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: Peter Osterlund <petero2@telia.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

1 files changed, 12 insertions, 4 deletions

diff --git a/drivers/input/mouse/sermouse.c b/drivers/input/mouse/sermouse.c
index a85d74710b44..0ac448a82bde 100644
--- a/drivers/input/mouse/sermouse.c
+++ b/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;
 }