netdev - Re: [PATCH v1] smsc911x: add second read of EEPROM mac when possible corruption seen

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Message-ID: <20250902120528.5adc9fb7@kernel.org>
Date: Tue, 2 Sep 2025 12:05:28 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Colin Foster <colin.foster@...advantage.com>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org, Steve Glendinning
 <steve.glendinning@...well.net>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH v1] smsc911x: add second read of EEPROM mac when
 possible corruption seen

On Tue, 2 Sep 2025 07:31:13 -0500 Colin Foster wrote:
> > > +	 * The first mac_read always returns 0. Re-read it to get the
> > > +	 * full MAC  
> > 
> > Always? Strange, why did nobody notice until now?  
> 
> For me it is 100% reproduceable. The first read is always 0. I've added
> delays in case timing was the issue. I've swapped ADDRH and ADDRL and
> the opposite effect happened (where the first four MAC octets were
> zero). Re-reads always succeed.
> 
> Without the patch, the last two MAC octets are always zero.
> 
> We didn't notice it until we started hooking multiple devices on the
> same network.
> 
> If there is anyone else running this hardware, I'd love verification.
> Its an SMSC9221.
> 
> That's a long way of saying "I don't know" unfortunately.

Right, I think we should avoid saying "always" in the comment then.
Let's weasel word it a little bit given the uncertainty..