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

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Message-ID: <aR5m174O7pklKrMR@zx2c4.com>
Date: Thu, 20 Nov 2025 01:54:47 +0100
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: Jakub Kicinski <kuba@...nel.org>
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 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.

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

Jason