net: ethtool: require drivers to set supported_coalesce_params

Now that all in-tree drivers have been updated we can
make the supported_coalesce_params mandatory.

To save debugging time in case some driver was missed
(or is out of tree) add a warning when netdev is registered
with set_coalesce but without supported_coalesce_params.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/ethtool.h

@@ -458,6 +458,8 @@ struct ethtool_ops {
 					 struct ethtool_stats *, u64 *);
 };
 
+int ethtool_check_ops(const struct ethtool_ops *ops);
+
 struct ethtool_rx_flow_rule {
 	struct flow_rule	*rule;
 	unsigned long		priv[0];

net/core/dev.c

@@ -9283,6 +9283,10 @@ int register_netdevice(struct net_device *dev)
 	BUG_ON(dev->reg_state != NETREG_UNINITIALIZED);
 	BUG_ON(!net);
 
+	ret = ethtool_check_ops(dev->ethtool_ops);
+	if (ret)
+		return ret;
+
 	spin_lock_init(&dev->addr_list_lock);
 	lockdep_set_class(&dev->addr_list_lock, &dev->addr_list_lock_key);
 

net/ethtool/common.c

@@ -289,3 +289,14 @@ out:
 	kfree(indir);
 	return ret;
 }
+
+int ethtool_check_ops(const struct ethtool_ops *ops)
+{
+	if (WARN_ON(ops->set_coalesce && !ops->supported_coalesce_params))
+		return -EINVAL;
+	/* NOTE: sufficiently insane drivers may swap ethtool_ops at runtime,
+	 * the fact that ops are checked at registration time does not
+	 * mean the ops attached to a netdev later on are sane.
+	 */
+	return 0;
+}

net/ethtool/ioctl.c

@@ -1519,9 +1519,6 @@ ethtool_set_coalesce_supported(struct net_device *dev,
 	u32 supported_params = dev->ethtool_ops->supported_coalesce_params;
 	u32 nonzero_params = 0;
 
-	if (!supported_params)
-		return true;
-
 	if (coalesce->rx_coalesce_usecs)
 		nonzero_params |= ETHTOOL_COALESCE_RX_USECS;
 	if (coalesce->rx_max_coalesced_frames)