can: rx-offload: add can_rx_offload_get_echo_skb_queue_tail()

Add can_rx_offload_get_echo_skb_queue_tail(). This function addds the
echo skb at the end of rx-offload the queue. This is intended for
devices without timestamp support.

Link: https://lore.kernel.org/all/20230718-gs_usb-rx-offload-v2-2-716e542d14d5@pengutronix.deSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/dev/rx-offload.c

 // SPDX-License-Identifier: GPL-2.0-only
 /* Copyright (c) 2014      Protonic Holland,
  *                         David Jander
- * Copyright (C) 2014-2021 Pengutronix,
+ * Copyright (C) 2014-2021, 2023 Pengutronix,
  *                         Marc Kleine-Budde <kernel@pengutronix.de>
  */
 
@@ -280,6 +280,31 @@ int can_rx_offload_queue_tail(struct can_rx_offload *offload,
 }
 EXPORT_SYMBOL_GPL(can_rx_offload_queue_tail);
 
+unsigned int
+can_rx_offload_get_echo_skb_queue_tail(struct can_rx_offload *offload,
+				       unsigned int idx,
+				       unsigned int *frame_len_ptr)
+{
+	struct net_device *dev = offload->dev;
+	struct net_device_stats *stats = &dev->stats;
+	struct sk_buff *skb;
+	unsigned int len;
+	int err;
+
+	skb = __can_get_echo_skb(dev, idx, &len, frame_len_ptr);
+	if (!skb)
+		return 0;
+
+	err = can_rx_offload_queue_tail(offload, skb);
+	if (err) {
+		stats->rx_errors++;
+		stats->tx_fifo_errors++;
+	}
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(can_rx_offload_get_echo_skb_queue_tail);
+
 void can_rx_offload_irq_finish(struct can_rx_offload *offload)
 {
 	unsigned long flags;

include/linux/can/rx-offload.h

@@ -3,7 +3,7 @@
  * linux/can/rx-offload.h
  *
  * Copyright (c) 2014 David Jander, Protonic Holland
- * Copyright (c) 2014-2017 Pengutronix, Marc Kleine-Budde <kernel@pengutronix.de>
+ * Copyright (c) 2014-2017, 2023 Pengutronix, Marc Kleine-Budde <kernel@pengutronix.de>
  */
 
 #ifndef _CAN_RX_OFFLOAD_H
@@ -49,6 +49,9 @@ unsigned int can_rx_offload_get_echo_skb_queue_timestamp(struct can_rx_offload *
 							 unsigned int *frame_len_ptr);
 int can_rx_offload_queue_tail(struct can_rx_offload *offload,
 			      struct sk_buff *skb);
+unsigned int can_rx_offload_get_echo_skb_queue_tail(struct can_rx_offload *offload,
+						    unsigned int idx,
+						    unsigned int *frame_len_ptr);
 void can_rx_offload_irq_finish(struct can_rx_offload *offload);
 void can_rx_offload_threaded_irq_finish(struct can_rx_offload *offload);
 void can_rx_offload_del(struct can_rx_offload *offload);