[Mesa-dev] st/pbo: fix pbo uploads without PIPE_CAP_TGSI_VS_LAYER_VIEWPORT

[Ilia Mirkin]

Hey Mike,

This is in reference to your change
https://cgit.freedesktop.org/mesa/mesa/commit/?id=614c77772ac2f48955537efcfefaf0609d6c03e5
.

A fragment shader should still be able to read gl_Layer even without
PIPE_CAP_TGSI_VS_LAYER_VIEWPORT. A frag shader can read gl_Layer any
time ARB_fragment_layer_viewport is supported -- I forget the precise
conditions for it, but basically any DX10 hardware supports that.

However the VS_LAYER_VIEWPORT feature isn't supported on any NVIDIA
hardware until fairly late models (GM20x+). So this will regress the
majority case (single-layer) on all NVIDIA hw.

Can you instead adjust the conditions to allow this for the drivers
that implement layer/viewport sysvals in frag shaders? Or just
implement ARB_fragment_layer_viewport in zink?

Thanks,

  -ilia