[Bug 107583] Linux: REGRESSION: drm: cmdline EDID override mechanisms broken since 4.15

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=107583

harish.chegondi at intel.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |harish.chegondi at intel.com
             Status|NEW                         |ASSIGNED

--- Comment #19 from harish.chegondi at intel.com ---
(In reply to Jani Nikula from comment #18)
> 
> I think there's a conflicting set of valid requirements here, and the only
> way to preserve functionality for all cases is to add another level of
> connector force probe, which skips DDC probe in case of override/firmware
> EDID.

If I understand Jani's comment correctly, in drm_get_edid(), DDC probe should
be skipped if the connector force is unspecified and EDID has to be overridden.
When I analyzed the code further, I felt the check that does DDC probe if
connector force is unspecified can be eliminated and will also fix this bug. I
mentioned my proposed change below. I also submitted this change to trybot and
it was successful.

--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -1724,9 +1724,6 @@ struct edid *drm_get_edid(struct drm_connector
*connector,
        if (connector->force == DRM_FORCE_OFF)
                return NULL;

-       if (connector->force == DRM_FORCE_UNSPECIFIED &&
!drm_probe_ddc(adapter))
-               return NULL;
-
        edid = drm_do_get_edid(connector, drm_do_probe_ddc_edid, adapter);
        if (edid)
                drm_get_displayid(connector, edid);

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