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From: Harry Wentland <harry.wentland@amd.com>
To: "Cornij, Nikola" <Nikola.Cornij@amd.com>,
	Daniel Vetter <daniel@ffwll.ch>, Arnd Bergmann <arnd@kernel.org>
Cc: "Ben Skeggs" <bskeggs@redhat.com>,
	"David Airlie" <airlied@linux.ie>,
	"Lyude Paul" <lyude@redhat.com>, "Arnd Bergmann" <arnd@arndb.de>,
	"Ville Syrjälä" <ville.syrjala@linux.intel.com>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	"Nouveau Dev" <nouveau@lists.freedesktop.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] drm/nouveau/kms/nv50-: fix build failure with CONFIG_BACKLIGHT=n
Date: Fri, 23 Jul 2021 15:54:07 -0400	[thread overview]
Message-ID: <d59abe80-ab45-1b66-48c9-1d56075232d4@amd.com> (raw)
In-Reply-To: <DM5PR12MB467963EB0A4E98B2182C6745EEE59@DM5PR12MB4679.namprd12.prod.outlook.com>



On 2021-07-23 3:14 p.m., Cornij, Nikola wrote:
> [AMD Official Use Only]
> 
> +Harry
> 
> -----Original Message-----
> From: Daniel Vetter <daniel@ffwll.ch>
> Sent: Friday, July 23, 2021 11:23 AM
> To: Arnd Bergmann <arnd@kernel.org>
> Cc: Daniel Vetter <daniel@ffwll.ch>; Ben Skeggs <bskeggs@redhat.com>; David Airlie <airlied@linux.ie>; Lyude Paul <lyude@redhat.com>; Arnd Bergmann <arnd@arndb.de>; Ville Syrjälä <ville.syrjala@linux.intel.com>; Cornij, Nikola <Nikola.Cornij@amd.com>; dri-devel <dri-devel@lists.freedesktop.org>; Nouveau Dev <nouveau@lists.freedesktop.org>; Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
> Subject: Re: [PATCH] drm/nouveau/kms/nv50-: fix build failure with CONFIG_BACKLIGHT=n
> 
> On Fri, Jul 23, 2021 at 12:16:31PM +0200, Arnd Bergmann wrote:
>> On Fri, Jul 23, 2021 at 11:25 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>>>
>>> On Fri, Jul 23, 2021 at 11:15 AM Arnd Bergmann <arnd@kernel.org> wrote:
>>>>
>>>> From: Arnd Bergmann <arnd@arndb.de>
>>>>
>>>> When the backlight support is disabled, the driver fails to build:
>>>>
>>>> drivers/gpu/drm/nouveau/dispnv50/disp.c: In function 'nv50_sor_atomic_disable':
>>>> drivers/gpu/drm/nouveau/dispnv50/disp.c:1665:59: error: 'struct nouveau_connector' has no member named 'backlight'
>>>>  1665 |         struct nouveau_backlight *backlight = nv_connector->backlight;
>>>>       |                                                           ^~
>>>> drivers/gpu/drm/nouveau/dispnv50/disp.c:1670:35: error: invalid use of undefined type 'struct nouveau_backlight'
>>>>  1670 |         if (backlight && backlight->uses_dpcd) {
>>>>       |                                   ^~
>>>> drivers/gpu/drm/nouveau/dispnv50/disp.c:1671:64: error: invalid use of undefined type 'struct nouveau_backlight'
>>>>  1671 |                 ret = drm_edp_backlight_disable(aux, &backlight->edp_info);
>>>>       |                                                                ^~
>>>>
>>>> The patch that introduced the problem already contains some #ifdef
>>>> checks, so just add another one that makes it build again.
>>>>
>>>> Fixes: 6eca310e8924 ("drm/nouveau/kms/nv50-: Add basic DPCD
>>>> backlight support for nouveau")
>>>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>>>
>>> Can we just toss the idea that BACKTLIGHT=n is a reasonable config
>>> for drm drivers using backlights, and add depends BACKLIGHT to all
>>> of them?
>>>
>>> I mean this is a perfect source of continued patch streams to keep
>>> us all busy, but beyond that I really don't see the point ... I
>>> frankly have better things to do, and especially with the big
>>> drivers we have making backlight optional saves comparitively nothing.
>>> -Daniel
>>
>> Yes! I'd definitely be in favor of that, I've wasted way too much time
>> trying to sort through dependency loops and other problems with backlight support.
>>
>> Maybe we should leave the drivers/video/fbdev/ drivers untouched in
>> this regard, at least for the moment, but for the drivers/gpu/drm
>> users of backlight that would be a nice simplification, and even the
>> smallest ones are unlikely to be used on systems that are too memory
>> constrained to deal with 4KB extra .text.
> 
> Yeah I think we can do this entirely ad-hoc, i.e. any time the backlight wheel wobbles off again we nail it down for good for that driver with a depends on BACKGLIGHT and remove any lingering #ifdef all over.
> 
> If you want maybe start out with the biggest drm drivers in a series, I think if nouveau/amdgpu/i915 folks ack this you're good to go to just convert as things get in the way.

Sounds like a good idea to me.

Harry

> -Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch/>> 


  reply	other threads:[~2021-07-23 19:54 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-23  9:15 [PATCH] drm/nouveau/kms/nv50-: fix build failure with CONFIG_BACKLIGHT=n Arnd Bergmann
2021-07-23  9:24 ` Daniel Vetter
2021-07-23 10:10   ` Karol Herbst
2021-07-23 10:12     ` Karol Herbst
2021-07-23 10:16   ` Arnd Bergmann
2021-07-23 15:23     ` Daniel Vetter
2021-07-23 19:14       ` Cornij, Nikola
2021-07-23 19:54         ` Harry Wentland [this message]
2021-07-23 16:12   ` Lyude Paul
2021-07-23 15:10 ` Randy Dunlap
2021-07-23 15:15   ` Karol Herbst
2021-07-23 16:31     ` Randy Dunlap
2021-07-23 16:34       ` Karol Herbst
2021-07-23 18:40         ` Arnd Bergmann
2021-07-23 18:48           ` Karol Herbst

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