[Intel-gfx] [PATCH v2 2/2] drm/i915: Don't advertise modes that exceed the max plane size

[Maarten Lankhorst]

Op 18-09-2019 om 17:07 schreef Ville Syrjala:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> Modern platforms allow the transcoders hdisplay/vdisplay to exceed the
> planes' max resolution. This has the nasty implication that modes on the
> connectors' mode list may not be usable when the user asks for a
> fullscreen plane. Seeing as that is the most common use case it seems
> prudent to filter out modes that don't allow for fullscreen planes to
> be enabled.
>
> Let's do that in the connetor .mode_valid() hook so that normally
> such modes are kept hidden but the user is still able to forcibly
> specify such a mode if they know they don't need fullscreen planes.
>
> This is in line with ealier policies regarding certain clock limits.
> The idea is to prevent the casual user from encountering a mode that
> would fail under typical conditions, but allow the expert user to
> force things if they so wish.
>
> Maybe in the future we should consider automagically using two
> planes when one can't cover the entire screen? Wouldn't be a
> great match for the current uapi with explicit planes though,
> but I guess no worse than using two pipes (which we apparently
> have to in the future anyway). Either that or we'd have to
> teach userspace to do it for us.

In theory this is what bigjoiner is doing, except the planes are on a different pipe.

Will be fun with SDR vs HDR planes though..