Re: [PATCH] drm/vc4: Allow fb modifiers early enough to fill IN_FORMATS property

From: Eric Anholt
Date: Thu Dec 27 2018 - 18:42:27 EST

Paul Kocialkowski <paul.kocialkowski@xxxxxxxxxxx> 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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