linux-kernel - Re: [PATCH] drm/vc4: Allow fb modifiers early enough to fill IN

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Message-ID: <878t0amtjf.fsf@anholt.net>
Date:   Thu, 27 Dec 2018 15:36:20 -0800
From:   Eric Anholt <eric@...olt.net>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     David Airlie <airlied@...ux.ie>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Eben Upton <eben@...pberrypi.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Subject: Re: [PATCH] drm/vc4: Allow fb modifiers early enough to fill IN_FORMATS property

Paul Kocialkowski <paul.kocialkowski@...tlin.com> writes:

> The KMS mode_config elements are currently configured in vc4_kms_load,
> that is called after all components are binded (component_bind_all).
> However, the CRTC component (for the Pixel Valve) needs to access the
> allow_fb_modifiers element at bind time, when initializing its planes
> through drm_universal_plane_init.
>
> This helpers checks allow_fb_modifiers to decide whether to fill the
> IN_FORMATS property. Because allow_fb_modifiers is still set to false
> at this point, the property is never filled and userspace cannot
> retrieve the combination of supported formats and modifiers.
>
> Fix this by setting allow_fb_modifiers right after calling
> drm_mode_config_init (which initializes the structure), before binding
> the components of the driver.

This makes me wonder if the flag could be removed and replaced with "did
non-NULL modifiers get supplied to plane init?"  I think I've tripped
over this flag in other KMS hacking, too.

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