From mboxrd@z Thu Jan 1 00:00:00 1970 From: Darren Hart Subject: Re: [PATCH] samsung-laptop: Add use_native_backlight quirk, and enable it on some models Date: Tue, 13 Jan 2015 09:53:12 -0800 Message-ID: <20150113175312.GA130525@vmdeb7> References: <1420812601-7983-1-git-send-email-hdegoede@redhat.com> <20150113040308.GA98306@vmdeb7> <54B4CC75.4030807@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from bombadil.infradead.org ([198.137.202.9]:55195 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751347AbbAMRxO (ORCPT ); Tue, 13 Jan 2015 12:53:14 -0500 Content-Disposition: inline In-Reply-To: <54B4CC75.4030807@redhat.com> Sender: platform-driver-x86-owner@vger.kernel.org List-ID: To: Hans de Goede Cc: stable@vger.kernel.org, platform-driver-x86@vger.kernel.org, Bertrik Sikken On Tue, Jan 13, 2015 at 08:42:45AM +0100, Hans de Goede wrote: > Hi, > > On 13-01-15 05:03, Darren Hart wrote: > >On Fri, Jan 09, 2015 at 03:10:01PM +0100, Hans de Goede wrote: > >>Since kernel 3.14 the backlight control has been broken on various Samsung > >>Atom based netbooks. This has been bisected and this problem happens since > >>commit b35684b8fa94 ("drm/i915: do full backlight setup at enable time") > >> > >>This has been reported and discussed in detail here: > >>http://lists.freedesktop.org/archives/intel-gfx/2014-July/049395.html > >> > >>Unfortunately no-one has been able to fix this. This only affects Samsung > >>Atom netbooks, and the Linux kernel and the BIOS of those laptops have never > >>worked well together. All affected laptops already have a quirk to avoid using > >>the standard acpi-video interface and instead use the samsung specific SABI > >>interface which samsung-laptop uses. It seems that recent fixes to the i915 > >>driver have also broken backlight control through the SABI interface. > >> > >>The intel_backlight driver OTOH works fine, and also allows for finer grained > >>backlight control. So add a new use_native_backlight quirk, and replace the > >>broken_acpi_video quirk with this quirk for affected models. This new quirk > >>disables acpi-video as before and also stops samsung-laptop from registering > > > > > >I take this to me this quirk is broken_acpi_video && use_native_backlight. > > In what it does yes, but I've chosen to make it a standalone quirk named after > the acpi/video.c use_native_backlight option, which also disables both acpi-video > and vendor backlight interfaces, so for consistency I'm using the same setup here. > > We cannot use the acpi/video.c option here because that option, which is on by > default, only triggers on win8 ready BIOS-es and these machines do not have such > a BIOS. > > Eventually I would like to see the acpi/video.c code switch away from having > the 2 semi-orthogonal kernel cmdline options it currently has, which are > acpi_backlight=[vendor|video] vs video.use_native_backlight=[0|1], while what > we really have is just three options: > > acpi_backlight=[vendor|video|native] > > I've explained what I would like to see happen / think needs to happen to clean > up this mess here: https://lkml.org/lkml/2014/12/27/54 > > So the way I see it the broken_acpi_video quirks means use acpi_backlight=vendor > where as the new use_native_backlight option means acpi_backlight=native, and > eventually these 2 quirks would end up in just one call in samsung-laptop.c, which > says: > > acpi_video_set_backlight_type(acpi_video_backlight_vendor); > > resp: > > acpi_video_set_backlight_type(acpi_video_backlight_native); > > So I really see this as an either or thing, yes native implies disabling > acpi_video# but that does not mean that it is the same thing as vendor. Thank you for the detailed response. Queued for 3.20. -- Darren Hart Intel Open Source Technology Center