Re: [PATCH] net: uclass: Save ethernet MAC address when generated

[Grygorii Strashko <grygorii.strashko@ti.com>]

On 02/11/2021 12:27, Michal Simek wrote:
> 
> 
> On 11/2/21 10:00, Michael Walle wrote:
>>> On Fri, Oct 29, 2021 at 2:14 PM Michal Simek <michal.simek@xilinx.com> wrote:
>>>>
>>>> When MAC address is randomly generated it should be also saved to
>>>> variables. This step is there when MAC address is passed via pdata but not
>>>> when it is randomly generated.
>>>>
>>>> Signed-off-by: Michal Simek <michal.simek@xilinx.com>
>>>> ---
>>>>
>>>>   net/eth-uclass.c | 2 ++
>>>>   1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/net/eth-uclass.c b/net/eth-uclass.c
>>>> index 0da0e85be031..58c308f33276 100644
>>>> --- a/net/eth-uclass.c
>>>> +++ b/net/eth-uclass.c
>>>> @@ -583,6 +583,8 @@ static int eth_post_probe(struct udevice *dev)
>>>>                  net_random_ethaddr(pdata->enetaddr);
>>>>                  printf("\nWarning: %s (eth%d) using random MAC address - %pM\n",
>>>>                         dev->name, dev_seq(dev), pdata->enetaddr);
>>>> +               eth_env_set_enetaddr_by_index("eth", dev_seq(dev),
>>>> +                                             pdata->enetaddr);
>>>>   #else
>>>>                  printf("\nError: %s address not set.\n",
>>>>                         dev->name);
>>>> -- 
>>>> 2.33.1
>>>>
>>> Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
>>
>> Please note, that this will change behavior. Before this commit, the
>> random mac address was local to u-boot (at least for most network drivers).
>> After this commit, it will also be communicated to linux.
>>
>> I'm not sure what to think of this. At the very least, this should be
>> documented in the commit message and in the Kconfig help text.
> 
> Thanks for bringing this up. I have no issue that this address is being propagated to Linux but others can feel this as an issue.
> I can definitely extend commit message to say it.

Propagating random MAC to Linux might be not a good idea as Linux will silently use it while in many cases it means that smth is wrong,
and message like "Driver uses random MAC!" helps narrow down issues earlier.
For example, we occasionally copy-pasted wrong mac in DT and detected this only after some time when started connecting
similar boards to each other :(
Also, Linux may have it's own way to retrieve MAC if not provided by u-boot.

Wouldn't be enough to just print MAC console when random is used?

> 
> I found this via net list command where you can see controllers but you can't see their mac addresses which is IMHO wrong.


-- 
Best regards,
grygorii