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

[[e-mail]: fix mismatched parentheses]
Signed-off-by: Patrick Pannuto <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

scripts/checkpatch.pl

···
 			}
 		}
 
+# 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";