[PATCH 4.4 13/86] can: dev: __can_get_echo_skb(): replace struct can_frame by canfd_frame to access frame length

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marc Kleine-Budde <mkl@pengutronix.de>

commit 200f5c49f7a2cd694436bfc6cb0662b794c96736 upstream.

This patch replaces the use of "struct can_frame::can_dlc" by "struct
canfd_frame::len" to access the frame's length. As it is ensured that
both structures have a compatible memory layout for this member this is
no functional change. Futher, this compatibility is documented in a
comment.

Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/net/can/dev.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -430,11 +430,14 @@ struct sk_buff *__can_get_echo_skb(struc
 	BUG_ON(idx >= priv->echo_skb_max);
 
 	if (priv->echo_skb[idx]) {
+		/* 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_frame *cf = (struct can_frame *)skb->data;
-		u8 dlc = cf->can_dlc;
+		struct canfd_frame *cf = (struct canfd_frame *)skb->data;
+		u8 len = cf->len;
 
-		*len_ptr = dlc;
+		*len_ptr = len;
 		priv->echo_skb[idx] = NULL;
 
 		return skb;