HID: hid-magicmouse: Magic Trackpad has 1 button, not 2

hid-magicmouse was advertising the Apple Magic Trackpad as having 2
buttons (left and right) when it actually only has 1 button.

Advertising multiple buttons makes Xorg disable all button 2 and 3
emulation (using multi-finger clicks). So Xorg users don't get working
right/middle-click emulation out of the box.

This patch makes hid-magicmouse correctly only report one real button
for Magic Trackpad, which in turn makes Xorg enable multi-finger click
support to emulate right/middle buttons.

[http://launchpad.net/bugs/862094]
Signed-off-by: Daniel van Vugt <vanvugt@gmail.com>
Reviewed-by: Chase Douglas <chase.douglas@canonical.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-magicmouse.c

@@ -405,6 +405,13 @@ static void magicmouse_setup_input(struct input_dev *input, struct hid_device *h
 			__set_bit(REL_HWHEEL, input->relbit);
 		}
 	} else { /* USB_DEVICE_ID_APPLE_MAGICTRACKPAD */
+		/* input->keybit is initialized with incorrect button info
+		 * for Magic Trackpad. There really is only one physical
+		 * button (BTN_LEFT == BTN_MOUSE). Make sure we don't
+		 * advertise buttons that don't exist...
+		 */
+		__clear_bit(BTN_RIGHT, input->keybit);
+		__clear_bit(BTN_MIDDLE, input->keybit);
 		__set_bit(BTN_MOUSE, input->keybit);
 		__set_bit(BTN_TOOL_FINGER, input->keybit);
 		__set_bit(BTN_TOOL_DOUBLETAP, input->keybit);