checkpatch: add warning for unnamed function definition arguments

Function definitions without identifiers like
	 int foo(int)
are not preferred.  Emit a warning when they occur.

Link: http://lkml.kernel.org/r/94fe6378504745991b650f48fc92bb4648f25706.1474925354.git.joe@perches.com
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

@@ -5794,6 +5794,19 @@ sub process {
 			     "externs should be avoided in .c files\n" .  $herecurr);
 		}
 
+		if ($realfile =~ /\.[ch]$/ && defined $stat &&
+		    $stat =~ /^.\s*(?:extern\s+)?$Type\s*$Ident\s*\(\s*([^{]+)\s*\)\s*;/s &&
+		    $1 ne "void") {
+			my $args = trim($1);
+			while ($args =~ m/\s*($Type\s*(?:$Ident|\(\s*\*\s*$Ident?\s*\)\s*$balanced_parens)?)/g) {
+				my $arg = trim($1);
+				if ($arg =~ /^$Type$/ && $arg !~ /enum\s+$Ident$/) {
+					WARN("FUNCTION_ARGUMENTS",
+					     "function definition argument '$arg' should also have an identifier name\n" . $herecurr);
+				}
+			}
+		}
+
 # checks for new __setup's
 		if ($rawline =~ /\b__setup\("([^"]*)"/) {
 			my $name = $1;