[PATCH] drm/doc: Document that modifiers are always required for fb

[Daniel Vetter]

On Wed, Sep 2, 2020 at 2:40 PM Simon Ser <contact at emersion.fr> wrote:
>
> Looks fine to me!
>
> Acked-by: Simon Ser <contact at emersion.fr>
>
> I suppose something similar happens in user-space: gbm_bo_create
> without modifiers needs to properly set the implicit modifier, ie.
> gbm_bo_get_modifier needs to return the effective modifier. Is this
> something already documented?

I don't think that happens, but it has come up in discussions. It's
kinda different scenario though: getfb2 is for cross-compositor stuff,
enabling smooth transitions at boot-up and when switching. So you have
a legit reason for mixing modifier-aware userspace with
non-modifier-aware userspace. And the modifier-aware userspace would
like that everything works with modifiers consistently, including
getfb2. But gbm is just within a single process, and that should
either run all with modifiers, or not at all, since these worlds just
dont mix well. Hence I'm not seeing much use for that, -modesetting
being a confused mess nonwithstanding :-)

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