Input: atkbd - fix multi-byte scancode handling on reconnect

On resume from suspend there is a possibility for multi-byte scancodes
to be handled incorrectly. atkbd_reconnect disables the processing of
scancodes in software by calling atkbd_disable, but the keyboard may
still be active because no disconnect command was sent. Later, software
handling is re-enabled. If a multi-byte scancode sent from the keyboard
straddles the re-enable, only the latter byte(s) will be handled.

In practice, this leads to cases where multi-byte break codes (ex. "e0
4d" - break code for right-arrow) are misread as make codes ("4d" - make
code for numeric 6), leading to one or more unwanted, untyped characters
being interpreted.

The solution implemented here involves sending command f5 (reset
disable) to the keyboard prior to disabling software handling of codes.
Later, the command to re-enable the keyboard is sent only after we are
prepared to handle scancodes.

Signed-off-by: Shawn Nematbakhsh <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/keyboard/atkbd.c

···
 	serio_continue_rx(atkbd->ps2dev.serio);
 }
 
+static int atkbd_activate(struct atkbd *atkbd)
+{
+	struct ps2dev *ps2dev = &atkbd->ps2dev;
+
+/*
+ * Enable the keyboard to receive keystrokes.
+ */
+
+	if (ps2_command(ps2dev, NULL, ATKBD_CMD_ENABLE)) {
+		dev_err(&ps2dev->serio->dev,
+			"Failed to enable keyboard on %s\n",
+			ps2dev->serio->phys);
+		return -1;
+	}
+
+	return 0;
+}
+
+/*
+ * atkbd_deactivate() resets and disables the keyboard from sending
+ * keystrokes.
+ */
+
+static void atkbd_deactivate(struct atkbd *atkbd)
+{
+	struct ps2dev *ps2dev = &atkbd->ps2dev;
+
+	if (ps2_command(ps2dev, NULL, ATKBD_CMD_RESET_DIS))
+		dev_err(&ps2dev->serio->dev,
+			"Failed to deactivate keyboard on %s\n",
+			ps2dev->serio->phys);
+}
+
 /*
  * atkbd_probe() probes for an AT keyboard on a serio port.
  */
···
 			"Use i8042.direct=1 to disable translation.\n");
 		return -1;
 	}
+
+/*
+ * Make sure nothing is coming from the keyboard and disturbs our
+ * internal state.
+ */
+	atkbd_deactivate(atkbd);
 
 	return 0;
 }
···
 	param[0] = 0;
 	if (ps2_command(ps2dev, param, ATKBD_CMD_SETREP))
 		return -1;
-
-	return 0;
-}
-
-static int atkbd_activate(struct atkbd *atkbd)
-{
-	struct ps2dev *ps2dev = &atkbd->ps2dev;
-
-/*
- * Enable the keyboard to receive keystrokes.
- */
-
-	if (ps2_command(ps2dev, NULL, ATKBD_CMD_ENABLE)) {
-		dev_err(&ps2dev->serio->dev,
-			"Failed to enable keyboard on %s\n",
-			ps2dev->serio->phys);
-		return -1;
-	}
 
 	return 0;
 }
···
 
 		atkbd->set = atkbd_select_set(atkbd, atkbd_set, atkbd_extra);
 		atkbd_reset_state(atkbd);
-		atkbd_activate(atkbd);
 
 	} else {
 		atkbd->set = 2;
···
 		goto fail3;
 
 	atkbd_enable(atkbd);
+	if (serio->write)
+		atkbd_activate(atkbd);
 
 	err = input_register_device(atkbd->dev);
 	if (err)
···
 		if (atkbd->set != atkbd_select_set(atkbd, atkbd->set, atkbd->extra))
 			goto out;
 
-		atkbd_activate(atkbd);
-
 		/*
 		 * Restore LED state and repeat rate. While input core
 		 * will do this for us at resume time reconnect may happen
···
 
 	}
 
+	/*
+	 * Reset our state machine in case reconnect happened in the middle
+	 * of multi-byte scancode.
+	 */
+	atkbd->xl_bit = 0;
+	atkbd->emul = 0;
+
 	atkbd_enable(atkbd);
+	if (atkbd->write)
+		atkbd_activate(atkbd);
+
 	retval = 0;
 
  out: