Date: Thu, 2 Oct 2025 11:06:06 -0700 From: Mark Millard <marklmi@yahoo.com> To: ziaee@freebsd.org, dev-commits-src-main@freebsd.org Subject: RE: git: 2ed9833791f2 - main - thunderbolt: Import USB4 code [more explicit note now that Thunderbotl 3 is mentioned] Message-ID: <51FCEFDE-7112-4C60-AE63-77E814967A63@yahoo.com> References: <51FCEFDE-7112-4C60-AE63-77E814967A63.ref@yahoo.com>
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Alexander Ziaee <ziaee_at_FreeBSD.org> wrote on Date: Thu, 02 Oct 2025 15:38:02 UTC : > The branch main has been updated by ziaee: >=20 > URL: = https://cgit.FreeBSD.org/src/commit/?id=3De4e412e45a17d2f63f6693d41b274379= d108c82f >=20 > commit e4e412e45a17d2f63f6693d41b274379d108c82f > Author: Alexander Ziaee <ziaee@FreeBSD.org> > AuthorDate: 2025-10-02 15:27:43 +0000 > Commit: Alexander Ziaee <ziaee@FreeBSD.org> > CommitDate: 2025-10-02 15:37:12 +0000 >=20 > thunderbolt.4: Mention Thunderbolt 3 >=20 > MFC after: 1 hr > Reported by: emaste > Fixes: 2f7a796b590e (thunderbolt.4: Initial manual) > --- > share/man/man4/thunderbolt.4 | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) >=20 > diff --git a/share/man/man4/thunderbolt.4 = b/share/man/man4/thunderbolt.4 > index 3477c11fb60d..fd7cb1f3f338 100644 > --- a/share/man/man4/thunderbolt.4 > +++ b/share/man/man4/thunderbolt.4 > @@ -14,7 +14,7 @@ > .Sh HARDWARE > The > .Nm > -driver supports USB4 controllers. > +driver supports Thunderbolt 3 and USB4 controllers. USB4 V1 and V2 both have a Chapter 13, "Interoperability with Thunderbolt(tm) 3 systems" that "describes the additional requirements for a Router that supports TBT3-compatible interoperability". Also: "When interoperating with a TBT3 product, Thunderbolt Alt Mode is established on the link between products. The USB Type-C Specification describes how a USB4 product negotiates and enters Thunderbolt Alt Mode." Quoting USB4 V2: "A USB4 Host or USB4 Peripheral Device can optionally support interoperability with Thunderbolt 3 (TBT3) products." Quoting USB4 V1: "A USB4 host or USB4 peripheral device can optionally support interoperability with Thunderbolt 3 (TBT3) products." Given this context, = https://lists.freebsd.org/archives/dev-commits-src-main/2025-September/036= 033.html had written: QUOTE For context, older TB chips implemented the connection manager in firmware (ICM) instead of in the OS (HCM), but maintaining the ICM code would be a huge burden for not many chips. END QUOTE That seems to leave out at least some "Thunderbolt 3 controllers". It had been my impression that the above meant not meeting the full USB4 V1 or V2 criteria for claiming the optional support of Thunderbolt 3 inoperability by the USB4 V1 or V2 chapter 13 criteria and possibly material elsewhere in USB4 V1 and or V2 or in USB Type-C Specification's Thunderbolt Alt Mode material. May be the implication is interoperability with only some types of Thunderbolt 3 contexts but not meeting the official criteria for the range of USB4 Thunderbolt 3 support? My impressions are definitely not those of an expert. This seems to be an area where implications of loose statements are not clearly traceable to clear answers, unfortunately. Another area of note: Being explicit about USB4 V2 vs. USB4 V1 likely is important. It seems that in some ways V2 has dropped some V1 criteria in ways that simplify some things, although I'm not sure how much that applies to hosts. A non-host example is USB4 V2 Dock's do not need their upstream facing port to support "TBT3-compatibility" but USB4 V1 requires that support. > .Sh HISTORY > The > .Nm =3D=3D=3D Mark Millard marklmi at yahoo.com
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