Re: [PATCH] HID: wacom: Stop mapping touch usages after processing HID_DG_CONTACTCOUNT
flat view
From: Benjamin Tissoires <hidden>
Date: 2016-07-12 07:32:55
Hi Jason, On Jul 11 2016 or thereabouts, Jason Gerecke wrote:
If a touchscreen contains both multitouch and single-touch reports in its descriptor in that order, the driver may overwrite information it saved about the format of the multitouch report. This can cause the report processing code to get tripped up and send an incorrect event stream to userspace. In particular, this can cause last_slot_field to be overwritten with the result that the driver prematurely assumes it has finished processing a slot and sending the ABS_MT_SLOT event at the wrong point in time, associating events for the current contact with the following contact instead. To prevent this from occuring, we stop mapping usages after having seen HID_DG_CONTACTCOUNT. This usage is only present in multitouch reports, so the format of any following single-touch reports will have no effect.
I had a quick look at the driver, and it looks like the Cintiq Companion 2 has more than one multitouch collection (see 499522c "HID: wacom: Tie cached HID_DG_CONTACTCOUNT indices to report ID"). So if this doesn't break the cintiq companion 2, you have my reviewed-by, but I'd rather be sure (and please see if we really need to keep 499522c then). Cheers, Benjamin
quoted hunk ↗ jump to hunk
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com> --- drivers/hid/wacom_wac.c | 5 +++++ 1 file changed, 5 insertions(+)diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c index fcf2264..e499cdb 100644 --- a/drivers/hid/wacom_wac.c +++ b/drivers/hid/wacom_wac.c@@ -1560,6 +1560,11 @@ static void wacom_wac_finger_usage_mapping(struct hid_device *hdev, struct input_dev *input = wacom_wac->touch_input; unsigned touch_max = wacom_wac->features.touch_max; + /* stop processing after the first multitouch report */ + if (wacom_wac->hid_data.cc_report && + wacom_wac->hid_data.cc_report != field->report->id) + return; + switch (usage->hid) { case HID_GD_X: features->last_slot_field = usage->hid;-- 2.9.0