From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Bagwell Subject: Re: [PATCH 2/2]input - wacom_w8001: Add one finger touch support Date: Fri, 10 Dec 2010 07:47:36 -0600 Message-ID: References: <1291857829-13804-1-git-send-email-pinglinux@gmail.com> <20101209195035.GD23781@core.coreip.homeip.net> <20101210073813.GB21009@core.coreip.homeip.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Return-path: Received: from mail-gw0-f42.google.com ([74.125.83.42]:64051 "EHLO mail-gw0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750993Ab0LJNrh (ORCPT ); Fri, 10 Dec 2010 08:47:37 -0500 Received: by gwb20 with SMTP id 20so3045878gwb.1 for ; Fri, 10 Dec 2010 05:47:36 -0800 (PST) In-Reply-To: <20101210073813.GB21009@core.coreip.homeip.net> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Dmitry Torokhov Cc: Ping Cheng , linux-input@vger.kernel.org On Fri, Dec 10, 2010 at 1:38 AM, Dmitry Torokhov wrote: > On Thu, Dec 09, 2010 at 03:21:34PM -0600, Chris Bagwell wrote: >> >> For first point, your right that (123,78) is just a good "known >> starting value" if a driver is going to use that concept because it >> could be filtered just as easy as (0,0). > > I am afraid I did not explain myself well enough. (0,0) is valid > coordinate, same as (123, 78). Thus, even if we try to make driver send > (0,0, !touch), input core may suppress it and never deliver to > userspace if last touching point happened to be also (0,0). Thus > userspace should not rely on having coordinates reset I think. > I had understood ya. What I meant is if a driver sends (0,0,!touch) and a sync when switching tools then you do not need to buffer previous values but instead can imply what previous values are. Userland would still need to account for case of filtered events. Its a memset() vs. a memcpy() when switching tools. Anyways, I'm not recommending any behavior; just letting you know some existing assumptions on driver behavior. Thanks, Chris