Lenovo Thinkpad T480 + TB3 dock - how do I debug ?

[Poul-Henning Kamp]

I'm trying to find out how to debug why my external monitor does
not come back when I plug my TB3 dock back in, and I could use some
pointers.

My situation is this:

	Lenovo T480, Thunderbolt3 dock

	amd64, 12.0-ALPHA8 #13 r339250M

	drm-next-kmod-4.11.g20180822

	libdrm-2.4.93,1

	xf86-video-intel-2.99.917.20180512_2

	External monitor plugged into TB3 Dock with displayport

If I plug the TB3 dock in and startx, the external monitor is
found as "DP-1-1" and works as expected.
(xrandr:  DP-1-1 connected)

If I unplug the TB3 dock, the external monitor goes away, as expected.
(xrandr:  DP-1-1 disconnected)

If I plug the TB3 dock back in, the external monitor does not come back.
(xrandr:  DP-1-1 disconnected)

If I then quit X and startx again, then the external monitor is back again.
(xrandr:  DP-1-1 connected)

Where do I start looking for debugging info for this ?

Poul-Henning


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