On 03/20/2015 01:31 PM, Joonas Lahtinen wrote:
[snip]
Hm, rotation info is not considered in comparing views, it is just a
bucket of data passed around between layers. So I suppose private data
under your design. Since there is no private union yet, maybe do this later?
Why not? Isn't a 270 degree rotated view substantially different from a
90 degree rotated view (even when the difference technically is just
some bit flip somewhere else).
At least I would be pretty upset if I was returned the address for 90
degree rotated view when I wanted 270 rotated. If multiple rotated views
are not possible, then it is again an implicit thing.
There are quite a lot of hardware constraints like this that appear in
the code implicitly, which IMHO makes the code hard to follow at times.
So I'd try to make it more explicit that the views are not the same,
there just can be one rotated view at a time (if that is the case).
90 and 270 views are indeed the same page layout - same address for
scanout. And there can only be one such VMA for an object at a time.
But how this mapping needs to look like is determined by more than the
object itself - framebuffer geometry defines it. The private data in the
view is used to transfer that meta-data so the GTT core can build the
appropriate view.
Right, I think I understand your viewpoint now. I would still prefer it
to be even more explicit like I915_GGTT_VIEW_Yf_SCANOUT, because what it
really does is rearranges the pages to layout suitable for rotated
scanout, not making the view rotated in itself.
Ha, not sure what you mean, but Yf is definitely not the right name for
it since it is a different thing altogether.
It is rotated in a way that tiles (==pages) are rotated by 90 degrees.
But content within the tile is not (display engine handles that bit). In
your mind that would maybe be
I915_GGTT_VIEW_ROTATED_PAGES_FOR_ROTATED_SCANOUT? :) I am guessing only,
but I still think I915_GGTT_VIEW_ROTATED is fine.
Regards,
Tvrtko
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