[Mesa-dev] [PATCH] egl/wayland: Set __DRI_IMAGE_USE_SCANOUT for shared buffers

[Daniel Vetter]

On Tue, May 03, 2016 at 05:24:02PM +0100, Daniel Stone wrote:
> On 3 May 2016 at 14:52, Daniel Vetter <daniel at ffwll.ch> wrote:
> > Having read the thread I think fixing up the validation part on the
> > compositor side would be the correct fix short term for this. That will
> > keep all options open for the future to optimize this however we want,
> > without the need for flag days across all mesa drivers.
> >
> > And yes, adding required additional metadata to the wayland drm proto will
> > be a bit of work, since to make it all work we'd also need to add import
> > support for that to gbm.
> 
> Right, the GBM API needs to expose modifiers for this to be useful.
> And whilst doing that, really you want to be adding multi-plane
> support at the same time. Once you've got that far, it's presumably an
> extra DRIimage usage flag, to declare that the client is aware of
> modifiers. Something I've not yet had time for, sadly.

Quick correction, since I learned a few things from Kristian and Daniel
yesterday about wayland:
- for wayland we wouldn't need gbm import support at all, since the buffer
  sharing is implemented purely within libEGL - it registers/uses private
  wl protocol extensions. Therefore we wouldn't need to add any new public
  interfaces anywhere when we add fb_modifiers to the wl_drm proto.

  We would need to add a new interface on the gbm -> drm_fb path though,
  but one suggestion from Kristian was that gbm simply creates the drm_fb
  directly. That would take out one needless step every time we add more
  metadata.

- For DRI3 I think we'd still need gbm import support, since there the
  protocol is partially handled outside of the ddx (and hence no way to
  just let glamor/libEGL handle it all). Which also means we need to rev
  to DRI3.1, hooray. DRI2 is probably similar, but meh.

Cheers, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch