From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: Re: [PATCH] ACPI: Disable Windows 8 compatibility for some Lenovo ThinkPads Date: Mon, 11 Feb 2013 19:09:14 +0000 Message-ID: <20130211190914.GA27364@srcf.ucam.org> References: <1360599681-24781-1-git-send-email-seth.forshee@canonical.com> <20130211175213.GA25139@srcf.ucam.org> <20130211190617.GH13768@thinkpad-t410> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from cavan.codon.org.uk ([93.93.128.6]:41851 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758700Ab3BKTJT (ORCPT ); Mon, 11 Feb 2013 14:09:19 -0500 Content-Disposition: inline In-Reply-To: <20130211190617.GH13768@thinkpad-t410> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Seth Forshee Cc: Len Brown , "Rafael J. Wysocki" , linux-acpi@vger.kernel.org, Ben Jencks , joeyli On Mon, Feb 11, 2013 at 01:06:17PM -0600, Seth Forshee wrote: > On Mon, Feb 11, 2013 at 05:52:13PM +0000, Matthew Garrett wrote: > > So the problem is that userspace is writing values that don't happen to > > be aligned with the values the hardware reacts to, and so nothing gets > > changed? > > Yes. The values are valid according to to _BCL, but _BCM is discarding > any values that aren't contained in an array named BRTW. BRTW is > literally the object returned by _BCL returns for !Windows 2012. Here's > a link to the AML if you'd like to take a look. Right. My concern here is that Windows clearly doesn't trigger the issue, and so there's some chance that we'll see similar issues on other machines. Disabling Windows 8 compatibility isn't really an option. One choice might be to have the ACPI video driver set all intermediate values if the system makes the Windows 8 OSI call? -- Matthew Garrett | mjg59@srcf.ucam.org