kconfig: support simply expanded variable

The previous commit added variable and user-defined function.  They
work similarly in the sense that the evaluation is deferred until
they are used.

This commit adds another type of variable, simply expanded variable,
as we see in Make.

The := operator defines a simply expanded variable, expanding the
righthand side immediately.  This works like traditional programming
language variables.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

4 files changed, 27 insertions, 7 deletions

diff --git a/scripts/kconfig/lkc_proto.h b/scripts/kconfig/lkc_proto.h
index 2b16d6e1b2dbd..6303193f43f21 100644
--- a/scripts/kconfig/lkc_proto.h
+++ b/scripts/kconfig/lkc_proto.h
@@ -49,8 +49,13 @@ const char * sym_get_string_value(struct symbol *sym);
 const char * prop_get_type_name(enum prop_type type);
 
 /* preprocess.c */
+enum variable_flavor {
+	VAR_SIMPLE,
+	VAR_RECURSIVE,
+};
 void env_write_dep(FILE *f, const char *auto_conf_name);
-void variable_add(const char *name, const char *value);
+void variable_add(const char *name, const char *value,
+		  enum variable_flavor flavor);
 void variable_all_del(void);
 char *expand_string(const char *in);
 char *expand_dollar(const char **str);
diff --git a/scripts/kconfig/preprocess.c b/scripts/kconfig/preprocess.c
index 46487fe6b36cd..d103683b386ed 100644
--- a/scripts/kconfig/preprocess.c
+++ b/scripts/kconfig/preprocess.c
@@ -185,6 +185,7 @@ static LIST_HEAD(variable_list);
 struct variable {
 	char *name;
 	char *value;
+	enum variable_flavor flavor;
 	struct list_head node;
 };
 
@@ -203,15 +204,22 @@ static struct variable *variable_lookup(const char *name)
 static char *variable_expand(const char *name, int argc, char *argv[])
 {
 	struct variable *v;
+	char *res;
 
 	v = variable_lookup(name);
 	if (!v)
 		return NULL;
 
-	return expand_string_with_args(v->value, argc, argv);
+	if (v->flavor == VAR_RECURSIVE)
+		res = expand_string_with_args(v->value, argc, argv);
+	else
+		res = xstrdup(v->value);
+
+	return res;
 }
 
-void variable_add(const char *name, const char *value)
+void variable_add(const char *name, const char *value,
+		  enum variable_flavor flavor)
 {
 	struct variable *v;
 
@@ -224,7 +232,12 @@ void variable_add(const char *name, const char *value)
 		list_add_tail(&v->node, &variable_list);
 	}
 
-	v->value = xstrdup(value);
+	v->flavor = flavor;
+
+	if (flavor == VAR_SIMPLE)
+		v->value = expand_string(value);
+	else
+		v->value = xstrdup(value);
 }
 
 static void variable_del(struct variable *v)
diff --git a/scripts/kconfig/zconf.l b/scripts/kconfig/zconf.l
index dd08f7a38ccd2..376af6cf2f65e 100644
--- a/scripts/kconfig/zconf.l
+++ b/scripts/kconfig/zconf.l
@@ -114,7 +114,8 @@ n	[A-Za-z0-9_-]
 		yylval.string = text;
 		return T_VARIABLE;
 	}
-	"="	{ BEGIN(ASSIGN_VAL); return T_ASSIGN; }
+	"="	{ BEGIN(ASSIGN_VAL); yylval.flavor = VAR_RECURSIVE; return T_ASSIGN; }
+	":="	{ BEGIN(ASSIGN_VAL); yylval.flavor = VAR_SIMPLE; return T_ASSIGN; }
 	[[:blank:]]+
 	.	warn_ignored_character(*yytext);
 	\n	{
diff --git a/scripts/kconfig/zconf.y b/scripts/kconfig/zconf.y
index e15e8c7063e04..6f9b0aa32a822 100644
--- a/scripts/kconfig/zconf.y
+++ b/scripts/kconfig/zconf.y
@@ -41,6 +41,7 @@ static struct menu *current_menu, *current_entry;
 	struct expr *expr;
 	struct menu *menu;
 	const struct kconf_id *id;
+	enum variable_flavor flavor;
 }
 
 %token <id>T_MAINMENU
@@ -78,7 +79,7 @@ static struct menu *current_menu, *current_entry;
 %token T_OPEN_PAREN
 %token T_EOL
 %token <string> T_VARIABLE
-%token T_ASSIGN
+%token <flavor> T_ASSIGN
 %token <string> T_ASSIGN_VAL
 
 %left T_OR
@@ -517,7 +518,7 @@ word_opt: /* empty */			{ $$ = NULL; }
 
 /* assignment statement */
 
-assignment_stmt:  T_VARIABLE T_ASSIGN assign_val T_EOL	{ variable_add($1, $3); free($1); free($3); }
+assignment_stmt:  T_VARIABLE T_ASSIGN assign_val T_EOL	{ variable_add($1, $3, $2); free($1); free($3); }
 
 assign_val:
 	/* empty */		{ $$ = xstrdup(""); };