Hector Martin

oh, yep. i'm using this for a usb C hub (with PD, ethernet, vga, etc) and all the usb C features work, but the "usb 2.0" devices connected to the hub don't work unless i flip the extension cable

The cable can't be to spec because Type-C extension cables are, by definition, in violation of the spec. It's not a CC problem. The problem is that Type-C has two sets of USB2.0 pins but only one set is supposed to be connected across the cable.

yeah, i theorised this before I heard about PD working etc. All female connectors in practice break out all 4 D+ and D- pins, and connecting them together on the female connector on the extension cable should work fine

obviously not to spec, but i'm failing to imagine how exactly it breaks things

This would work for standard cables, but captive alternate mode, dock, or other detachable applications are allowed to redefine the second D+/D- pair so this could cause a problem for those.

Of course those have to deal with dumb USB2.0 only Type C devices that short the pins anyway, but those wouldn't trigger the alternate mode. A hacky extension cable that shorts them *would* allow that, and that could cause a short circuit between different data lines.

(This is of course quite spec-lawyering, I had to go through and check every for any allowed usage of B6/B7)