Re: An EGLStreams backend for KWin

On Mon, Nov 12, 2018 at 10:44 PM Erik Kurzinger <[email protected]> wrote:
>
> Hi Everyone,
>
> ...
>
> Cheers,
> Erik

Hi Erik,

thanks for the heads up and in general thank you and Nvidia for
contributing to KWin. I'm looking forward to you sharing the code.

One aspect to not forget is that our current screen sharing solution
in KWin/KWayland is based on GBM buffer sharing (and subsequent
Pipewire). So long-term there needs to be an additional code path for
EGLStreams or a replacement in some way.

Short-term there are currently some soon to be merged patches
abstracting DrmOutput properties onto an higher level
(https://phabricator.kde.org/D16794). They don't touch the GBM/EGL
code paths very much and are probably therefore not that relevant to
your EGLStreams implementation, but better still take a look to make
sure you don't need to do large changes to your branch after they
landed.

At the end some questions:

Do you and Nvidia plan on maintaining the EGLStreams code path
afterwards? This does not mean it's all upon you then, just if you
will be still around after the code has been merged. In the past there
were some Nvidia-specific issues with KWin on X, which took way too
long to be fixed. So more contributions by Nvidia engineers would be
very welcomed.

At some point we want to implement multi-GPU support in our Wayland
session. Is this with EGLStreams still possible? I.e. to drive an
Nvidia card together with an Intel or AMD graphics chip?

Is Nvidia despite EGLStreams then being available in KWin and Mutter
still willing to look into creating a cross-vendor solution, which is
attractive to Mesa based drivers as well? Competing APIs can be a good
idea from time to time to drive progress, but on a larger time scale
converging to a unified solution is also important. I'm asking this
because at XDC this year there was no new info about the Unix Device
Memory Allocator library, which had been proposed by Nvidia at some
point in the past.

Cheers,
Roman