Input: i8042 - fix locking in interrupt routine

We need to protect not only i8042 status and data register from concurrent
access from IRQ 1 and 12 but the rest of the shared state as well, so let's
move release of i8042_lock in i8042_interrupt() a little bit further down.
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/serio/i8042.c

@@ -368,6 +368,25 @@ static void i8042_stop(struct serio *serio)
 	port->serio = NULL;
 }
 
+/*
+ * i8042_filter() filters out unwanted bytes from the input data stream.
+ * It is called from i8042_interrupt and thus is running with interrupts
+ * off and i8042_lock held.
+ */
+static bool i8042_filter(unsigned char data, unsigned char str)
+{
+	if (unlikely(i8042_suppress_kbd_ack)) {
+		if ((~str & I8042_STR_AUXDATA) &&
+		    (data == 0xfa || data == 0xfe)) {
+			i8042_suppress_kbd_ack--;
+			dbg("Extra keyboard ACK - filtered out\n");
+			return true;
+		}
+	}
+
+	return false;
+}
+
 /*
  * i8042_interrupt() is the most important function in this driver -
  * it handles the interrupts from the i8042, and sends incoming bytes
@@ -381,9 +400,11 @@ static irqreturn_t i8042_interrupt(int irq, void *dev_id)
 	unsigned char str, data;
 	unsigned int dfl;
 	unsigned int port_no;
+	bool filtered;
 	int ret = 1;
 
 	spin_lock_irqsave(&i8042_lock, flags);
+
 	str = i8042_read_status();
 	if (unlikely(~str & I8042_STR_OBF)) {
 		spin_unlock_irqrestore(&i8042_lock, flags);
@@ -391,8 +412,8 @@ static irqreturn_t i8042_interrupt(int irq, void *dev_id)
 		ret = 0;
 		goto out;
 	}
+
 	data = i8042_read_data();
-	spin_unlock_irqrestore(&i8042_lock, flags);
 
 	if (i8042_mux_present && (str & I8042_STR_AUXDATA)) {
 		static unsigned long last_transmit;
@@ -447,14 +468,11 @@ static irqreturn_t i8042_interrupt(int irq, void *dev_id)
 	    dfl & SERIO_PARITY ? ", bad parity" : "",
 	    dfl & SERIO_TIMEOUT ? ", timeout" : "");
 
-	if (unlikely(i8042_suppress_kbd_ack))
-		if (port_no == I8042_KBD_PORT_NO &&
-		    (data == 0xfa || data == 0xfe)) {
-			i8042_suppress_kbd_ack--;
-			goto out;
-		}
+	filtered = i8042_filter(data, str);
+
+	spin_unlock_irqrestore(&i8042_lock, flags);
 
-	if (likely(port->exists))
+	if (likely(port->exists && !filtered))
 		serio_interrupt(port->serio, data, dfl);
 
  out: