Input: elantech - fix detection of touchpad on ASUS s301l

commit 271329b3 upstream.

Adjust Elantech signature validation to account fo rnewer models of
touchpads.
Reported-and-tested-by: Màrius Monton <marius.monton@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/input/mouse/elantech.c

@@ -1130,6 +1130,13 @@ static bool elantech_is_signature_valid(const unsigned char *param)
 	if (param[1] == 0)
 		return true;
 
+	/*
+	 * Some models have a revision higher then 20. Meaning param[2] may
+	 * be 10 or 20, skip the rates check for these.
+	 */
+	if (param[0] == 0x46 && (param[1] & 0xef) == 0x0f && param[2] < 40)
+		return true;
+
 	for (i = 0; i < ARRAY_SIZE(rates); i++)
 		if (param[2] == rates[i])
 			return false;