egl image creation in case of atomic

[Hosokawa, Kenji (ADITG/ESB)]

> -----Original Message-----
> From: Pekka Paalanen <ppaalanen at gmail.com>
> Sent: Dienstag, 11. September 2018 16:35
> To: Hosokawa, Kenji (ADITG/ESB) <khosokawa at de.adit-jv.com>
> Cc: wayland-devel at lists.freedesktop.org
> Subject: Re: egl image creation in case of atomic
> 
> On Tue, 11 Sep 2018 16:10:17 +0300
> Pekka Paalanen <ppaalanen at gmail.com> wrote:
> 
> > On Tue, 11 Sep 2018 12:47:15 +0000
> > "Hosokawa, Kenji (ADITG/ESB)" <khosokawa at de.adit-jv.com> wrote:
> >
> > > We would like to discuss the following part.
> > > >Creating egl images are not needed at all, when the client buffer
> > > >can be imported to a DRM plane. We would like to reduce CPU usage of
> > > >weston in that case.
> >
> > Hi,
> >
> > ok, that sounds fine to me. Maybe something like this: the GL-renderer
> > attach hook just unrefs existing EGLImages but does not create new
> > ones. New ones are created at repaint time on demand. This should
> > implictly result in composite-bypass avoiding the EGLImage creation,
> > because the renderer does not repaint those views.

Hi Pekka,

I was just thinking like that.

> >
> > Does this answer your question?
> >
> > This is just off the top of my head, I didn't actually check how the
> > code would allow this.
> 
> Oh, one important detail:
> 
> One cannot skip creating the EGLImage in the zwp_linux_buffer_params_v1.create path, because it is the test to see if the
> compositor can use the dmabuf at all. It must be done at the create step, so that potential failure can be communicated gracefully.
> 
> One might be able to argue, that skipping the initial import test in create_immed path is ok, because it is meant to be unchecked
> anyway and documented to result in fatal protocol errors if anything fails.
> 
> So you may not be able to eliminate the EGLImage creation during wl_buffer creation, but you should be able to eliminate or optimize
> the EGLImage creation when an existing wl_buffer is re-used. I hope that is sufficient for your use cases.

Thank you so much for the knowledge. I wanted to know such high-level design information.
I thought that some EGLimage creation would be necessary but I was not sure. I will look at there.

Best regards

Kenji Hosokawa
Engineering Software Base (ADITG/ESB)