From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751126AbdBTW0W (ORCPT ); Mon, 20 Feb 2017 17:26:22 -0500 Received: from bubo.tul.cz ([147.230.16.1]:56606 "EHLO bubo.tul.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750827AbdBTW0T (ORCPT ); Mon, 20 Feb 2017 17:26:19 -0500 X-Greylist: delayed 320 seconds by postgrey-1.27 at vger.kernel.org; Mon, 20 Feb 2017 17:26:18 EST Subject: Re: [PATCH v9 1/8] drivers:input:tsc2007: add new common binding names, pre-calibration, flipping and rotation To: "H. Nikolaus Schaller" , Pavel Machek References: <20170218225435.GA4693@amd> <20170219141715.GA7159@amd> <05F3816F-46E6-4BC2-9E2E-F20E645F7197@goldelico.com> <20170219171518.GA12833@amd> <20170219190547.GA17292@amd> <20170219205708.GA9641@amd> <6DF7B03A-8B63-422C-9561-69A34A7FBF35@goldelico.com> <20170219221930.GA1568@amd> <6610D852-4717-47A7-BFDE-52C8E9E614BB@goldelico.com> Cc: Dmitry Torokhov , Sebastian Reichel , Mark Rutland , =?UTF-8?Q?Beno=c3=aet_Cousson?= , Tony Lindgren , Russell King , Arnd Bergmann , Michael Welling , =?UTF-8?Q?Mika_Penttil=c3=a4?= , Javier Martinez Canillas , Igor Grinberg , "Andrew F. Davis" , Mark Brown , Jonathan Cameron , Rob Herring , Alexander Stein , Eric Engestrom , Hans de Goede , Benjamin Tissoires , Mauro Carvalho Chehab , Hans Verkuil , Nick Dyer , Siebren Vroegindeweij , Michel Verlaan , linux-input@vger.kernel.org, devicetree , LKML , linux-omap , Discussions about the Letux Kernel , linux-iio@vger.kernel.org, kernel@pyra-handheld.com, Aaro Koskinen , =?UTF-8?Q?Pali_Roh=c3=a1r?= , Andrey Gelman , Haibo Chen From: Petr Cvek Message-ID: Date: Mon, 20 Feb 2017 23:26:59 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <6610D852-4717-47A7-BFDE-52C8E9E614BB@goldelico.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Dne 20.2.2017 v 17:50 H. Nikolaus Schaller napsal(a): > Hi Pavel, > >> Am 19.02.2017 um 23:19 schrieb Pavel Machek : >> >> hi! >> >>>>> But as said I don't think we need float or fixed point for practical systems >>>>> at all. >>>> >>>> So you are going to loose precision. And if userspace decides to >>>> calibrate it slightly differently from kernel, lost precision will >>>> matter. >>> >>> Really? >> >> Really. >> >>> Example: >>> >>> ADC values go 100 .. 3995 (i.e. touch margin is 100 steps in pre-calibration) >>> >>> This is scaled to let's say 0..640. >> >> Ok. Now userspace realizes that kernel alignemnt is off, and it would >> want to scale it to 1..642. > > Screen coordinates are still 0..639. > >> That will mean that single pixel will be >> inaccessible, right? > > Yes, that can happen if the additional user-space scale is > 1.0. > > As long as it is small (I expect <1.01 = 1% error in scale) it is > barely noticeable. > > Therefore, I asked before: how big in pixels is your finger or stylus? > Does this effect matter? > > A resistive touch is a man-machine-interface where people press buttons of at > least 12x12 pixels size (or they are no longer visually recognizable). Smallest kernel font is 4x6 (i think) and I'm regularly using 8x8. I would like to be able to select a single letter in the console. cheers, Petr