This is a note to let you know that I've just added the patch titled
HID: wacom: Ignore the confidence flag when a touch is removed
to the 5.16-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
hid-wacom-ignore-the-confidence-flag-when-a-touch-is-removed.patch
and it can be found in the queue-5.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From df03e9bd6d4806619b4cdc91a3d7695818a8e2b7 Mon Sep 17 00:00:00 2001
From: Jason Gerecke <killertofu@xxxxxxxxx>
Date: Tue, 18 Jan 2022 14:37:56 -0800
Subject: HID: wacom: Ignore the confidence flag when a touch is removed
From: Jason Gerecke <killertofu@xxxxxxxxx>
commit df03e9bd6d4806619b4cdc91a3d7695818a8e2b7 upstream.
AES hardware may internally re-classify a contact that it thought was
intentional as a palm. Intentional contacts are reported as "down" with
the confidence bit set. When this re-classification occurs, however, the
state transitions to "up" with the confidence bit cleared. This kind of
transition appears to be legal according to Microsoft docs, but we do
not handle it correctly. Because the confidence bit is clear, we don't
call `wacom_wac_finger_slot` and update userspace. This causes hung
touches that confuse userspace and interfere with pen arbitration.
This commit adds a special case to ignore the confidence flag if a contact
is reported as removed. This ensures we do not leave a hung touch if one
of these re-classification events occured. Ideally we'd have some way to
also let userspace know that the touch has been re-classified as a palm
and needs to be canceled, but that's not possible right now :)
Link: https://github.com/linuxwacom/input-wacom/issues/288
Fixes: 7fb0413baa7f (HID: wacom: Use "Confidence" flag to prevent reporting invalid contacts)
CC: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jason Gerecke <jason.gerecke@xxxxxxxxx>
Reviewed-by: Ping Cheng <ping.cheng@xxxxxxxxx>
Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/hid/wacom_wac.c | 29 ++++++++++++++++++++++++++---
1 file changed, 26 insertions(+), 3 deletions(-)
--- a/drivers/hid/wacom_wac.c
+++ b/drivers/hid/wacom_wac.c
@@ -2588,6 +2588,24 @@ static void wacom_wac_finger_slot(struct
}
}
+static bool wacom_wac_slot_is_active(struct input_dev *dev, int key)
+{
+ struct input_mt *mt = dev->mt;
+ struct input_mt_slot *s;
+
+ if (!mt)
+ return false;
+
+ for (s = mt->slots; s != mt->slots + mt->num_slots; s++) {
+ if (s->key == key &&
+ input_mt_get_value(s, ABS_MT_TRACKING_ID) >= 0) {
+ return true;
+ }
+ }
+
+ return false;
+}
+
static void wacom_wac_finger_event(struct hid_device *hdev,
struct hid_field *field, struct hid_usage *usage, __s32 value)
{
@@ -2638,9 +2656,14 @@ static void wacom_wac_finger_event(struc
}
if (usage->usage_index + 1 == field->report_count) {
- if (equivalent_usage == wacom_wac->hid_data.last_slot_field &&
- wacom_wac->hid_data.confidence)
- wacom_wac_finger_slot(wacom_wac, wacom_wac->touch_input);
+ if (equivalent_usage == wacom_wac->hid_data.last_slot_field) {
+ bool touch_removed = wacom_wac_slot_is_active(wacom_wac->touch_input,
+ wacom_wac->hid_data.id) && !wacom_wac->hid_data.tipswitch;
+
+ if (wacom_wac->hid_data.confidence || touch_removed) {
+ wacom_wac_finger_slot(wacom_wac, wacom_wac->touch_input);
+ }
+ }
}
}
Patches currently in stable-queue which might be from killertofu@xxxxxxxxx are
queue-5.16/hid-wacom-reset-expected-and-received-contact-counts-at-the-same-time.patch
queue-5.16/hid-wacom-ignore-the-confidence-flag-when-a-touch-is-removed.patch
queue-5.16/hid-wacom-avoid-using-stale-array-indicies-to-read-contact-count.patch
