Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754909Ab2F2MYl (ORCPT ); Fri, 29 Jun 2012 08:24:41 -0400 Received: from mail-bk0-f46.google.com ([209.85.214.46]:55654 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751917Ab2F2MYk (ORCPT ); Fri, 29 Jun 2012 08:24:40 -0400 MIME-Version: 1.0 In-Reply-To: <20120628193652.GB10945@srcf.ucam.org> References: <1340910426-13269-1-git-send-email-seth.forshee@canonical.com> <20120628191043.GA9777@srcf.ucam.org> <20120628193017.GA29456@thinkpad-t410> <20120628193652.GB10945@srcf.ucam.org> Date: Fri, 29 Jun 2012 14:24:38 +0200 Message-ID: Subject: Re: [PATCH] backlight: add support for disabling backlights via sysfs From: Corentin Chary To: Matthew Garrett Cc: Richard Purdie , linux-kernel@vger.kernel.org, platform-driver-x86@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2220 Lines: 49 On Thu, Jun 28, 2012 at 9:36 PM, Matthew Garrett wrote: > On Thu, Jun 28, 2012 at 02:30:17PM -0500, Seth Forshee wrote: > >> I actually don't think Corentin's solution is a bad one. It does suffer >> from a couple of shortcomings though. First, it only works for broken >> ACPI backlights, and some platforms have other backlight interfaces that >> are broken (e.g. the i915 backlight on the MacBook Pro 8,2). Second, >> marking backlights as broken in the kernel necessitates ever-expanding >> dmi blacklists in some of the platform drivers, unless we can get >> vendors to stop providing broken backlight interfaces. > > Userspace should already be prioritising platform interfaces over raw > interfaces, so if gmux works on the Mac then there's no problem. Hehe, sometime the platform interface doesn't work and the raw does. That's the case on various samsung-laptop since we have absolutely no documentation about SABI and no known way to probe if the implementation is working or not. But anyway, for samsung-laptop it's disabled by default in favor of acpi_video (which is also broken most of the time on samsung laptops). > DMI > lists should, broadly speaking, be unnecessary - they're mostly a > symptom of us not understanding how the hardware is expected to work. > >> I'm all for fixing integration bugs in the ACPI backlight >> implementations if we can, but some vendor implementations are just >> flat-out broken, and it isn't always possible to get vendor cooperation. >> In the case of Toshiba I've tried reaching out to them to work on ACPI >> integration issues, but they flat out refused. > > We already know that our implementation of the IGD opregion is broken, > but Intel won't hand over newer versions of the spec. If you see > problems with the acpi backlight interface on Intel graphics then that > should be the default assumption. > > -- > Matthew Garrett | mjg59@srcf.ucam.org -- Corentin Chary http://xf.iksaif.net -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/