[Intel-gfx] [PATCH 3/3] drm/atomic: Refuse to steal encoders from connectors not part of the state.

Daniel Vetter daniel at ffwll.ch
Thu Feb 18 12:43:11 UTC 2016

On Thu, Feb 18, 2016 at 12:18:53PM +0100, Maarten Lankhorst wrote:
> Op 18-02-16 om 12:07 schreef Daniel Vetter:
> > On Thu, Feb 18, 2016 at 09:54:43AM +0100, Maarten Lankhorst wrote:
> >> Because encoder <-> connector mapping is fixed when not moving to
> >> another crtc we can just reject connectors trying to steal an encoder
> >> from a connector not part of the state. This won't break MST on i915
> >> because in that case connectors will be part of the state if you switch
> >> them between crtc's. If they're not they stay on the same crtc, and
> >> encoder stealing would have failed anyway.
> > We must do this for backwards compat. setCrtc on a connector that needs an
> > encoder already used on some other crtc is supposed to disable that
> > encoder (and the entire pipe if it's all unused) if we need it.
> > -Daniel
> >
> Could this be done from the setcrtc helper? Seems with atomic that wouldn't be desired behavior.

If you want to avoid stealing with atomic, supply _all_ the
connectors/crtcs when doing an atomic modeset. After all the point of
atomic is to do global updates. I don't think it makes sense to have a
special case just for setcrtc, since it makes compat/transition
unecesserily complicated. And we do this kind of stealing in other places
too with public api objects, e.g. if you move a plane.
Daniel Vetter
Software Engineer, Intel Corporation

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