From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756389Ab2CNFxB (ORCPT ); Wed, 14 Mar 2012 01:53:01 -0400 Received: from charybdis-ext.suse.de ([195.135.221.2]:24122 "EHLO nat.nue.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755152Ab2CNFw7 (ORCPT ); Wed, 14 Mar 2012 01:52:59 -0400 Subject: Re: [PATCH] Added backlight driver for Acer Aspire 4736 From: joeyli To: Pradeep Subrahmanion Cc: Matthew Garrett , rpurdie@rpsys.net, FlorianSchandinat@gmx.de, akpm@linux-foundation.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <1331692996.3052.8.camel@debian.Gayathri> References: <1331608337.2267.67.camel@debian.Gayathri> <20120312175130.GA18002@srcf.ucam.org> <1331640592.3485.50.camel@debian.Gayathri> <20120313124738.GB10822@srcf.ucam.org> <20120313133458.GA11574@srcf.ucam.org> <1331688294.2577.19.camel@debian.Gayathri> <1331680373.10557.169.camel@linux-s257.site> <1331692996.3052.8.camel@debian.Gayathri> Content-Type: text/plain; charset="UTF-8" Date: Wed, 14 Mar 2012 13:51:18 +0800 Message-ID: <1331704278.10557.190.camel@linux-s257.site> Mime-Version: 1.0 X-Mailer: Evolution 2.28.2 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 於 三，2012-03-14 於 08:13 +0530，Pradeep Subrahmanion 提到： > Hi Joey , > > > Per my understood, EC firmware should change brightness but didn't do > > that, another > > way is touch i915 register in _BCM. > > how do we do this ? you mean change the _BCM implementation ? "BIOS guy" should do something like this: Method (AINT, 2, NotSerialized) { ... If (LEqual (Arg0, One)) { Store (Divide (Multiply (Arg1, 0xFF), 0x64, ), BCLP) Or (BCLP, 0x80000000, BCLP) <=== touch BCLP register Store (0x02, ASLC) } Method (_BCM, 1, NotSerialized) { If (LAnd (LGreaterEqual (Arg0, Zero), LLessEqual (Arg0, 0x64))) { AINT (One, Arg0) <=== call AINT method Store (Arg0, BRTL) } } Just for reference, they should do that when EC didn't wire to backlight. > > > > Acer machine provide a broken _BCM implementation and they didn't test > > it. > > > > > > > By ' ACPI interface' , I mean 'acpi_video0' inside the > > > > > /sys/class/backlight. I havn't tried the /sys/class/backlight interface > > > > > directly . I will try that also. > > > > > > > > So writing values into /sys/class/backlight/acpi_video0/brightness does > > > > nothing? > > > > > > > > > No change in value when writing > > > to /sys/class/backlight/acpi_video0/brightness. > > > > > > Another thing is that when i did boot with acpi_backlight = 'acer_wmi' , > > > in new kernel (3.3.0-rc7) , it shows following messages , > > > > > > [ 8.350825] wmi: Mapper loaded > > > [ 10.363975] acer_wmi: Acer Laptop ACPI-WMI Extras > > > [ 10.396186] acer_wmi: Function bitmap for Communication Device: 0x91 > > > [ 10.396385] acer_wmi: Brightness must be controlled by generic video > > > driver > > > > > > Also there was no interface inside /sys/class/backlight for acer_wmi. > > > > > > > Yes, acer_wmi support backlight control with AMW0 interface, your > > machine didn't have AMW0 interface. > > > > Normally, backlight should control by standard acpi interface. > > > > > I also tried writing directly to Embedded controller register .But no > > > change. > > > > The machine has broken _BCM method, because EC should do something after > > _BCM changed EC register. > > Thanks , > > Pradeep Subrahmanion Why they didn't find _BCM not work? My guess is: Because the backlight control is through WDDM driver on Windows platform but not through standard ACPI method _BCM. They only test Windows platform, so, they didn't find _BCM broken. And, they also didn't really follow Microsoft WDDM spec: http://msdn.microsoft.com/en-us/windows/hardware/gg487382.aspx Per spec, ODM should keep _BCM works fine for any other OS didn't support WDDM driver, but they didn't. At last year, I told Acer PM one time for this issue, they said will check but finally didn't response me. Thanks Joey Lee