From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752456AbeCZOz2 (ORCPT ); Mon, 26 Mar 2018 10:55:28 -0400 Received: from mga06.intel.com ([134.134.136.31]:29316 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752309AbeCZOzY (ORCPT ); Mon, 26 Mar 2018 10:55:24 -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="211393188" Message-ID: <1522076116.16723.13.camel@linux.intel.com> Subject: Re: [PATCH v3] x86: i8237: Register based on FADT legacy boot flag From: Alan Cox To: hpa@zytor.com, Thomas Gleixner , Rajneesh Bhardwaj Cc: Anshuman Gupta , glx@linutronix.de, x86@kernel.org, mingo@redhat.com, rjw@rjwysocki.net, andriy.shevchenko@linux.intel.com, linux-kernel@vger.kernel.org Date: Mon, 26 Mar 2018 15:55:16 +0100 In-Reply-To: <8A68406D-B05E-4953-89D1-D2AB49904644@zytor.com> References: <1521714118-31282-1-git-send-email-anshuman.gupta@intel.com> <20180326054833.GA25173@raj-desk2.iind.intel.com> <8A68406D-B05E-4953-89D1-D2AB49904644@zytor.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 > Can we probe safely for this device? 99% of the time yes the inb gives us a straight answer. However (and we've hit this with port 0x81 for real) there are concerns that some systems will trap those addresses into SMM and do weirdness that makes the 0xFF check fail. Alan