On Mon, 8 Nov 2021, Jason Gerecke wrote: > The HID descriptor of many of Wacom's touch input devices include a > "Confidence" usage that signals if a particular touch collection contains > useful data. The driver does not look at this flag, however, which causes > even invalid contacts to be reported to userspace. A lucky combination of > kernel event filtering and device behavior (specifically: contact ID 0 == > invalid, contact ID >0 == valid; and order all data so that all valid > contacts are reported before any invalid contacts) spare most devices from > any visibly-bad behavior. > > The DTH-2452 is one example of an unlucky device that misbehaves. It uses > ID 0 for both the first valid contact and all invalid contacts. Because > we report both the valid and invalid contacts, the kernel reports that > contact 0 first goes down (valid) and then goes up (invalid) in every > report. This causes ~100 clicks per second simply by touching the screen. > > This patch inroduces new `confidence` flag in our `hid_data` structure. > The value is initially set to `true` at the start of a report and can be > set to `false` if an invalid touch usage is seen. > > Link: https://github.com/linuxwacom/input-wacom/issues/270 > Fixes: f8b6a74719b5 ("HID: wacom: generic: Support multiple tools per report") > Signed-off-by: Jason Gerecke <jason.gerecke@xxxxxxxxx> > Tested-by: Joshua Dickens <joshua.dickens@xxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> Applied, thanks Jason. -- Jiri Kosina SUSE Labs
