[Mesa-dev] [PATCH mesa] meson: add missing tegra vdpau driver

[Thierry Reding]

On Tue, Dec 18, 2018 at 11:34:31AM -0800, Dylan Baker wrote:
> Quoting Eric Engestrom (2018-12-18 09:43:18)
> > 
> > 
> > On December 18, 2018 5:36:19 PM UTC, Dylan Baker <dylan at pnwbakers.com> wrote:
> > > Quoting Ilia Mirkin (2018-12-06 09:39:25)
> > > > On Thu, Dec 6, 2018 at 12:17 PM Eric Engestrom
> > > <eric.engestrom at intel.com> wrote:
> > > > >
> > > > > On Thursday, 2018-12-06 12:07:06 -0500, Ilia Mirkin wrote:
> > > > > > Under what circumstances would tegra have a vdpau
> > > implementation?
> > > > >
> > > > > I don't know about that, but this patch brings meson on par with
> > > > > autotools. Are you saying autotools was wrong and it should be
> > > removed
> > > > > there instead?
> > > > >
> > > > > FtR, src/gallium/targets/vdpau/Makefile.am includes
> > > > > src/gallium/drivers/tegra/Automake.inc which adds tegra to the
> > > > > TARGET_DRIVERS, which in turn produces libvdpau_tegra.so
> > > > >
> > > > > If this was wrong, then that include on line 60 of
> > > > > src/gallium/targets/vdpau/Makefile.am should be removed.
> > > > >
> > > > > This line was added by Thierry Reding (cc'ed) when he first
> > > introduced
> > > > > tegra support in 1755f608f5201e0a23f00 "tegra: Initial support".
> > > > 
> > > > I'd like to hear tagr opine on this, but AFAIK tegra is a
> > > > renderonly-style driver, which uses nouveau as its actual rendering
> > > > backend. While nouveau does support VDPAU, the decoding engines are
> > > > not available as part of the GPU device on Tegra platforms. They
> > > still
> > > > have decoders, they're just separate platform devices (which I
> > > suspect
> > > > operate very similarly to their desktop GPU counterparts, but that's
> > > a
> > > > separate matter).
> > > > 
> > > >   -ilia
> > > 
> > > Ping?
> > 
> > I suggest we land this patch to bring meson on par with autotools, and if we decide later
> > that autotools was wrong, we can just remove it from both places at once; ack?
> 
> I'd vote lets at least give Thierry till tomorrow to respond, and we can merge
> it tomorrow around this time if he hasn't, with the remove fallback if tegra
> shouldn't have a vdpau module? Does that sound reasonable to everyone?

Sorry, I completely missed this. Ilia is right, Tegra doesn't have any
decoding engines in the GPU. Ilia is also correct that the engines are
separate devices and similar to their desktop GPU counterparts. While
it'd technically be possible to somehow enable video decoding in the
Tegra gallium driver (I had done some prototyping on this a while ago),
it doesn't look like the best option at this point. The problem is that
gallium makes a bunch of assumptions that just don't apply to Tegra.

At this point, it seems more likely that video decoding will be
implemented as V4L2 memory-to-memory drivers.

So I think we should just remove the vdpau support for Tegra from the
autotools build. It's completely non-functional and there are no plans
to make it work.

Thierry
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