Subject: [net/devlink] Question about possible CMD misuse in devlink_nl_port_new_doit()

From: Chenyuan Yang <[email-masked]>
Date: Sat, 16 Mar 2024 21:57:19 -0500

Dear Devlink Developers,

We are curious whether the function `devlink_nl_port_new_doit()` might have a incorrect command value `DEVLINK_CMD_NEW`, which should be `DEVLINK_CMD_PORT_NEW`.

The function is https://elixir.bootlin.com/linux/v6.8/source/net/devlink/port.c#L844
and the relevant code is
```
int devlink_nl_port_new_doit(struct sk_buff *skb, struct genl_info *info)
{
	...
	err = devlink_nl_port_fill(msg, devlink_port, DEVLINK_CMD_NEW,
				   info->snd_portid, info->snd_seq, 0, NULL);
	if (WARN_ON_ONCE(err))
		goto err_out_msg_free;
	...
}
```

In `devlink_nl_port_fill`, all other places use `DEVLINK_CMD_PORT_NEW` as the command value. However, in `devlink_nl_port_new_doit`, it uses `DEVLINK_CMD_NEW`. This might be a misuse, also according to https://lore.kernel.org/netdev/[email-masked]/T/.

Based on our understanding, a possible fix would be
```
-  err = devlink_nl_port_fill(msg, devlink_port, DEVLINK_CMD_NEW,
+  err = devlink_nl_port_fill(msg, devlink_port, DEVLINK_CMD_PORT_NEW,
```

Please kindly correct us if we missed any key information. Looking forward to your response!

Best,
Chenyuan