open_handle_port required a PortState for every port<N> directory open,
but hub child ports have no PortState until the hub daemon triggers
attach_device via port<N>/attach — an endpoint that itself is
state-free (open_handle_attach_device). This made XhciClientHandle::new
fail with ENOENT for unenumerated hub children, deadlocking the attach
flow: usbhubd could never start enumeration for a device behind a
non-root hub (panic at startup, caught by test-usb-hub-qemu.sh).
Open the directory with the static listing when no PortState exists
yet; state-dependent subpaths (descriptors, state, configure) still
gate on the PortState being present.
Red Bear OS
d7f31916bc