checkpatch: check trace-events code style

According to CODING_STYLE, check that in trace-events:
1. hex numbers are prefixed with '0x'
2. '#' flag of printf is not used
3. The exclusion from 1. are period-separated groups of numbers

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170731160135.12101-4-vsementsov@virtuozzo.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

scripts/checkpatch.pl

@@ -1337,6 +1337,25 @@ sub process {
 			$rpt_cleaners = 1;
 		}
 
+# checks for trace-events files
+		if ($realfile =~ /trace-events$/ && $line =~ /^\+/) {
+			if ($rawline =~ /%[-+ 0]*#/) {
+				ERROR("Don't use '#' flag of printf format ('%#') in " .
+				      "trace-events, use '0x' prefix instead\n" . $herecurr);
+			} else {
+				my $hex =
+					qr/%[-+ *.0-9]*([hljztL]|ll|hh)?(x|X|"\s*PRI[xX][^"]*"?)/;
+
+				# don't consider groups splitted by [.:/ ], like 2A.20:12ab
+				my $tmpline = $rawline =~ s/($hex[.:\/ ])+$hex//gr;
+
+				if ($tmpline =~ /(?<!0x)$hex/) {
+					ERROR("Hex numbers must be prefixed with '0x'\n" .
+					      $herecurr);
+				}
+			}
+		}
+
 # check we are in a valid source file if not then ignore this hunk
 		next if ($realfile !~ /\.(h|c|cpp|s|S|pl|py|sh)$/);