kconfig: add an option to determine a menu's visibility

This option is aimed to add the possibility to control a menu's visibility
without adding dependency to the expression to all the submenu.

Signed-off-by: Arnaud Lacombe <lacombar@gmail.com>
Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/scripts/kconfig/zconf.y b/scripts/kconfig/zconf.y
index 2abd3c7..49fb4ab 100644
--- a/scripts/kconfig/zconf.y
+++ b/scripts/kconfig/zconf.y
@@ -36,7 +36,7 @@
 #define YYERROR_VERBOSE
 #endif
 %}
-%expect 28
+%expect 30
 
 %union
 {
@@ -68,6 +68,7 @@
 %token <id>T_DEFAULT
 %token <id>T_SELECT
 %token <id>T_RANGE
+%token <id>T_VISIBLE
 %token <id>T_OPTION
 %token <id>T_ON
 %token <string> T_WORD
@@ -123,7 +124,7 @@
 ;
 
 option_name:
-	T_DEPENDS | T_PROMPT | T_TYPE | T_SELECT | T_OPTIONAL | T_RANGE | T_DEFAULT
+	T_DEPENDS | T_PROMPT | T_TYPE | T_SELECT | T_OPTIONAL | T_RANGE | T_DEFAULT | T_VISIBLE
 ;
 
 common_stmt:
@@ -359,7 +360,7 @@
 	printd(DEBUG_PARSE, "%s:%d:menu\n", zconf_curname(), zconf_lineno());
 };
 
-menu_entry: menu depends_list
+menu_entry: menu visibility_list depends_list
 {
 	$$ = menu_add_menu();
 };
@@ -430,6 +431,19 @@
 	printd(DEBUG_PARSE, "%s:%d:depends on\n", zconf_curname(), zconf_lineno());
 };
 
+/* visibility option */
+
+visibility_list:
+	  /* empty */
+	| visibility_list visible
+	| visibility_list T_EOL
+;
+
+visible: T_VISIBLE if_expr
+{
+	menu_add_visibility($2);
+};
+
 /* prompt statement */
 
 prompt_stmt_opt:
@@ -526,6 +540,7 @@
 	case T_IF:		return "if";
 	case T_ENDIF:		return "endif";
 	case T_DEPENDS:		return "depends";
+	case T_VISIBLE:		return "visible";
 	}
 	return "<token>";
 }