HID: lenovo: Use native middle-button mode for compact keyboards

By default the middle button is in a compatibility mode, and generates
standard wheel events when dragging with the middle trackpoint button.
Unfortunately this is buggy:
* The middle button comes up before starting wheel events, causing a middle
  click on whatever the mouse cursor was sitting on
* The USB keyboard always generates the "native" horizontal wheel event,
  regardless of mode.

Instead, enable the "native" mode the Windows driver uses, and add support
for the custom events this generates. This fixes the USB keyboard wheel
events, and the middle-click up event comes after the wheel events.

Signed-off-by: Jamie Lentin <jm@lentin.co.uk>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-lenovo.c

@@ -92,6 +92,38 @@ static int lenovo_input_mapping_cptkbd(struct hid_device *hdev,
 		case 0x00fa: /* Fn-Esc: Fn-lock toggle */
 			map_key_clear(KEY_FN_ESC);
 			return 1;
+		case 0x00fb: /* Middle mouse button (in native mode) */
+			map_key_clear(BTN_MIDDLE);
+			return 1;
+		}
+	}
+
+	/* Compatibility middle/wheel mappings should be ignored */
+	if (usage->hid == HID_GD_WHEEL)
+		return -1;
+	if ((usage->hid & HID_USAGE_PAGE) == HID_UP_BUTTON &&
+			(usage->hid & HID_USAGE) == 0x003)
+		return -1;
+	if ((usage->hid & HID_USAGE_PAGE) == HID_UP_CONSUMER &&
+			(usage->hid & HID_USAGE) == 0x238)
+		return -1;
+
+	/* Map wheel emulation reports: 0xffa1 = USB, 0xff10 = BT */
+	if ((usage->hid & HID_USAGE_PAGE) == 0xff100000 ||
+	    (usage->hid & HID_USAGE_PAGE) == 0xffa10000) {
+		field->flags |= HID_MAIN_ITEM_RELATIVE | HID_MAIN_ITEM_VARIABLE;
+		field->logical_minimum = -127;
+		field->logical_maximum = 127;
+
+		switch (usage->hid & HID_USAGE) {
+		case 0x0000:
+			hid_map_usage(hi, usage, bit, max, EV_REL, 0x06);
+			return 1;
+		case 0x0001:
+			hid_map_usage(hi, usage, bit, max, EV_REL, 0x08);
+			return 1;
+		default:
+			return -1;
 		}
 	}
 
@@ -633,6 +665,11 @@ static int lenovo_probe_cptkbd(struct hid_device *hdev)
 	if (ret)
 		hid_warn(hdev, "Failed to switch F7/9/11 mode: %d\n", ret);
 
+	/* Switch middle button to native mode */
+	ret = lenovo_send_cmd_cptkbd(hdev, 0x09, 0x01);
+	if (ret)
+		hid_warn(hdev, "Failed to switch middle button: %d\n", ret);
+
 	/* Set keyboard settings to known state */
 	cptkbd_data->fn_lock = true;
 	cptkbd_data->sensitivity = 0x05;