.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.\" Copyright (c) 2025 Alexander Ziaee
.\" Copyright (c) 2026 The FreeBSD Foundation
.\"
.\" Portions of this software were developed by Aymeric Wibo
.\" <obiwac@freebsd.org> under sponsorship from the FreeBSD Foundation.
.\"
.Dd June 19, 2026
.Dt THUNDERBOLT 4
.Os
.Sh NAME
.Nm thunderbolt
.Nd Thunderbolt / USB4 Native Host Interface driver
.Sh SYNOPSIS
.Cd device thunderbolt
.Sh DESCRIPTION
The
.Nm
driver attaches to the Thunderbolt and Generic USB4 Native Host Interface
.Pq NHI
found on Intel and AMD platforms.
The NHI is the host-side controller that manages communication with
Thunderbolt and USB4 routers.
.Pp
The driver initializes the NHI hardware and can read from and write to its
configuration space in order to suspend or resume it.
.Pp
.Em This driver does not provide working Thunderbolt or USB4 support .
The primary purpose of loading this driver is to allow the system
to assert ownership of the NHI device so that PCI power management
can place it into a low-power state.
On platforms that support S0ix
.Pq such as S0i3 ,
an unsuspended NHI will block entry into the deepest idle states, and the NHI
is put in an active state by the pre-OS connection manager at boot.
Loading
.Nm
prevents that blockage.
Users who do not require S0ix idle states have no need to load this driver for
the time being.
.Sh HARDWARE
The
.Nm
driver only attaches to generic USB4 controllers, that is devices matching PCI
class
.Dv PCIC_SERIALBUS ,
subclass
.Dv PCIS_SERIALBUS_USB ,
and programming interface
.Dv PCIP_SERIALBUS_USB_USB4 .
.Sh HISTORY
The
.Nm
driver appeared in
.Fx 16.0 .
.Sh CAVEATS
This driver is under active development and is not feature-complete.
The interface and behaviour are subject to change without notice.
Do not rely on this driver for Thunderbolt or USB4 device connectivity.