1 files changed, 76 insertions, 0 deletions

diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
index 583f6405f01d..f81f263b64f2 100644
--- a/scripts/kconfig/confdata.c
+++ b/scripts/kconfig/confdata.c
@@ -457,6 +457,82 @@ static void conf_write_symbol(struct symbol *sym, enum symbol_type type,
         }
 }
 
+/*
+ * Write out a minimal config.
+ * All values that has default values are skipped as this is redundant.
+ */
+int conf_write_defconfig(const char *filename)
+{
+        struct symbol *sym;
+        struct menu *menu;
+        FILE *out;
+
+        out = fopen(filename, "w");
+        if (!out)
+                return 1;
+
+        sym_clear_all_valid();
+
+        /* Traverse all menus to find all relevant symbols */
+        menu = rootmenu.list;
+
+        while (menu != NULL)
+        {
+                sym = menu->sym;
+                if (sym == NULL) {
+                        if (!menu_is_visible(menu))
+                                goto next_menu;
+                } else if (!sym_is_choice(sym)) {
+                        sym_calc_value(sym);
+                        if (!(sym->flags & SYMBOL_WRITE))
+                                goto next_menu;
+                        sym->flags &= ~SYMBOL_WRITE;
+                        /* If we cannot change the symbol - skip */
+                        if (!sym_is_changable(sym))
+                                goto next_menu;
+                        /* If symbol equals to default value - skip */
+                        if (strcmp(sym_get_string_value(sym), sym_get_string_default(sym)) == 0)
+                                goto next_menu;
+
+                        /*
+                         * If symbol is a choice value and equals to the
+                         * default for a choice - skip.
+                         * But only if value equal to "y".
+                         */
+                        if (sym_is_choice_value(sym)) {
+                                struct symbol *cs;
+                                struct symbol *ds;
+
+                                cs = prop_get_symbol(sym_get_choice_prop(sym));
+                                ds = sym_choice_default(cs);
+                                if (sym == ds) {
+                                        if ((sym->type == S_BOOLEAN ||
+                                        sym->type == S_TRISTATE) &&
+                                        sym_get_tristate_value(sym) == yes)
+                                                goto next_menu;
+                                }
+                        }
+                        conf_write_symbol(sym, sym->type, out, true);
+                }
+next_menu:
+                if (menu->list != NULL) {
+                        menu = menu->list;
+                }
+                else if (menu->next != NULL) {
+                        menu = menu->next;
+                } else {
+                        while ((menu = menu->parent)) {
+                                if (menu->next != NULL) {
+                                        menu = menu->next;
+                                        break;
+                                }
+                        }
+                }
+        }
+        fclose(out);
+        return 0;
+}
+
 int conf_write(const char *name)
 {
         FILE *out;