From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gerecke Subject: Re: [PATCH] HID: wacom: Stop mapping touch usages after processing HID_DG_CONTACTCOUNT Date: Wed, 20 Jul 2016 09:36:28 -0700 Message-ID: References: <20160711175950.17121-1-killertofu@gmail.com> <20160712073250.GE4663@mail.corp.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-pf0-f195.google.com ([209.85.192.195]:33860 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752388AbcGTQgb (ORCPT ); Wed, 20 Jul 2016 12:36:31 -0400 Received: by mail-pf0-f195.google.com with SMTP id g202so3772199pfb.1 for ; Wed, 20 Jul 2016 09:36:31 -0700 (PDT) In-Reply-To: <20160712073250.GE4663@mail.corp.redhat.com> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Benjamin Tissoires Cc: linux-input@vger.kernel.org, Ping Cheng , Aaron Skomra , Jason Gerecke On 07/12/2016 12:32 AM, Benjamin Tissoires wrote: > Hi Jason, >=20 > On Jul 11 2016 or thereabouts, Jason Gerecke wrote: >> If a touchscreen contains both multitouch and single-touch reports i= n its >> descriptor in that order, the driver may overwrite information it sa= ved >> 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 processin= g a >> slot and sending the ABS_MT_SLOT event at the wrong point in time, >> associating events for the current contact with the following contac= t >> instead. >> >> To prevent this from occuring, we stop mapping usages after having s= een >> HID_DG_CONTACTCOUNT. This usage is only present in multitouch report= s, >> so the format of any following single-touch reports will have no eff= ect. >=20 > I had a quick look at the driver, and it looks like the Cintiq Compan= ion > 2 has more than one multitouch collection (see 499522c "HID: wacom: T= ie > cached HID_DG_CONTACTCOUNT indices to report ID"). >=20 > 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). >=20 > Cheers, > Benjamin >=20 Thanks for the reminder about 499522c. This patch should supersede it i= n terms of functionality, so I can make a patch to remove it instead. As far as compatibility goes, I don't have a Companion 2 to actually test, but looking at the descriptor [1], it shouldn't pose any problems= : the second report containing HID_DG_CONTACTCOUNT is the single-touch report that we don't want to use anyway. [1]: https://github.com/linuxwacom/wacom-hid-descriptors/blob/master/Wacom%2= 0Cintiq%20Companion%202/0003:056A:0326.0002.hid.txt Jason --- Now instead of four in the eights place / you=E2=80=99ve got three, =E2=80=98Cause you added one / (That is to say, eight) to the two, / But you can=E2=80=99t take seven from three, / So you look at the sixty-fours.... >> >> Signed-off-by: Jason Gerecke >> --- >> 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(st= ruct hid_device *hdev, >> struct input_dev *input =3D wacom_wac->touch_input; >> unsigned touch_max =3D wacom_wac->features.touch_max; >> =20 >> + /* stop processing after the first multitouch report */ >> + if (wacom_wac->hid_data.cc_report && >> + wacom_wac->hid_data.cc_report !=3D field->report->id) >> + return; >> + >> switch (usage->hid) { >> case HID_GD_X: >> features->last_slot_field =3D usage->hid; >> --=20 >> 2.9.0 >> -- To unsubscribe from this list: send the line "unsubscribe linux-input" = in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html