Sparsely populated TTM bos

[Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>]

Hi, Christian,

We have an upcoming use-case in i915 where one solution would be 
sparsely populated TTM bos.

We had that at one point where ttm_tt pages were allocated on demand, 
but this time we'd rather be looking at multiple struct ttm_resources 
per bo and those resources could be from different managers.

There might theoretically be other ways we can handle this use-case but 
I wanted to check with you whether this is something AMD is already 
looking into and if not, your general opinion.

Thanks,
Thomas