diff --git a/drivers/firewire/device-attribute-test.c b/drivers/firewire/device-attribute-test.c
index 97478a96d1c9..2c482afca8f1 100644
--- a/drivers/firewire/device-attribute-test.c
+++ b/drivers/firewire/device-attribute-test.c
@@ -86,7 +86,7 @@ static void device_attr_simple_avc(struct kunit *test)
 			.type = &fw_device_type,
 		},
 		.config_rom = simple_avc_config_rom,
-		.config_rom_length = sizeof(simple_avc_config_rom),
+		.config_rom_length = ARRAY_SIZE(simple_avc_config_rom),
 	};
 	static const struct fw_unit unit0 = {
 		.device = {
@@ -168,7 +168,7 @@ static void device_attr_legacy_avc(struct kunit *test)
 			.type = &fw_device_type,
 		},
 		.config_rom = legacy_avc_config_rom,
-		.config_rom_length = sizeof(legacy_avc_config_rom),
+		.config_rom_length = ARRAY_SIZE(legacy_avc_config_rom),
 	};
 	static const struct fw_unit unit0 = {
 		.device = {
diff --git a/include/linux/firewire.h b/include/linux/firewire.h
index 9d5a42724f1a..dbb5c825a1cc 100644
--- a/include/linux/firewire.h
+++ b/include/linux/firewire.h
@@ -224,7 +224,7 @@ struct fw_device {
 	struct mutex client_list_mutex;
 	struct list_head client_list;
 
-	const u32 *config_rom;
+	const u32 *config_rom __counted_by_ptr(config_rom_length);
 	size_t config_rom_length;
 	int config_rom_retries;
 	unsigned is_local:1;