From mboxrd@z Thu Jan 1 00:00:00 1970 From: Henrik Rydberg Subject: Re: [PATCH 7/7] elantech: average the two coordinates when 2 fingers Date: Mon, 02 Aug 2010 13:46:19 +0200 Message-ID: <4C56B00B.50204@euromail.se> References: <4C1FD2B0.1080504@tudelft.nl> <4C1FD454.4050807@tudelft.nl> <20100721033655.GA9070@core.coreip.homeip.net> <4C532009.4020103@tudelft.nl> <4C533DC3.9070001@euromail.se> <4C54ABFE.8050106@tudelft.nl> <4C554058.6080203@euromail.se> <4C555A44.5050505@tudelft.nl> <4C557D3A.3050501@euromail.se> <4C567F27.7070900@tudelft.nl> <4C5697C4.1020801@euromail.se> <4C56A81E.3040703@tudelft.nl> <4C56AA67.8000902@euromail.se> <4C56AD12.1080106@tudelft.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from ch-smtp03.sth.basefarm.net ([80.76.149.214]:46106 "EHLO ch-smtp03.sth.basefarm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752152Ab0HBLqr (ORCPT ); Mon, 2 Aug 2010 07:46:47 -0400 In-Reply-To: <4C56AD12.1080106@tudelft.nl> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: =?ISO-8859-1?Q?=C9ric_Piel?= Cc: Chris Bagwell , Dmitry Torokhov , "linux-input@vger.kernel.org" , Florian Ragwitz On 08/02/2010 01:33 PM, =C9ric Piel wrote: > Op 02-08-10 13:22, Henrik Rydberg schreef: >> On 08/02/2010 01:12 PM, =C9ric Piel wrote: > : >>>> You need to add the tracking id and a couple of lines, but i do no= t see why the >>>> 2->1 transition would be treated any differently. The one-finger c= oordinate >>>> would be close to either position[0] or position[1], which would d= etermine the >>>> tracking id to keep. Every time you add a finger you add a new tra= cking id. What >>>> is your planned support for three fingers? >>> Yes, yes, it's probably fairly easy to do some kind of tracking. Bu= t I >>> think that as long as the hardware does not provide such a thing, i= t's >>> better to do the minimum in kernel space, just enough to be meaning= ful, >>> and leave the rest to userspace. >> >> >> The implemented part could also be done in userspace. Going half-way= just to >> circumvent buggy behavior in synaptics is really not a good idea. > No, we've been going from protocol 0.5 (report max/min coordinates) t= o > protocol A.5 (report finger positions, often with correct track ID). = My > argument is that it's not because we are half-way to B, by chance, th= at > we should go up to it. We do just the minimum to respect the minimum > protocol. Once the driver respects that protocol, all the fancy stuff > has to stay in userspace. There is already mtdev (I'm sure I don't ha= ve > to tell you ;-) ), I don't see the point of doing some copy-pasting. Without this patch, the driver reports two points, the lower-left and upper-right of a rectangle. With this patch, the driver reports two poi= nts, which is either equal to the two actual fingers, or, after resting the = fingers horizontally, two random opposite corners of a rectangle. Doing userspace tracking without the patch results in properly followin= g the lower-left and upper-right corners of a triangle. Doing userspace track= ing with the patch results in properly following two random opposite corners of = a rectangle. Without this patch, synaptics shows jerky behavior. With this patch, sy= naptics works a bit better. The above tells me that the MT situation did not improve much, and that= the major improvement is to paper over the synaptics problem. The argument to go forward implementing protocol B is that the current = patch actually does proper two-finger tracking to the extent that it is possi= ble. Since mtdev cannot improve the fact that this device does not following= fingers but corners, it makes sense to treat this device specially, and impleme= nt the extra lines in the kernel to make it as good as it can be. Alternativel= y, one can give up the idea of using MT in this driver altogether, and just im= plement the mean position ABS_X/Y, old-style. Henrik -- 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