Input: alps - report V2 Dualpoint Stick events via the right evdev node

On V2 devices the DualPoint Stick reports bare packets, these should be
reported via the "AlpsPS/2 ALPS DualPoint Stick" dev2 evdev node, which also
has the INPUT_PROP_POINTING_STICK propbit set.

Note that since there is no way to distinguish these packets from an external
PS/2 mouse (insofar as these laptops have an external PS/2 port) this means
that we will be reporting PS/2 mouse events via this evdev node too, as we've
been doing in kernel 3.19 and older.

This has been tested on a Dell Latitude D620 and a Dell Latitude E6400,
which both have a V2 touchpad + a DualPoint Stick which reports bare packets.

Signed-off-by: Hans de Goede <[e-mail]>
Reviewed-by: Pali Rohár <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/mouse/alps.c

···
 	struct alps_data *priv = psmouse->private;
 	struct input_dev *dev;
 
-	if (unlikely(IS_ERR_OR_NULL(priv->dev3))) {
+	/* Figure out which device to use to report the bare packet */
+	if (priv->proto_version == ALPS_PROTO_V2 &&
+	    (priv->flags & ALPS_DUALPOINT)) {
+		/* On V2 devices the DualPoint Stick reports bare packets */
+		dev = priv->dev2;
+	} else if (unlikely(IS_ERR_OR_NULL(priv->dev3))) {
 		/* Register dev3 mouse if we received PS/2 packet first time */
 		if (!IS_ERR(priv->dev3))
 			psmouse_queue_work(psmouse, &priv->dev3_register_work,