[PATCH 1/2] drm/edid: Make EDID header fixup threshold configurable

Adam Jackson ajax at redhat.com
Tue Apr 27 08:26:40 PDT 2010


On Tue, 2010-04-27 at 10:47 -0400, Alex Deucher wrote:
> On Tue, Apr 27, 2010 at 10:30 AM, Adam Jackson <ajax at redhat.com> wrote:
> > That's a valid point though: we currently don't distinguish between
> > "connected but with broken EDID" and "disconnected".  I think it sounds
> > reasonable to treat the former as connector_status_unknown instead.
> > That way, if nothing else is connected, X will still light you up at the
> > fallback size.  Sound right?
> 
> Or maybe just mention the EDID is bad and may cause problems, but then
> use as much of it as possible.  That has the best chance of a
> satisfied user and a native mode being selected.

That would require a lot more parser work to make it robust in the face
of suspicious-looking subsections.  Not that we should never do that,
but that I think it's the wrong strategy in general.  I've really tended
to shy away from being too permissive in what we accept from EDID,
because the failure mode is picking a mode that the display doesn't
support and coming up blank.  I'd much rather play it safe if we're not
100% sure, especially since you can jam the correct mode in later with
RANDR if you come up in a conservative mode.

One thing that _would_ be cool is figuring out the common ways of
writing to EDID EEPROMs and exposing some I-know-what-I'm-doing way of
trying them, so we could repair bad displays.  Also, DDC/CI sometimes
gives you a way of knowing whether the monitor has synced, which would
let us know whether a given mode was bad or not.

- ajax
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