checkpatch: prefer __printf over __attribute__((format(printf,...)))

Add a warn for not using __printf.

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

@@ -3114,6 +3114,12 @@ sub process {
 			     "__aligned(size) is preferred over __attribute__((aligned(size)))\n" . $herecurr);
 		}
 
+# Check for __attribute__ format(printf, prefer __printf
+		if ($line =~ /\b__attribute__\s*\(\s*\(\s*format\s*\(\s*printf/) {
+			WARN("PREFER_PRINTF",
+			     "__printf(string-index, first-to-check) is preferred over __attribute__((format(printf, string-index, first-to-check)))\n" . $herecurr);
+		}
+
 # check for sizeof(&)
 		if ($line =~ /\bsizeof\s*\(\s*\&/) {
 			WARN("SIZEOF_ADDRESS",