[Mesa-dev] [PATCH] i965: consider a 'base level' when calculating width0, height0, depth0

[Kenneth Graunke]

On Thursday, October 11, 2018 11:58:40 AM PDT Kenneth Graunke wrote:
> On Tuesday, October 2, 2018 9:16:01 AM PDT asimiklit.work at gmail.com wrote:
> > From: Andrii Simiklit <andrii.simiklit at globallogic.com>
> > 
> > I guess that when we calculating the width0, height0, depth0
> > to use for function 'intel_miptree_create' we need to consider
> > the 'base level' like it is done in the 'intel_miptree_create_for_teximage'
> > function.
> > 
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107987
> > Signed-off-by: Andrii Simiklit <andrii.simiklit at globallogic.com>
> > ---
> >  .../drivers/dri/i965/intel_tex_validate.c     | 26 ++++++++++++++++++-
> >  1 file changed, 25 insertions(+), 1 deletion(-)
> 
> I believe this patch is correct - we're assembling things into a new
> miptree, which we start at level 0 - so we need the sizes for level 0.
> 
> Alternatively, we might be able to pass validate_first_level instead
> of 0 when calling intel_miptree_create, to make one that's only good
> up until the new base...and have to re-assemble it the next time they
> change the base.  It would save memory potentially.  But more copies.
> I don't have a strong preference which is better.
> 
> Please do make a Piglit or dEQP test for this.
> 
> Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

Sorry, withdrawing my review. :(  Chris Forbes pointed out on IRC that
your reproducer case is backwards:

miplevel 0 - 1x1
miplevel 1 - 2x2
miplevel 2 - 4x4

That's upside down.  A proper miptree would have the base be largest:

miplevel 0 - 4x4
miplevel 1 - 2x2
miplevel 2 - 1x1

So, yes, I could see this tripping an assert...but such a crazy texture
will never be mipmap complete.  If they're expecting mipmapping, then
it seems like they should get a fallback black texture (which normally
happens for incomplete textures).  If not, maybe they should get a
single miplevel?  Either way, seems like we should detect insanity and
bail, rather than change size calculations for the normal sane case.
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