https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=297584
Bug ID: 297584
Summary: x11-servers/xorg-server: Xorg does not automatically
detect outputs/monitors on a USB hub
Product: Ports & Packages
Version: Latest
Hardware: amd64
OS: Any
Status: New
Severity: Affects Only Me
Priority: ---
Component: Individual Port(s)
Assignee: [email protected]
Reporter: [email protected]
Flags: maintainer-feedback?([email protected])
Assignee: [email protected]
(Preface: I don't know whether this is actually a libudev-devd issue;
I'm filing it as an xorg-server issue because it's the component whose
behavior I am able to observe.)
Short version: I have a laptop, a USB hub, and 2 HDMI monitors plugged
into the hub. When I plug the hub into the laptop, a running Xorg server
appears never to automatically detect the new outputs.
Workaround: switching to a text vt (one of the ones running getty) and
then back to the vt where Xorg is running causes the server to detect
the hub's outputs & that monitors are connected.
Desired behavior: I'd like it if Xorg could detect the USB hub's
outputs & connected monitors without having to do vt switching. (IDK
if this is merely a "nice to have" or "wishlist" request. 25 years of
running X on PC hardware has made me wary of vt switching to/from X:
it has always seemed prone to sporadically wedge a video driver or
hardware. But that's just my paranoia, and I'd be happy to learn if
this is an obsolete worry nowadays.)
Hardware info:
Lenovo X1 Carbon 6th Generation (manufactured 2018)
GPU: Intel Kaby Lake (i915kms driver)
Builtin monitor
Relevant ports:
2 USB-C ports
1 HDMI port
VVB VB038A 14-in-1 USB-C hub (manufactured 2026)
Relevant ports:
2 HDMI ports
1 DisplayPort
ASUS VS239 HDMI monitor
Acer SB220Q HDMI monitor
Relevant software:
$ freebsd-version -kru
14.4-RELEASE-p8
14.4-RELEASE-p7
14.4-RELEASE-p8
$ pkg info --regex 'gpu.*|libudev-dev|xorg-server'
gpu-firmware-intel-kmod-kabylake-20260519.1404000
libudev-devd-0.6.0
xorg-server-21.1.24,1
Reproduction steps:
1. While the hub plugged is not plugged in, either start Xorg or log
in to a display manager.
2. 'xrandr | grep '[^[:space:]]' shows the following "outputs"
Screen 0: minimum 320 x 200, current 2560 x 1440, maximum 16384 x 16384
eDP-1 connected primary 2560x1440+0+0 (normal left inverted right x axis y
axis) 309mm x 174mm
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
HDMI-2 disconnected (normal left inverted right x axis y axis)
(Aside: I can verify that DP-1 and DP-2 correspond to the laptop's 2
USB-C ports. As there is only one HDMI port, I don't know why xrandr
shows two HDMI outputs, but I'm supposing that's an irrelevant &
orthogonal quirk.)
3. Plug the USB hub in to the laptop.
4. The xrandr output remains unchanged since step 2.
5. [workaround] After switching to a text vt and then back to the vt
where X is running, the filtered xrandr output contains 3 more
outputs, 2 of them "connected". (I presume DP-1-3 represents the
hub's DisplayPort, which I'm not using.)
Screen 0: minimum 320 x 200, current 2560 x 1440, maximum 16384 x 16384
eDP-1 connected primary 2560x1440+0+0 (normal left inverted right x axis y
axis) 309mm x 174mm
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
HDMI-2 disconnected (normal left inverted right x axis y axis)
DP-1-1 connected (normal left inverted right x axis y axis)
DP-1-2 connected (normal left inverted right x axis y axis)
DP-1-3 disconnected (normal left inverted right x axis y axis)
Potentially relevant diagnostic information:
- While on one of the text vts, when I plug in the USB hub, after
about 5 or 6 seconds the HDMI monitors mirror the built-in monitor
(modulo resolution issues).
- Here's a diff of 'devinfo -rv' outupt upon plugging in the USB hub.
@@ -1800,6 +1874,9 @@
iicbus5 <Philips I2C bus>
iic5 <I2C generic I/O> at addr=0
drm5
+ drm6
+ drm7
+ drm8
lkpi_iic0 <LinuxKPI I2C>
iicbus0 <Philips I2C bus>
iic0 <I2C generic I/O> at addr=0
@@ -1900,6 +1977,12 @@
lkpi_iic35 <LinuxKPI I2C>
iicbus36 <Philips I2C bus>
iic36 <I2C generic I/O> at addr=0
+ lkpi_iic36 <LinuxKPI I2C>
+ iicbus37 <Philips I2C bus>
+ iic37 <I2C generic I/O> at addr=0
+ lkpi_iic37 <LinuxKPI I2C>
+ iicbus38 <Philips I2C bus>
+ iic38 <I2C generic I/O> at addr=0
- I also have an ASUS MB16ACV USB-C portable monitor (manufactured
2021). When I plug this in to one of the laptop's built-in
USB-C ports, xrandr promptly shows either of DP-1 or DP-2 as
"connected".
My interpretation of the first 2 points is that drivers are
automatically detecting the ports & monitors. I don't know what to
make of the third point, except to infer that Xorg (or libudev-devd)
is watching for at least some state changes.
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