From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Torokhov Subject: Re: [PATCH] alps: Fix finger jumps on lifting 2 fingers on v7 touchpad Date: Wed, 20 May 2015 11:00:06 -0700 Message-ID: <20150520180006.GE23809@dtor-ws> References: <1432113413-7007-1-git-send-email-hdegoede@redhat.com> <20150520164016.GB23809@dtor-ws> <555CC6E4.8020806@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-ie0-f169.google.com ([209.85.223.169]:34651 "EHLO mail-ie0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752759AbbETSAL (ORCPT ); Wed, 20 May 2015 14:00:11 -0400 Received: by ieczm2 with SMTP id zm2so45388338iec.1 for ; Wed, 20 May 2015 11:00:10 -0700 (PDT) Content-Disposition: inline In-Reply-To: <555CC6E4.8020806@redhat.com> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Hans de Goede Cc: Peter Hutterer , Benjamin Tissoires , linux-input@vger.kernel.org On Wed, May 20, 2015 at 07:39:48PM +0200, Hans de Goede wrote: > Hi, > > On 20-05-15 18:40, Dmitry Torokhov wrote: > >On Wed, May 20, 2015 at 11:16:53AM +0200, Hans de Goede wrote: > >>On v7 touchpads sometimes when 2 fingers are moved down on the touchpad > >>until they "fall of" the touchpad, the second touch will report 0 for y > >>(max y really since the y axis is inverted) and max x as coordinates, > >>rather then reporting 0, 0 as is expected for a non touching finger. > >> > >>This commit detects this and treats these touches as non touching. > >> > >>See the evemu-recording here: > >>https://bugzilla.redhat.com/attachment.cgi?id=1025058 > >> > >>BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1221200 > >>Signed-off-by: Hans de Goede > >>--- > >> drivers/input/mouse/alps.c | 5 +++++ > >> 1 file changed, 5 insertions(+) > >> > >>diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c > >>index 745921f..9bc4343 100644 > >>--- a/drivers/input/mouse/alps.c > >>+++ b/drivers/input/mouse/alps.c > >>@@ -949,6 +949,11 @@ static void alps_get_finger_coordinate_v7(struct input_mt_pos *mt, > >> case V7_PACKET_ID_TWO: > >> mt[1].x &= ~0x000F; > >> mt[1].y |= 0x000F; > >>+ /* Detect false-postive touches where x & y report max value */ > >>+ if (mt[1].y == 0x7ff && mt[1].x == 0xff0) { > >>+ mt[1].x = 0; > >>+ /* y gets set to 0 at the end of this function */ > > > >I think this is too fragile; I believe we can spare an assignment and > >maybe compiler will optimize it out. > > > >I can fix it up locally unless there are objections to having this extra > >assignment. > > I object to having the extra assignment, the comment is there, because the setting > to 0 at the end of the function is done in the form of: > > mt[0].y = 0x7FF - mt[0].y; > mt[1].y = 0x7FF - mt[1].y; > > So if you add a "mt[1].y = 0" assignment in stead of the comment then you're > actually making mt[1].y = 0x7ff instead of 0, that is why there is a comment > there instead of an assignment. Feel free to modify the comment to make this > more clear ... > > And yes normally the firmware sends 0x7ff for y and 0 for x when there is no touch, > except sometimes it glitches and it sends 0x7ff for y and 0xff0 for x when there is > no touch, which is what this commit catches (this has been tested by the reporter). Ah, I see. Thanks. -- Dmitry