[PATCH 0/9] drm/i915: Plane rotation support

Ville Syrjälä ville.syrjala at linux.intel.com
Mon Sep 30 11:36:59 PDT 2013

On Mon, Sep 30, 2013 at 08:21:33PM +0200, Daniel Vetter wrote:
> On Mon, Sep 30, 2013 at 7:46 PM, Rob Clark <robdclark at gmail.com> wrote:
> > I guess the main thing I care about is that we don't advertise things
> > to userspace that we can't actually do.  I'm not sure what other hw
> > out there supports rotation in hw in some form or another, but it
> > might be a good time to hear from 'em about whether these property
> > values work for them or not.
> Hm, I've thought the plan was to let userspace figure that out with a
> dry-run flag, and if a certain configuration doesn't work it needs to
> fall back to rendering-based compositioning for the given surface. I
> don't think there's really much more we can do for fully generic
> compositors.

Yeah, if no one comes up with anything better, the trial and error
approach is the plan in my mind.

But in case the hardware never ever supports certain property/value I
think we shouldn't expose it. Like 90/270 degree rotation in case of
intel hardware.

> Tha might leave strange hw in the dust where planes aren't symmetric
> in capabilities and hence a simple linear walk over surfaces/planes,
> ordered by bw-savings or so, yields extermely bad surface->plane
> assignements. But  my impression is that hw is moving to unified
> stacks of planes so I hope we can punt on solving this in a generic
> way (and resort to quick platform hacks in userspace where it's really
> needed to hit e.g. video playback power targets).

Right. If someone has really specific needs I think they can just go
and write their own compositor (or plugin if the compositor in question
has such things).

Ville Syrjälä
Intel OTC

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