kconfig: fix savedefconfig with choice marked optional

savedefconfig failed to save the correct minimal config
when it encountered a choice marked optional.

Consider following minimal configuration:
$cat Kconfig
choice
	prompt "choice"
	optional

config A
	bool "a"

config B
	bool "b"

endchoice

$cat .config | grep -v ^#
CONFIG_A=y

$conf --savedefconfig=defconfig Kconfig

would before this fix result in an empty file, because
kconfig would assume that CONFIG_A=y is a default value.
But because the choice is optional the default is that
both A and B are =n.

Fix so we handle optional choices correct.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>

1 files changed, 4 insertions, 2 deletions

diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
index c39327e60ea4..515253fe46cf 100644
--- a/scripts/kconfig/confdata.c
+++ b/scripts/kconfig/confdata.c
@@ -497,7 +497,9 @@ int conf_write_defconfig(const char *filename)
                         /*
                          * If symbol is a choice value and equals to the
                          * default for a choice - skip.
-                         * But only if value is bool and equal to "y" .
+                         * But only if value is bool and equal to "y" and
+                         * choice is not "optional".
+                         * (If choice is "optional" then all values can be "n")
                          */
                         if (sym_is_choice_value(sym)) {
                                 struct symbol *cs;
@@ -505,7 +507,7 @@ int conf_write_defconfig(const char *filename)
 
                                 cs = prop_get_symbol(sym_get_choice_prop(sym));
                                 ds = sym_choice_default(cs);
-                                if (sym == ds) {
+                                if (!sym_is_optional(cs) && sym == ds) {
                                         if ((sym->type == S_BOOLEAN) &&
                                             sym_get_tristate_value(sym) == yes)
                                                 goto next_menu;