[Intel-gfx] [PATCH v3] drm/i915: add immutable zpos plane properties

[Ville Syrjälä]

On Tue, Apr 16, 2019 at 03:28:15PM +0200, Maarten Lankhorst wrote:
> Op 16-04-2019 om 15:20 schreef Ville Syrjälä:
> > On Sat, Apr 13, 2019 at 11:13:27AM +0000, Simon Ser wrote:
> >> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> >>
> >> This adds basic immutable support for the zpos property. The zpos increases
> >> from bottom to top: primary, sprites, cursor.
> > I was thinking a bit about how we might go about testing this.
> >
> > We probably want a basic test that just checks that if any
> > plane has a zpos prop then all planes should have it.
> This would be a good test for BAT.
> > A functional test would stack the planes up in some way and
> > compare against a software rendered reference. IIRC there was 
> > a zpos test case floating around but that depended on alpha
> > blending which we don't necessarily have.
> 
> But with semi-overlapping planes you would accomplish the same, without alpha dependency.
> 
> Something like this?
> 
> [BG]   [Sprite 1]    [Cursor]
>   [Primary]   [Sprite 2]

Should probably be good enough. Though I was pondering is there a
way to position an arbitraty number of planes such that the
resulting picture has a visible region for every possible
combination of planes?

> 
> Perhaps primary fullscreen to prevent issues with hw that doesn't support partial planes?

I guess. And maybe a second test that disables the primary
so that we can also get the bg color into the picture?

-- 
Ville Syrjälä
Intel