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From: Simon Ser <contact@emersion.fr>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Daniel Vetter" <daniel.vetter@intel.com>,
	"Marek Olšák" <maraeo@gmail.com>,
	"Juston Li" <juston.li@intel.com>,
	"Daniel Stone" <daniels@collabora.com>,
	"DRI Development" <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH] drm/doc: Document that modifiers are always required for fb
Date: Wed, 02 Sep 2020 12:49:25 +0000
Message-ID: <ap5W_r98yx5DpM1jFkrof6yWGWPtxbyObFp3iIP1-hm-SD_-Jij72KZK2VhVV2p-34EqdVE6T1JeW4zAgjnNsxv_CtULfvg2ASY3xECXMuY=@emersion.fr> (raw)
In-Reply-To: <CAKMK7uFztTjjvQvM-toeZv3hps+NMJFXV7s=Dzs5PwG3J+7wjw@mail.gmail.com>

On Wednesday, September 2, 2020 2:44 PM, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:

> > 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 :-)

Well… There's also the case where some legacy Wayland client talks to a
modifier-aware compositor. gbm_bo_import would be called without a
modifier, but the compositor expects gbm_bo_get_modifier to work.

Also, wlroots will call gbm_bo_create without a modifier to only let
the driver pick "safe" modifiers in case passing the full list of
modifiers results in a black screen. Later on wlroots will call
gbm_bo_get_modifier to figure out what modifier the driver picked.
dri-devel mailing list

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Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-02 10:24 Daniel Vetter
2020-09-02 11:02 ` Pekka Paalanen
2020-09-02 11:15   ` Daniel Vetter
2020-09-02 11:34     ` Pekka Paalanen
2020-09-02 12:40 ` Simon Ser
2020-09-02 12:44   ` Daniel Vetter
2020-09-02 12:49     ` Simon Ser [this message]
2020-09-02 12:56       ` Daniel Stone
2020-09-02 14:29       ` Bas Nieuwenhuizen
2020-09-02 14:29       ` Daniel Vetter
2020-09-02 14:59         ` Simon Ser
2020-09-07  8:31           ` Daniel Vetter
2020-09-07  8:37             ` Simon Ser
2020-09-07  8:41               ` Daniel Vetter
2020-09-07  9:07                 ` Pekka Paalanen
2020-09-07 13:51                   ` Daniel Vetter
2020-09-17 16:47 Daniel Vetter
2020-09-17 17:24 ` Bas Nieuwenhuizen
2020-09-23 15:53   ` Daniel Vetter

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