From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Torokhov Subject: Re: [PATCH] Input: touchscreen: AD7879: prevent invalid finger data reports Date: Fri, 22 Oct 2010 09:30:49 -0700 Message-ID: <20101022163049.GA20816@core.coreip.homeip.net> References: <1287408804-19789-1-git-send-email-michael.hennerich@analog.com> <20101022050007.GB10493@core.coreip.homeip.net> <544AC56F16B56944AEC3BD4E3D59177130945B1763@LIMKCMBX1.ad.analog.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-iw0-f174.google.com ([209.85.214.174]:64185 "EHLO mail-iw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754468Ab0JVQa5 (ORCPT ); Fri, 22 Oct 2010 12:30:57 -0400 Received: by iwn34 with SMTP id 34so1123902iwn.19 for ; Fri, 22 Oct 2010 09:30:57 -0700 (PDT) Content-Disposition: inline In-Reply-To: <544AC56F16B56944AEC3BD4E3D59177130945B1763@LIMKCMBX1.ad.analog.com> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: "Hennerich, Michael" Cc: "linux-input@vger.kernel.org" , "device-drivers-devel@blackfin.uclinux.org" , Drivers On Fri, Oct 22, 2010 at 08:16:48AM +0100, Hennerich, Michael wrote: > Dmitry Torokhov wrote on 2010-10-22: > > Hi Michael, > > > > On Mon, Oct 18, 2010 at 03:33:24PM +0200, michael.hennerich@analog.com > > wrote: > >> From: Michael Hennerich > >> > >> Considering following scenario - the touch is present on the screen at > >> the beginning of the last conversion sequence, but by the time the last > >> sequence is finished, the finger is lift off. The AD7879 data available > >> interrupt signals (DAV) completion, however some X,Y values are not > >> valid because the screen inputs were floating during the acquisition. > >> > >> The AD7877 acts differently here, since it only asserts DAV if the > >> touch is still present when the conversion sequence finished. > >> > >> Based on the fact that this can only happen in the last sample of the > >> repeated conversion sequence. We simply skip the last. (Short glitches > >> are filtered by the AD7879 internal median and average filters) This > >> doesn't cause noticeable side effects, since the minimum conversion > >> interval is 9.44ms. We receive ~100 waypoint samples per second, so we > >> simply delay the result by 9.44ms. > >> > >> Actually this patch repeats the first waypoint twice and then skips > > the last. > > > > Input core won't actually pass the 2nd instance through. I think the > > whole thing should look like the patch below. > > I know input core suppresses identical events. > Your patch looks nicer, however it will delay the first response by one > Interrupt. Considering the minimum automatic conversion interval of 9.44ms > - Not sure how much this really matters. > > Acked-by: Michael Hennerich > Thanks Michael. I think 10-15ms delay should not be noticeable for user input, however you have the hardware, any chance you could try and see? -- Dmitry