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, 14 insertions, 0 deletions

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"));