netdev - [can-next 3/5] can: move frame length from private headroom to struct sk

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Message-ID: <20260112150908.5815-4-socketcan@hartkopp.net>
Date: Mon, 12 Jan 2026 16:09:06 +0100
From: Oliver Hartkopp <socketcan@...tkopp.net>
To: linux-can@...r.kernel.org,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	Jakub Kicinski <kuba@...nel.org>
Cc: Vincent Mailhol <mailhol@...nel.org>,
	netdev@...r.kernel.org,
	Paolo Abeni <pabeni@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Simon Horman <horms@...nel.org>,
	davem@...emloft.net,
	Oliver Hartkopp <socketcan@...tkopp.net>
Subject: [can-next 3/5] can: move frame length from private headroom to struct sk_buff

The can_skb_priv::frame_len variable is used to cache a previous
calculated CAN frame length to be passed to BQL queueing disciplines.

To maintain a compilable migration step the frame_len value in struct
can_skb_priv is only renamed but not removed.

Patch 3/5 to remove the private CAN bus skb headroom infrastructure.

Signed-off-by: Oliver Hartkopp <socketcan@...tkopp.net>
---
 drivers/net/can/dev/skb.c | 8 +++-----
 include/linux/can/skb.h   | 3 +--
 include/linux/skbuff.h    | 2 ++
 3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index b54474687aaa..ffd71ad0252a 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -72,11 +72,11 @@ int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
 		/* make settings for echo to reduce code in irq context */
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 		skb->dev = dev;
 
 		/* save frame_len to reuse it when transmission is completed */
-		can_skb_prv(skb)->frame_len = frame_len;
+		skb->can_framelen = frame_len;
 
 		if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)
 			skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
 
 		skb_tx_timestamp(skb);
@@ -109,20 +109,19 @@ __can_get_echo_skb(struct net_device *dev, unsigned int idx,
 	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_skb_priv *can_skb_priv = can_skb_prv(skb);
 
 		if (skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS)
 			skb_tstamp_tx(skb, skb_hwtstamps(skb));
 
 		/* get the real payload length for netdev statistics */
 		*len_ptr = can_skb_get_data_len(skb);
 
 		if (frame_len_ptr)
-			*frame_len_ptr = can_skb_priv->frame_len;
+			*frame_len_ptr = skb->can_framelen;
 
 		priv->echo_skb[idx] = NULL;
 
 		if (skb->pkt_type == PACKET_LOOPBACK) {
 			skb->pkt_type = PACKET_BROADCAST;
@@ -178,14 +177,13 @@ void can_free_echo_skb(struct net_device *dev, unsigned int idx,
 		return;
 	}
 
 	if (priv->echo_skb[idx]) {
 		struct sk_buff *skb = priv->echo_skb[idx];
-		struct can_skb_priv *can_skb_priv = can_skb_prv(skb);
 
 		if (frame_len_ptr)
-			*frame_len_ptr = can_skb_priv->frame_len;
+			*frame_len_ptr = skb->can_framelen;
 
 		dev_kfree_skb_any(skb);
 		priv->echo_skb[idx] = NULL;
 	}
 }
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
index 679ea4c851ac..eba9557e2c1e 100644
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -46,15 +46,14 @@ bool can_dropped_invalid_skb(struct net_device *dev, struct sk_buff *skb);
  * skb_copy() needs to be used instead of skb_clone().
  */
 
 /**
  * struct can_skb_priv - private additional data inside CAN sk_buffs
- * @frame_len:	length of CAN frame in data link layer
  * @cf:		align to the following CAN frame at skb->data
  */
 struct can_skb_priv {
-	unsigned int frame_len;
+	unsigned int frame_len_to_be_removed;
 	struct can_frame cf[];
 };
 
 static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb)
 {
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index ab415de74466..eccd0b3898a0 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -862,10 +862,11 @@ enum skb_tstamp_type {
  *		at the tail of an sk_buff
  *	@vlan_all: vlan fields (proto & tci)
  *	@vlan_proto: vlan encapsulation protocol
  *	@vlan_tci: vlan tag control information
  *	@can_iif: ifindex of the first interface the CAN frame appeared on
+ *	@can_framelen: cached echo CAN frame length for bql
  *	@inner_protocol: Protocol (encapsulation)
  *	@inner_ipproto: (aka @inner_protocol) stores ipproto when
  *		skb->inner_protocol_type == ENCAP_TYPE_IPPROTO;
  *	@inner_transport_header: Inner transport layer header (encapsulation)
  *	@inner_network_header: Network layer header (encapsulation)
@@ -1083,10 +1084,11 @@ struct sk_buff {
 		};
 
 		/* space for protocols without protocol/header encapsulation */
 		struct {
 			int	can_iif;
+			__u16	can_framelen;
 		};
 	};
 
 	__be16			protocol;
 	__u16			transport_header;
-- 
2.47.3