The usage Confidence is mandary to Windows Precision Touchpad devices. The
appearance of this usage is checked in hidinput_connect but the quirk
MT_QUIRK_VALID_IS_CONFIDENCE is not applied to the device accordingly.
Apply this quirk and also remove quirk MT_QUIRK_ALWAYS_VALID to enable the
palm rejection for the devices which implement the usage confidence in its
input reports.

Tested on Dell XPS 13 laptop.

Signed-off-by: Allen Hung <redacted>
---
 drivers/hid/hid-multitouch.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 426b2f1..661de1d 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c

@@ -448,6 +448,8 @@ static int mt_touch_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 			mt_store_field(usage, td, hi);
 			return 1;
 		case HID_DG_CONFIDENCE:
+			cls->quirks &= ~MT_QUIRK_ALWAYS_VALID;
+			cls->quirks |= MT_QUIRK_VALID_IS_CONFIDENCE;
 			mt_store_field(usage, td, hi);
 			return 1;
 		case HID_DG_TIPSWITCH:

-- 
1.9.1