Re: [PATCH 3/3] can/peak_usb: add support of ONE_SHOT mode

[Oliver Hartkopp <socketcan@xxxxxxxxxxxx>]

On 09.03.21 11:36, Marc Kleine-Budde wrote:
> On 3/9/21 9:21 AM, Stephane Grosjean wrote:
> > This patch adds "ONE-SHOT" mode support to the following CAN-USB
> > PEAK-System GmbH interfaces:
> > - PCAN-USB X6
> > - PCAN-USB FD
> > - PCAN-USB Pro FD
> > - PCAN-Chip USB
> > - PCAN-USB Pro
> >
> > Signed-off-by: Stephane Grosjean <s.grosjean@xxxxxxxxxxxxxxx>
>
> What happens if in one shot mode and the frame is not send? Who takes care of
> the echo skb?

ONE-SHOT only means that the CAN controller would not retry the 
transmission when e.g. loosing the arbitration or getting an error flag.

The sja1000 does it this way, when the TX interrupt flag is set in the 
interrupt register:

                if (isrc & IRQ_TI) {
                        /* transmission buffer released */
                        if (priv->can.ctrlmode & CAN_CTRLMODE_ONE_SHOT &&
                            !(status & SR_TCS)) {
                                stats->tx_errors++;
                                can_free_echo_skb(dev, 0);
                        } else {
                                /* transmission complete */
                                stats->tx_bytes +=
                                        priv->read_reg(priv, 
SJA1000_FI) & 0xf;
                                stats->tx_packets++;
                                can_get_echo_skb(dev, 0, NULL);
                        }
                        netif_wake_queue(dev);
                        can_led_event(dev, CAN_LED_EVENT_TX);
                }


Do we need to check this for the other drivers?

Regards,
Oliver