checkpatch: add test for repeated words

Try to avoid adding repeated words either on the same line or consecutive
comment lines in a block

e.g.:

duplicated word in comment block

	/*
	 * this is a comment block where the last word of the previous
	 * previous line is also the first word of the next line
	 */

and simple duplication

	/* test this this again */
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/cda9b566ad67976e1acd62b053de50ee44a57250.camel@perches.comInspired-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -588,6 +588,8 @@ our @mode_permission_funcs = (
 	["__ATTR", 2],
 );
 
+my $word_pattern = '\b[A-Z]?[a-z]{2,}\b';
+
 #Create a search pattern for all these functions to speed up a loop below
 our $mode_perms_search = "";
 foreach my $entry (@mode_permission_funcs) {
@@ -3312,6 +3314,42 @@ sub process {
 			}
 		}
 
+# check for repeated words separated by a single space
+		if ($rawline =~ /^\+/) {
+			while ($rawline =~ /\b($word_pattern) (?=($word_pattern))/g) {
+
+				my $first = $1;
+				my $second = $2;
+
+				if ($first =~ /(?:struct|union|enum)/) {
+					pos($rawline) += length($first) + length($second) + 1;
+					next;
+				}
+
+				next if ($first ne $second);
+				next if ($first eq 'long');
+
+				if (WARN("REPEATED_WORD",
+					 "Possible repeated word: '$first'\n" . $herecurr) &&
+				    $fix) {
+					$fixed[$fixlinenr] =~ s/\b$first $second\b/$first/;
+				}
+			}
+
+			# if it's a repeated word on consecutive lines in a comment block
+			if ($prevline =~ /$;+\s*$/ &&
+			    $prevrawline =~ /($word_pattern)\s*$/) {
+				my $last_word = $1;
+				if ($rawline =~ /^\+\s*\*\s*$last_word /) {
+					if (WARN("REPEATED_WORD",
+						 "Possible repeated word: '$last_word'\n" . $hereprev) &&
+					    $fix) {
+						$fixed[$fixlinenr] =~ s/(\+\s*\*\s*)$last_word /$1/;
+					}
+				}
+			}
+		}
+
 # check for space before tabs.
 		if ($rawline =~ /^\+/ && $rawline =~ / \t/) {
 			my $herevet = "$here\n" . cat_vet($rawline) . "\n";