[RFC PATCH 2/2] vc4: introduce DMA-BUF heap

[Simon Ser]

On Friday, November 10th, 2023 at 15:13, Maxime Ripard <mripard at kernel.org> wrote:

> > > > We've talked with Sima at XDC about adding a symlink pointing to the
> > > > DMA heap and extra metadata files describing priorities and such.
> > > > However we don't actually need that part for the purposes of v3d --
> > > > I think I'd rather defer that until more DMA heaps are plumbed
> > > > across the DRM drivers.
> > > 
> > > Honestly, I don't think we can afford to only consider vc4/v3d here. The
> > > issue you described seem to affect any SoC with a split scanout/GPU,
> > > which is pretty much all of them? And if they are all affected, we
> > > should design something that fixes it once and for all.
> > 
> > We don't need any sysfs stuff to fix the primary node and DRM dumb buffer
> > issues in Mesa's kmsro/renderonly. The sysfs stuff is only required for a fully
> > generic buffer placement constraint/compatibility uAPI. Which would be super
> > useful in compositors, but let's do one step at a time.
> 
> I don't think a solution that further fragments the ecosystem is worth
> taking, sorry. What you're doing is valuable, we should totally fix the
> issue you have, but not at the expense of making vc4 special on one of
> the platforms it supports.

This does not fragment the ecosystem. It moves the ecosystem bit by bit
towards the final solution.