tracing/events: simplify system_enable_read()

A smarter way to figure out the output of an enable file.

[ Impact: clean up ]
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A0399A5.2080603@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/trace/trace_events.c

@@ -414,10 +414,11 @@ static ssize_t
 system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
 		   loff_t *ppos)
 {
+	const char set_to_char[4] = { '?', '0', '1', 'X' };
 	const char *system = filp->private_data;
 	struct ftrace_event_call *call;
 	char buf[2];
-	int set = -1;
+	int set = 0;
 	int ret;
 
 	mutex_lock(&event_mutex);
@@ -433,47 +434,18 @@ system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
 		 * or if all events or cleared, or if we have
 		 * a mixture.
 		 */
-		if (call->enabled) {
-			switch (set) {
-			case -1:
-				set = 1;
-				break;
-			case 0:
-				set = 2;
-				break;
-			}
-		} else {
-			switch (set) {
-			case -1:
-				set = 0;
-				break;
-			case 1:
-				set = 2;
-				break;
-			}
-		}
+		set |= (1 << !!call->enabled);
+
 		/*
 		 * If we have a mixture, no need to look further.
 		 */
-		if (set == 2)
+		if (set == 3)
 			break;
 	}
 	mutex_unlock(&event_mutex);
 
+	buf[0] = set_to_char[set];
 	buf[1] = '\n';
-	switch (set) {
-	case 0:
-		buf[0] = '0';
-		break;
-	case 1:
-		buf[0] = '1';
-		break;
-	case 2:
-		buf[0] = 'X';
-		break;
-	default:
-		buf[0] = '?';
-	}
 
 	ret = simple_read_from_buffer(ubuf, cnt, ppos, buf, 2);