linux-kernel - Re: [PATCHv6 net-next 6/7] net: ibm: emac: generate random MAC if not found

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Message-ID: <20241012131651.GE77519@kernel.org>
Date: Sat, 12 Oct 2024 14:16:51 +0100
From: Simon Horman <horms@...nel.org>
To: Rosen Penev <rosenp@...il.com>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Andrew Lunn <andrew@...n.ch>,
	Shannon Nelson <shannon.nelson@....com>,
	Uwe Kleine-König <u.kleine-koenig@...libre.com>,
	Breno Leitao <leitao@...ian.org>,
	Jeff Johnson <quic_jjohnson@...cinc.com>,
	Christian Marangi <ansuelsmth@...il.com>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv6 net-next 6/7] net: ibm: emac: generate random MAC if
 not found

On Fri, Oct 11, 2024 at 12:56:21PM -0700, Rosen Penev wrote:
> On this Cisco MX60W, u-boot sets the local-mac-address property.
> Unfortunately by default, the MAC is wrong and is actually located on a
> UBI partition. Which means nvmem needs to be used to grab it.
> 
> In the case where that fails, EMAC fails to initialize instead of
> generating a random MAC as many other drivers do.
> 
> Match behavior with other drivers to have a working ethernet interface.
> 
> Signed-off-by: Rosen Penev <rosenp@...il.com>
> ---
>  drivers/net/ethernet/ibm/emac/core.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ibm/emac/core.c b/drivers/net/ethernet/ibm/emac/core.c
> index b9ccaae61c48..faa483790b29 100644
> --- a/drivers/net/ethernet/ibm/emac/core.c
> +++ b/drivers/net/ethernet/ibm/emac/core.c
> @@ -2937,9 +2937,12 @@ static int emac_init_config(struct emac_instance *dev)
>  
>  	/* Read MAC-address */
>  	err = of_get_ethdev_address(np, dev->ndev);
> -	if (err)
> -		return dev_err_probe(&dev->ofdev->dev, err,
> -				     "Can't get valid [local-]mac-address from OF !\n");
> +	if (err == -EPROBE_DEFER)
> +		return err;
> +	if (err) {
> +		dev_warn(&dev->ofdev->dev, "Can't get valid mac-address. Generating random.");
> +		eth_hw_addr_random(dev->ndev);
> +	}

The above seems to take the random path for all errors other than
-EPROBE_DEFER. That seems too broad to me, and perhaps it would
be better to be more specific. Assuming the case that needs
to be covered is -EINVAL (a guess on my part), perhaps something like this
would work? (Completely untested!)

	err = of_get_ethdev_address(np, dev->ndev);
	if (err == -EINVAL) {
		/* An explanation should go here, mentioning Cisco MX60W
		 * Maybe the logic should even be specific to that hw?
		 */
		dev_warn(&dev->ofdev->dev, "Can't get valid mac-address. Generating random.");
		eth_hw_addr_random(dev->ndev);
	} else if (err) {
		return dev_err_probe(&dev->ofdev->dev, err,
				     "Can't get valid [local-]mac-address from OF !\n");
	}

Also, should this be a bug fix with a Fixes tag for net?

>  
>  	/* IAHT and GAHT filter parameterization */
>  	if (emac_has_feature(dev, EMAC_FTR_EMAC4SYNC)) {
> -- 
> 2.47.0
>