git: 9fd0c7c520a4 - main - thunderbolt.4: Explain what driver does in manpage

The branch main has been updated by obiwac:

URL: https://cgit.FreeBSD.org/src/commit/?id=9fd0c7c520a4427e1de5a8b733851deca561b79c

commit 9fd0c7c520a4427e1de5a8b733851deca561b79c
Author:     Aymeric Wibo <obiwac@FreeBSD.org>
AuthorDate: 2026-06-19 18:48:38 +0000
Commit:     Aymeric Wibo <obiwac@FreeBSD.org>
CommitDate: 2026-06-19 20:18:45 +0000

    thunderbolt.4: Explain what driver does in manpage
    
    Reviewed by:    ziaee, ngie
    Approved by:    ziaee
    Fixes:  2f7a796b590e ("thunderbolt.4: Initial manual for HW Relnotes")
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D57668
---
 share/man/man4/thunderbolt.4 | 49 +++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 44 insertions(+), 5 deletions(-)

diff --git a/share/man/man4/thunderbolt.4 b/share/man/man4/thunderbolt.4
index fd7cb1f3f338..7d162614d7f7 100644
--- a/share/man/man4/thunderbolt.4
+++ b/share/man/man4/thunderbolt.4
@@ -1,22 +1,61 @@
 .\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
 .\" Copyright (c) 2025 Alexander Ziaee
+.\" Copyright (c) 2026 The FreeBSD Foundation
 .\"
-.\" SPDX-License-Identifier: BSD-2-Clause
+.\" Portions of this software were developed by Aymeric Wibo
+.\" <obiwac@freebsd.org> under sponsorship from the FreeBSD Foundation.
 .\"
-.Dd October 2, 2025
+.Dd June 19, 2026
 .Dt THUNDERBOLT 4
 .Os
 .Sh NAME
 .Nm thunderbolt
-.Nd USB4 controller driver
+.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 supports Thunderbolt 3 and USB4 controllers.
+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 15.0 .
+.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.