btw, ink api works fine on nocturne even when rotated. 

I tested eve + m68 + ARC N and got the same behavior.
maybe it's expected?

Daniele, can you take a look?

----
From: marcheu@

Then maybe Chrome isn't using these properly. Daniele do we use the
rotations on overlays when they're available?

Stéphane

On Tue, Nov 6, 2018 at 4:12 PM Dominik Behr <dbehr@google.com> wrote:
>
> shows current rotation and all available rotations
>
>
>        if (INTEL_GEN(dev_priv) >= 9) {
>                 supported_rotations =
>                         DRM_ROTATE_0 | DRM_ROTATE_90 |
>                         DRM_ROTATE_180 | DRM_ROTATE_270;
>         } else if (INTEL_GEN(dev_priv) >= 4) {
>                 supported_rotations =
>                         DRM_ROTATE_0 | DRM_ROTATE_180;
>         } else {
>                 supported_rotations = DRM_ROTATE_0;
>         }
>
>         if (INTEL_GEN(dev_priv) >= 4)
>                 drm_plane_create_rotation_property(&primary->base,
>                                                    DRM_ROTATE_0,
>                                                    supported_rotations);--
> Dominik

Rotations on Intel depends on the buffers modifiers. We currently
don't use the actual buffers for the atomic test and we test with
buffers without modifiers.
We had to disable 90 and 270 rotations:
https://cs.chromium.org/chromium/src/ui/ozone/platform/drm/gpu/hardware_display_plane_atomic.cc?l=49&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fui%252Fozone%252Fplatform%252Fdrm%252Fgpu%252Fhardware_display_plane_atomic.cc%253Froot%253Dchromium-chromeos%2523PX0BIVmBu5jVzX1E0oe3GW%25252FNqBoWxYgwfQgMnG%25252B8Jtc%25253D&gsn=IsRotationTransformSupported&ct=xref_usages

AFAIK all the low latencies app counter rotates their buffers so that they end on screen without rotation, that's why ink works.

So just to be sure: this is true for all intel devices like e.g. eve?

The app should handle the rotation instead. This is how low latency stylus apps work when the display is rotated.

Yeah what I have expected. This is easy for Android to do (as that is the standard) but we have disabled it as we did not want to let the compositor handling that. Well - we will have to re-consider this then for Q.

BUT: Is there any way to get this going for intel - or is this a hard "Hardware cannot do it"?

Overlay doesn't work even for youtube video when rotated, so I think we still should fix this regardless of arc++ app. According to dcastagna@ and rjkroege@, we can fix this when migrated to viz.