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

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Hey,

Op 18-02-16 om 13:59 schreef Ville Syrjälä:
> On Thu, Feb 18, 2016 at 01:43:11PM +0100, Daniel Vetter wrote:
>> 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.
> I disagree. Having properties change magically is just a bad idea IMO.
> As far as checking for conflicts, IIRC I did that with a few bitmasks
> in my original atomic code, and it was pretty trivial. The current
> stealing  code we have is way too complicated for what it does IMO.
>
>> And we do this kind of stealing in other places
>> too with public api objects, e.g. if you move a plane.
> Mm. What exactly do we steal with planes?
I've sent a v2 that works nicely with "[IGT PATCH] tests/kms_setmode: Add tests when not stealing encoders on same crtc."
For all other calls disabling connectors to steal its encoder is rejected, but the behavior is preserved for set_config only.

~Maarten
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