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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 B8145C43381 for ; Thu, 28 Mar 2019 14:28:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8F1C721773 for ; Thu, 28 Mar 2019 14:28:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726332AbfC1O2A (ORCPT ); Thu, 28 Mar 2019 10:28:00 -0400 Received: from mga18.intel.com ([134.134.136.126]:57199 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725948AbfC1O2A (ORCPT ); Thu, 28 Mar 2019 10:28:00 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Mar 2019 07:27:59 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,280,1549958400"; d="scan'208";a="156050992" Received: from smile.fi.intel.com (HELO smile) ([10.237.72.86]) by fmsmga002.fm.intel.com with ESMTP; 28 Mar 2019 07:27:57 -0700 Received: from andy by smile with local (Exim 4.92) (envelope-from ) id 1h9W0a-0003RH-Cm; Thu, 28 Mar 2019 16:27:56 +0200 Date: Thu, 28 Mar 2019 16:27:56 +0200 From: Andy Shevchenko To: Borislav Petkov Cc: "H. Peter Anvin" , x86@kernel.org, Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 7/7] x86/boot: Support nocfg parameter for earlyprintk Message-ID: <20190328142756.GF9224@smile.fi.intel.com> References: <20190319184325.72807-1-andriy.shevchenko@linux.intel.com> <20190319184325.72807-8-andriy.shevchenko@linux.intel.com> <20190328130317.GG22720@zn.tnic> <20190328132153.GZ9224@smile.fi.intel.com> <20190328134213.GJ22720@zn.tnic> <20190328140039.GC9224@smile.fi.intel.com> <20190328141307.GM22720@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190328141307.GM22720@zn.tnic> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 28, 2019 at 03:13:07PM +0100, Borislav Petkov wrote: > On Thu, Mar 28, 2019 at 04:00:39PM +0200, Andy Shevchenko wrote: > > If it's _non-standard_ serial interface (by meaning of I/O accessors and port > > addresses), user may consider to use this options in case the interface to > > communicate with kernel is serial one and its configuration is done by other > > means (firmware / bootloader / EFI / etc). > > And is this non-standard interface out there in the wild or only at > Intel's labs? Of course in the wild. > Are there boxes like that out there? One at hand now is called Intel Edison. > If I go to the store and buy a box, how do I know whether that box would > need "nocfg"? Do I look in the BIOS or how do I find out I need to supply > "nocfg"? By reading some technical documentation I suppose. What is your point here? earlyprintk is a mechanism for _debugging_, I suppose the user should have slightly more knowledge than user. > > If by BIOS or by other means the serial port is configured > > How do I find out that the serial port is configured? If you _already_ connected via it and get firmware / bootloader messages. -- With Best Regards, Andy Shevchenko