linux-kernel - Re: [PATCH net-next v3 11/11] wireguard: netlink: generate netlink code

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Message-ID: <20251119184436.1e97aeab@kernel.org>
Date: Wed, 19 Nov 2025 18:44:36 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: Asbjørn Sloth Tønnesen
 <ast@...erby.net>, Donald Hunter <donald.hunter@...il.com>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo
 Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, Jacob Keller
 <jacob.e.keller@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>,
 wireguard@...ts.zx2c4.com, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, Jordan Rife <jordan@...fe.io>
Subject: Re: [PATCH net-next v3 11/11] wireguard: netlink: generate netlink
 code

On Thu, 20 Nov 2025 01:54:47 +0100 Jason A. Donenfeld wrote:
> On Tue, Nov 18, 2025 at 05:00:45PM -0800, Jakub Kicinski wrote:
> > On Tue, 18 Nov 2025 23:51:37 +0100 Jason A. Donenfeld wrote:  
> > > I mean, there is *tons* of generated code in the kernel. This is how it
> > > works. And you *want the output to change when the tool changes*. That's
> > > literally the point. It would be like if you wanted to check in all the
> > > .o files, in case the compiler started generating different output, or
> > > if you wanted the objtool output or anything else to be checked in. And
> > > sheerly from a git perspective, it seems outrageous to touch a zillion
> > > files every time the ynl code changes. Rather, the fact that it's
> > > generated on the fly ensures that the ynl generator stays correctly
> > > implemented. It's the best way to keep that code from rotting.  
> > 
> > CI checks validate that the files are up to date.
> > There has been no churn to the kernel side of the generated code.
> > Let's be practical.  
> 
> Okay, it sounds like neither of you want to do this. Darn. I really hate
> having generated artifacts laying around that can be created efficiently
> at compile time. But okay, so it goes. I guess we'll do that.
> 
> I would like to ask two things, then, which may or may not be possible:
> 
> 1) Can we put this in drivers/net/wireguard/generated/netlink.{c.h}
>    And then in the Makefile, do `wireguard-y += netlink.o generated/netlink.o`
>    on one line like that. I prefer this to keeping it in the same
>    directory with the awkward -gen suffix.

That should work, I think.

> 2) In the header of each generated file, automatically write out the
>    command that was used to generate it. Here's an example of this good
>    habit from Go: https://github.com/golang/go/blob/master/src/syscall/zsyscall_linux_amd64.go

You don't like the runes? :)

/* Do not edit directly, auto-generated from: */
/*	$YAML-path */
/* YNL-GEN [kernel|user|uapi] [source|header] */
/* YNL-ARG $extra-args */

Do you care about the exact cmdline of the python tool, or can we just
append:

/* To regenerate run: tools/net/ynl/ynl-regen.sh */