From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: Re: [PATCH] ACPI: disable the ACPI backlight control on laptops with buggy _BCL methods Date: Thu, 8 Jan 2009 12:43:42 +0000 Message-ID: <20090108124342.GA10458@srcf.ucam.org> References: <1231383496.20746.44.camel@rzhang-dt> <20090108033250.GA2550@srcf.ucam.org> <1231396321.20746.79.camel@rzhang-dt> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from cavan.codon.org.uk ([93.93.128.6]:58169 "EHLO vavatch.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751068AbZAHMnq (ORCPT ); Thu, 8 Jan 2009 07:43:46 -0500 Content-Disposition: inline In-Reply-To: <1231396321.20746.79.camel@rzhang-dt> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Zhang Rui Cc: Len Brown , linux-acpi , "trenn@suse.de" On Thu, Jan 08, 2009 at 02:32:01PM +0800, Zhang Rui wrote: > > Why? These all seem to behave consistently, so I can't see any prob= lem=20 > > with us simply adding support for this varient. > the problem is that the ACPI backlight I/F and the platform I/F coexi= sts > before commit =EF=BB=BFc3d6de698c84efdbdd3781b7058bcc339ab43da8 appli= ed, and the > platform I/F is preferred. =46or the machines you've looked at - we don't know if that's true for = all=20 hardware that behaves this way. > =EF=BB=BFin bug 12249 and 12037, > 1. the first two elements in _BCL are NOT the backlight levels when t= he > platform is on AC or battery. We can detect that easily and adjust behaviour accordingly. > 2. _BQC returns the index of the current brightness =EF=BB=BF=EF=BB=BF= in _BCL package > rather than the value, which surely breaks the ACPI video driver. And again, we can handle that. > 2. every elements in the _BCL package is not a percentage of the maxi= mum > brightness, which is also a violation of ACPI spec. This seems pretty irrelevant - nothing in the code depends on these=20 being percentages. > yes, we can make the ACPI backlight control work by using customized > DSDT. But that's not the fix neither. I don't have any better ideas t= han > disable them. Just fix up video.c to handle these cases. --=20 Matthew Garrett | mjg59@srcf.ucam.org -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html