net: devlink: make the devlink_ops::info_get() callback optional

Some drivers only reported the driver name in their
devlink_ops::info_get() callback. Now that the core provides this
information, the callback became empty. For such drivers, just
removing the callback would prevent the core from executing
devlink_nl_info_fill() meaning that "devlink dev info" would not
return anything.

Make the callback function optional by executing
devlink_nl_info_fill() even if devlink_ops::info_get() is NULL.

N.B.: the drivers with devlink support which previously did not
implement devlink_ops::info_get() will now also be able to report
the driver name.
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Reviewed-by: Jacob Keller  <jacob.e.keller@intel.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/devlink.c

@@ -6847,9 +6847,11 @@ devlink_nl_info_fill(struct sk_buff *msg, struct devlink *devlink,
 		goto err_cancel_msg;
 
 	req.msg = msg;
+	if (devlink->ops->info_get) {
 		err = devlink->ops->info_get(devlink, &req, extack);
 		if (err)
 			goto err_cancel_msg;
+	}
 
 	err = devlink_nl_driver_info_get(dev->driver, &req);
 	if (err)
@@ -6870,9 +6872,6 @@ static int devlink_nl_cmd_info_get_doit(struct sk_buff *skb,
 	struct sk_buff *msg;
 	int err;
 
-	if (!devlink->ops->info_get)
-		return -EOPNOTSUPP;
-
 	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
 	if (!msg)
 		return -ENOMEM;
@@ -6898,7 +6897,7 @@ static int devlink_nl_cmd_info_get_dumpit(struct sk_buff *msg,
 	int err = 0;
 
 	devlinks_xa_for_each_registered_get(sock_net(msg->sk), index, devlink) {
-		if (idx < start || !devlink->ops->info_get)
+		if (idx < start)
 			goto inc;
 
 		devl_lock(devlink);