[PATCH v9 2/7] can: skb: add skb CAN frame data length helpers

[Oliver Hartkopp <socketcan@hartkopp.net>]

Add two helpers to retrieve the data length from CAN sk_buffs and prepare
the length information to be a uint16 value for the CAN XL support.

Acked-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
 drivers/net/can/dev/rx-offload.c |  2 +-
 drivers/net/can/dev/skb.c        | 12 ++++--------
 include/linux/can/skb.h          | 24 +++++++++++++++++++++++-
 3 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/drivers/net/can/dev/rx-offload.c b/drivers/net/can/dev/rx-offload.c
index a32a01c172d4..8505e547e922 100644
--- a/drivers/net/can/dev/rx-offload.c
+++ b/drivers/net/can/dev/rx-offload.c
@@ -245,11 +245,11 @@ unsigned int can_rx_offload_get_echo_skb(struct can_rx_offload *offload,
 					 unsigned int *frame_len_ptr)
 {
 	struct net_device *dev = offload->dev;
 	struct net_device_stats *stats = &dev->stats;
 	struct sk_buff *skb;
-	u8 len;
+	unsigned int len;
 	int err;
 
 	skb = __can_get_echo_skb(dev, idx, &len, frame_len_ptr);
 	if (!skb)
 		return 0;
diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index f457c94ba82f..b896e1ce3b47 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -89,12 +89,12 @@ int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
 	return 0;
 }
 EXPORT_SYMBOL_GPL(can_put_echo_skb);
 
 struct sk_buff *
-__can_get_echo_skb(struct net_device *dev, unsigned int idx, u8 *len_ptr,
-		   unsigned int *frame_len_ptr)
+__can_get_echo_skb(struct net_device *dev, unsigned int idx,
+		   unsigned int *len_ptr, unsigned int *frame_len_ptr)
 {
 	struct can_priv *priv = netdev_priv(dev);
 
 	if (idx >= priv->echo_skb_max) {
 		netdev_err(dev, "%s: BUG! Trying to access can_priv::echo_skb out of bounds (%u/max %u)\n",
@@ -106,20 +106,16 @@ __can_get_echo_skb(struct net_device *dev, unsigned int idx, u8 *len_ptr,
 		/* Using "struct canfd_frame::len" for the frame
 		 * length is supported on both CAN and CANFD frames.
 		 */
 		struct sk_buff *skb = priv->echo_skb[idx];
 		struct can_skb_priv *can_skb_priv = can_skb_prv(skb);
-		struct canfd_frame *cf = (struct canfd_frame *)skb->data;
 
 		if (skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS)
 			skb_tstamp_tx(skb, skb_hwtstamps(skb));
 
 		/* get the real payload length for netdev statistics */
-		if (cf->can_id & CAN_RTR_FLAG)
-			*len_ptr = 0;
-		else
-			*len_ptr = cf->len;
+		*len_ptr = can_skb_get_data_len(skb);
 
 		if (frame_len_ptr)
 			*frame_len_ptr = can_skb_priv->frame_len;
 
 		priv->echo_skb[idx] = NULL;
@@ -145,11 +141,11 @@ __can_get_echo_skb(struct net_device *dev, unsigned int idx, u8 *len_ptr,
  */
 unsigned int can_get_echo_skb(struct net_device *dev, unsigned int idx,
 			      unsigned int *frame_len_ptr)
 {
 	struct sk_buff *skb;
-	u8 len;
+	unsigned int len;
 
 	skb = __can_get_echo_skb(dev, idx, &len, frame_len_ptr);
 	if (!skb)
 		return 0;
 
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
index 27ebfc28510f..ddffc2fc008c 100644
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -18,11 +18,12 @@
 
 void can_flush_echo_skb(struct net_device *dev);
 int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
 		     unsigned int idx, unsigned int frame_len);
 struct sk_buff *__can_get_echo_skb(struct net_device *dev, unsigned int idx,
-				   u8 *len_ptr, unsigned int *frame_len_ptr);
+				   unsigned int *len_ptr,
+				   unsigned int *frame_len_ptr);
 unsigned int __must_check can_get_echo_skb(struct net_device *dev,
 					   unsigned int idx,
 					   unsigned int *frame_len_ptr);
 void can_free_echo_skb(struct net_device *dev, unsigned int idx,
 		       unsigned int *frame_len_ptr);
@@ -111,6 +112,27 @@ static inline bool can_is_canfd_skb(const struct sk_buff *skb)
 
 	/* the CAN specific type of skb is identified by its data length */
 	return (skb->len == CANFD_MTU && cfd->len <= CANFD_MAX_DLEN);
 }
 
+/* get length element value from can[fd]_frame structure */
+static inline unsigned int can_skb_get_len_val(struct sk_buff *skb)
+{
+	const struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
+
+	return cfd->len;
+}
+
+/* get needed data length inside CAN frame for all frame types (RTR aware) */
+static inline unsigned int can_skb_get_data_len(struct sk_buff *skb)
+{
+	unsigned int len = can_skb_get_len_val(skb);
+	const struct can_frame *cf = (struct can_frame *)skb->data;
+
+	/* RTR frames have an actual length of zero */
+	if (can_is_can_skb(skb) && cf->can_id & CAN_RTR_FLAG)
+		return 0;
+
+	return len;
+}
+
 #endif /* !_CAN_SKB_H */
-- 
2.30.2