Re: [PATCH net-next] net: enetc: Support ethernet aliases in dts.

[Vladimir Oltean <vladimir.oltean@nxp.com>]

On Tue, Feb 25, 2025 at 03:44:58PM -0600, Shenwei Wang wrote:
> Retrieve the "ethernet" alias ID from the DTS and assign it as the
> interface name (e.g., "eth0", "eth1"). This ensures predictable naming
> aligned with the DTS's configuration.
> 
> If no alias is defined, fall back to the kernel's default enumeration
> to maintain backward compatibility.
> 
> Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
> ---
>  drivers/net/ethernet/freescale/enetc/enetc4_pf.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc4_pf.c b/drivers/net/ethernet/freescale/enetc/enetc4_pf.c
> index fc41078c4f5d..5ec8dc59e809 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc4_pf.c
> +++ b/drivers/net/ethernet/freescale/enetc/enetc4_pf.c
> @@ -622,10 +622,20 @@ static int enetc4_pf_netdev_create(struct enetc_si *si)
>  	struct device *dev = &si->pdev->dev;
>  	struct enetc_ndev_priv *priv;
>  	struct net_device *ndev;
> +	char ifname[IFNAMSIZ];
>  	int err;
>  
> -	ndev = alloc_etherdev_mqs(sizeof(struct enetc_ndev_priv),
> -				  si->num_tx_rings, si->num_rx_rings);
> +	err = of_alias_get_id(dev->of_node, "ethernet");
> +	if (err >= 0) {
> +		snprintf(ifname, IFNAMSIZ, "eth%d", err);
> +		ndev = alloc_netdev_mqs(sizeof(struct enetc_ndev_priv),
> +					ifname, NET_NAME_PREDICTABLE, ether_setup,
> +					si->num_tx_rings, si->num_rx_rings);
> +	} else {
> +		ndev = alloc_etherdev_mqs(sizeof(struct enetc_ndev_priv),
> +					  si->num_tx_rings, si->num_rx_rings);
> +	}
> +
>  	if (!ndev)
>  		return  -ENOMEM;
>  

Shenwei, you don't want the kernel to attempt to be very smart about the
initial netdev naming. You will inevitably run into the situation where
"eth%d" is already the name chosen for the kernel for a different
net_device without a predictable name (e.g. e1000e PCIe card) which has
been allocated already. Then you'll want to fix that somehow, and the
stream of patches will never stop, because the kernel will never be able
to fulfill all requirements. Look at the udev naming rules for dpaa2 and
enetc on Layerscape and build something like that. DSA switch included -
the "label" device tree property is considered legacy.

Nacked-by: Vladimir Oltean <vladimir.oltean@nxp.com>