TTM tt size larger than buffer object?

[Thomas Hellström]

Hi, Christian.

We have a use-case with i915 where the data representation of a buffer 
object is larger in system memory than in LMEM/VRAM. Hence we'd like to 
create a ttm_tt that is larger than the buffer object itself. Quickly 
auditing the TTM code it looks like that should be pretty safe, as 
ttm->num_pages is not really much accessed outside the tt code and the 
pool code where we're doing the right thing.

The additional data will really only be accessed by the blitter so when 
cpu-mapping, mapping just the original buffer object size is correct. 
However with swapping the additional data needs to be swapped out and 
the code is doing that correctly as well.

Do you think this is an acceptable solution?

/Thomas