checkpatch: prefer usleep_range over udelay

When possible, sleeping is (usually) better than delaying; however, don't
bother callers of udelay < 10us, as those cases are generally not worth
the switch to usleep

[akpm@linux-foundation.org: fix mismatched parentheses]
Signed-off-by: NPatrick Pannuto <ppannuto@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -2584,6 +2584,14 @@ sub process {
 			}
 		}
 
+# prefer usleep_range over udelay
+		if ($line =~ /\budelay\s*\(\s*(\w+)\s*\)/) {
+			# ignore udelay's < 10, however
+			if (! (($1 =~ /(\d+)/) && ($1 < 10)) ) {
+				CHK("usleep_range is preferred over udelay; see Documentation/timers/timers-howto.txt\n" . $line);
+			}
+		}
+
 # warn about #ifdefs in C files
 #		if ($line =~ /^.\s*\#\s*if(|n)def/ && ($realfile =~ /\.c$/)) {
 #			print "#ifdef in C files should be avoided\n";