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=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham 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 B5436C10F14 for ; Thu, 11 Apr 2019 15:28:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8CFD72173C for ; Thu, 11 Apr 2019 15:28:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726735AbfDKP2u (ORCPT ); Thu, 11 Apr 2019 11:28:50 -0400 Received: from bastet.se.axis.com ([195.60.68.11]:54997 "EHLO bastet.se.axis.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726137AbfDKP2t (ORCPT ); Thu, 11 Apr 2019 11:28:49 -0400 Received: from localhost (localhost [127.0.0.1]) by bastet.se.axis.com (Postfix) with ESMTP id 7B47E18670; Thu, 11 Apr 2019 17:28:47 +0200 (CEST) X-Axis-User: NO X-Axis-NonUser: YES X-Virus-Scanned: Debian amavisd-new at bastet.se.axis.com Received: from bastet.se.axis.com ([IPv6:::ffff:127.0.0.1]) by localhost (bastet.se.axis.com [::ffff:127.0.0.1]) (amavisd-new, port 10024) with LMTP id LCcmIKMGFwow; Thu, 11 Apr 2019 17:28:46 +0200 (CEST) Received: from boulder02.se.axis.com (boulder02.se.axis.com [10.0.8.16]) by bastet.se.axis.com (Postfix) with ESMTPS id 06ACD18699; Thu, 11 Apr 2019 17:28:45 +0200 (CEST) Received: from boulder02.se.axis.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C0E0C1A090; Thu, 11 Apr 2019 17:28:45 +0200 (CEST) Received: from boulder02.se.axis.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B5AAF1A08E; Thu, 11 Apr 2019 17:28:45 +0200 (CEST) Received: from thoth.se.axis.com (unknown [10.0.2.173]) by boulder02.se.axis.com (Postfix) with ESMTP; Thu, 11 Apr 2019 17:28:45 +0200 (CEST) Received: from lnxartpec.se.axis.com (lnxartpec.se.axis.com [10.88.4.9]) by thoth.se.axis.com (Postfix) with ESMTP id A9EF521E; Thu, 11 Apr 2019 17:28:45 +0200 (CEST) Received: by lnxartpec.se.axis.com (Postfix, from userid 10564) id 9B48E80DB0; Thu, 11 Apr 2019 17:28:45 +0200 (CEST) Date: Thu, 11 Apr 2019 17:28:45 +0200 From: Vincent Whitchurch To: "Enrico Weigelt, metux IT consult" Cc: Greg KH , jslaby@suse.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] tty: Add NULL TTY driver Message-ID: <20190411152845.xomzmhtyejzr4r35@axis.com> References: <20190403113327.3628-1-vincent.whitchurch@axis.com> <20190403131213.GA4246@kroah.com> <20190403141109.3mdmqbt3mjxrie6k@axis.com> <20190405090043.vnsftwpdm56cx2hr@axis.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-TM-AS-GCONF: 00 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 05, 2019 at 02:32:41PM +0200, Enrico Weigelt, metux IT consult wrote: > On 05.04.19 11:00, Vincent Whitchurch wrote: > > On Fri, Apr 05, 2019 at 10:39:43AM +0200, Enrico Weigelt, metux IT consult wrote: > >> On 03.04.19 16:11, Vincent Whitchurch wrote: > >> > >>> Especially on embedded systems, it would be convenient to have a simple > >>> way to disable the console (both for kernel and userspace) on a system > >>> which normally uses it, to free up the UART for other things. > >> > >> Just symlinking to /dev/null does not work ? > > > > No, /dev/null does not support the TTY ioctls. > > hmm, wo (which programs) do you need, that really need them ? I think it was systemd's debug-shell which complained about the ioctls. > >> OTOH, if you're introducing a dummy console, wouldn't a ringbuffer that, > >> can be read out later, a better option ? > > > > There is already a ttyprintk driver in mainline to send these messages > > to the printk ring buffer if one is actually intrested in what is > > written to the console. There's no option to enable it via console= in > > mainline but I have a patch for that too. > > Great. IMHO, that would be the better way. Like Krzysztof explained, sometimes you just want to discard these messages.