[Mesa-dev] [PATCH 14/30] intel/isl: Add an enum for describing auxiliary compression state

[Jason Ekstrand]

On Tue, Jun 6, 2017 at 10:11 PM, Chad Versace <chad at kiwitree.net> wrote:

> On Tue 06 Jun 2017, Jason Ekstrand wrote:
> > On Tue, Jun 6, 2017 at 6:00 PM, Chad Versace <chad at kiwitree.net> wrote:
> >
> > > On Tue 06 Jun 2017, Jason Ekstrand wrote:
> > > > On Tue, Jun 6, 2017 at 1:32 PM, Jason Ekstrand <jason at jlekstrand.net
> >
> > > wrote:
> > > >
> > > > > On Tue, Jun 6, 2017 at 1:22 PM, Chad Versace <
> chadversary at chromium.org
> > > >
> > > > > wrote:
> > > > >
> > > > >> On Fri 26 May 2017, Jason Ekstrand wrote:
> > >
> > > > > How about a section after the auxiliary compression ops section
> which
> > > goes
> > > > > into detail on each of the compression types and discusses which
> > > states are
> > > > > valid etc.
> > > > >
> > > >
> > > > How does this look:
> > > >
> > > > https://cgit.freedesktop.org/~jekstrand/mesa/commit/?h=wip/
> > > i965-resolve-rework-v3&id=8478b102c99e3ec43ec687b3f4e52acb9acbd5ba
> > > >
> > > > I'll squash it in if you like it.
> > >
> > > Please squash that in, with fixes :)
> > >
> > > I don't believe the pass-through state is impossible with MCS, because
> > > there is no single surface for write to "pass through" to. The aux
> > > surface can never be ignored with MCS. Another bit of evidence for this
> > > is that there exists no MCS ambiguate op, and therefore no arrow can
> > > exist in the diagram that carries the "resolved" box to the
> > > pass-through" box.
> > >
> >
> > Too many negatives going on...  I think you meant "I belive the
> > pass-through state is impossible" :-)
>
> Right... sloppy me.
>
> > I do not agree.  While no resolve has been written, one could easily do
> > so.  It would be implemented most likely as a blit from the surface to
> > itself with MCS enabled on the source and disabled for the destination
> > followed by blasting the appropriate value into the MCS.  Modulo issues
> > with the order in which pixels are dispatched (which I don't think is an
> > actual issue so long as SIMD > num_samples), the result should be a
> surface
> > in the pass-through state which can safely be rendered to with MCS
> > disabled.  Now, why anyone would ever want to do that is beyond me.  The
> > state which doesn't exist is the regular resolved state because, as with
> > CCS and MCS, the aux surface stores so little data, that there isn't
> really
> > any room for compression when the main surface contains valid data.
>
> Thanks for taking the time to explain that corner case to stubborn me.
> Such a state is so far outside of realistic usage that I failed to see
> it earlier.
>

I'll freely admit that it's highly exotic and will never be seen in the
wild.


> This patch, with extras squashed in, is
>

Done.


> Reviewed-by: Chad Versace <chadversary at chromium.org>
>

Thanks!  And thank you for being careful and making me document even more
things.
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