From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jani Nikula Subject: Re: [PATCH 07/32] acpi-video-detect: Rewrite backlight interface selection logic Date: Thu, 11 Jun 2015 15:28:52 +0300 Message-ID: <87bngm5szf.fsf@intel.com> References: <1433941292-21530-1-git-send-email-hdegoede@redhat.com> <1433941292-21530-8-git-send-email-hdegoede@redhat.com> <20150611091922.GB19820@pali> <557954F4.3050709@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <557954F4.3050709@redhat.com> Sender: platform-driver-x86-owner@vger.kernel.org To: Hans de Goede , Pali =?utf-8?Q?Roh=C3=A1r?= Cc: Matthew Garrett , Ike Panhc , linux-acpi@vger.kernel.org, ibm-acpi-devel@lists.sourceforge.net, Henrique de Moraes Holschuh , acpi4asus-user@lists.sourceforge.net, "Rafael J. Wysocki" , dri-devel@lists.freedesktop.org, Azael Avalos , Lee Chun-Yi , Mattia Dongili , Cezary Jackiewicz , Ben Skeggs , Corentin Chary , Darren Hart , platform-driver-x86@vger.kernel.org, Aaron Lu List-Id: linux-acpi@vger.kernel.org On Thu, 11 Jun 2015, Hans de Goede wrote: > Hi, > > On 11-06-15 11:19, Pali Roh=C3=A1r wrote: >> On Wednesday 10 June 2015 15:01:07 Hans de Goede wrote: >>> Currently we have 2 kernel commandline options + dmi-quirks in 3 pl= aces all >>> interacting (in interesting ways) to select which which backlight i= nterface >>> to use. On the commandline we've acpi_backlight=3D[video|vendor] an= d >>> video.use_native_backlight=3D[0|1]. DMI quirks we have in >>> acpi/video-detect.c, acpi/video.c and drivers/platform/x86/*.c . >>> >>> This commit is the first step to cleaning this up, replacing the 2 = cmdline >>> options with just acpi_video.backlight=3D[video|vendor|native|none]= , and >>> adding a new API to video_detect.c to reflect this. >>> >>> Follow up commits will also move other related code, like unregiste= ring the >>> acpi_video backlight interface if it was registered before other dr= ivers >>> which take priority over it are loaded, to video_detect.c where thi= s >>> logic really belongs. >>> >>> Signed-off-by: Hans de Goede >> >> Hello, >> >> lot of people are using acpi_backlight parameter in kernel cmdline t= o >> fix some of problems. I would like to see this parameter still worki= ng >> and to not break existing configuration. E.g acpi_backlight=3Dvendor= to >> use dell-laptop.ko or thinkpad_acpi.ko backlight. > > I would have like to keep acpi_backlight=3D for that exact same reaso= n, > but that is not possible while keeping acpi_video as a module. > > Thinking more about this, this is not strictly true, we could make > some other (core) part of the acpi code use __setup to get the > acpi_backlight=3D value and have that part export the value for use > in the acpi_video module. This is not really pretty, but I think it > may be the best way to solve this. It just might be a good idea to try to not change the backlight related parameters all the time... See [1]. I probably forgot a few. BR, Jani. [1] http://nikula.org/~jani/backlight/#index11h2 > >> It is still nightmare to get laptop panel backlight working on diffe= rent >> (broken) laptops > > Well one reason it is a nightmare is because there are too many > backlight drivers fighting for control and there is not an easy > way to tell the kernel only register this one, this is exactly > what this patch-set is trying to address :) People may still > need to use a cmdline option but now there is only one option to > play with. > > > and people learnt to try to use acpi_backlight > > parameter for quit/hot fixing these problems. > > People who need to pass a kernel commandline option really should > report a bug once they have figured out what option to use. > > Fedora users are getting pretty good at this as the Fedora kernel > maintainers punt all such bug reports to me and I properly deal > with them verifying the users solution is sane and then submitting > a patch with a dmi based quirk for the users laptop upstream. > > > Upgrading kernel (if you >> remove acpi_backlight parameter) just break it again. > > I think that is actually (partially) a good thing, as said people > who rely on cmdline workarounds should file bugs, so that we can > add a quirk. Had the users done so, the quirk would be long in > place and the changing of the cmdline option name would not be > an issue for them. > > I realize that this knife cuts both ways, and that this will > cause unhappy users, as said if it had been possible to not change > the cmdline option name in a clean way I would have done so. > > If everyone agrees with the solution I've outlined above, we > can actually make it so as to not break things for users > who's setup relies on acpi_backlight=3Dfoo > > Regards, > > Hans > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/dri-devel --=20 Jani Nikula, Intel Open Source Technology Center