Re: [PATCH v5 4/7] can: Add Nuvoton NCT6694 CAN support

[Ming Yu]

Hi Vincent,

I will remove priv->tx_skb in the next patch, but it seems that
can_flush_echo_skb() has not been EXPORT_SYMBOL_GPL().

I would like to know if nct6694_can_clean() requires modification.

Vincent Mailhol <mailhol.vincent@xxxxxxxxxx> 於 2025年1月16日 週四 上午12:45寫道：
> > +static void nct6694_can_clean(struct net_device *ndev)
> > +{
> > +     struct nct6694_can_priv *priv = netdev_priv(ndev);
> > +
> > +     if (priv->tx_skb || netif_queue_stopped(ndev))
> > +             ndev->stats.tx_errors++;
> > +     dev_kfree_skb(priv->tx_skb);
>
> Use:
>
>         can_flush_echo_skb(ndev);
>
> (related to the following comments).
>
> > +     priv->tx_skb = NULL;
> > +}
>
> (...)
>
> > +static void nct6694_can_tx_work(struct work_struct *work)
> > +{
> > +     struct nct6694_can_priv *priv = container_of(work,
> > +                                                  struct nct6694_can_priv,
> > +                                                  tx_work);
> > +     struct net_device *ndev = priv->ndev;
> > +
> > +     guard(mutex)(&priv->lock);
> > +
> > +     if (priv->tx_skb) {
> > +             if (priv->can.state == CAN_STATE_BUS_OFF) {
>
> Just stop the queue when the can bus is off so that you do not have do
> check the bus status each time a frame is sent.
>
> > +                     nct6694_can_clean(ndev);
> > +             } else {
> > +                     nct6694_can_tx(ndev);
> > +                     can_put_echo_skb(priv->tx_skb, ndev, 0, 0);
> > +                     priv->tx_skb = NULL;
> > +             }
> > +     }
> > +}
> > +
> > +static netdev_tx_t nct6694_can_start_xmit(struct sk_buff *skb,
> > +                                       struct net_device *ndev)
> > +{
> > +     struct nct6694_can_priv *priv = netdev_priv(ndev);
> > +
> > +     if (can_dev_dropped_skb(ndev, skb))
> > +             return NETDEV_TX_OK;
> > +
> > +     if (priv->tx_skb) {
> > +             netdev_err(ndev, "hard_xmit called while tx busy\n");
> > +             return NETDEV_TX_BUSY;
> > +     }
> > +
> > +     netif_stop_queue(ndev);
> > +     priv->tx_skb = skb;
>
> Here, you can directly do:
>
>         can_put_echo_skb(skb, ndev, 0, 0);
>
> The skb remains accessible under priv->can.echo_skb[0]. With this, you
> can remove the priv->tx_skb field.
>
> > +     queue_work(priv->wq, &priv->tx_work);
> > +
> > +     return NETDEV_TX_OK;
> > +}
>

Thanks,
Ming