checkpatch: add a multiple blank lines test

Multiple consecutive blank lines waste screen space.  Emit a --strict
only message with these blank lines.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -1642,6 +1642,8 @@ sub process {
 
 	my $non_utf8_charset = 0;
 
+	my $last_blank_line = 0;
+
 	our @report = ();
 	our $cnt_lines = 0;
 	our $cnt_error = 0;
@@ -2308,6 +2310,15 @@ sub process {
 			    "Please use a blank line after function/struct/union/enum declarations\n" . $hereprev);
 		}
 
+# check for multiple consecutive blank lines
+		if ($prevline =~ /^[\+ ]\s*$/ &&
+		    $line =~ /^\+\s*$/ &&
+		    $last_blank_line != ($linenr - 1)) {
+			CHK("LINE_SPACING",
+			    "Please don't use multiple blank lines\n" . $hereprev);
+			$last_blank_line = $linenr;
+		}
+
 # check for missing blank lines after declarations
 		if ($sline =~ /^\+\s+\S/ &&			#Not at char 1
 			# actual declarations