If we can query the capability of the root hub among the whole system, to indicate if kernel should
notice userspace that the device is pluged into a inappropriate port. When a port with higher speed and/or more capabilities the
device required is available. eg a dp display device on a normal typec even usb 2.0 only, or a superspeed device on a usb 2.0 port.
(Windows DID that)
Also some non-standard device only provide a usb superspeed without usb 2.0 even the specifaction says
> 11.3 USB 3.2 Device Support for USB 2.0
>USB 3.2 device certification requirements require support for USB 2.0 for all user attached devices.
I looked up the USB BOS descriptor and found that the field describing the device's speed capabilities is one-hot coded.
So also the device can put a billboard or BOS on usb2.0 to indicate it cannot run on such a port.
struct _SUPER_SPEED_USB_DEVICE_CAPABILITY_DESCRIPTOR
{
BYTE bLength;
BYTE bDescriptorType;
BYTE bDevCapabilityType; // ONE HOT BIT CODING!
BYTE bmAttributes;
WORD wSpeedsSupported;
BYTE bFunctionalitySupport;
BYTE bU1DevExitLat;
WORD wU2DevExitLat;
}SUPER_SPEED_USB_DEVICE_CAPABILITY_DESCRIPTOR
I search the kernel source, but nothing shows that kernel trying to notice user or even a pr_info when situations above happened.
