output matrix
+#       (corresponds to <avb><vbmeta-version> tag)
+# LOCAL_ASSEMBLE_VINTF_ENV_VARS: Add a list of environment variable names from global variables in
+#       the build system that is lazily evaluated (e.g. PRODUCT_ENFORCE_VINTF_MANIFEST).
+# LOCAL_ASSEMBLE_VINTF_ENV_VARS_OVERRIDE: Add a list of environment variables that is local to
+#       assemble_vintf invocation. Format is "VINTF_ENFORCE_NO_UNUSED_HALS=true".
+# LOCAL_ASSEMBLE_VINTF_FLAGS: Add additional command line arguments to assemble_vintf invocation.
+# LOCAL_KERNEL_VERSIONS: Parse kernel configurations and add to the output matrix
+#       (corresponds to <kernel> tags.)
+# LOCAL_GEN_FILE_DEPENDENCIES: A list of additional dependencies for the generated file.
+
 ifndef LOCAL_MODULE
 $(error LOCAL_MODULE must be defined.)
 endif
@@ -81,13 +102,17 @@
 	$(addprefix $(LOCAL_PATH)/,$(LOCAL_SRC_FILES)) \
 	$(LOCAL_GENERATED_SOURCES)
 
-ifneq (,$(strip $(LOCAL_WARN_REQUIRED_HALS)))
-$(GEN): PRIVATE_ADDITIONAL_ENV_VARS += PRODUCT_ENFORCE_VINTF_MANIFEST=true
-$(GEN): PRIVATE_COMMAND_TAIL := || (echo $(strip $(LOCAL_WARN_REQUIRED_HALS)) && false)
+$(GEN): PRIVATE_ADDITIONAL_ENV_VARS := $(LOCAL_ASSEMBLE_VINTF_ENV_VARS_OVERRIDE)
+
+ifneq (,$(strip $(LOCAL_ASSEMBLE_VINTF_ERROR_MESSAGE)))
+$(GEN): PRIVATE_COMMAND_TAIL := || (echo $(strip $(LOCAL_ASSEMBLE_VINTF_ERROR_MESSAGE)) && false)
 endif
 
 $(GEN): PRIVATE_SRC_FILES := $(my_matrix_src_files)
 $(GEN): $(my_matrix_src_files) $(HOST_OUT_EXECUTABLES)/assemble_vintf
+	$(foreach varname,$(PRIVATE_ENV_VARS),\
+		$(if $(findstring $(varname),$(PRIVATE_ADDITIONAL_ENV_VARS)),\
+			$(error $(varname) should not be overridden by LOCAL_ASSEMBLE_VINTF_ENV_VARS_OVERRIDE.)))
 	$(foreach varname,$(PRIVATE_ENV_VARS),$(varname)="$($(varname))") \
 		$(PRIVATE_ADDITIONAL_ENV_VARS) \
 		$(HOST_OUT_EXECUTABLES)/assemble_vintf \
@@ -101,8 +126,9 @@
 
 LOCAL_ADD_VBMETA_VERSION :=
 LOCAL_ASSEMBLE_VINTF_ENV_VARS :=
+LOCAL_ASSEMBLE_VINTF_ENV_VARS_OVERRIDE :=
+LOCAL_ASSEMBLE_VINTF_ERROR_MESSAGE :=
 LOCAL_ASSEMBLE_VINTF_FLAGS :=
-LOCAL_WARN_REQUIRED_HALS :=
 LOCAL_KERNEL_VERSIONS :=
 LOCAL_GEN_FILE_DEPENDENCIES :=
 my_matrix_src_files :=