kconfig: suppress "configuration written to .config" for syncconfig

The top-level Makefile invokes "make syncconfig" when necessary.
Then, Kconfig displays the following message when .config is updated.

  #
  # configuration written to .config
  #

It is distracting because "make syncconfig" happens during the build
stage, and does nothing important in most cases.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/scripts/kconfig/conf.c b/scripts/kconfig/conf.c
index b35cc9303979..7b2b37260669 100644
--- a/scripts/kconfig/conf.c
+++ b/scripts/kconfig/conf.c
@@ -508,6 +508,11 @@ int main(int ac, char **av)
                 input_mode = (enum input_mode)opt;
                 switch (opt) {
                 case syncconfig:
+                        /*
+                         * syncconfig is invoked during the build stage.
+                         * Suppress distracting "configuration written to ..."
+                         */
+                        conf_set_message_callback(NULL);
                         sync_kconfig = 1;
                         break;
                 case defconfig: