Re: Thunderbolt3/USB4 targeting: should the wiki materials be more explicit about Thunderbolt 3 vs. Thunderbolt 4 distinctions?

Hi Mark!

On Thu, Jan 30, 2025 at 4:38 PM Mark Millard <marklmi@yahoo.com> wrote:

> On Jan 30, 2025, at 05:17, Mohammad Noureldin <mohammad@thelightbird.com>
> wrote:
>
>
> --snip--

> > How are you doing ?
>
> I'm doing okay. You?
>

I am doing OK, thanks for asking :).


>
> > Very glad to see you interested in USB4 and it's related technologies,
> and I do notice that you are, just like myself, also generally interested
> in USB based on some encounters on mailing lists and Discord.
> >
> > To help make this discussion thread be more productive and to make sure
> it goes in the right direction, allow me to ask a couple of questions
> before I respond with any answers or opinions:
> > - Which wiki materials you are referring to ?
>
> https://wiki.freebsd.org/MohammadNoureldin/FreeBSDUSB4TBT3Support
>
> has
>
> --snip--

>
> However, from such materials I can not tell the intent
> for the likes of what I listed in the original Email.
>

The wiki pages are more like personal notes for myself and for others who
might be interested to know what I am busy with. They are not meant to be a
Technical Reference of any sort just yet. I am adding more and more details
as I go.

Whenever there is something to test or to release, a more clear and
specific details will be shared accordingly and via/in the correct channels
and places. Notice that the wiki pages are under my name at the moment and
more official details should be under a top level section in the wiki. For
example "/USB4" or something like that.


>
>
> > - Would you please share the resources based on which you extracted this
> information ? This will allow me, and hopefully others, to review them and
> see if we all come to the same conclusions or insights
>
> Listing of differences between Thunderbolt 3 and 4 (4 is a
> generalization compared to 3):
>
>
> https://www.intel.com/content/www/us/en/architecture-and-technology/thunderbolt/thunderbolt-3-vs-4.html
>
> However, nothing directly presents the view of getting Thunderbolt3
> functionality from USB4/Thunderbolt4 capable hardware, as is now becoming
> fairly common for some categories of machines.
>
> I happen to have access to a https://www.owc.com/solutions/thunderbolt-hub
> that supports forming a star instead of just a daisy-chain: more than 2
> thunderbolt ports. I could not tell from the existing FreeBSD materials
> about the plans if it was hoped that the hub would be useful vs. not. That
> is an example issue.
>
> I also referenced:
>
>
> https://www.cablematters.com/Blog/Thunderbolt/usb4-vs-thunderbolt-3?srsltid=AfmBOopHWeXCGYCXo3F8pG63Oztk-cQFCZtjr_bsZljM2vtMWSU1gNAG
>
>
> https://www.macworld.com/article/675887/thunderbolt-4-vs-thunderbolt-3-vs-usb-4.html
>
> That last has more notes about PCs and Thunderbolt 3 vs. 4. Mac's
> tend to have fewer differences via having systematically implemented
> more optional aspects for Thunderbolt 3. (Mac centric information
> sources tend to indicate fewer potential differences unless they also
> happen to discuss PCs explicitly, as that last does to some extent.)
>
> I hope that helps.
>

Yes it does help and now I see where the confusion came from. A couple of
points to put in consideration as mentioned in the wiki notes:
1- Priority 1 goes to full USB4 support
2- If/When possible, to make drivers also support TBT3

Notice this is from the perspective of the drivers which are running on the
Host. Meaning, if only the 1st goal has been reached a user would need to
have a Host platform with USB4 support, that could be a platform with:
- USB4 only support
- USB4 support included (TBT4 and 5)

According to USB4 specs:
- "A USB4 Host or USB4 Peripheral Device can optionally support
interoperability with Thunderbolt 3 (TBT3) products."
- "A USB4 Hub is required to support interoperability with Thunderbolt 3
products on all of its Downstream Facing Ports [(DFP)]."
- "A USB4 Hub may optionally support TBT3-Compatibility on its Upstream
Facing Port [(UFP)]."

According to the reading materials available on both Intel and Thunderbolt
Technology websites, TBT4 and 5 include (amongst other things) support for
both the Required and Optional features of USB4.

Now back to your question with the Thunderbolt Hub you have access to:
- Given our 1st in priority goals and if you have a Host with USB4 support
then the answer is: Yes it should work without any issues.
- If and when we succeed to also support TBT3 hosts then the answer is: Yes
it should work >>> given the specs of your hub <<<.

I will try to save up and get myself one of that hub as well for my own
tests.

--snip--

>
>
> ===
> Mark Millard
> marklmi at yahoo.com
>
>
I would like to end my email with notes and a question to you:
- Thanks for reading the wiki pages and pointing out that it needs some
more details (as promised above I will work on that as I go)
- Thanks for sharing which HW you have access to and that you would like to
see it work
- Question:
-# Which host(s) HW do you happen to have ?

Looking forward to your reply

-- 
Thanks
- Mohammad Noureldin
--
"Life is like riding a bicycle. To keep your balance you must keep moving"
- Albert Einstein