Re: [Mesa3d-dev] RFC: allow resource_copy_region between different (yet compatabile) formats

[Luca B. <lu...@lu...>]

> When I said it won't work with decent hardware, I really meant it won't
> work due to compression. Now, it's quite possible this can be disabled
> on any chip, but you don't know that before hence you need to jump
> through hoops to get an uncompressed version of your compressed buffer
> later.

Well, you can render to a compressed depth buffer and then bind it as
a depth texture (routinely done for shadows), so there needs to be a
way to get compressed data to the sampler either directly or via the
driver automagically converting it with a blit beforehand.

Of course, this may not actually work for stencil too, or might not
allow to let you interpret depth as 8-bit color components, or perhaps
not use directly as a render target, but it seems possible, especially
on modern flexible hardware and on older dumber hardware that
lacks/doesn't force compression.

I haven't checked any hardware docs though, beyond the fact that nvfx
currently doesn't support any compression and thus can "just do it".