Re: [PATCH net-next v10 4/5] net: devmem: document NETDEV_A_DMABUF_AUTORELEASE netlink attribute

Jakub Kicinski
2026-01-27T01:26:48Z

On Wed, 21 Jan 2026 20:07:11 -0800 Stanislav Fomichev wrote:
> On 01/21, Jakub Kicinski wrote:
> > On Wed, 21 Jan 2026 19:25:27 -0800 Bobby Eshleman wrote:
> > > Good point. The only real use case for autorelease=on is for backwards
> > > compatibility... so I thought maybe DEVMEM_A_DMABUF_COMPAT_TOKEN
> > > or DEVMEM_A_DMABUF_COMPAT_DONTNEED would be clearer?
> >
> > Hm. Maybe let's return to naming once we have consensus on the uAPI.
> >
> > Does everyone think that pushing this via TCP socket opts still makes
> > sense, even tho in practice the TCP socket is just how we find the
> > binding?
>
> I'm not a fan of the existing cmsg scheme, but we already have userspace
> using it, so getting more performance out of it seems like an easy win?

I don't like:
- the fact that we have to add the binding to a socket (extra field)
- single socket can only serve single binding, there's no technical
reason for this really, AFAICT, just the fact that we have a single
pointer in the sock struct
- the 7 levels of indentation in tcp_recvmsg_dmabuf()

I understand your argument, but as is this series feels closer to a PoC
than an easy win (the easy part should imply minor changes and no
detrimental effect on code quality IMHO).