[PATCH v2] checkpatch: validate MODULE_LICENSE content

[Bjorn Andersson <bjorn.andersson@sonymobile.com>]

There is a well defined list of expected values for MODULE_LICENSE so
warn the user upon usage of unknown values.

Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
---

Thanks for the review Joe!

"Proprietary" is in the list because this is the full list of "valid" values
mentioned in include/linux/module.h. So it's the list of licenses valid for
submission, but rather the list of valid values.

Changes since v1:
- Fixed nits pointed out by Joe
- Added comment to clarify the purpose, as well as origin of the values

 scripts/checkpatch.pl | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 9a8b2bd..ca10d79 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5431,6 +5431,24 @@ sub process {
 				}
 			}
 		}
+
+# validate content of MODULE_LICENSE against list from include/linux/module.h
+		if ($line =~ /\bMODULE_LICENSE\s*\(\s*($String)\s*\)/) {
+			my $extracted_string = get_quoted_string($line, $rawline);
+			my $valid_licenses = qr{
+						GPL|
+						GPL\ v2|
+						GPL\ and\ additional\ rights|
+						Dual\ BSD/GPL|
+						Dual\ MIT/GPL|
+						Dual\ MPL/GPL|
+						Proprietary
+					}x;
+			if ($extracted_string !~ /^"(?:$valid_licenses)"$/x) {
+				WARN("MODULE_LICENSE",
+				     "unknown module license " . $extracted_string . "\n" . $herecurr);
+			}
+		}
 	}
 
 	# If we have no input at all, then there is nothing to report on
-- 
1.8.2.2