From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Henrik Rydberg" Subject: Re: [PATCH] CHROMIUM: Input: synaptics - filter out the events with low z values Date: Fri, 24 Feb 2012 10:08:35 +0100 Message-ID: <20120224090835.GA2154@polaris.bitmath.org> References: <1329896503-28394-1-git-send-email-cywang@chromium.org> <20120222083858.GA26570@polaris.bitmath.org> <20120222110459.GA28126@polaris.bitmath.org> <20120222152425.GA29436@polaris.bitmath.org> <20120224082706.GB18291@core.coreip.homeip.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from smtprelay-b12.telenor.se ([62.127.194.21]:55647 "EHLO smtprelay-b12.telenor.se" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755548Ab2BXJIk (ORCPT ); Fri, 24 Feb 2012 04:08:40 -0500 Content-Disposition: inline In-Reply-To: <20120224082706.GB18291@core.coreip.homeip.net> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Dmitry Torokhov Cc: Daniel Kurtz , Chung-yih Wang , Alessandro Rubini , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org > > The most striking effect is the ability to better retain a > > drag. Although the statement was made in light of possible > > (1-strong,1-weak) packets, it should help in the 2-weak case too. > > The bigger question is why is this needed in kernel. The original > hysteresis with BTN_TOUCH was done for sole benefit of mousedev so that > we could allow somewhat better transition from standard PS/2 mode into > native Synaptics mode with absolute coordinates at time when barely > anyone had Synaptics X driver installed. This was, what, 10 years ago? The semi-mt behavior is obviously a special case, where userspace relies on the reported number of fingers to transition between one touch and two touches. There is no pressure information sent to userspace in this case, so the situation is in fact quite similar to the ancient mousedev situation. Henrik