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=-3.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,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 1A414C47423 for ; Fri, 2 Oct 2020 14:02:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C2540206DB for ; Fri, 2 Oct 2020 14:02:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601647356; bh=7mcTQgDWOtJnBVSbqdjsF917iDbLlax02nmVJNarDGc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=EfCMeq15yT5Fp2X8iaIcocEvJp7ZXLR261JkI1/Tn2HXfzWbe7DlmErIOVbW+upVa hV77BEPM5vKPH1m4hBAY7okuDfzh97/8BdqJgXexn9jGKxbqeIBGxaZJxB9bOoc1bV g9BqGTc0WoElPU6c/JK3Gb0LhQIX5ctkaN64VXBY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388028AbgJBOCf (ORCPT ); Fri, 2 Oct 2020 10:02:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:48886 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726176AbgJBOCf (ORCPT ); Fri, 2 Oct 2020 10:02:35 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 6335D206CD; Fri, 2 Oct 2020 14:02:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601647355; bh=7mcTQgDWOtJnBVSbqdjsF917iDbLlax02nmVJNarDGc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sW++Yg9WhnPHK3hiOfg6ugibvA5KBRUa4bTSQqM/2jFPntVet/W4HmT4y3Ob/6xTN BPoDcS9HdCedWycnvZhDXoM+x6pzRUB29m6x5jmE8hbpBqAZVcK5Ff/jh+VZd2ZOT9 29rLfivzZPY7q67012thrjkfNoL8Me/mSMdoruFA= Date: Fri, 2 Oct 2020 16:02:33 +0200 From: Greg Kroah-Hartman To: Andrzej Pietrasiewicz Cc: linux-kernel@vger.kernel.org, Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Jiri Slaby , Dmitry Torokhov , linux-input@vger.kernel.org, dri-devel@lists.freedesktop.org, kernel@collabora.com Subject: Re: [PATCH v3 2/2] tty/sysrq: Add configurable handler to execute a compound action Message-ID: <20201002140233.GB3475053@kroah.com> References: <20200818112825.6445-1-andrzej.p@collabora.com> <20200818112825.6445-3-andrzej.p@collabora.com> <20201002125429.GA3350322@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 02, 2020 at 03:42:52PM +0200, Andrzej Pietrasiewicz wrote: > Hi, > > W dniu 02.10.2020 o 14:54, Greg Kroah-Hartman pisze: > > On Tue, Aug 18, 2020 at 01:28:25PM +0200, Andrzej Pietrasiewicz wrote: > > > Userland might want to execute e.g. 'w' (show blocked tasks), followed > > > by 's' (sync), followed by 1000 ms delay and then followed by 'c' (crash) > > > upon a single magic SysRq. Or one might want to execute the famous "Raising > > > Elephants Is So Utterly Boring" action. This patch adds a configurable > > > handler, triggered with 'C', for this exact purpose. The user specifies the > > > composition of the compound action using syntax similar to getopt, where > > > each letter corresponds to an individual action and a colon followed by a > > > number corresponds to a delay of that many milliseconds, e.g.: > > > > > > ws:1000c > > > > > > or > > > > > > r:100eis:1000ub > > > > A macro language for sysrq commands, who would have thought... > > > > Anyway, _why_ would userland want to do something so crazy as this? > > What is the use-case here? > > > > A use-case is Chromebooks which do want to execute 'w', 's', > wait 1000ms and then 'c' under one key combination. Having that supported > upstream brings us one little step closer to those machines running > upstream kernel. Who is causing that to "execute"? Some daemon/program? > Another argument for such a "macro language" is when a machine's system > keeps degrading over time, possibly degrading (relatively) fast. > "Raising Elephants Is So Utterly Boring" consists of 6 actions, each > of which requires pressing several keys. The user might be unable > to complete all the 6 steps, while a "macro" requires user's involvement > for carrying out just one step. So you want to "preload" some commands ahead of time, for when you get in trouble? These should just be debugging / last resort types of things, how regular are they being used in your systems? thanks, greg k-h