linux-kernel - [PATCH 5.4 209/214] kheaders: explain why include/config/autoconf.h is excluded from md5sum

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Date:   Tue,  1 Sep 2020 17:11:29 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Matthias Maennich <maennich@...gle.com>
Subject: [PATCH 5.4 209/214] kheaders: explain why include/config/autoconf.h is excluded from md5sum

From: Masahiro Yamada <yamada.masahiro@...ionext.com>

commit f276031b4e2f4c961ed6d8a42f0f0124ccac2e09 upstream.

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@...ionext.com>
Signed-off-by: Matthias Maennich <maennich@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- 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"	|