netdev - Re: [PATCH net-next] devlink: Notify eswitch mode changes to devlink monitor

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Message-ID: <20251118121552.7e1bae0c@kernel.org>
Date: Tue, 18 Nov 2025 12:15:52 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Parav Pandit <parav@...dia.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "davem@...emloft.net"
 <davem@...emloft.net>, "edumazet@...gle.com" <edumazet@...gle.com>,
 "pabeni@...hat.com" <pabeni@...hat.com>, "horms@...nel.org"
 <horms@...nel.org>, Jiri Pirko <jiri@...dia.com>
Subject: Re: [PATCH net-next] devlink: Notify eswitch mode changes to
 devlink monitor

On Tue, 18 Nov 2025 05:25:23 +0000 Parav Pandit wrote:
> > From: Jakub Kicinski <kuba@...nel.org>
> > Sent: 18 November 2025 09:11 AM
> > 
> > On Sat, 15 Nov 2025 04:51:25 +0200 Parav Pandit wrote:  
> > > +	err = devlink_nl_eswitch_fill(msg, devlink,  
> > DEVLINK_CMD_ESWITCH_SET,
> > 
> > I've never seen action command ID being used for a notification.
> > Either use an existing type which has the same message format, or if no
> > message which naturally fits exists allocate a new ID.  
> 
> I am not sure fully.
> 1. devlink_notify() uses DEVLINK_CMD_NEW.
> 
> 2. devlink_port_notify() uses DEVLINK_CMD_PORT_NEW which is the input
> cmd on port creation supplied by the user space.
> 
> 3. devlink_params_notify_register() uses DEVLINK_CMD_PARAM_NEW.
> 
> Do you mean #1 and #3 are not user-initiated commands, hence such an
> action command ID is ok vs #2 is not ok? I probably misunderstanding
> your comment.

Let me put it more simply at some cost to accuracy..
The notification types and command ids usually match the response
to a GET command. Please TAL at the messages which are generated 
in response to a GET for the objects you listed...

Netlink command IDs are not required to match in a request-response
pair. In "modern" families we recommend that they do match, not because
the old model was wrong, but because a casual contributors usually got
it wrong.