kconfig: add savedefconfig

savedefconfig will save a minimal config to a file
named "defconfig".

The config symbols are saved in the same order as
they appear in the menu structure so it should
be possible to map them to the relevant menus
if desired.

The implementation was tested against several minimal
configs for arm which was created using brute-force.

There was one regression related to default numbers
which had their valid range further limited by another symbol.

Sample:

config FOO
	int "foo"
	default 4

config BAR
	int "bar"
	range 0 FOO

If FOO is set to 3 then BAR cannot take a value higher than 3.
But the current implementation will set BAR equal to 4.

This is seldomly used and the final configuration is OK,
and the fix was non-trivial.
So it was documented in the code and left as is.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Michal Marek <mmarek@suse.cz>

1 files changed, 74 insertions, 0 deletions

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;