What does "EHCI HUB functionality limitation" mean?

[evgenyerlihman]

Hello,

I am reading through the release notes of MQX4.2. And in the known issues and limitations i see:

"The HUB functionality of the EHCI is not fully supported (dynamically attach/detach is not supported). This issue will be fixed in upcoming releases."

What exactly does this mean? That attaching/detaching a USB HUB any time after reboot wont work properly?

Thanks,

Evgeny

[danielchen · Accepted solution]

Hi Evgeny:

There are two usb stacks in MQX4.2, one is legacy usb stack, the other is USB_V2.

This limitation applies for the legacy USB stack. And I don't think this issue would be fixed in the legacy USB stack. In the stack v2.0, this issue is fixed.

This issue scenario is hot plug with HUB would cause the host malfunction due to the incomplete machine state implementation in the HUB class, you would find some issues with hub hot plug.

Regards

Daniel

[evgenyerlihman]

Hi Daniel,

Just to be sure, is USB stack v2 backward compatible?

Thanks,

Evgeny

[danielchen]

Hi Evgeny:

No, USB stack V2 is a new design

Regards

Daniel