Input: i8042 - i8042_flush fix for a full 8042 buffer

When 8042 internal data buffer is full, the driver
erroneously decides that the controller is not present.

i8042_flush returns the number of flushed bytes, which is
in 0 - I8042_BUFFER_SIZE range inclusive. Therefore, i8042_flush
has no way to indicate an error. Moreover i8042_controller_check
takes initially full buffer (i8042_flush returned
I8042_BUFFER_SIZE) as a sign of absence of the controller.

Let's change i8042 to return success/error instead and make sure
we do not return error prematurely.
Signed-off-by: NAndrey Moiseev <o2g.org.ru@gmail.com>
Signed-off-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/serio/i8042.c

@@ -223,21 +223,26 @@ static int i8042_flush(void)
 {
 	unsigned long flags;
 	unsigned char data, str;
-	int i = 0;
+	int count = 0;
+	int retval = 0;
 
 	spin_lock_irqsave(&i8042_lock, flags);
 
-	while (((str = i8042_read_status()) & I8042_STR_OBF) && (i < I8042_BUFFER_SIZE)) {
+	while ((str = i8042_read_status()) & I8042_STR_OBF) {
+		if (count++ < I8042_BUFFER_SIZE) {
 			udelay(50);
 			data = i8042_read_data();
-		i++;
 			dbg("%02x <- i8042 (flush, %s)\n",
 			    data, str & I8042_STR_AUXDATA ? "aux" : "kbd");
+		} else {
+			retval = -EIO;
+			break;
+		}
 	}
 
 	spin_unlock_irqrestore(&i8042_lock, flags);
 
-	return i;
+	return retval;
 }
 
 /*
@@ -849,7 +854,7 @@ static int __init i8042_check_aux(void)
 
 static int i8042_controller_check(void)
 {
-	if (i8042_flush() == I8042_BUFFER_SIZE) {
+	if (i8042_flush()) {
 		pr_err("No controller found\n");
 		return -ENODEV;
 	}