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From:   Karol Herbst <kherbst@redhat.com>
Date:   Sat, 24 Jul 2021 11:54:30 +0200
Message-ID: <CACO55tuNWk6emjnnukgv9h-9jbpVP564Ogmi7TGbybc9n5v+ZQ@mail.gmail.com>
Subject: Re: [PATCH] nouveau: make backlight support non optional
To:     Arnd Bergmann <arnd@kernel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Lyude Paul <lyude@redhat.com>, Ben Skeggs <bskeggs@redhat.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Daniel Vetter <daniel@ffwll.ch>,
        ML nouveau <nouveau@lists.freedesktop.org>,
        dri-devel <dri-devel@lists.freedesktop.org>
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On Sat, Jul 24, 2021 at 8:55 AM Arnd Bergmann <arnd@kernel.org> wrote:
>
> On Sat, Jul 24, 2021 at 12:47 AM Karol Herbst <kherbst@redhat.com> wrote:
> >
> > In the past this only led to compilation issues. Also the small amount of
> > extra .text shouldn't really matter compared to the entire nouveau driver
> > anyway.
> >
>
> >         select DRM_TTM_HELPER
> > -       select BACKLIGHT_CLASS_DEVICE if DRM_NOUVEAU_BACKLIGHT
> > -       select ACPI_VIDEO if ACPI && X86 && BACKLIGHT_CLASS_DEVICE && INPUT
> > +       select BACKLIGHT_CLASS_DEVICE
> > +       select ACPI_VIDEO if ACPI && X86 && INPUT
> >         select X86_PLATFORM_DEVICES if ACPI && X86
> >         select ACPI_WMI if ACPI && X86
>
> I think the logic needs to be the reverse: instead of 'select
> BACKLIGHT_CLASS_DEVICE',
> this should be 'depends on BACKLIGHT_CLASS_DEVICE', and the same for ACPI_VIDEO.
>
> We may want to add 'default DRM || FB' to BACKLIGHT_CLASS_DEVICE in the
> process so we don't lose it for users doing 'make oldconfig' or 'make defconfig'
>

yeah.. not sure. I tested it locally (config without backlight
enabled) and olddefconfig just worked. I think the problem with
"depends" is that the user needs to enable backlight support first
before even seeing nouveau and I don't know if that makes sense. But
maybe "default" is indeed helping here in this case.

> The rest of the patch looks good to me.
>
>        Arnd
>