can: netlink: add can_ctrlmode_changelink()

Split the control mode change link logic into a new function:
can_ctrlmode_changelink(). The purpose is to increase code readability
by preventing can_changelink() from becoming too big.

Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
Link: https://patch.msgid.link/20250923-canxl-netlink-prep-v4-11-e720d28f66fe@kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Author: vincent-mailhol

drivers/net/can/dev/netlink.c

@@ -172,6 +172,59 @@ static int can_validate(struct nlattr *tb[], struct nlattr *data[],
 	return 0;
 }
 
+static int can_ctrlmode_changelink(struct net_device *dev,
+				   struct nlattr *data[],
+				   struct netlink_ext_ack *extack)
+{
+	struct can_priv *priv = netdev_priv(dev);
+	struct can_ctrlmode *cm;
+	u32 maskedflags;
+	u32 ctrlstatic;
+
+	if (!data[IFLA_CAN_CTRLMODE])
+		return 0;
+
+	/* Do not allow changing controller mode while running */
+	if (dev->flags & IFF_UP)
+		return -EBUSY;
+
+	cm = nla_data(data[IFLA_CAN_CTRLMODE]);
+	maskedflags = cm->flags & cm->mask;
+	ctrlstatic = can_get_static_ctrlmode(priv);
+
+	/* check whether provided bits are allowed to be passed */
+	if (maskedflags & ~(priv->ctrlmode_supported | ctrlstatic))
+		return -EOPNOTSUPP;
+
+	/* do not check for static fd-non-iso if 'fd' is disabled */
+	if (!(maskedflags & CAN_CTRLMODE_FD))
+		ctrlstatic &= ~CAN_CTRLMODE_FD_NON_ISO;
+
+	/* make sure static options are provided by configuration */
+	if ((maskedflags & ctrlstatic) != ctrlstatic)
+		return -EOPNOTSUPP;
+
+	/* If a top dependency flag is provided, reset all its dependencies */
+	if (cm->mask & CAN_CTRLMODE_FD)
+		priv->ctrlmode &= ~CAN_CTRLMODE_FD_TDC_MASK;
+
+	/* clear bits to be modified and copy the flag values */
+	priv->ctrlmode &= ~cm->mask;
+	priv->ctrlmode |= maskedflags;
+
+	/* Wipe potential leftovers from previous CAN FD config */
+	if (!(priv->ctrlmode & CAN_CTRLMODE_FD)) {
+		memset(&priv->fd.data_bittiming, 0,
+		       sizeof(priv->fd.data_bittiming));
+		priv->ctrlmode &= ~CAN_CTRLMODE_FD_TDC_MASK;
+		memset(&priv->fd.tdc, 0, sizeof(priv->fd.tdc));
+	}
+
+	can_set_default_mtu(dev);
+
+	return 0;
+}
+
 static int can_tdc_changelink(struct data_bittiming_params *dbt_params,
 			      const struct nlattr *nla,
 			      struct netlink_ext_ack *extack)
@@ -315,48 +368,7 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[],
 	/* We need synchronization with dev->stop() */
 	ASSERT_RTNL();
 
-	if (data[IFLA_CAN_CTRLMODE]) {
-		struct can_ctrlmode *cm;
-		u32 ctrlstatic;
-		u32 maskedflags;
-
-		/* Do not allow changing controller mode while running */
-		if (dev->flags & IFF_UP)
-			return -EBUSY;
-		cm = nla_data(data[IFLA_CAN_CTRLMODE]);
-		ctrlstatic = can_get_static_ctrlmode(priv);
-		maskedflags = cm->flags & cm->mask;
-
-		/* check whether provided bits are allowed to be passed */
-		if (maskedflags & ~(priv->ctrlmode_supported | ctrlstatic))
-			return -EOPNOTSUPP;
-
-		/* do not check for static fd-non-iso if 'fd' is disabled */
-		if (!(maskedflags & CAN_CTRLMODE_FD))
-			ctrlstatic &= ~CAN_CTRLMODE_FD_NON_ISO;
-
-		/* make sure static options are provided by configuration */
-		if ((maskedflags & ctrlstatic) != ctrlstatic)
-			return -EOPNOTSUPP;
-
-		/* If a top dependency flag is provided, reset all its dependencies */
-		if (cm->mask & CAN_CTRLMODE_FD)
-			priv->ctrlmode &= ~CAN_CTRLMODE_FD_TDC_MASK;
-
-		/* clear bits to be modified and copy the flag values */
-		priv->ctrlmode &= ~cm->mask;
-		priv->ctrlmode |= maskedflags;
-
-		/* Wipe potential leftovers from previous CAN FD config */
-		if (!(priv->ctrlmode & CAN_CTRLMODE_FD)) {
-			memset(&priv->fd.data_bittiming, 0,
-			       sizeof(priv->fd.data_bittiming));
-			priv->ctrlmode &= ~CAN_CTRLMODE_FD_TDC_MASK;
-			memset(&priv->fd.tdc, 0, sizeof(priv->fd.tdc));
-		}
-
-		can_set_default_mtu(dev);
-	}
+	can_ctrlmode_changelink(dev, data, extack);
 
 	if (data[IFLA_CAN_BITTIMING]) {
 		struct can_bittiming bt;