can: esd_usb: Add support for CAN_CTRLMODE_BERR_REPORTING

Announce that the driver supports CAN_CTRLMODE_BERR_REPORTING by means
of priv->can.ctrlmode_supported. Until now berr reporting always has
been active without taking care of the berr-reporting parameter given
to an "ip link set ..." command.

Additionally apply some changes to function esd_usb_rx_event():
- If berr reporting is off and it is also no state change, then
immediately return.
- Unconditionally (even in case of the above "immediate return") store
tx- and rx-error counters, so directly use priv->bec.txerr and
priv->bec.rxerr instead of intermediate variables.
- Not directly related, but to better point out the linkage between a
failed alloc_can_err_skb() and stats->rx_dropped++:
Move the increment of the rx_dropped statistic counter (back) to
directly behind the err_skb allocation.

Signed-off-by: Frank Jungclaus <frank.jungclaus@esd.eu>
Link: https://lore.kernel.org/all/20230330184446.2802135-1-frank.jungclaus@esd.eu
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/usb/esd_usb.c b/drivers/net/can/usb/esd_usb.c
index e78bb46..d33bac3 100644 (file)
--- a/drivers/net/can/usb/esd_usb.c
+++ b/drivers/net/can/usb/esd_usb.c
@@ -237,14 +237,23 @@ static void esd_usb_rx_event(struct esd_usb_net_priv *priv,
        if (id == ESD_EV_CAN_ERROR_EXT) {
                u8 state = msg->rx.ev_can_err_ext.status;
                u8 ecc = msg->rx.ev_can_err_ext.ecc;
-               u8 rxerr = msg->rx.ev_can_err_ext.rec;
-               u8 txerr = msg->rx.ev_can_err_ext.tec;
+
+               priv->bec.rxerr = msg->rx.ev_can_err_ext.rec;
+               priv->bec.txerr = msg->rx.ev_can_err_ext.tec;
 
                netdev_dbg(priv->netdev,
                           "CAN_ERR_EV_EXT: dlc=%#02x state=%02x ecc=%02x rec=%02x tec=%02x\n",
-                          msg->rx.dlc, state, ecc, rxerr, txerr);
+                          msg->rx.dlc, state, ecc,
+                          priv->bec.rxerr, priv->bec.txerr);
+
+               /* if berr-reporting is off, only pass through on state change ... */
+               if (!(priv->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) &&
+                   state == priv->old_state)
+                       return;
 
                skb = alloc_can_err_skb(priv->netdev, &cf);
+               if (!skb)
+                       stats->rx_dropped++;
 
                if (state != priv->old_state) {
                        enum can_state tx_state, rx_state;
@@ -265,14 +274,14 @@ static void esd_usb_rx_event(struct esd_usb_net_priv *priv,
                                break;
                        default:
                                new_state = CAN_STATE_ERROR_ACTIVE;
-                               txerr = 0;
-                               rxerr = 0;
+                               priv->bec.txerr = 0;
+                               priv->bec.rxerr = 0;
                                break;
                        }
 
                        if (new_state != priv->can.state) {
-                               tx_state = (txerr >= rxerr) ? new_state : 0;
-                               rx_state = (txerr <= rxerr) ? new_state : 0;
+                               tx_state = (priv->bec.txerr >= priv->bec.rxerr) ? new_state : 0;
+                               rx_state = (priv->bec.txerr <= priv->bec.rxerr) ? new_state : 0;
                                can_change_state(priv->netdev, cf,
                                                 tx_state, rx_state);
                        }
@@ -304,17 +313,12 @@ static void esd_usb_rx_event(struct esd_usb_net_priv *priv,
                        cf->data[3] = ecc & SJA1000_ECC_SEG;
                }
 
-               priv->bec.txerr = txerr;
-               priv->bec.rxerr = rxerr;
-
                if (skb) {
                        cf->can_id |= CAN_ERR_CNT;
-                       cf->data[6] = txerr;
-                       cf->data[7] = rxerr;
+                       cf->data[6] = priv->bec.txerr;
+                       cf->data[7] = priv->bec.rxerr;
 
                        netif_rx(skb);
-               } else {
-                       stats->rx_dropped++;
                }
        }
 }
@@ -1016,7 +1020,8 @@ static int esd_usb_probe_one_net(struct usb_interface *intf, int index)
 
        priv->can.state = CAN_STATE_STOPPED;
        priv->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY |
-               CAN_CTRLMODE_CC_LEN8_DLC;
+               CAN_CTRLMODE_CC_LEN8_DLC |
+               CAN_CTRLMODE_BERR_REPORTING;
 
        if (le16_to_cpu(dev->udev->descriptor.idProduct) ==
            USB_CANUSBM_PRODUCT_ID)