From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aaron Lu Subject: Re: [PATCH] acpi: video: no automatic brightness changes by firmware Date: Fri, 05 Jul 2013 09:15:39 +0800 Message-ID: <51D61E3B.2000205@intel.com> References: <51B98CFD.7090409@intel.com> <51BE5FD6.6070405@intel.com> <20130617224040.GB14793@srcf.ucam.org> <51BFA628.8000804@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from mga11.intel.com ([192.55.52.93]:4187 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751781Ab3GEBPA (ORCPT ); Thu, 4 Jul 2013 21:15:00 -0400 In-Reply-To: <51BFA628.8000804@intel.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Matthew Garrett , "Rafael J. Wysocki" Cc: Len Brown , ACPI Devel Mailing List , Zhang Rui , Micael Dias , Dan Garton , Bob Ziuchkovski On 06/18/2013 08:13 AM, Aaron Lu wrote: > On 06/18/2013 06:40 AM, Matthew Garrett wrote: >> On Mon, Jun 17, 2013 at 09:01:10AM +0800, Aaron Lu wrote: >>> Starting from win8, MS backlight control driver will set bit 2 of the >>> parameter of control method _DOS, to inform firmware it should not >>> perform any automatic brightness changes. This mostly affects hotkey >>> notification deliver - if we do not set this bit, on hotkey press, >>> firmware may choose to adjust brightness level instead of sending out >>> notification and doing nothing. >> >> It's worth noting that this is a change in behaviour, and there's at >> least one VIA-based netbook where making this change breaks backlight >> control. > > Thanks for pointing this out. > Do you have any more information about this system, like its ACPI dump? > > BTW, perhaps we should make this behavior change only for win8 systems? Just checked all affected systems: https://bugzilla.kernel.org/show_bug.cgi?id=51051 https://bugzilla.kernel.org/show_bug.cgi?id=56711 https://bugzilla.kernel.org/show_bug.cgi?id=52951 All systems claim win8 in _OSI, so I suppose I'll make this behavior change only for those systems with the help of the recently proposed "Expose OSI version" patchset. Please let me know if you disagree, thanks. -Aaron