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=-4.0 required=3.0 tests=BAYES_00,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 87C09C04FF3 for ; Mon, 24 May 2021 15:17:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5695E6101B for ; Mon, 24 May 2021 15:17:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233538AbhEXPSz convert rfc822-to-8bit (ORCPT ); Mon, 24 May 2021 11:18:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:44100 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233119AbhEXPQa (ORCPT ); Mon, 24 May 2021 11:16:30 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E48F961057; Mon, 24 May 2021 15:15:01 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1llCIF-003FbG-Pc; Mon, 24 May 2021 16:14:59 +0100 Date: Mon, 24 May 2021 16:14:59 +0100 Message-ID: <87h7isw4cs.wl-maz@kernel.org> From: Marc Zyngier To: Marek =?UTF-8?B?QmVow7pu?= Cc: Pali =?UTF-8?B?Um9ow6Fy?= , Lorenzo Pieralisi , Thomas Petazzoni , Rob Herring , Bjorn Helgaas , Russell King , Remi Pommarel , Xogium , Tomasz Maciej Nowak , linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 15/42] PCI: aardvark: Change name of INTx irq_chip to advk-INT In-Reply-To: <20210524163651.430e5497@thinkpad> References: <20210506153153.30454-1-pali@kernel.org> <20210506153153.30454-16-pali@kernel.org> <87im3uq5bx.wl-maz@kernel.org> <20210524163651.430e5497@thinkpad> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: kabel@kernel.org, pali@kernel.org, lorenzo.pieralisi@arm.com, thomas.petazzoni@bootlin.com, robh@kernel.org, bhelgaas@google.com, rmk+kernel@armlinux.org.uk, repk@triplefau.lt, contact@xogium.me, tmn505@gmail.com, linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Mon, 24 May 2021 15:36:51 +0100, Marek Behún wrote: > > On Fri, 07 May 2021 10:08:18 +0100 > Marc Zyngier wrote: > > > On Thu, 06 May 2021 16:31:26 +0100, > > Pali Rohár wrote: > > > > > > This name is visible in /proc/interrupts file and for better reading it > > > should have at most 8 characters. Also there is no need to allocate this > > > name dynamically, since there is only one PCIe controller on Armada 37xx. > > > This aligns with how the MSI irq_chip in this driver names it's interrupt > > > ("advk-MSI"). > > > > And *because* the name is visible in /proc/interrupts, it has become > > an ABI, and cannot be changed anymore. > > > > We had the exact same issue with Tegra this merge window as I > > accidentally changed "Tegra" to "tegra", resulting in userspace > > programs failing find stuff in /proc/interrupts. > > > > Please keep the name as is, no matter how ugly it is. > > Hmm, I am 99% sure that for the A3720 platform this ABI change would not > affect anybody. And it does make the driver's irq names confusing. > Can't we really do anything here? No, this is final. Show anything in /proc/*, maintain it forever. We already went there with the bogomips crap showing up in /proc/cpuinfo. There is no way you can know what userspace does, and the best course of action is not to change things for some dubious value of "nicer" or "less confusing". > Note that there were suggestions from some people to completely remove > this driver due to the many problems it has which Pali is trying to > solve. But if the driver was removed and then later introduced again > without these problems, the new version would use the "advk-INT" IRQ > name... No, you would have to keep the *exact same output*. Userspace doesn't know about drivers, and expect things in /proc to be stable. Frankly, there are more important things to do than to worry about the shape of /proc/interrupts. And if we could change it, I'd simply get rid of it (you really should look at it on a system that has ~200 CPUs...). Thanks, M. -- Without deviation from the norm, progress is not possible.