diff options
| author | Jason Gerecke <killertofu@gmail.com> | 2021-11-08 16:31:01 -0800 |
|---|---|---|
| committer | Jiri Kosina <jkosina@suse.cz> | 2021-11-10 10:02:06 +0100 |
| commit | 7fb0413baa7f8a04caef0c504df9af7e0623d296 (patch) | |
| tree | b014f5c0a02c3b7ffefc908ee4d4336513e35f12 /drivers/hid/wacom_wac.c | |
| parent | 304dd3680b56a2a5c8eaff41bcf1a3e49adf7dfc (diff) | |
HID: wacom: Use "Confidence" flag to prevent reporting invalid contacts
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@wacom.com>
Tested-by: Joshua Dickens <joshua.dickens@wacom.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'drivers/hid/wacom_wac.c')
| -rw-r--r-- | drivers/hid/wacom_wac.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c index 33a6908995b1..2a4cc39962e7 100644 --- a/drivers/hid/wacom_wac.c +++ b/drivers/hid/wacom_wac.c @@ -2603,6 +2603,9 @@ static void wacom_wac_finger_event(struct hid_device *hdev, return; switch (equivalent_usage) { + case HID_DG_CONFIDENCE: + wacom_wac->hid_data.confidence = value; + break; case HID_GD_X: wacom_wac->hid_data.x = value; break; @@ -2635,7 +2638,8 @@ static void wacom_wac_finger_event(struct hid_device *hdev, } if (usage->usage_index + 1 == field->report_count) { - if (equivalent_usage == wacom_wac->hid_data.last_slot_field) + 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); } } @@ -2653,6 +2657,8 @@ static void wacom_wac_finger_pre_report(struct hid_device *hdev, wacom_wac->is_invalid_bt_frame = false; + hid_data->confidence = true; + for (i = 0; i < report->maxfield; i++) { struct hid_field *field = report->field[i]; int j; |