Hacker News Reader

Comment by PeCaN | Hacker News Reader

Most of the machines NetBSD runs on don't have USB 3 ports.

Also, isn't 3.0 fully backward compatible with 2.0? I imagine this would affect how critical people would classify support to be developed, if everything already works, just slower.

It's backwards compatible on the device side (you can plug a 3.0 device into a 2.0 port and work at lower speed). But I really doubt that you can use an xHCI controller through EHCI drivers.

> But I really doubt that you can use an xHCI controller through EHCI drivers.

Indeed, you can't. xHCI subsumes all USB operation and doesn't need companion controllers, but presents a _very_ different interface. That's different from the USB1/2 transition where USB2 was a separate controller that could take over the ports from a USB1 controller, giving them back if a USB1 device is attached.

Some boards/chipsets do that with EHCI and xHCI to support operating systems without xhci drivers, but that's getting rarer.

I'm fascinated this has worked so well in all operating systems I've used that I've never had reason to acquire this knowledge.

I'm simultaneously disappointed that this is not (as far as I can tell) widely known information. It sounds like the thing that may prevent you from going on goose chase if you ever need to debug it.

As soon as you write an USB controller driver, you'll stumble over that quickly. The EHCI and XHCI specs are freely available and describe this in detail. It's just that only few people need to write such drivers. :-)

As for it working so well, that's mostly on the EE side: they were _very_ careful to provide this hardware based routing with defaults that make sure that old OSes continue to work while new OSes (or new drivers for old OSes) can make use of the new controllers.

and usb3 is such a large piece of interface I'm not sad netbsd is taking its sweet time to make it solid.

just in time it's beginning to be replaced.

who's trying to eat usb3 ?

- USB 3.1

- USB-C power delivery

- USB-C alternate modes, such as DisplayPort and Thunderbolt 3

Thanks to the USB 3.0 Promoter Group, USB 3.1 Gen 1 (a.k.a. USB 3.0) devices have been rebranded as USB 3.2 Gen 1x1.

https://en.wikipedia.org/wiki/USB_3.0#USB_3.2

The USB 3.2 standard is backward compatible with USB 3.1/3.0 and USB 2.0. It defines the following transfer modes:

USB 3.2 Gen 1x1 - SuperSpeed, 5 Gbit/s (0.625 GB/s) data signaling rate over 1 lane using 8b/10b encoding, the same as USB 3.1 Gen 1 and USB 3.0. USB 3.2 Gen 1x2 - SuperSpeed+, new 10 Gbit/s (1.25 GB/s) data rate over 2 lanes using 8b/10b encoding. USB 3.2 Gen 2x1 - SuperSpeed+, 10 Gbit/s (1.25 GB/s) data rate over 1 lane using 128b/132b encoding, the same as USB 3.1 Gen 2. USB 3.2 Gen 2x2 - SuperSpeed+, new 20 Gbit/s (2.5 GB/s) data rate over 2 lanes using 128b/132b encoding.

USB 3.2 is supported with the default Windows 10 USB drivers and in Linux Kernel 4.18.

I wish this was satire

aight, I conflated all in usb3

But is that a cause or effect of NetBSD not supporting USB3?

A lot of NetBSD platforms predate USB3, so presumably not an effect. Keep in mind it runs on very old stuff like the Dreamcast and OMRON LUNA and very small stuff like tiny ARM boards and MIPS routers.

That was true before USB3 even existed, but USB3 could be part of a greater set of features which suffer from a similar problem.

A domino effect perhaps, or the result of finding a niche?

Reply on news.ycombinator.com