can: kvaser_pciefd: Continue parsing DMA buf after dropped RX

Going bus-off on a channel doing RX could result in dropped packets.

As netif_running() gets cleared before the channel abort procedure,
the handling of any last RDATA packets would see netif_rx() return
non-zero to signal a dropped packet. kvaser_pciefd_read_buffer() dealt
with this "error" by breaking out of processing the remaining DMA RX
buffer.

Only return an error from kvaser_pciefd_read_buffer() due to packet
corruption, otherwise handle it internally.

Cc: stable@vger.kernel.org
Signed-off-by: Axel Forsman <axfo@kvaser.com>
Tested-by: Jimmy Assarsson <extja@kvaser.com>
Reviewed-by: Jimmy Assarsson <extja@kvaser.com>
Link: https://patch.msgid.link/20250520114332.8961-4-axfo@kvaser.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Author: axelf4

drivers/net/can/kvaser_pciefd.c

@@ -1209,7 +1209,7 @@ static int kvaser_pciefd_handle_data_packet(struct kvaser_pciefd *pcie,
 		skb = alloc_canfd_skb(priv->dev, &cf);
 		if (!skb) {
 			priv->dev->stats.rx_dropped++;
-			return -ENOMEM;
+			return 0;
 		}
 
 		cf->len = can_fd_dlc2len(dlc);
@@ -1221,7 +1221,7 @@ static int kvaser_pciefd_handle_data_packet(struct kvaser_pciefd *pcie,
 		skb = alloc_can_skb(priv->dev, (struct can_frame **)&cf);
 		if (!skb) {
 			priv->dev->stats.rx_dropped++;
-			return -ENOMEM;
+			return 0;
 		}
 		can_frame_set_cc_len((struct can_frame *)cf, dlc, priv->ctrlmode);
 	}
@@ -1239,7 +1239,9 @@ static int kvaser_pciefd_handle_data_packet(struct kvaser_pciefd *pcie,
 	priv->dev->stats.rx_packets++;
 	kvaser_pciefd_set_skb_timestamp(pcie, skb, p->timestamp);
 
-	return netif_rx(skb);
+	netif_rx(skb);
+
+	return 0;
 }
 
 static void kvaser_pciefd_change_state(struct kvaser_pciefd_can *can,