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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 863CFC74A21 for ; Wed, 10 Jul 2019 15:46:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 661152086D for ; Wed, 10 Jul 2019 15:46:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728278AbfGJPqM (ORCPT ); Wed, 10 Jul 2019 11:46:12 -0400 Received: from smtprelay0051.hostedemail.com ([216.40.44.51]:58243 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725832AbfGJPqL (ORCPT ); Wed, 10 Jul 2019 11:46:11 -0400 Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay05.hostedemail.com (Postfix) with ESMTP id C502F1802912E; Wed, 10 Jul 2019 15:46:09 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: range96_50d7d845d712e X-Filterd-Recvd-Size: 3121 Received: from XPS-9350 (cpe-23-242-196-136.socal.res.rr.com [23.242.196.136]) (Authenticated sender: joe@perches.com) by omf13.hostedemail.com (Postfix) with ESMTPA; Wed, 10 Jul 2019 15:45:54 +0000 (UTC) Message-ID: Subject: Re: [PATCH 00/12] treewide: Fix GENMASK misuses From: Joe Perches To: Russell King - ARM Linux admin , Johannes Berg Cc: Andrew Morton , Patrick Venture , Nancy Yuen , Benjamin Fair , Andrew Jeffery , openbmc@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-aspeed@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, netdev@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-stm32@st-md-mailman.stormreply.com, linux-wireless@vger.kernel.org, linux-media@vger.kernel.org, linux-iio@vger.kernel.org, devel@driverdev.osuosl.org, alsa-devel@alsa-project.org, linux-mmc@vger.kernel.org, dri-devel@lists.freedesktop.org Date: Wed, 10 Jul 2019 08:45:53 -0700 In-Reply-To: <20190710094337.wf2lftxzfjq2etro@shell.armlinux.org.uk> References: <5fa1fa6998332642c49e2d5209193ffe2713f333.camel@sipsolutions.net> <20190710094337.wf2lftxzfjq2etro@shell.armlinux.org.uk> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.30.5-0ubuntu0.18.10.1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Wed, 2019-07-10 at 10:43 +0100, Russell King - ARM Linux admin wrote: > On Wed, Jul 10, 2019 at 11:17:31AM +0200, Johannes Berg wrote: > > On Tue, 2019-07-09 at 22:04 -0700, Joe Perches wrote: > > > These GENMASK uses are inverted argument order and the > > > actual masks produced are incorrect. Fix them. > > > > > > Add checkpatch tests to help avoid more misuses too. > > > > > > Joe Perches (12): > > > checkpatch: Add GENMASK tests > > > > IMHO this doesn't make a lot of sense as a checkpatch test - just throw > > in a BUILD_BUG_ON()? I tried that. It'd can't be done as it's used in declarations and included in asm files and it uses the UL() macro. I also tried just making it do the right thing whatever the argument order. Oh well. > My personal take on this is that GENMASK() is really not useful, it's > just pure obfuscation and leads to exactly these kinds of mistakes. > > Yes, I fully understand the argument that you can just specify the > start and end bits, and it _in theory_ makes the code more readable. > > However, the problem is when writing code. GENMASK(a, b). Is a the > starting bit or ending bit? Is b the number of bits? It's confusing > and causes mistakes resulting in incorrect code. A BUILD_BUG_ON() > can catch some of the cases, but not all of them. It's a horrid little macro and I agree with Russell. I also think if it existed at all it should have been GENMASK(low, high) not GENMASK(high, low). I