Question USB Power Bidirection starts when?

[rockman413]

Hi there,
I'm confused about when is the start of USB power bidirectional? I mean, for example, you can use an usb/thunderbolt hub with PD to charge your macbook pro, etc..
Is it USB3.0 which supports bidirectional power? 3.1 Gen1 ? Gen2? Any USB devices with USB 3.1 no matter without the "PD" mark can also charge your macbook pro too?

Thanks!

 

[rockman413]

Hi there,
I'm confused about when is the start of USB power bidirectional? I mean, for example, you can use an usb/thunderbolt hub with PD to charge your macbook pro, etc..
Is it USB3.0 which supports bidirectional power? 3.1 Gen1 ? Gen2? Any USB devices with USB 3.1 no matter without the "PD" mark can also charge your macbook pro too?

Thanks!