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

[Jakub Kicinski]

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?

> -     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;
>       }