From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752269AbeCZOwm (ORCPT ); Mon, 26 Mar 2018 10:52:42 -0400 Received: from mga07.intel.com ([134.134.136.100]:60780 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751132AbeCZOwl (ORCPT ); Mon, 26 Mar 2018 10:52:41 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.48,365,1517904000"; d="scan'208";a="28522101" Message-ID: <1522075953.16723.11.camel@linux.intel.com> Subject: Re: [PATCH v3] x86: i8237: Register based on FADT legacy boot flag From: Alan Cox To: Thomas Gleixner , Anshuman Gupta Cc: glx@linutronix.de, x86@kernel.org, mingo@redhat.com, hpa@zytor.com, rjw@rjwysocki.net, andriy.shevchenko@linux.intel.com, linux-kernel@vger.kernel.org, rajneesh.bhardwaj@intel.com Date: Mon, 26 Mar 2018 15:52:33 +0100 In-Reply-To: References: <1521714118-31282-1-git-send-email-anshuman.gupta@intel.com> Organization: Intel Corporation Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.24.6 (3.24.6-1.fc26) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Please explain WHY 2017 is the cut-off date. I still have no clue how > that > is decided aside of being a random number. Because if it's prior to 2017 then it'll almost certainly have those registers even if the firmware says otherwise. After that point we think the firmware is going to give valid answers (although the 0xFF check is actually the important one in reality). Alan