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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 18B5BC433FE for ; Mon, 25 Oct 2021 12:58:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F2B2B61027 for ; Mon, 25 Oct 2021 12:58:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233417AbhJYNBP (ORCPT ); Mon, 25 Oct 2021 09:01:15 -0400 Received: from mga14.intel.com ([192.55.52.115]:27939 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233392AbhJYNBO (ORCPT ); Mon, 25 Oct 2021 09:01:14 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10147"; a="229913159" X-IronPort-AV: E=Sophos;i="5.87,180,1631602800"; d="scan'208";a="229913159" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Oct 2021 05:58:52 -0700 X-IronPort-AV: E=Sophos;i="5.87,180,1631602800"; d="scan'208";a="571607199" Received: from smile.fi.intel.com ([10.237.72.184]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Oct 2021 05:58:47 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.95) (envelope-from ) id 1mezYX-000cfz-I6; Mon, 25 Oct 2021 15:58:25 +0300 Date: Mon, 25 Oct 2021 15:58:25 +0300 From: Andy Shevchenko To: Patrick Williams Cc: Greg Kroah-Hartman , Frank Rowand , Zev Weiss , kvm@vger.kernel.org, "Rafael J. Wysocki" , Kirti Wankhede , Jeremy Kerr , Rajat Jain , Jianxiong Gao , Dave Jiang , Saravana Kannan , Mauro Carvalho Chehab , openbmc@lists.ozlabs.org, devicetree@vger.kernel.org, Konrad Rzeszutek Wilk , Alex Williamson , Rob Herring , Bhaskar Chowdhury , Thomas Gleixner , Andrew Jeffery , Cornelia Huck , linux-kernel@vger.kernel.org, Vinod Koul , dmaengine@vger.kernel.org Subject: Re: [PATCH 4/5] driver core: inhibit automatic driver binding on reserved devices Message-ID: References: <20211022020032.26980-1-zev@bewilderbeest.net> <20211022020032.26980-5-zev@bewilderbeest.net> <627101ee-7414-57d1-9952-6e023b8db317@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org On Mon, Oct 25, 2021 at 06:44:26AM -0500, Patrick Williams wrote: > On Mon, Oct 25, 2021 at 08:15:41AM +0200, Greg Kroah-Hartman wrote: > > On Mon, Oct 25, 2021 at 12:38:08AM -0500, Frank Rowand wrote: > > > On 10/23/21 3:56 AM, Greg Kroah-Hartman wrote: > > > We have the bind/unbind ability today, from userspace, that can control > > this. Why not just have Linux grab the device when it boots, and then > > when userspace wants to "give the device up", it writes to "unbind" in > > sysfs, and then when all is done, it writes to the "bind" file and then > > Linux takes back over. > > > > Unless for some reason Linux should _not_ grab the device when booting, > > then things get messier, as we have seen in this thread. > > This is probably more typical on a BMC than atypical. The systems often require > the BMC (running Linux) to be able to reboot independently from the managed host > (running anything). In the example Zev gave, the BMC rebooting would rip away > the BIOS chip from the running host. > > The BMC almost always needs to come up in a "I don't know what could possibly be > going on in the system" state and re-discover where the system was left off. Isn't it an architectural issue then? -- With Best Regards, Andy Shevchenko