dri-devel Archive on lore.kernel.org
 help / color / Atom feed
From: Simon Ser <contact@emersion.fr>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: "Daniel Stone" <daniels@collabora.com>,
	"Marek Olšák" <maraeo@gmail.com>,
	"Daniel Vetter" <daniel.vetter@ffwll.ch>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Juston Li" <juston.li@intel.com>
Subject: Re: [PATCH] drm/doc: Document that modifiers are always required for fb
Date: Mon, 07 Sep 2020 08:37:31 +0000
Message-ID: <jjQkalouYz08npkZ2r2MPoXoGML4DkABCtPEZYJkHgR9dGOQCcICe_oq_rpBVnzkpxK4SwDXY9gF8zlhfMWqiWoHHpP5N08nUmo-tA3jIW4=@emersion.fr> (raw)
In-Reply-To: <20200907083133.GS2352366@phenom.ffwll.local>

On Monday, September 7, 2020 10:31 AM, Daniel Vetter <daniel@ffwll.ch> wrote:

> On Wed, Sep 02, 2020 at 02:59:49PM +0000, Simon Ser wrote:
>
> > On Wednesday, September 2, 2020 4:29 PM, Daniel Vetter daniel.vetter@ffwll.ch wrote:
> >
> > > On Wed, Sep 2, 2020 at 2:49 PM Simon Ser contact@emersion.fr wrote:
> > >
> > > > 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.
> > >
> > > gbm_bo_import is a different thing from gbm_bo_create. Former I agree
> > > should figure out the right modifiers (and I think it does that, at
> > > least on intel mesa). For gbm_bo_create I'm not sure we should/need to
> > > require that.
> >
> > I guess the compositor will just forward the value returned by
> > gbm_bo_get_modifier in any case, so returning INVALID would be fine
> > too (to mean "implicit modifier").
> > In both the create and import cases, other metadata like pitches and
> > offsets should be correctly set I think?
>
> Well if you have a modifier format underneath, the non-modifiered offsets
> and pitches might be pure fiction. Also, they might not be sufficient, if
> the modifier adds more planes.

In this case (gbm_bo_create without modifiers), we're discussing
whether we require gbm_bo_get_modifier to return a valid modifier, or
if INVALID is fine.

> So I'm not sure how we can let the "implicit modifier" go through once a
> stack is converted to support modifiers. In a way modifiers are one-way
> compatible only: implicit modifiers -> explicit modifiers should be
> well-defined, the other way just looses information and doesn't work.

That makes sense to me, and still works fine with the two use-cases
outlined above.
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

  reply index

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
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 [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='jjQkalouYz08npkZ2r2MPoXoGML4DkABCtPEZYJkHgR9dGOQCcICe_oq_rpBVnzkpxK4SwDXY9gF8zlhfMWqiWoHHpP5N08nUmo-tA3jIW4=@emersion.fr' \
    --to=contact@emersion.fr \
    --cc=daniel.vetter@ffwll.ch \
    --cc=daniel.vetter@intel.com \
    --cc=daniel@ffwll.ch \
    --cc=daniels@collabora.com \
    --cc=dri-devel@lists.freedesktop.org \
    --cc=juston.li@intel.com \
    --cc=maraeo@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

dri-devel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/dri-devel/0 dri-devel/git/0.git
	git clone --mirror https://lore.kernel.org/dri-devel/1 dri-devel/git/1.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dri-devel dri-devel/ https://lore.kernel.org/dri-devel \
		dri-devel@lists.freedesktop.org
	public-inbox-index dri-devel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.freedesktop.lists.dri-devel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git