]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
HID: wacom: Ignore the confidence flag when a touch is removed
authorJason Gerecke <killertofu@gmail.com>
Tue, 18 Jan 2022 22:37:56 +0000 (14:37 -0800)
committerJiri Kosina <jkosina@suse.cz>
Fri, 21 Jan 2022 14:10:02 +0000 (15:10 +0100)
commitdf03e9bd6d4806619b4cdc91a3d7695818a8e2b7
treee49f3b3fdc5c5871e2e5c817414da92760dfc9cf
parent546e41ac994cc185ef3de610ca849a294b5df3ba
HID: wacom: Ignore the confidence flag when a touch is removed

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@vger.kernel.org
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Reviewed-by: Ping Cheng <ping.cheng@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
drivers/hid/wacom_wac.c