[PATCH net-next 06/11] ethtool: Add MAC loopback support via ethtool_ops

["Björn Töpel" <bjorn@kernel.org>]

Extend struct ethtool_ops with three loopback callbacks that drivers
can implement for MAC-level loopback control:

 - get_loopback(dev, name, id, entry): exact lookup by name and
   instance id, used by doit (single-entry GET) requests.

 - get_loopback_by_index(dev, index, entry): flat enumeration by
   index, used by dumpit (multi-entry GET) requests to iterate all
   loopback points on a device.

 - set_loopback(dev, entry, extack): apply a loopback configuration
   change. Returns 1 if hardware state changed, 0 if no-op.

Wire the MAC component into loopback.c's dispatch functions. For dump
enumeration, MAC entries are tried first via the driver's
get_loopback_by_index() op, then MODULE/CMIS entries follow at the
next index offset.

Signed-off-by: Björn Töpel <bjorn@kernel.org>
---
 include/linux/ethtool.h |  7 ++++++
 net/ethtool/loopback.c  | 56 ++++++++++++++++++++++++++++++++---------
 2 files changed, 51 insertions(+), 12 deletions(-)

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index c9beca11fc40..8893e732f930 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -1321,6 +1321,13 @@ struct ethtool_ops {
 	int	(*set_mm)(struct net_device *dev, struct ethtool_mm_cfg *cfg,
 			  struct netlink_ext_ack *extack);
 	void	(*get_mm_stats)(struct net_device *dev, struct ethtool_mm_stats *stats);
+	int	(*get_loopback)(struct net_device *dev, const char *name,
+				u32 id, struct ethtool_loopback_entry *entry);
+	int	(*get_loopback_by_index)(struct net_device *dev, u32 index,
+					 struct ethtool_loopback_entry *entry);
+	int	(*set_loopback)(struct net_device *dev,
+				const struct ethtool_loopback_entry *entry,
+				struct netlink_ext_ack *extack);
 };
 
 int ethtool_check_ops(const struct ethtool_ops *ops);
diff --git a/net/ethtool/loopback.c b/net/ethtool/loopback.c
index ed184f45322e..9c5834be743f 100644
--- a/net/ethtool/loopback.c
+++ b/net/ethtool/loopback.c
@@ -86,6 +86,10 @@ static int loopback_get(struct net_device *dev,
 			struct ethtool_loopback_entry *entry)
 {
 	switch (component) {
+	case ETHTOOL_LOOPBACK_COMPONENT_MAC:
+		if (!dev->ethtool_ops->get_loopback)
+			return -EOPNOTSUPP;
+		return dev->ethtool_ops->get_loopback(dev, name, id, entry);
 	case ETHTOOL_LOOPBACK_COMPONENT_MODULE:
 		return ethtool_cmis_get_loopback(dev, name, entry);
 	default:
@@ -93,10 +97,22 @@ static int loopback_get(struct net_device *dev,
 	}
 }
 
-static int loopback_get_by_index(struct net_device *dev, u32 index,
+static int loopback_get_by_index(struct net_device *dev,
+				 enum ethtool_loopback_component component,
+				 u32 index,
 				 struct ethtool_loopback_entry *entry)
 {
-	return ethtool_cmis_get_loopback_by_index(dev, index, entry);
+	switch (component) {
+	case ETHTOOL_LOOPBACK_COMPONENT_MAC:
+		if (!dev->ethtool_ops->get_loopback_by_index)
+			return -EOPNOTSUPP;
+		return dev->ethtool_ops->get_loopback_by_index(dev, index,
+							       entry);
+	case ETHTOOL_LOOPBACK_COMPONENT_MODULE:
+		return ethtool_cmis_get_loopback_by_index(dev, index, entry);
+	default:
+		return -EOPNOTSUPP;
+	}
 }
 
 static int loopback_prepare_data(const struct ethnl_req_info *req_base,
@@ -116,7 +132,8 @@ static int loopback_prepare_data(const struct ethnl_req_info *req_base,
 		ret = loopback_get(dev, req_info->component, req_info->id,
 				   req_info->name, &data->entry);
 	else
-		ret = loopback_get_by_index(dev, req_info->index, &data->entry);
+		ret = loopback_get_by_index(dev, req_info->component,
+					    req_info->index, &data->entry);
 
 	ethnl_ops_complete(dev);
 
@@ -225,6 +242,10 @@ static int __loopback_set(struct net_device *dev,
 			  struct netlink_ext_ack *extack)
 {
 	switch (entry->component) {
+	case ETHTOOL_LOOPBACK_COMPONENT_MAC:
+		if (!dev->ethtool_ops->set_loopback)
+			return -EOPNOTSUPP;
+		return dev->ethtool_ops->set_loopback(dev, entry, extack);
 	case ETHTOOL_LOOPBACK_COMPONENT_MODULE:
 		return ethtool_cmis_set_loopback(dev, entry, extack);
 	default:
@@ -274,20 +295,31 @@ static int loopback_dump_one_dev(struct sk_buff *skb,
 {
 	struct loopback_req_info *req_info =
 		container_of(ctx->req_info, struct loopback_req_info, base);
+	/* pos_sub encodes: upper 16 bits = component phase, lower 16 = index
+	 * within that component. dump_one_dev is called repeatedly with
+	 * increasing pos_sub until all components are exhausted.
+	 */
+	enum ethtool_loopback_component phase = *pos_sub >> 16;
+	u32 idx = *pos_sub & 0xffff;
 	int ret;
 
-	for (;; (*pos_sub)++) {
-		req_info->index = *pos_sub;
-		ret = ethnl_default_dump_one(skb, ctx->req_info->dev, ctx,
-					     info);
-		if (ret == -EOPNOTSUPP)
-			break;
-		if (ret)
-			return ret;
+	for (; phase <= ETHTOOL_LOOPBACK_COMPONENT_MODULE; phase++) {
+		for (;; idx++) {
+			req_info->component = phase;
+			req_info->index = idx;
+			ret = ethnl_default_dump_one(skb, ctx->req_info->dev,
+						     ctx, info);
+			if (ret == -EOPNOTSUPP)
+				break;
+			if (ret) {
+				*pos_sub = ((unsigned long)phase << 16) | idx;
+				return ret;
+			}
+		}
+		idx = 0;
 	}
 
 	*pos_sub = 0;
-
 	return 0;
 }
 
-- 
2.53.0