Re: [git pull] drm for 5.8-rc1

From: Karol Herbst <kherbst@redhat.com>
To: James Jones <jajones@nvidia.com>
Cc: dri-devel <dri-devel@lists.freedesktop.org>,
	Thierry Reding <treding@nvidia.com>,
	Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Subject: Re: [git pull] drm for 5.8-rc1
Date: Thu, 13 Aug 2020 17:39:39 +0200	[thread overview]
Message-ID: <CACO55tsfV9pGijOF5F=dLqFhpXgPSArGHXa44Mt3eRBk7z-X=g@mail.gmail.com> (raw)
In-Reply-To: <CACO55tu1RWZ0ZGcMcrU-snT3CkJtwxawwJ9990-5a+hpByh-Hw@mail.gmail.com>

btw, I just noticed that wayland with gnome-shell is totally busted.
With this MR it at least displays something, but without it doesn't
work at all.

On Thu, Aug 13, 2020 at 3:00 PM Karol Herbst <kherbst@redhat.com> wrote:
>
> At least for now I've created an MR to revert the change:
> https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6300
>
> But it seems like there was probably a good reason why it got added?
> Happy to have better fixes, but that's the best we've got so far I
> think?
>
> Thierry, what do you think?
>
> On Wed, Aug 12, 2020 at 8:51 PM Karol Herbst <kherbst@redhat.com> wrote:
> >
> > in case you all were wondering, it works on xorg-server git because of
> > this commit: https://gitlab.freedesktop.org/xorg/xserver/-/commit/9b8999411033c9473cd68e92e4690a91aecf5b95
> >
> > On Wed, Aug 12, 2020 at 8:25 PM James Jones <jajones@nvidia.com> wrote:
> > >
> > > On 8/12/20 10:40 AM, Alyssa Rosenzweig wrote:
> > > >> ...and in merging my code with Alyssa's new panfrost format modifier
> > > >> support, I see panfrost does the opposite of this and treats a format
> > > >> modifier list of only INVALID as "don't care".  I modeled the new nouveau
> > > >> behavior on the Iris driver.  Now I'm not sure which is correct :-(
> > > >
> > > > ....and neither am I. Uh-oh.
> > > >
> > > > I modeled the panfrost code after v3d_resource_create_with_modifiers,
> > > > which treats INVALID as "don't care". I can confirm the panfrost code
> > > > works (in the sense that it's functional on the machines I've tested),
> > > > but I don't know if it is actually correct. I think it is, since
> > > > otherwise you end up using linear in places it's unnecessary, but I'm
> > > > not sure where this is spec'd.
> > >
> > > It would depend on whether an app actually calls the function this way,
> > > and whether that app was tested I suppose.  If I'm interpreting the Iris
> > > code correctly and it doesn't break anything, then I'm assuming both
> > > implementations are equally valid in that nothing exercises this path,
> > > but it would be good to have the intended behavior documented somewhere
> > > so we can try to work towards consistent in case someone tries it in the
> > > future.
> > >
> > > My nouveau change runs afoul of assumptions in the tegra driver, but
> > > that's easy enough to fix in lockstep if desired.
> > >
> > > Also, heads up: I'll ping you on my format modifier cleanup MR once I've
> > > pushed the latest version.  The panfrost modifier usage was harder to
> > > merge into the refactoring than most, so it'll be good to have your
> > > review and if you have time, some testing.  I think I landed on an
> > > elegant solution, but open to suggestions.
> > >
> > > Thanks,
> > > -James
> > >

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