[Mesa-dev] [PATCH 5/7] i965: use _mesa_geometry_width/height/layers/samples for programming geometry of framebuffer to GEN

[Kenneth Graunke]

On Friday, April 24, 2015 04:02:18 PM Rogovin, Kevin wrote:
> 
> > Actually I realized that you add quite a bit of support to gen4-6 logic that 
> > _isn't_ used for gen7 and higher. In the last patch of the series you claim to enable this only for gen7 and higher - I'm confused.
> 
> There are two reasons:
> 1. Because atoms get reused all the time across generations, it is just easier to use
> the _mesa_geomety_* functions in any batch buffer builder that is concerned 
> about the geometry of the render target. It keeps  the code consistent and much
> easier than checking what functions and atoms are directly or indirectly used by 
> different Gens. However,  blorp, blitting and a few others are left untouched since 
> they want to talk about the buffer, not really 3D pipeline rasterization things. 
> 
> 2. At first I was going to support pre Gen7 hardware with the series. However,
> I do not have hardware on which to test it. In truth I want this to also run on 
> pre-Gen7, but without testing on device, I cannot vouch for the patches. 
> I believe it should just work for pre Gen7 (by just tweaking the last patch to 
> enable it on pre Gen7), but I would rather be careful than in this case. I also 
> confess, it is a silly extension for pre Gen7 anyways...
> 
>  -Kevin

A couple of us chatted about this, and we all agreed that it's probably
not useful to enable ARB_framebuffer_no_attachments on pre-Gen7.  We
don't expose atomics, SSBOs, or image load/store on those platforms (and
probably won't), so the only way fragment shaders can output any data is
via framebuffer writes.

So I'd be inclined to just not touch the pre-Gen7 code at all.
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