From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8CF35C2D0E4 for ; Wed, 18 Nov 2020 00:32:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 33EFA2067D for ; Wed, 18 Nov 2020 00:32:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="MBy/50CU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726977AbgKRAbw (ORCPT ); Tue, 17 Nov 2020 19:31:52 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51040 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726815AbgKRAbw (ORCPT ); Tue, 17 Nov 2020 19:31:52 -0500 Received: from mail-pl1-x641.google.com (mail-pl1-x641.google.com [IPv6:2607:f8b0:4864:20::641]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3AC03C0617A6; Tue, 17 Nov 2020 16:31:52 -0800 (PST) Received: by mail-pl1-x641.google.com with SMTP id d17so33504plr.5; Tue, 17 Nov 2020 16:31:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=C5V5guK8eJ/RbQCaxbWVa238p+t1xonan72j5q2VmeI=; b=MBy/50CUa+jztmeopmG8F27CpTzEVBkeEl5dssXIHAeFD8q8yUh2jYucGHJZYnvRj8 7diIxGD8b9+P7u+r8ia6cEamyYZZN5CmDrCvclbyU9b/MxSNz+mkM8qjed+bTQzrIOu+ 9tfeHyCPdh+Vgol7tk9dSf6BQJqaNVMFl4XnB6/UPRi5c7PeWMaVs15w3FcFgzwmBTsv wIk+VLKMn6Fm5W5Wbe5A1o+nnBacvj8kuVFoFfTRgRunXT3OVWu1jaAXMghNdqnM89lF wFZuUvA66eg0jP5eor3ZEZ9Oy+Ch4HfOvCEcEyXeAmT1XVIzHxIQuKoB+3r+t1MesrOm pwUA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=C5V5guK8eJ/RbQCaxbWVa238p+t1xonan72j5q2VmeI=; b=REOgol5Q2ooIT+u2uFwtiNnNkVAarOS5h8CIX/XKJw7nFkghaD55azKoNUriiJQ0bU HhzTl6L4hDdFAD72CPo3wXgAKXw/9SL97e3XWWOBo2fDVl75O+4uIEwAzi+G1q6wV3nb hLg84vs9ITs0e5l18PYGOJk8YzkjBgKW+k579xSvk210kQLyQTh5cC/S2tTuavNZxCbG M+9AMN021mCEO7VnYZhwRD6FvboC9OfNK0yteVFV1y6pGihyrrPsZmj1ArVTYrVjX/Xu 6GtS/CxlqHeqPvkyDcgukZWX72gAIh53MxzF+EJan68/FoDxQt31947QQTH3YAt0tVgX Axow== X-Gm-Message-State: AOAM531TO1XO3LRAqVPg3GxYzlJdOFUbpkF2bUWL2GkjjTYFW2yksP73 jho6Zdu8Gu4sMrMIgdT6XeE= X-Google-Smtp-Source: ABdhPJx+YQj/eEH6ERLBPN/Nf2YGJ3MJRIg0PFJtp84QY8Bf+8zvtebywcZN7G7kPB/oeUsjk/I1iA== X-Received: by 2002:a17:902:8506:b029:d9:6dd:45ea with SMTP id bj6-20020a1709028506b02900d906dd45eamr2072035plb.72.1605659511654; Tue, 17 Nov 2020 16:31:51 -0800 (PST) Received: from dtor-ws ([2620:15c:202:201:a6ae:11ff:fe11:fcc3]) by smtp.gmail.com with ESMTPSA id e22sm252397pjh.45.2020.11.17.16.31.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Nov 2020 16:31:50 -0800 (PST) Date: Tue, 17 Nov 2020 16:31:48 -0800 From: Dmitry Torokhov To: Oleksij Rempel Cc: Alexandru Ardelean , Mark Brown , David Jander , kernel@pengutronix.de, linux-kernel@vger.kernel.org, linux-input@vger.kernel.org, linux-spi@vger.kernel.org Subject: Re: [PATCH v1] Input: touchscreen: ads7846.c: fix integer overflow on Rt calculation Message-ID: <20201118003148.GE2009714@dtor-ws> References: <20201113112240.1360-1-o.rempel@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201113112240.1360-1-o.rempel@pengutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-input@vger.kernel.org On Fri, Nov 13, 2020 at 12:22:40PM +0100, Oleksij Rempel wrote: > In some rare cases the 32 bit Rt value will overflow if z2 and x is max, > z1 is minimal value and x_plate_ohms is relatively high (for example 800 > ohm). This would happen on some screen age with low pressure. > > There are two possible fixes: > - make Rt 64bit > - reorder calculation to avoid overflow > > The second variant seems to be preferable, since 64 bit calculation on > 32 bit system is a bit more expensive. > > Fixes: ffa458c1bd9b6f653008d450f337602f3d52a646 ("spi: ads7846 driver") > Co-Developed-by: David Jander > Signed-off-by: David Jander > Signed-off-by: Oleksij Rempel Applied, thank you. -- Dmitry