[Buildroot] [PATCH] infra/pkg-kconfig: fix saving the config file

Yann E. MORIN yann.morin.1998 at free.fr
Mon Oct 20 20:23:36 UTC 2014


When saving (aka updating) the configuration file of a kconfig package,
a subsequent call to "make" would rebuild the package, even though the
configuration did not actually change.

It took quite a while to understand why. But the reason is so simple and
obvious, when you think about it:

  - $(@D)/.config depends on the config file $(BUSYBOX_CONFIG_FILE)
  - busybox-update-config then copies $(@D)/.config back to the config
    file $(BUSYBOX_CONFIG_FILE)
  - so the config file is newer than $(@D)/.config

So, in the next run, pkg-kconfig believes that it has to rebuild
busybox. Bummer... :-/

So, the fix is very trivial, and just requires asking "cp" to preserve
timestamps, so the dependency does not kick in at the next run.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
Cc: Thomas De Schampheleire <patrickdepinguin at gmail.com>
---
 package/pkg-kconfig.mk | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package/pkg-kconfig.mk b/package/pkg-kconfig.mk
index 071153a..ec58d69 100644
--- a/package/pkg-kconfig.mk
+++ b/package/pkg-kconfig.mk
@@ -66,7 +66,7 @@ $$(addprefix $(1)-,$$($(2)_KCONFIG_EDITORS)): $$($(2)_DIR)/.stamp_kconfig_fixup_
 
 # Target to copy back the configuration to the source configuration file
 $(1)-update-config: $$($(2)_DIR)/.stamp_kconfig_fixup_done
-	cp -f $$($(2)_DIR)/.config $$($(2)_KCONFIG_FILE)
+	cp --preserve=timestamps -f $$($(2)_DIR)/.config $$($(2)_KCONFIG_FILE)
 
 endef # inner-kconfig-package
 
-- 
1.9.1



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