[PATCH v3 1/2] checkpatch: add Kconfig 'default n' test

[Yingjoe Chen <yingjoe.chen@mediatek.com>]

If a Kconfig config option doesn't specify 'default', the default
will be n. Adding 'default n' is unnecessary.

Add a test to warn about this.

Signed-off-by: Yingjoe Chen <yingjoe.chen@mediatek.com>
---
For this series, rebase to v4.7-rc1 and dropped 'relax Kconfig help text
line number threshold' patch.

Let me know what you think. Thanks.


Change in v3:
- Rebase to v4.7-rc1

Change in v2:
- Change according to Joe Perches' suggesti

 scripts/checkpatch.pl | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 6750595..f5ce804 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2683,6 +2683,13 @@ sub process {
 			     "Use of boolean is deprecated, please use bool instead.\n" . $herecurr);
 		}
 
+# discourage the use of default n
+		if ($realfile =~ /Kconfig/ &&
+		    $line =~ /^\+\s*default\s*n\s*(#.*|$)/i) {
+			WARN("CONFIG_DEFAULT_N",
+			     "Use of default n is unnecessary, default is n when omitted.\n" . $herecurr);
+		}
+
 		if (($realfile =~ /Makefile.*/ || $realfile =~ /Kbuild.*/) &&
 		    ($line =~ /\+(EXTRA_[A-Z]+FLAGS).*/)) {
 			my $flag = $1;
-- 
1.9.1