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[v5.4,5/6] kheaders: explain why include/config/autoconf.h is excluded from md5sum

Message ID 20200826162828.3330007-6-maennich@google.com
State New
Headers show
Series Build time improvements | expand

Commit Message

Matthias Maennich Aug. 26, 2020, 4:28 p.m. UTC 
From: Masahiro Yamada <yamada.masahiro@socionext.com>


This comment block explains why include/generated/compile.h is omitted,
but nothing about include/generated/autoconf.h, which might be more
difficult to understand. Add more comments.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

(cherry picked from commit f276031b4e2f4c961ed6d8a42f0f0124ccac2e09)
Signed-off-by: Matthias Maennich <maennich@google.com>

---
 kernel/gen_kheaders.sh | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

-- 
2.28.0.297.g1956fa8f8d-goog
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Patch

diff --git a/kernel/gen_kheaders.sh b/kernel/gen_kheaders.sh
index dc5744b93f8c..e13ca842eb7e 100755
--- a/kernel/gen_kheaders.sh
+++ b/kernel/gen_kheaders.sh
@@ -32,8 +32,15 @@  fi
 all_dirs="$all_dirs $dir_list"
 
 # include/generated/compile.h is ignored because it is touched even when none
-# of the source files changed. This causes pointless regeneration, so let us
-# ignore them for md5 calculation.
+# of the source files changed.
+#
+# When Kconfig regenerates include/generated/autoconf.h, its timestamp is
+# updated, but the contents might be still the same. When any CONFIG option is
+# changed, Kconfig touches the corresponding timestamp file include/config/*.h.
+# Hence, the md5sum detects the configuration change anyway. We do not need to
+# check include/generated/autoconf.h explicitly.
+#
+# Ignore them for md5 calculation to avoid pointless regeneration.
 headers_md5="$(find $all_dirs -name "*.h"			|
 		grep -v "include/generated/compile.h"	|
 		grep -v "include/generated/autoconf.h"	|