Previously, the function would always return the max_len parameter.
This poses two issues:
1. the API requires to return the actual packet size
2. the API requires that if the packet is larger than max_len, the
packet is flushed and -ENOBUFS is returned
3. this basically bypasses the packet flushing, consequtive _recv()
would return the last packet again
This commit fixes those issues.
This adds an early exit when the usb interface with the data endpoints
is not activated. This prevents the cdc_ecm_netdev code from attempting
to send the PDU when the USB device is not yet initialized or activated
by a host.
