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authorJason Gerecke <killertofu@gmail.com>2021-11-09 03:31:01 +0300
committerJiri Kosina <jkosina@suse.cz>2021-11-10 12:02:06 +0300
commit7fb0413baa7f8a04caef0c504df9af7e0623d296 (patch)
treeb014f5c0a02c3b7ffefc908ee4d4336513e35f12 /drivers/hid
parent304dd3680b56a2a5c8eaff41bcf1a3e49adf7dfc (diff)
downloadlinux-7fb0413baa7f8a04caef0c504df9af7e0623d296.tar.xz
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')
-rw-r--r--drivers/hid/wacom_wac.c8
-rw-r--r--drivers/hid/wacom_wac.h1
2 files changed, 8 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;
diff --git a/drivers/hid/wacom_wac.h b/drivers/hid/wacom_wac.h
index 8b2d4e5b2303..466b62cc16dc 100644
--- a/drivers/hid/wacom_wac.h
+++ b/drivers/hid/wacom_wac.h
@@ -301,6 +301,7 @@ struct hid_data {
bool barrelswitch;
bool barrelswitch2;
bool serialhi;
+ bool confidence;
int x;
int y;
int pressure;