checkpatch: Check for illegal return codes

The only legal integer return is 0, anything else
following "return" should be -ERRCODE or a function.

http://lkml.org/lkml/2010/7/23/318
  There's lots of "return -1;" statements in this patch - it's obscene
  that this is used to indicate "some error occurred" in kernel space
  rather than a real errno value - even when an existing function
  (eg, request_irq) gave you an error code already.

  Please note this for the future - and please review patches on this
  point internally first.

Change-Id: I16268b2ee034f0b3b899115e45c28acfa734ddec
Signed-off-by: Patrick Pannuto <ppannuto@codeaurora.org>
(cherry picked from commit 39531a47164294315b5a7256b520fe22d6e87013)
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index b10a16d..9904e6a 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5808,6 +5808,12 @@
 			     "switch default: should use break\n" . $herectx);
 		}
 
+# check for return codes on error paths
+		if ($line =~ /\breturn\s+-\d+/) {
+			ERROR("NO_ERROR_CODE",
+			      "illegal return value, please use an error code");
+		}
+
 # check for gcc specific __FUNCTION__
 		if ($line =~ /\b__FUNCTION__\b/) {
 			if (WARN("USE_FUNC",