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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,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 31EECC433E6 for ; Mon, 18 Jan 2021 14:59:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E833922D2C for ; Mon, 18 Jan 2021 14:59:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393094AbhARO7F (ORCPT ); Mon, 18 Jan 2021 09:59:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:51404 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2393088AbhARO7C (ORCPT ); Mon, 18 Jan 2021 09:59:02 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id BCFAF22C7E; Mon, 18 Jan 2021 14:58:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1610981901; bh=nh5KakTK6nTSgE6PtzTNzNznKC5ibgWCISjQhk0kTsA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=LzyfKaPVnpa7W9U9p8yK5Gg7abCBOku3OUsP8ZijR04c9zrMXFLkPHFqZLGxHWP5E X+ZFlhny43fdMOkjqHkDBRQR9i9OpakW9pPLEZNJidMO+OB46d6WJvYhCYJqkxQti4 cZlQfHEKanVkrtkO2zRv66ft+IeLGDQxMXwT/U7k= Date: Mon, 18 Jan 2021 15:58:18 +0100 From: Greg Kroah-Hartman To: Andy Shevchenko Cc: Mika Westerberg , "Rafael J. Wysocki" , Kai-Heng Feng , lennart@poettering.net, ACPI Devel Maling List , LKML Subject: Re: Multiple MODALIAS= in uevent file confuses userspace Message-ID: References: <20210118141238.GQ968855@lahna.fi.intel.com> <20210118144853.GP4077@smile.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210118144853.GP4077@smile.fi.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Mon, Jan 18, 2021 at 04:48:53PM +0200, Andy Shevchenko wrote: > On Mon, Jan 18, 2021 at 03:26:28PM +0100, Greg Kroah-Hartman wrote: > > On Mon, Jan 18, 2021 at 04:12:38PM +0200, Mika Westerberg wrote: > > > On Mon, Jan 18, 2021 at 02:50:33PM +0100, Rafael J. Wysocki wrote: > > > > On Mon, Jan 18, 2021 at 8:27 AM Kai-Heng Feng > > > > wrote: > > > > > On Sat, Jan 9, 2021 at 12:25 AM Kai-Heng Feng > > > > > wrote: > > > > > > > > > > > > Commit 8765c5ba19490 ("ACPI / scan: Rework modalias creation when > > > > > > "compatible" is present") creates two modaliases for certain ACPI > > > > > > devices. However userspace (systemd-udevd in this case) assumes uevent > > > > > > file doesn't have duplicated keys, so two "MODALIAS=" breaks the > > > > > > assumption. > > > > > > > > > > > > Based on the assumption, systemd-udevd internally uses hashmap to > > > > > > store each line of uevent file, so the second modalias always replaces > > > > > > the first modalias. > > > > > > > > > > > > My attempt [1] is to add a new key, "MODALIAS1" for the second > > > > > > modalias. This brings up the question of whether each key in uevent > > > > > > file is unique. If it's no unique, this may break may userspace. > > > > > > > > > > Does anyone know if there's any user of the second modalias? > > > > > If there's no user of the second one, can we change it to OF_MODALIAS > > > > > or COMPAT_MODALIAS? > > > > > > The only users I'm aware are udev and the busybox equivalent (udev, > > > mdev) but I'm not sure if they use the second second modalias at all so > > > OF_MODALIAS for the DT compatible string sounds like a good way to solve > > > this. > > > > As udev seems to "break" with this (which is where we got the original > > report from), I don't think you need to worry about that user :) > > > Does anyone use mdev anymore, and in any ACPI-supported systems? > > Yes, regularly. Ok, and how badly does it break when MODALIAS is multiple lines like this? Or can it handle it? thanks, greg k-h