Input: sermouse - improve protocol error recovery

When using MS protocol the driver should wait for a byte with
bit 6 set before assuming that it sees beginning of a data packet.
This should allow driver better cope with lost bytes and prevent
spurious left/right button events when serial communication is
disturbed by a CPU-hungry real-time process.

Also fix some formatting.
Signed-off-by: NPeter Osterlund <petero2@telia.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>

drivers/input/mouse/sermouse.c

@@ -69,7 +69,8 @@ static void sermouse_process_msc(struct sermouse *sermouse, signed char data)
 	switch (sermouse->count) {
 
 		case 0:
-			if ((data & 0xf8) != 0x80) return;
+			if ((data & 0xf8) != 0x80)
+				return;
 			input_report_key(dev, BTN_LEFT,   !(data & 4));
 			input_report_key(dev, BTN_RIGHT,  !(data & 1));
 			input_report_key(dev, BTN_MIDDLE, !(data & 2));
@@ -107,7 +108,10 @@ static void sermouse_process_ms(struct sermouse *sermouse, signed char data)
 	struct input_dev *dev = sermouse->dev;
 	signed char *buf = sermouse->buf;
 
-	if (data & 0x40) sermouse->count = 0;
+	if (data & 0x40)
+		sermouse->count = 0;
+	else if (sermouse->count == 0)
+		return;
 
 	switch (sermouse->count) {
 
@@ -169,7 +173,8 @@ static void sermouse_process_ms(struct sermouse *sermouse, signed char data)
 
 		case 5:
 		case 7: /* Ignore anything besides MZ++ */
-			if (sermouse->type != SERIO_MZPP) break;
+			if (sermouse->type != SERIO_MZPP)
+				break;
 
 			switch (buf[1]) {
 
@@ -206,13 +211,16 @@ static irqreturn_t sermouse_interrupt(struct serio *serio,
 {
 	struct sermouse *sermouse = serio_get_drvdata(serio);
 
-	if (time_after(jiffies, sermouse->last + HZ/10)) sermouse->count = 0;
+	if (time_after(jiffies, sermouse->last + HZ/10))
+		sermouse->count = 0;
+
 	sermouse->last = jiffies;
 
 	if (sermouse->type > SERIO_SUN)
 		sermouse_process_ms(sermouse, data);
 	else
 		sermouse_process_msc(sermouse, data);
+
 	return IRQ_HANDLED;
 }