Re: [PATCH net-next 07/11] net: devmem: support TX over NETMEM_TX_NO_DMA devices

Bobby Eshleman
2026-05-01T01:07:35Z

On Thu, Apr 30, 2026 at 05:57:24PM -0700, Jakub Kicinski wrote:
> On Tue, 28 Apr 2026 15:42:04 -0700 Bobby Eshleman wrote:
> > shinfo = skb_shinfo(skb);
> > + if (shinfo->nr_frags == 0)
> > + goto out;
>
> Feels tempting to cover the NETMEM_TX_NO_DMA / NETMEM_TX_NONE
> cases here before we even look at the frags?

That sounds good to me (had considered it, but opted out cause I felt it
might look odd with the switch-case that follows). And I'll address the
bug(s) the model called out here/elsewhere too.

Thanks,
Bobby

>
> > - if (shinfo->nr_frags > 0) {
> > - niov = netmem_to_net_iov(skb_frag_netmem(&shinfo->frags[0]));
> > - if (net_is_devmem_iov(niov) &&
> > - READ_ONCE(net_devmem_iov_binding(niov)->dev) != dev)
> > + niov = netmem_to_net_iov(skb_frag_netmem(&shinfo->frags[0]));
> > + if (!net_is_devmem_iov(niov))
> > + goto out;
> > +
> > + binding = net_devmem_iov_binding(niov);
> > +
> > + switch (dev->netmem_tx) {
> > + case NETMEM_TX_DMA:
> > + if (READ_ONCE(binding->dev) != dev)
> > goto out_free;
> > + break;
> > + case NETMEM_TX_NO_DMA:
> > + break;
> > + default: /* NETMEM_TX_NONE */
> > + goto out_free;
> > }