kconfig: support append assignment operator

Support += operator.  This appends a space and the text on the
righthand side to a variable.

The timing of the evaluation of the righthand side depends on the
flavor of the variable.  If the lefthand side was originally defined
as a simple variable, the righthand side is expanded immediately.
Otherwise, the expansion is deferred.  Appending something to an
undefined variable results in a recursive variable.

To implement this, we need to remember the flavor of variables.

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

3 files changed, 27 insertions, 3 deletions

diff --git a/scripts/kconfig/lkc_proto.h b/scripts/kconfig/lkc_proto.h
index 6303193f43f2..a8b7a330587e 100644
--- a/scripts/kconfig/lkc_proto.h
+++ b/scripts/kconfig/lkc_proto.h
@@ -52,6 +52,7 @@ const char * prop_get_type_name(enum prop_type type);
 enum variable_flavor {
         VAR_SIMPLE,
         VAR_RECURSIVE,
+        VAR_APPEND,
 };
 void env_write_dep(FILE *f, const char *auto_conf_name);
 void variable_add(const char *name, const char *value,
diff --git a/scripts/kconfig/preprocess.c b/scripts/kconfig/preprocess.c
index d103683b386e..56aa1f0bad04 100644
--- a/scripts/kconfig/preprocess.c
+++ b/scripts/kconfig/preprocess.c
@@ -222,11 +222,23 @@ void variable_add(const char *name, const char *value,
                   enum variable_flavor flavor)
 {
         struct variable *v;
+        char *new_value;
+        bool append = false;
 
         v = variable_lookup(name);
         if (v) {
-                free(v->value);
+                /* For defined variables, += inherits the existing flavor */
+                if (flavor == VAR_APPEND) {
+                        flavor = v->flavor;
+                        append = true;
+                } else {
+                        free(v->value);
+                }
         } else {
+                /* For undefined variables, += assumes the recursive flavor */
+                if (flavor == VAR_APPEND)
+                        flavor = VAR_RECURSIVE;
+
                 v = xmalloc(sizeof(*v));
                 v->name = xstrdup(name);
                 list_add_tail(&v->node, &variable_list);
@@ -235,9 +247,19 @@ void variable_add(const char *name, const char *value,
         v->flavor = flavor;
 
         if (flavor == VAR_SIMPLE)
-                v->value = expand_string(value);
+                new_value = expand_string(value);
         else
-                v->value = xstrdup(value);
+                new_value = xstrdup(value);
+
+        if (append) {
+                v->value = xrealloc(v->value,
+                                    strlen(v->value) + strlen(new_value) + 2);
+                strcat(v->value, " ");
+                strcat(v->value, new_value);
+                free(new_value);
+        } else {
+                v->value = new_value;
+        }
 }
 
 static void variable_del(struct variable *v)
diff --git a/scripts/kconfig/zconf.l b/scripts/kconfig/zconf.l
index 376af6cf2f65..a6cbe2d06d01 100644
--- a/scripts/kconfig/zconf.l
+++ b/scripts/kconfig/zconf.l
@@ -116,6 +116,7 @@ n	[A-Za-z0-9_-]
         }
         "="     { BEGIN(ASSIGN_VAL); yylval.flavor = VAR_RECURSIVE; return T_ASSIGN; }
         ":="    { BEGIN(ASSIGN_VAL); yylval.flavor = VAR_SIMPLE; return T_ASSIGN; }
+        "+="    { BEGIN(ASSIGN_VAL); yylval.flavor = VAR_APPEND; return T_ASSIGN; }
         [[:blank:]]+
         .       warn_ignored_character(*yytext);
         \n      {