checkpatch: add 'Prefer ARRAY_SIZE" test

Add a test for sizeof(foo)/sizeof(foo[0]) that could be ARRAY_SIZE(foo).
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -3227,6 +3227,19 @@ sub process {
 				$herecurr);
                }
 
+# check for sizeof(foo)/sizeof(foo[0]) that could be ARRAY_SIZE(foo)
+		if ($line =~ m@\bsizeof\s*\(\s*($Lval)\s*\)@) {
+			my $array = $1;
+			if ($line =~ m@\b(sizeof\s*\(\s*\Q$array\E\s*\)\s*/\s*sizeof\s*\(\s*\Q$array\E\s*\[\s*0\s*\]\s*\))@) {
+				my $array_div = $1;
+				if (WARN("ARRAY_SIZE",
+					 "Prefer ARRAY_SIZE($array)\n" . $herecurr) &&
+				    $fix) {
+					$fixed[$fixlinenr] =~ s/\Q$array_div\E/ARRAY_SIZE($array)/;
+				}
+			}
+		}
+
 # check for function declarations without arguments like "int foo()"
 		if ($line =~ /(\b$Type\s+$Ident)\s*\(\s*\)/) {
 			if (ERROR("FUNCTION_WITHOUT_ARGS",