Re: [PATCH 3/3] net: add generic MAC address derivation from machine ID

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello Sascha,

On 12.09.23 14:34, Ahmad Fatoum wrote:
> On 12.09.23 12:49, Sascha Hauer wrote:
>> I think this deserves a cleanup before we merge this. The original
>> reason to introduce a postenvironment_initcall() for getting the MAC
>> address from nvmem was:
>>
>>> We do this in a very late initcall, because we don't want to enforce a
>>> probe a probe order between nvmem providers and network devices. We
>>> can't do it at randomization time, because we need to fixup Ethernet mac
>>> addresses, even when barebox itself doesn't ifup the netdev.
>>
>> I think we should have one centralized function that retrieves the MAC
>> address for an ethernet device. That should be called when we actually
>> need that MAC address, so once in net_new() and once at of_fixup time.
>>
>> Right now the behaviour is inconsistent with regard to random MAC
>> addresses. Currently we propagate the random MAC address to the Linux
>> device tree when we use ethernet in barebox, but we don't propagate it
>> when we do not use ethernet in barebox. We should decide what the
>> desired behaviour is and do it consistently regardless if we use
>> ethernet in barebox or not. This could be cleaned up along the way.
> 
> Randomized MAC addresses are a necessary evil when barebox needs to do
> networking and doesn't have a stable address. If we have a stable address,
> we shouldn't randomize.
> 
> Fixing up a randomized MAC address is a lesser evil than having different
> MAC addresses for barebox and Linux. If we don't need a MAC address in barebox,
> we shouldn't generate a random one just to fix it up.
> 
> If we have a stable address, we should tell Linux about it.
> 
> That's the logic of the current code and it's sensible to me. Why change it?

We have had two boards trying to add something similar in the last couple of
months. I still need your input here on how to proceed.

Thanks,
Ahmad

> 
> Cheers,
> Ahmad
> 
>>
>> Sascha
>>
> 

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