Docks on a USB4 port: their monitors may stay dark

docs/hardware.md

@@ -102,7 +102,7 @@ let the row's note name what did not work:
 | an external monitor on HDMI or DisplayPort, plugged in while the desktop runs | the desktop reaches it within seconds, and `kryptik display` lists it with its scale |
 | an external monitor on a laptop with two GPUs, an AMD one beside the built-in | it shows the desktop, whose frames wlroots copies to the second GPU's ports; dark, the row's note names both, as the listing's `display` line does |
 | a laptop with NVIDIA's graphics beside Intel's or AMD's | the desktop shows on the built-in screen; a monitor on a port the NVIDIA chip drives stays dark, as 1.0 drives none, and the listing's `gpu` line says whether that chip stayed powered |
-| a USB-C or Thunderbolt dock: its monitor, its USB ports and its Ethernet | the monitor shows where the laptop drives USB-C itself; a Thunderbolt or USB4 dock's own USB ports and Ethernet stay dark, as 1.0 builds no Thunderbolt driver, and the row's note says which worked |
+| a USB-C or Thunderbolt dock: its monitor, its USB ports and its Ethernet | the monitor shows where the laptop drives USB-C itself; a Thunderbolt or USB4 dock's own USB ports and Ethernet stay dark, as 1.0 builds no Thunderbolt driver, and on a Thunderbolt or USB4 port its monitors may too; the row's note says which worked, and on which port |
 | closed on its dock, then the dock unplugged | it sleeps within seconds, as a lid closed undocked does |
 | the state passphrase at boot, typed on the built-in keyboard | it unlocks, whether the keyboard is on PS/2 or on I2C behind Intel's LPSS or AMD's DesignWare controller; the row's note names which (`/proc/bus/input/devices`). One that types nothing there is among those status.md lists, and a plain USB keyboard is the way through |
 | `k` and a zone's number in the menu, then a program there that records video | a USB camera records; one the listing's `camera` line puts behind an IPU does not, as 1.0 drives none |

docs/status.md

@@ -57,7 +57,9 @@ media it tested.
   USB ports and Ethernet, behind its own PCIe controllers, stay dark; a USB4
   or Thunderbolt 4 dock's USB devices run at USB 2's speed, which needs no
   tunnel. A monitor over USB-C works where the laptop's controller drives
-  it. Building them comes with a policy for which plugged devices are let in.
+  it; on a USB4 port, a USB4 or Thunderbolt dock's monitors may stay dark,
+  as nothing sets up the DisplayPort it tunnels. Building them comes with a
+  policy for which plugged devices are let in.
 - The state passphrase is asked in sysinit, before eudev loads any module,
   so only a keyboard whose drivers are built in types it: PS/2 (atkbd), a
   USB keyboard the generic HID driver takes, and HID over I2C behind

docs/user-guide.md

@@ -720,8 +720,14 @@ shows each timer, its timeout and whether it is running.
 - Thunderbolt and USB4 are not built, so nothing lets in what a Thunderbolt
   or USB4 dock carries over PCIe or USB 3: its Ethernet may stay dark, and
   its USB ports work at USB 2's speed, which USB-C carries by itself, or not
-  at all. A monitor over USB-C works where the laptop's own USB-C controller
-  drives it, as on most, and many docks fall back to plain USB-C.
+  at all. A monitor plugged straight into a USB-C port, or through a plain
+  USB-C dock, works where the laptop's own USB-C controller drives it, as on
+  most. A Thunderbolt or USB4 dock on a Thunderbolt or USB4 port (usually
+  a lightning mark, or 40Gbps beside it; the laptop's specifications say
+  which ports are USB4) connects as USB4, and its monitors may stay dark
+  too, as nothing sets up the DisplayPort it carries: plug
+  such a dock into a plain USB-C port, where many fall back to USB-C, or
+  the monitor into the laptop itself.
 - The state passphrase at boot is asked before any driver module loads, so
   it is typed on a keyboard whose driver is in the kernel itself: a laptop's
   built-in keyboard on its PS/2 controller, as most are, or on I2C behind