[En-Nut-Discussion] Network Link state on at91_emac and others

[Ole Reinhardt]

Hi all,

Especialy the at91_emac driver is polling the link state during the
reset sequence and does not continue with the initialisation until a
cable is connected (auto negotiation is complete) or a timeout occurs.
This is done by simply polling the NIC_PHY_BMSR_ANCOMPL bit. If the bit
is not set, the loop will do busy polling for at least a maximum of
1.000.000 times. So if no cable is connected the NutRegisterDevice hangs
for a very very long time.

My questions:

- is it necessary to wait until autonegotiation is complete to do the
  nic reset?

- Is there any way to check the current link state? AFAIK right now no
  one of the network drivers support checking the link state, right?

- What should correctly happen if a link loss is detected? From my
  understanding, this should be communicated up to the socket layer to
  abort the currently opened sockets and set the socket error
  appropriate, right?

- On the other hand this should perhaps influence the dhcp thread to
  request a new ip address after link establishment, right?

- Any further ideas / requirements?

These functions are realy missing in NutOS, so I'd like to start a
discussion how to _correctly_ implement these features.

Regards,

Ole Reinhardt

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