Input: add BTN_TOOL_QUINTTAP for reporting 5 fingers on touchpad

"4-finger scroll" is a gesture supported by some applications and
operating systems.

"Resting thumb" is when a clickpad user rests a finger (e.g., a
thumb), in a "click zone" (typically the bottom of the touchpad) in
anticipation of click+move=select gestures.

Thus, "4-finger scroll + resting thumb" is a 5-finger gesture.
To allow userspace to detect this gesture, we send BTN_TOOL_QUINTTAP.
Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Acked-by: Chase Douglas <chase.douglas@canonical.com>
Acked-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/input-mt.c

@@ -117,6 +117,7 @@ void input_mt_report_finger_count(struct input_dev *dev, int count)
 	input_event(dev, EV_KEY, BTN_TOOL_DOUBLETAP, count == 2);
 	input_event(dev, EV_KEY, BTN_TOOL_TRIPLETAP, count == 3);
 	input_event(dev, EV_KEY, BTN_TOOL_QUADTAP, count == 4);
+	input_event(dev, EV_KEY, BTN_TOOL_QUINTTAP, count == 5);
 }
 EXPORT_SYMBOL(input_mt_report_finger_count);
 

include/linux/input.h

@@ -503,6 +503,7 @@ struct input_keymap_entry {
 #define BTN_TOOL_FINGER		0x145
 #define BTN_TOOL_MOUSE		0x146
 #define BTN_TOOL_LENS		0x147
+#define BTN_TOOL_QUINTTAP	0x148	/* Five fingers on trackpad */
 #define BTN_TOUCH		0x14a
 #define BTN_STYLUS		0x14b
 #define BTN_STYLUS2		0x14c