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=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 F2F8BC433E2 for ; Thu, 25 Mar 2021 19:57:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C8EA761A41 for ; Thu, 25 Mar 2021 19:57:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230300AbhCYT5F (ORCPT ); Thu, 25 Mar 2021 15:57:05 -0400 Received: from alln-iport-5.cisco.com ([173.37.142.92]:33594 "EHLO alln-iport-5.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229576AbhCYT47 (ORCPT ); Thu, 25 Mar 2021 15:56:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=1794; q=dns/txt; s=iport; t=1616702219; x=1617911819; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=pu2I9fiU+I/A1fLeU7DBkeJ7rBv/7jFx5HzFlCmOGBA=; b=f1D0CuijH8Ug4coijfTkQIyxFLwbf0r4En58Yne3AmGuFSyv+Z8eikI3 3RM2fgdAQIHkZvq0BfS4SZsLtm4p4R1Uyc4SZLtZdk2CmlHLETZ+x7wg/ NSLXB4bNrI+C2gYRNhT02i8n72w/q9dM8YoJINFaruC3nwx4Axxy8Ryab 8=; X-IPAS-Result: =?us-ascii?q?A0AjAACo6lxgmIoNJK1aGwEBAQEBAQEBBQEBARIBAQEDA?= =?us-ascii?q?wEBAUCBPgQBAQELAYN2ATmWPAOQB4pbgXwLAQEBDQEBNAQBAYRQAoF8AiU2B?= =?us-ascii?q?w4CAwEBAQMCAwEBAQEFAQEBAgEGBBQBAQEBAQEBAYZDhkUBAgM6PxALGC48G?= =?us-ascii?q?wYsgleDCKspdYE0iRaBRBQOgRcBjUImHIFJQoQuPoQxhWMiBIJGF3mBCGcVB?= =?us-ascii?q?GI1kCxRjQuKQ5BIgRSDEIEimEiCaTEQgziKbZYbuBACBAYFAhaBWgExgVszG?= =?us-ascii?q?ggbFTuCak8ZDY44jk8hA2cCBgoBAQMJhSqCQwEB?= IronPort-HdrOrdr: A9a23:EyzLJ6OQ0cmmLsBcT5r155DYdL4zR+YMi2QD/UoZc3NoW+afkN 2jm+le+B/vkTAKWGwhn9foAtjkfVr385lp7Y4NeYqzRQWOghrLEKhO5ZbvqgeLJwTQ7ehYvJ 0MT4FfD5nKAUF+nYLG5mCDYrId6f2m1IztuuvE1XdqSmhRGsJdxiN0EBySHEEzZCQuP/sEPa GR7MZGuDasEE5/Bq+GL0IIUOTZq9rAmIiOW347LiQ64wqDhy7A0tDHOiWfty1zbxp/hZ8/7G 6AqADi/6Olqf3+8APEznTe9Y4+oqqH9vJzQOqRl8MSNjLgziGvaYgJYcz6gBkF5Mey9V0tjN 7A5y0FAv02wXbQcmapyCGdvTXd7A== X-IronPort-Anti-Spam-Filtered: true X-IronPort-AV: E=Sophos;i="5.81,278,1610409600"; d="scan'208";a="686872034" Received: from alln-core-5.cisco.com ([173.36.13.138]) by alln-iport-5.cisco.com with ESMTP/TLS/DHE-RSA-SEED-SHA; 25 Mar 2021 19:56:56 +0000 Received: from zorba ([10.24.0.17]) by alln-core-5.cisco.com (8.15.2/8.15.2) with ESMTPS id 12PJurCb006095 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Thu, 25 Mar 2021 19:56:55 GMT Date: Thu, 25 Mar 2021 12:56:53 -0700 From: Daniel Walker To: Christophe Leroy Cc: Will Deacon , Rob Herring , Daniel Gimpelevich , Andrew Morton , x86@kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, xe-linux-external@cisco.com, Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/7] powerpc: convert config files to generic cmdline Message-ID: <20210325195653.GL109100@zorba> References: <20210309000247.2989531-4-danielwa@cisco.com> <5f865584-09c9-d21f-ffb7-23cf07cf058e@csgroup.eu> <20210309212944.GR109100@zorba> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Auto-Response-Suppress: DR, OOF, AutoReply X-Outbound-SMTP-Client: 10.24.0.17, [10.24.0.17] X-Outbound-Node: alln-core-5.cisco.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 24, 2021 at 05:59:59PM +0100, Christophe Leroy wrote: > > I think my changes maintain most of this due to the override of > > CONFIG_CMDLINE_PREPEND. This is an upgrade and the inflexibility in powerpc is > > an example of why these changes were created in the first place. > > "inflexibility in powerpc" : Can you elaborate ? the prom environment. > > > > For example , say the default command line is "root=/dev/issblk0" from iss476 > > platform. And the bootloader adds "root=/dev/sda1" > > > > The result is . > > > I'm still having hard time understanding the benefit of having both and . > Could you please provide a complete exemple from real life, ie what exactly > the problem is and what it solves ? Say the boot loader of an old product is released with a command line of "root=/dev/sda" and per the needs of the company or product the boot loader can not be upgraded to change this command line. To change this behavior you would need append or EXTEND. Below I detail an example of PREPEND due to your list question. > > > > Then you have, > > > > root=/dev/issblk0 root=/dev/sda1 > > > > and the bootloader has precedent over the default command line. So root= in the > > above cases is defined by the bootloader. A person could input a command line into a boot loader, and it would override the PREPEND values. Can you imagine you have a default command line which makes root=/dev/issblk0 , but that doesn't work for you testing purpose. So you input into the boot loader root=/dev/sda1 , since you have the default input in the bootloader OVERRIDEABLE you can do this without re-compiling and just input the single root= command into the bootloader. Daniel