The device has LEDs, but they are entirely controlled by firmware. The behaviour
can be configured from the EEPROM. Writing to the EEPROM involves stopping
the firmware on the device. There are no temperature sensors, or maybe there are,
but the firmware hides them from us.
That keeps thinks simpler.
There is no physical access to the MDIO bus, as MAC and PHY are in the same
chip. I hope that otherwise we are safe from firmware interference, though.
It is the sort of thing which you find out in time. As you have seen,
there can be race conditions, and there could be issues hiding until
specific timing is hit to trigger them. But there is little we can do
about that, so lets just go with what you have.
Andrew