linux-kernel - Re: [PATCH] net: ethernet: ti: am65-cpsw-nuss: create platform device for port nodes

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Date: Mon, 6 May 2024 14:52:49 -0300
From: Hiago De Franco <hiagofranco@...il.com>
To: "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Sean Anderson <sean.anderson@...ux.dev>, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Hiago De Franco <hiago.franco@...adex.com>, 
	João Paulo Gonçalves <jpaulo.silvagoncalves@...il.com>
Subject: Re: [PATCH] net: ethernet: ti: am65-cpsw-nuss: create platform
 device for port nodes

Dear Maintainers,

On Fri, May 03, 2024 at 05:00:38PM -0300, Hiago De Franco wrote:
> From: Hiago De Franco <hiago.franco@...adex.com>
> 
> After this change, an 'of_node' link from '/sys/devices/platform' to
> '/sys/firmware/devicetree' will be created. The 'ethernet-ports' device
> allows multiple netdevs to have the exact same parent device, e.g. port@x
> netdevs are child nodes of ethernet-ports.
> 
> When ethernet aliases are used (e.g. 'ethernet0 = &cpsw_port1' and
> 'ethernet1 = &cpsw_port2') in the device tree, without an of_node
> device exposed to the userspace, it is not possible to determine where
> exactly the alias is pointing to.
> 
> As an example, this is essential for applications like systemd, which rely
> on the of_node information to identify and manage Ethernet devices
> using device tree aliases introduced in the v251 naming scheme.
> 
> Signed-off-by: Hiago De Franco <hiago.franco@...adex.com>
> ---
>  drivers/net/ethernet/ti/am65-cpsw-nuss.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> index 1d00e21808c1..f74915f56fa2 100644
> --- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> +++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> @@ -2091,6 +2091,13 @@ static int am65_cpsw_nuss_init_slave_ports(struct am65_cpsw_common *common)
>  		if (strcmp(port_np->name, "port"))
>  			continue;
>  
> +		if (!of_platform_device_create(port_np, NULL, NULL)) {
> +			dev_err(dev, "%pOF error creating port platform device\n",
> +				port_np);
> +			ret = -ENODEV;
> +			goto of_node_put;
> +		}
> +
>  		ret = of_property_read_u32(port_np, "reg", &port_id);
>  		if (ret < 0) {
>  			dev_err(dev, "%pOF error reading port_id %d\n",
> -- 
> 2.43.0
> 

Apologies, I believe this patch is not 100% complete, there might be
something missing. Please keep this on hold, there is something not
working as expected that I am currently investigating.

My goal was to create an of_node device for the switch ports, which did
create under the /sys/devices/platform:

ls /sys/devices/platform/8000000.ethernet:ethernet-ports:port@1/
driver_override               power                         uevent
modalias                      subsystem                     waiting_for_supplier
of_node                       supplier:platform:104044.phy

However it is still missing under

find /sys/devices/platform/bus@...00/8000000.ethernet/net/eth0/ -name *of_node*

I will figure out how to do that and propose a new version.

Regards,

Hiago.