linux-kernel - Re: [PATCH] drm/amdgpu: Add 'modeset' module parameter

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Message-ID: <a38b92c1-50d9-52df-43b4-a7576531419e@redhat.com>
Date:   Thu, 12 May 2022 08:53:52 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Christian König <christian.koenig@....com>,
        Alex Deucher <alexdeucher@...il.com>,
        Lyude Paul <lyude@...hat.com>
Cc:     David Airlie <airlied@...ux.ie>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Solomon Chiu <solomon.chiu@....com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Alex Deucher <alexander.deucher@....com>,
        Evan Quan <evan.quan@....com>,
        Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH] drm/amdgpu: Add 'modeset' module parameter

On 5/12/22 08:17, Christian König wrote:
> Am 11.05.22 um 20:36 schrieb Alex Deucher:
>> On Wed, May 11, 2022 at 2:20 PM Lyude Paul <lyude@...hat.com> wrote:
>>> Many DRM drivers feature a 'modeset' argument, which can be used to
>>> enable/disable the entire driver (as opposed to passing nomodeset to the
>>> kernel, which would disable modesetting globally and make it difficult to
>>> load amdgpu afterwards). Apparently amdgpu is actually missing this
>>> however, so let's add it!
>> You can already do that by passing modprobe.blacklist=amdgpu on the
>> kernel command line.  I don't think we need another option to do that.
> 
> Yeah, this already came up multiple times and so far we have always 
> rejected it.
> 
> Stuffing that into drivers is not a good approach I think. If we want to 
> prevent some device from exposing it's display functionalities we should 
> rather push that into the drm layer.
>

Absolutely agree on this. I think what we want is a drm.modeset parameter
that would have more precedence than "nomodeset". Because the latter is a
built-in parameter and so it can't be disabled at runtime using sysfs.

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat