Re: [git pull] drm for 5.8-rc1

From: Karol Herbst <kherbst@redhat.com>
To: James Jones <jajones@nvidia.com>
Cc: Thierry Reding <treding@nvidia.com>,
	Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>,
	dri-devel <dri-devel@lists.freedesktop.org>
Subject: Re: [git pull] drm for 5.8-rc1
Date: Thu, 13 Aug 2020 19:48:39 +0200	[thread overview]
Message-ID: <CACO55tsZAh4aThBSqiQJ5o6jCi+6vcfXDEfCueyBmOK62ZsW5Q@mail.gmail.com> (raw)
In-Reply-To: <efb830fe-9ded-f5d3-6944-45adbb2a1f80@nvidia.com>

On Thu, Aug 13, 2020 at 7:45 PM James Jones <jajones@nvidia.com> wrote:
>
> I'll defer to Thierry, but I think that may be by design.  Tegra format
> modifiers were added to get things like this working in the first place,
> right?  It's not a regression, is it?
>

That would be slightly annoying as this would mean by design it's
broken by default :/ Also, we have no Xorg release supporting
modifiers anyway and it does seem to work with X 1.20.8 (which doesn't
enable modifier support). And I talked with Jonas (working on mutter)
about it and there were no plans to turn on modifier support by
default at this point.

> Thanks,
> -James
>
> On 8/13/20 10:19 AM, Karol Herbst wrote:
> > another thing: with gsettings set org.gnome.mutter
> > experimental-features '["kms-modifiers"]' it all just works out of the
> > box with wayland, but that won't be enabled for quite some time, so we
> > need to figure out what is broken (less so with my patch) under
> > wayland with gnome :)
> >
> > On Thu, Aug 13, 2020 at 5:39 PM Karol Herbst <kherbst@redhat.com> wrote:
> >>
> >> 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
> >>>>>
> >
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> >
>

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