[Bug 111045] [CI][BAT] igt at kms_chamelium@(hdmi|dp)-hpd-fast|igt at kms_chamelium@dp-edid-change-during-suspend - fail - Failed assertion: igt_hotplug_detected(mon, HOTPLUG_TIMEOUT)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=111045

--- Comment #36 from Imre Deak <imre.deak at intel.com> ---
(In reply to emersion from comment #34)
> (In reply to Imre Deak from comment #15)
> > If unplugging a DP-alt display while there is an active modeset on it, and
> > then replugging the DP-alt display, the HW/FW/driver won't signal the
> > corresponding plug-in hotplug event until the mode is disabled.
> 
> What happens if legacy userspace doesn't react to hotplug events? We need to
> re-enable the output automatically on hotplug. As of now, legacy userspace
> won't work on DP-alt.
> 
> I'm leaning towards marking this as a kernel bug. If userspace doesn't
> disable the mode, the kernel should re-enable it on hotplug.

The same is true for anything connected in DP-MST mode too though: you connect
an MST display, disconnect, then reconnect it, then the mode won't be
re-enabled automatically on the display, unless user space processes the
hotplug events. So the requirement for user space to do proper hotplug event
processing is not specific to USB-C connectors.

Why do you think we should handle USB-C connectors specially (and have the user
space hotplug processing requirement only for DP-MST connectors)? We would need
a very good justification listing the actual legacy userspace instances you
mentioned (since there hasn't been any actual complaints for these even for
MST).

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