Input: synaptics - handle spurious release of trackstick buttons

The Fimware 8.1 has a bug in which the extra buttons are only sent when the
ExtBit is 1.  This should be fixed in a future FW update which should have
a bump of the minor version.

Cc: stable@vger.kernel.org
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/synaptics.c

@@ -820,7 +820,7 @@ static void synaptics_report_semi_mt_data(struct input_dev *dev,
 	}
 }
 
-static void synaptics_report_buttons(struct psmouse *psmouse,
+static void synaptics_report_ext_buttons(struct psmouse *psmouse,
 					 const struct synaptics_hw_state *hw)
 {
 	struct input_dev *dev = psmouse->dev;
@@ -828,6 +828,28 @@ static void synaptics_report_buttons(struct psmouse *psmouse,
 	int ext_bits = (SYN_CAP_MULTI_BUTTON_NO(priv->ext_cap) + 1) >> 1;
 	int i;
 
+	if (!SYN_CAP_MULTI_BUTTON_NO(priv->ext_cap))
+		return;
+
+	/* Bug in FW 8.1, buttons are reported only when ExtBit is 1 */
+	if (SYN_ID_FULL(priv->identity) == 0x801 &&
+	    !((psmouse->packet[0] ^ psmouse->packet[3]) & 0x02))
+		return;
+
+	for (i = 0; i < ext_bits; i++) {
+		input_report_key(dev, BTN_0 + 2 * i,
+			hw->ext_buttons & (1 << i));
+		input_report_key(dev, BTN_1 + 2 * i,
+			hw->ext_buttons & (1 << (i + ext_bits)));
+	}
+}
+
+static void synaptics_report_buttons(struct psmouse *psmouse,
+				     const struct synaptics_hw_state *hw)
+{
+	struct input_dev *dev = psmouse->dev;
+	struct synaptics_data *priv = psmouse->private;
+
 	input_report_key(dev, BTN_LEFT, hw->left);
 	input_report_key(dev, BTN_RIGHT, hw->right);
 
@@ -839,12 +861,7 @@ static void synaptics_report_buttons(struct psmouse *psmouse,
 		input_report_key(dev, BTN_BACK, hw->down);
 	}
 
-	for (i = 0; i < ext_bits; i++) {
-		input_report_key(dev, BTN_0 + 2 * i,
-				 hw->ext_buttons & (1 << i));
-		input_report_key(dev, BTN_1 + 2 * i,
-				 hw->ext_buttons & (1 << (i + ext_bits)));
-	}
+	synaptics_report_ext_buttons(psmouse, hw);
 }
 
 static void synaptics_report_slot(struct input_dev *dev, int slot,