6 files changed, 171 insertions, 1 deletions

diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
index 72973591c0f1..c0e459e2b014 100644
--- a/scripts/kconfig/Makefile
+++ b/scripts/kconfig/Makefile
@@ -90,11 +90,14 @@ PHONY += allnoconfig allyesconfig allmodconfig alldefconfig randconfig
 allnoconfig allyesconfig allmodconfig alldefconfig randconfig: $(obj)/conf
         $< --$@ $(Kconfig)
 
-PHONY += listnewconfig oldnoconfig defconfig
+PHONY += listnewconfig oldnoconfig savedefconfig defconfig
 
 listnewconfig oldnoconfig: $(obj)/conf
         $< --$@ $(Kconfig)
 
+savedefconfig: $(obj)/conf
+        $< --$@=defconfig $(Kconfig)
+
 defconfig: $(obj)/conf
 ifeq ($(KBUILD_DEFCONFIG),)
         $< --defconfig $(Kconfig)
@@ -118,6 +121,7 @@ help:
         @echo  '  localyesconfig  - Update current config converting local mods to core'
         @echo  '  silentoldconfig - Same as oldconfig, but quietly, additionally update deps'
         @echo  '  defconfig       - New config with default from ARCH supplied defconfig'
+        @echo  '  savedefconfig   - Save current config as ./defconfig (minimal config)'
         @echo  '  allnoconfig     - New config where all options are answered with no'
         @echo  '  allyesconfig    - New config where all options are accepted with yes'
         @echo  '  allmodconfig    - New config selecting modules when possible'
diff --git a/scripts/kconfig/conf.c b/scripts/kconfig/conf.c
index c8bd33cb3bf7..010600ef58c0 100644
--- a/scripts/kconfig/conf.c
+++ b/scripts/kconfig/conf.c
@@ -30,6 +30,7 @@ enum input_mode {
         alldefconfig,
         randconfig,
         defconfig,
+        savedefconfig,
         listnewconfig,
         oldnoconfig,
 } input_mode = oldaskconfig;
@@ -444,6 +445,7 @@ static struct option long_opts[] = {
         {"oldconfig",       no_argument,       NULL, oldconfig},
         {"silentoldconfig", no_argument,       NULL, silentoldconfig},
         {"defconfig",       optional_argument, NULL, defconfig},
+        {"savedefconfig",   required_argument, NULL, savedefconfig},
         {"allnoconfig",     no_argument,       NULL, allnoconfig},
         {"allyesconfig",    no_argument,       NULL, allyesconfig},
         {"allmodconfig",    no_argument,       NULL, allmodconfig},
@@ -471,6 +473,7 @@ int main(int ac, char **av)
                         sync_kconfig = 1;
                         break;
                 case defconfig:
+                case savedefconfig:
                         defconfig_file = optarg;
                         break;
                 case randconfig:
@@ -526,6 +529,9 @@ int main(int ac, char **av)
                         exit(1);
                 }
                 break;
+        case savedefconfig:
+                conf_read(NULL);
+                break;
         case silentoldconfig:
         case oldaskconfig:
         case oldconfig:
@@ -591,6 +597,8 @@ int main(int ac, char **av)
         case defconfig:
                 conf_set_all_new_symbols(def_default);
                 break;
+        case savedefconfig:
+                break;
         case oldconfig:
         case oldaskconfig:
                 rootEntry = &rootmenu;
@@ -622,6 +630,12 @@ int main(int ac, char **av)
                         fprintf(stderr, _("\n*** Error during update of the kernel configuration.\n\n"));
                         return 1;
                 }
+        } else if (input_mode == savedefconfig) {
+                if (conf_write_defconfig(defconfig_file)) {
+                        fprintf(stderr, _("n*** Error while saving defconfig to: %s\n\n"),
+                                defconfig_file);
+                        return 1;
+                }
         } else if (input_mode != listnewconfig) {
                 if (conf_write(NULL)) {
                         fprintf(stderr, _("\n*** Error during writing of the kernel configuration.\n\n"));
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;
diff --git a/scripts/kconfig/lkc.h b/scripts/kconfig/lkc.h
index 755b8190eb64..76db065ed72c 100644
--- a/scripts/kconfig/lkc.h
+++ b/scripts/kconfig/lkc.h
@@ -127,6 +127,7 @@ void sym_clear_all_valid(void);
 void sym_set_all_changed(void);
 void sym_set_changed(struct symbol *sym);
 struct symbol *sym_choice_default(struct symbol *sym);
+const char *sym_get_string_default(struct symbol *sym);
 struct symbol *sym_check_deps(struct symbol *sym);
 struct property *prop_alloc(enum prop_type type, struct symbol *sym);
 struct symbol *prop_get_symbol(struct property *prop);
diff --git a/scripts/kconfig/lkc_proto.h b/scripts/kconfig/lkc_proto.h
index 7cadcad8233b..9a948c9ce44e 100644
--- a/scripts/kconfig/lkc_proto.h
+++ b/scripts/kconfig/lkc_proto.h
@@ -3,6 +3,7 @@
 P(conf_parse,void,(const char *name));
 P(conf_read,int,(const char *name));
 P(conf_read_simple,int,(const char *name, int));
+P(conf_write_defconfig,int,(const char *name));
 P(conf_write,int,(const char *name));
 P(conf_write_autoconf,int,(void));
 P(conf_get_changed,bool,(void));
diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index 0a013ab3ae27..e95718fea355 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -661,6 +661,80 @@ bool sym_set_string_value(struct symbol *sym, const char *newval)
         return true;
 }
 
+/*
+ * Find the default value associated to a symbol.
+ * For tristate symbol handle the modules=n case
+ * in which case "m" becomes "y".
+ * If the symbol does not have any default then fallback
+ * to the fixed default values.
+ */
+const char *sym_get_string_default(struct symbol *sym)
+{
+        struct property *prop;
+        struct symbol *ds;
+        const char *str;
+        tristate val;
+
+        sym_calc_visibility(sym);
+        sym_calc_value(modules_sym);
+        val = symbol_no.curr.tri;
+        str = symbol_empty.curr.val;
+
+        /* If symbol has a default value look it up */
+        prop = sym_get_default_prop(sym);
+        if (prop != NULL) {
+                switch (sym->type) {
+                case S_BOOLEAN:
+                case S_TRISTATE:
+                        /* The visibility imay limit the value from yes => mod */
+                        val = EXPR_AND(expr_calc_value(prop->expr), prop->visible.tri);
+                        break;
+                default:
+                        /*
+                         * The following fails to handle the situation
+                         * where a default value is further limited by
+                         * the valid range.
+                         */
+                        ds = prop_get_symbol(prop);
+                        if (ds != NULL) {
+                                sym_calc_value(ds);
+                                str = (const char *)ds->curr.val;
+                        }
+                }
+        }
+
+        /* Handle select statements */
+        val = EXPR_OR(val, sym->rev_dep.tri);
+
+        /* transpose mod to yes if modules are not enabled */
+        if (val == mod)
+                if (!sym_is_choice_value(sym) && modules_sym->curr.tri == no)
+                        val = yes;
+
+        /* transpose mod to yes if type is bool */
+        if (sym->type == S_BOOLEAN && val == mod)
+                val = yes;
+
+        switch (sym->type) {
+        case S_BOOLEAN:
+        case S_TRISTATE:
+                switch (val) {
+                case no: return "n";
+                case mod: return "m";
+                case yes: return "y";
+                }
+        case S_INT:
+        case S_HEX:
+                return str;
+        case S_STRING:
+                return str;
+        case S_OTHER:
+        case S_UNKNOWN:
+                break;
+        }
+        return "";
+}
+
 const char *sym_get_string_value(struct symbol *sym)
 {
         tristate val;