From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chase Douglas Subject: Re: [PATCH] Input: Document the device properties Date: Mon, 30 Jan 2012 18:05:55 +0100 Message-ID: <4F26CDF3.5080606@canonical.com> References: <1327912546-16960-1-git-send-email-rydberg@euromail.se> <4F268BCC.4000008@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from youngberry.canonical.com ([91.189.89.112]:40450 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752028Ab2A3RFL (ORCPT ); Mon, 30 Jan 2012 12:05:11 -0500 In-Reply-To: <4F268BCC.4000008@canonical.com> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Jussi Pakkanen Cc: Henrik Rydberg , Dmitry Torokhov , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org On 01/30/2012 01:23 PM, Jussi Pakkanen wrote: > On 01/30/2012 10:35 AM, Henrik Rydberg wrote: >> +INPUT_PROP_SEMI_MT: >> +------------------ >> +Some touchpads, most common between 2008 and 2011, can detect the presence >> +of multiple contacts without resolving the individual positions; only the >> +number of contacts and the corresponding bounding box is known. For such >> +touchpads, the semi-mt property should be set. > > A "corresponding bounding box" usually means "a bounding box that > contains all touches on the touchpad". I've been told (though I have not > checked it myself) that there are devices that don't do this. They only > report a bounding box for some subset of touches. If this is the case, > it should be documented here. Yeah, I thought Henrik's definition was correct for a long time, but when Derek Foreman (I think) proposed some patches for the latest synaptics devices I took a closer look at my semi-mt synaptics trackpad. The coordinates it gave were locations based on two of the touches. When three touches are on the touchpad, it gave a bounding box of two of the touches, and there's no way to tell which two. -- Chase