HID: wacom: generic: Send BTN_STYLUS3 when both barrel switches are set

The Wacom Pro Pen 3D includes a third barrel switch which is intended to
be particularly useful in applications where one frequency uses pan, zoom,
and rotate to navigate around a scene or model. The pen is compatible with
the MobileStudio Pro, 2nd-gen Intuos Pro, and Cintiq Pro. When the third
button is pressed, these devices set both the HID_DG_BARRELSWITCH and
HID_DG_BARRELSWITCH2 usages since their HID descriptors do not include a
usage specific to the button.

Rather than send both BTN_STYLUS and BTN_STYLUS2 when the third button is
pressed, userspace (libinput) has requested that we detect this condition
and report a newly-defined BTN_STYLUS3 event instead. We could define a
quirk specific to devices compatible with the Pro Pen 3D, but the liklihood
of seeing both barrel switch bits set with other pens/devices is low enough
to not worry about (pens mechanically prevent accidental activation of
multiple switches).

Signed-off-by: Jason Gerecke <[e-mail]>
Acked-by: Dmitry Torokhov <[e-mail]>
Acked-by: Peter Hutterer <[e-mail]>
Acked-by: Benjamin Tissoires <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/wacom_wac.c

···
 	case HID_DG_TIPSWITCH:
 		wacom_wac->hid_data.tipswitch |= value;
 		return;
+	case HID_DG_BARRELSWITCH:
+		wacom_wac->hid_data.barrelswitch = value;
+		return;
+	case HID_DG_BARRELSWITCH2:
+		wacom_wac->hid_data.barrelswitch2 = value;
+		return;
 	case HID_DG_TOOLSERIALNUMBER:
 		if (value) {
 			wacom_wac->serial[0] = (wacom_wac->serial[0] & ~0xFFFFFFFFULL);
···
 
 	if (!delay_pen_events(wacom_wac) && wacom_wac->tool[0]) {
 		int id = wacom_wac->id[0];
+		int sw_state = wacom_wac->hid_data.barrelswitch |
+			       (wacom_wac->hid_data.barrelswitch2 << 1);
+
+		input_report_key(input, BTN_STYLUS, sw_state == 1);
+		input_report_key(input, BTN_STYLUS2, sw_state == 2);
+		input_report_key(input, BTN_STYLUS3, sw_state == 3);
 
 		/*
 		 * Non-USI EMR tools should have their IDs mangled to
···
 	else
 		__set_bit(INPUT_PROP_POINTER, input_dev->propbit);
 
-	if (features->type == HID_GENERIC)
-		/* setup has already been done */
+	if (features->type == HID_GENERIC) {
+		/* setup has already been done; apply otherwise-undetectible quirks */
+		input_set_capability(input_dev, EV_KEY, BTN_STYLUS3);
 		return 0;
+	}
 
 	__set_bit(BTN_TOUCH, input_dev->keybit);
 	__set_bit(ABS_MISC, input_dev->absbit);

drivers/hid/wacom_wac.h

···
 	bool inrange_state;
 	bool invert_state;
 	bool tipswitch;
+	bool barrelswitch;
+	bool barrelswitch2;
 	int x;
 	int y;
 	int pressure;

include/uapi/linux/input-event-codes.h

···
 #define BTN_TOOL_MOUSE		0x146
 #define BTN_TOOL_LENS		0x147
 #define BTN_TOOL_QUINTTAP	0x148	/* Five fingers on trackpad */
+#define BTN_STYLUS3		0x149
 #define BTN_TOUCH		0x14a
 #define BTN_STYLUS		0x14b
 #define BTN_STYLUS2		0x14c