checkpatch: categorize some long line length checks

Many lines of code extend beyond the maximum line length.  Some of these
are possibly justified by use type.

For instance:

structure definitions where comments are added per member like:
struct foo {
	type member;		/* some long description */

And lines that don't fit the typical logging message style
where a string constant is used like:

        SOME_MACRO(args, "Some long string");

Categorize these long line types so that checkpatch can use a command-line
--ignore=<type> option to avoid emitting some long line warnings.

One of the existing checkpatch exclusions allowed kernel-doc argument
documentation to exceed 80 columns because old versions of kernel-doc
required single line documentation.  The requirement was removed in 2009
so remove that exclusion.

Add documentation to make the test a bit clearer.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Cc: Michael Shuey <shuey@purdue.edu>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -2517,17 +2517,57 @@ sub process {
 # check we are in a valid source file if not then ignore this hunk
 		next if ($realfile !~ /\.(h|c|s|S|pl|sh|dtsi|dts)$/);
 
-#line length limit
-		if ($line =~ /^\+/ && $prevrawline !~ /\/\*\*/ &&
-		    $rawline !~ /^.\s*\*\s*\@$Ident\s/ &&
-		    !($line =~ /^\+\s*$logFunctions\s*\(\s*(?:(KERN_\S+\s*|[^"]*))?$String\s*(?:|,|\)\s*;)\s*$/ ||
-		      $line =~ /^\+\s*$String\s*(?:\s*|,|\)\s*;)\s*$/ ||
-		      $line =~ /^\+\s*#\s*define\s+\w+\s+$String$/) &&
-		    $length > $max_line_length)
-		{
-			WARN("LONG_LINE",
+# line length limit (with some exclusions)
+#
+# There are a few types of lines that may extend beyond $max_line_length:
+#	logging functions like pr_info that end in a string
+#	lines with a single string
+#	#defines that are a single string
+#
+# There are 3 different line length message types:
+# LONG_LINE_COMMENT	a comment starts before but extends beyond $max_linelength
+# LONG_LINE_STRING	a string starts before but extends beyond $max_line_length
+# LONG_LINE		all other lines longer than $max_line_length
+#
+# if LONG_LINE is ignored, the other 2 types are also ignored
+#
+
+		if ($length > $max_line_length) {
+			my $msg_type = "LONG_LINE";
+
+			# Check the allowed long line types first
+
+			# logging functions that end in a string that starts
+			# before $max_line_length
+			if ($line =~ /^\+\s*$logFunctions\s*\(\s*(?:(?:KERN_\S+\s*|[^"]*))?($String\s*(?:|,|\)\s*;)\s*)$/ &&
+			    length(expand_tabs(substr($line, 1, length($line) - length($1) - 1))) <= $max_line_length) {
+				$msg_type = "";
+
+			# lines with only strings (w/ possible termination)
+			# #defines with only strings
+			} elsif ($line =~ /^\+\s*$String\s*(?:\s*|,|\)\s*;)\s*$/ ||
+				 $line =~ /^\+\s*#\s*define\s+\w+\s+$String$/) {
+				$msg_type = "";
+
+			# Otherwise set the alternate message types
+
+			# a comment starts before $max_line_length
+			} elsif ($line =~ /($;[\s$;]*)$/ &&
+				 length(expand_tabs(substr($line, 1, length($line) - length($1) - 1))) <= $max_line_length) {
+				$msg_type = "LONG_LINE_COMMENT"
+
+			# a quoted string starts before $max_line_length
+			} elsif ($sline =~ /\s*($String(?:\s*(?:\\|,\s*|\)\s*;\s*))?)$/ &&
+				 length(expand_tabs(substr($line, 1, length($line) - length($1) - 1))) <= $max_line_length) {
+				$msg_type = "LONG_LINE_STRING"
+			}
+
+			if ($msg_type ne "" &&
+			    (show_type("LONG_LINE") || show_type($msg_type))) {
+				WARN($msg_type,
 				     "line over $max_line_length characters\n" . $herecurr);
 			}
+		}
 
 # check for adding lines without a newline.
 		if ($line =~ /^\+/ && defined $lines[$linenr] && $lines[$linenr] =~ /^\\ No newline at end of file/) {