can: netlink: allow configuring of fixed data bit rates without need for...

can: netlink: allow configuring of fixed data bit rates without need for do_set_data_bittiming callback

This patch is similar to 7e193a42 ("can: netlink: allow
configuring of fixed bit rates without need for do_set_bittiming
callback") but for data bit rates instead of bit rates.

Usually CAN devices support configurable data bit rates. The limits
are defined by struct can_priv::data_bittiming_const. Another way is
to implement the struct can_priv::do_set_data_bittiming callback.

If the bit rate is configured via netlink, the can_changelink()
function checks that either can_priv::data_bittiming_const or struct
can_priv::do_set_data_bittiming is implemented.

In commit 431af779 ("can: dev: add CAN interface API for fixed
bitrates") an API for configuring bit rates on CAN interfaces that
only support fixed bit rates was added. The supported bit rates are
defined by struct can_priv::bitrate_const.

However the above mentioned commit forgot to add the struct
can_priv::data_bitrate_const to the check in can_changelink().

In order to avoid to implement a no-op can_priv::do_set_data_bittiming
callback on devices with fixed data bit rates, extend the check in
can_changelink() accordingly.

Link: https://lore.kernel.org/all/20220613143633.4151884-1-mkl@pengutronix.de
Fixes: 431af779 ("can: dev: add CAN interface API for fixed bitrates")
Acked-by: Max Staudt <max@enpas.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/dev/netlink.c

@@ -279,7 +279,8 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[],
 		 * directly via do_set_bitrate(). Bail out if neither
 		 * is given.
 		 */
-		if (!priv->data_bittiming_const && !priv->do_set_data_bittiming)
+		if (!priv->data_bittiming_const && !priv->do_set_data_bittiming &&
+		    !priv->data_bitrate_const)
 			return -EOPNOTSUPP;
 
 		memcpy(&dbt, nla_data(data[IFLA_CAN_DATA_BITTIMING]),