can: bittiming: change can_calc_tdco()'s prototype to not directly modify priv

The function can_calc_tdco() directly retrieves can_priv from the
net_device and directly modifies it.

This is annoying for the upcoming patch. In
drivers/net/can/dev/netlink.c:can_changelink(), the data bittiming are
written to a temporary structure and memcpyed to can_priv only after
everything succeeded. In the next patch, where we will introduce the
netlink interface for TDC parameters, we will add a new TDC block
which can potentially fail. For this reason, the data bittiming
temporary structure has to be copied after that to-be-introduced TDC
block. However, TDC also needs to access data bittiming information.

We change the prototype so that the data bittiming structure is passed
to can_calc_tdco() as an argument instead of retrieving it from
priv. This way can_calc_tdco() can access the data bittiming before it
gets memcpyed to priv.

Link: https://lore.kernel.org/all/20210918095637.20108-4-mailhol.vincent@wanadoo.fr
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/dev/bittiming.c

@@ -175,18 +175,15 @@ int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
 	return 0;
 }
 
-void can_calc_tdco(struct net_device *dev)
-{
-	struct can_priv *priv = netdev_priv(dev);
-	const struct can_bittiming *dbt = &priv->data_bittiming;
-	struct can_tdc *tdc = &priv->tdc;
-	const struct can_tdc_const *tdc_const = priv->tdc_const;
+void can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const,
+		   const struct can_bittiming *dbt,
+		   u32 *ctrlmode, u32 ctrlmode_supported)
 
-	if (!tdc_const ||
-	    !(priv->ctrlmode_supported & CAN_CTRLMODE_TDC_AUTO))
+{
+	if (!tdc_const || !(ctrlmode_supported & CAN_CTRLMODE_TDC_AUTO))
 		return;
 
-	priv->ctrlmode &= ~CAN_CTRLMODE_TDC_MASK;
+	*ctrlmode &= ~CAN_CTRLMODE_TDC_MASK;
 
 	/* As specified in ISO 11898-1 section 11.3.3 "Transmitter
 	 * delay compensation" (TDC) is only applicable if data BRP is
@@ -200,7 +197,7 @@ void can_calc_tdco(struct net_device *dev)
 		if (sample_point_in_tc < tdc_const->tdco_min)
 			return;
 		tdc->tdco = min(sample_point_in_tc, tdc_const->tdco_max);
-		priv->ctrlmode |= CAN_CTRLMODE_TDC_AUTO;
+		*ctrlmode |= CAN_CTRLMODE_TDC_AUTO;
 	}
 }
 #endif /* CONFIG_CAN_CALC_BITTIMING */

drivers/net/can/dev/netlink.c

@@ -189,7 +189,8 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[],
 
 		memcpy(&priv->data_bittiming, &dbt, sizeof(dbt));
 
-		can_calc_tdco(dev);
+		can_calc_tdco(&priv->tdc, priv->tdc_const, &priv->data_bittiming,
+			      &priv->ctrlmode, priv->ctrlmode_supported);
 
 		if (priv->do_set_data_bittiming) {
 			/* Finally, set the bit-timing registers */

include/linux/can/bittiming.h

@@ -123,7 +123,9 @@ struct can_tdc_const {
 int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
 		       const struct can_bittiming_const *btc);
 
-void can_calc_tdco(struct net_device *dev);
+void can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const,
+		   const struct can_bittiming *dbt,
+		   u32 *ctrlmode, u32 ctrlmode_supported);
 #else /* !CONFIG_CAN_CALC_BITTIMING */
 static inline int
 can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
@@ -133,7 +135,10 @@ can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
 	return -EINVAL;
 }
 
-static inline void can_calc_tdco(struct net_device *dev)
+static inline void
+can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const,
+	      const struct can_bittiming *dbt,
+	      u32 *ctrlmode, u32 ctrlmode_supported)
 {
 }
 #endif /* CONFIG_CAN_CALC_BITTIMING */