[PATCH 27/27] drm: Add default modes for connectors in unknown state

[Daniel Stone]

Hi,

On Fri, 26 Jun 2020 at 10:00, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> On Thu, 25 Jun 2020 12:44:36 +0200 Daniel Vetter <daniel at ffwll.ch> wrote:
> > Maybe an aside, but the guideline is for autoconfiguration:
> > - Light up everything that has connector status connected.
> > - If nothing has that status, try to light up the connectors with
> > status "unknown".
> >
> > This is only really relevant on older platforms, mostly for VGA and
> > somewhat for dvi outputs.
> >
> > Maybe another thing we should put down somewhere in the uapi docs ...
>
> As I had no idea what "unknown" means or when it can happen, I assumed
> that it must mean "the hardware cannot know". If the hardware cannot
> know, then I certainly will not be trying to enable that, unless
> explicitly configured to do so. Having a phantom output is worse than
> having a real output that does not light up, because it's not obvious at
> first with phantom output that anything is wrong. You may just be
> wondering where your windows disappear, or where did you mouse cursor
> go, or why you see a wallpaper but no login dialog, etc.

How about a refinement of Dan's suggestion, proceeding down this
logical order and breaking if true:
- ignore all disconnected outputs
- if any outputs are connected, ignore all unknown outputs
- if only one output is unknown, use only that output (with default
mode if need be)
- if any outputs are unknown but have EDID present, use only those outputs
- at this point, we have multiple unknown outputs with no EDID - break
and demand explicit user configuration

Cheers,
Daniel