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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1DB2EC433F5 for ; Wed, 16 Feb 2022 20:37:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232297AbiBPUiA (ORCPT ); Wed, 16 Feb 2022 15:38:00 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:34240 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229823AbiBPUiA (ORCPT ); Wed, 16 Feb 2022 15:38:00 -0500 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 74B912AEDA7; Wed, 16 Feb 2022 12:37:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: MIME-Version:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type: Content-ID:Content-Description:In-Reply-To:References; bh=CAZr9ArhphXYksCSRXhVyugFkJegaRMM9Fl5aGv+W/M=; b=XvlpqhEATsejxfxhR8Ie7y222j lzH+YO/rGSsW3Mw9NSj1DXsEm4l8qC4GeAQ4Vz7coHPHvhBV8VvM3rNYZ75PqQ9ZioEAjo8P/TlYP rWfheJ+n84yZn9gfYsIdhw5LPvJN1zNreK4SX3HFy+sS/ZquKCaNpxbPMucWLe6a74jSMxF0ogPzS QsGK43W4oEjy5BdT8kH1f/VkNft/fCYCm18jc8RGqz2d6B+mTc7nT6hx/LBEmB3RMqdiBxCANnLNl EW4TAIaS5Y4N0OO5aqtKe57bnQ+whEGIOgl9BzgyGBV3yAq97ukCOPXCNpHU6v9JVeb4YMHvxKTPf ny/EzStg==; Received: from [2601:1c0:6280:3f0::aa0b] (helo=bombadil.infradead.org) by bombadil.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nKR3a-008LEX-Fx; Wed, 16 Feb 2022 20:37:46 +0000 From: Randy Dunlap To: linux-kernel@vger.kernel.org Cc: Randy Dunlap , Petr Mladek , Sergey Senozhatsky , Steven Rostedt , John Ogness , Jonathan Corbet , linux-doc@vger.kernel.org Subject: [PATCH v2] Docs: printk: add 'console=null|""' to admin/kernel-parameters Date: Wed, 16 Feb 2022 12:37:45 -0800 Message-Id: <20220216203745.980-1-rdunlap@infradead.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Tell about 'console=null|""' and how to use it. It can be helpful to set (enable) CONFIG_NULL_TTY so that the ttynull driver is available. This avoids problems with stdin/stdout/stderr of the init process. Howevere, CONFIG_NULL_TTY cannot be enabled by default because it can be used by mistake [see commit a91bd6223ecd ("Revert "init/console: Use ttynull as a fallback when there is no console").] Signed-off-by: Randy Dunlap Cc: Petr Mladek Cc: Sergey Senozhatsky Cc: Steven Rostedt Cc: John Ogness Cc: Jonathan Corbet Cc: linux-doc@vger.kernel.org --- v2: "must be the only console=" instead of the first one. (Petr) Add info about CONFIG_NULL_TTY to the commit message. (Petr) Documentation/admin-guide/kernel-parameters.txt | 6 ++++++ 1 file changed, 6 insertions(+) --- linux-next-20220216.orig/Documentation/admin-guide/kernel-parameters.txt +++ linux-next-20220216/Documentation/admin-guide/kernel-parameters.txt @@ -724,6 +724,12 @@ hvc Use the hypervisor console device . This is for both Xen and PowerPC hypervisors. + { null | "" } + Use to disable console output, i.e., to have kernel + console messages discarded. + This must be only console= string used on the + kernel command line. + If the device connected to the port is not a TTY but a braille device, prepend "brl," before the device type, for instance console=brl,ttyS0