On Tuesday, 21 October 2025 at 11:40:07 Matias Ezequiel Vara Larsen <[email protected]> wrote: > On Mon, Oct 20, 2025 at 11:24:15PM +0200, Francesco Valla wrote: > > On Monday, 20 October 2025 at 16:56:08 Matias Ezequiel Vara Larsen > > <[email protected]> wrote: > > > On Tue, Oct 14, 2025 at 06:01:07PM +0200, Francesco Valla wrote: > > > > On Tuesday, 14 October 2025 at 12:15:12 Matias Ezequiel Vara Larsen > > > > <[email protected]> wrote: > > > > > On Thu, Sep 11, 2025 at 10:59:40PM +0200, Francesco Valla wrote: > > > > > > Hello Mikhail, Harald, > > > > > > > > > > > > hoping there will be a v6 of this patch soon, a few comments: > > > > > > > > > > > > On Monday, 8 January 2024 at 14:10:35 Mikhail Golubev-Ciuchea > > > > > > <[email protected]> wrote: > > > > > > > > > > > > [...] > > > > > > > + > > > > > > > +/* Compare with m_can.c/m_can_echo_tx_event() */ > > > > > > > +static int virtio_can_read_tx_queue(struct virtqueue *vq) > > > > > > > +{ > > > > > > > + struct virtio_can_priv *can_priv = vq->vdev->priv; > > > > > > > + struct net_device *dev = can_priv->dev; > > > > > > > + struct virtio_can_tx *can_tx_msg; > > > > > > > + struct net_device_stats *stats; > > > > > > > + unsigned long flags; > > > > > > > + unsigned int len; > > > > > > > + u8 result; > > > > > > > + > > > > > > > + stats = &dev->stats; > > > > > > > + > > > > > > > + /* Protect list and virtio queue operations */ > > > > > > > + spin_lock_irqsave(&can_priv->tx_lock, flags); > > > > > > > + > > > > > > > + can_tx_msg = virtqueue_get_buf(vq, &len); > > > > > > > + if (!can_tx_msg) { > > > > > > > + spin_unlock_irqrestore(&can_priv->tx_lock, flags); > > > > > > > + return 0; /* No more data */ > > > > > > > + } > > > > > > > + > > > > > > > + if (unlikely(len < sizeof(struct virtio_can_tx_in))) { > > > > > > > + netdev_err(dev, "TX ACK: Device sent no result code\n"); > > > > > > > + result = VIRTIO_CAN_RESULT_NOT_OK; /* Keep things going > > > > > > > */ > > > > > > > + } else { > > > > > > > + result = can_tx_msg->tx_in.result; > > > > > > > + } > > > > > > > + > > > > > > > + if (can_priv->can.state < CAN_STATE_BUS_OFF) { > > > > > > > + /* Here also frames with result != VIRTIO_CAN_RESULT_OK > > > > > > > are > > > > > > > + * echoed. Intentional to bring a waiting process in an > > > > > > > upper > > > > > > > + * layer to an end. > > > > > > > + * TODO: Any better means to indicate a problem here? > > > > > > > + */ > > > > > > > + if (result != VIRTIO_CAN_RESULT_OK) > > > > > > > + netdev_warn(dev, "TX ACK: Result = %u\n", > > > > > > > result); > > > > > > > > > > > > Maybe an error frame reporting CAN_ERR_CRTL_UNSPEC would be better? > > > > > > > > > > > I am not sure. In xilinx_can.c, CAN_ERR_CRTL_UNSPEC is indicated > > > > > during > > > > > a problem in the rx path and this is the tx path. I think the comment > > > > > refers to improving the way the driver informs this error to the user > > > > > but I may be wrong. > > > > > > > > > > > > > Since we have no detail of what went wrong here, I suggested > > > > CAN_ERR_CRTL_UNSPEC as it is "unspecified error", to be coupled with a > > > > controller error with id CAN_ERR_CRTL; however, a different error might > > > > be > > > > more appropriate. > > > > > > > > For sure, at least in my experience, having a warn printed to kmsg is > > > > *not* > > > > enough, as the application sending the message(s) would not be able to > > > > detect > > > > the error. > > > > > > > > > > > > > > For sure, counting the known errors as valid tx_packets and tx_bytes > > > > > > is misleading. > > > > > > > > > > > > > > > > I'll remove the counters below. > > > > > > > > > > > > > We don't really know what's wrong here - the packet might have been > > > > sent and > > > > and then not ACK'ed, as well as any other error condition (as it > > > > happens in the > > > > reference implementation from the original authors [1]). Echoing the > > > > packet > > > > only "to bring a waiting process in an upper layer to an end" and > > > > incrementing > > > > counters feels wrong, but maybe someone more expert than me can advise > > > > better > > > > here. > > > > > > > > > > > > > > I agree. IIUC, in case there has been a problem during transmission, I > > > should 1) indicate this by injecting a CAN_ERR_CRTL_UNSPEC package with > > > netif_rx() and 2) use can_free_echo_skb() and increment the tx_error > > > stats. Is this correct? > > > > > > Matias > > > > > > > > > > That's my understanding too! stats->tx_dropped should be the right value to > > increment (see for example [1]). > > > > [1] > > https://elixir.bootlin.com/linux/v6.17.3/source/drivers/net/can/ctucanfd/ctucanfd_base.c#L1035 > > > > I think the counter to increment would be stats->tx_errors in this case ... >
I don't fully agree. tx_errors is for CAN frames that got transmitted but then lead to an error (e.g.: no ACK), while here we might be dealing with frames that didn't even manage to reach the transmission queue [1]. An exception to this may arise when the VIRTIO_CAN_F_CAN_LATE_TX_ACK feature is negotiated; in this case, a VIRTIO_CAN_RESULT_NOT_OK may indicate either a dropped frame (tx_dropped) or a failed transmission (tx_error) [2]. [1] https://github.com/oasis-tcs/virtio-spec/blob/master/device-types/can/description.tex#L139 [2] https://github.com/oasis-tcs/virtio-spec/blob/master/device-types/can/description.tex#L196 BR, Francesco
