Prepare more generic ethnl DUMP hanldling, by allowing netlink commands
to register their own dump_one_dev() callback. This avoids having to
roll with a fully custom genl ->dumpit callback, allowing the re-use
of some ethnl plumbing.

Fallback to the default dump_one_dev behaviour when no custom callback
is found.

The command dump context is maintained within the ethnl_dump_ctx, that
we move in netlink.h so that command handlers can access it.

This context can be allocated/freed in new ->dump_start() and
->dump_done() callbacks.  

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
V4 : No changes

 net/ethtool/netlink.c | 61 +++++++++++++++++++++++++------------------
 net/ethtool/netlink.h | 35 +++++++++++++++++++++++++
 2 files changed, 70 insertions(+), 26 deletions(-)

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index 63ede3638708..0345bffa0678 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c

@@ -339,24 +339,6 @@ int ethnl_multicast(struct sk_buff *skb, struct

net_device *dev) 
 /* GET request helpers */
 
-/**
- * struct ethnl_dump_ctx - context structure for generic dumpit() callback
- * @ops:        request ops of currently processed message type
- * @req_info:   parsed request header of processed request
- * @reply_data: data needed to compose the reply
- * @pos_ifindex: saved iteration position - ifindex
- *
- * These parameters are kept in struct netlink_callback as context preserved
- * between iterations. They are initialized by ethnl_default_start() and used
- * in ethnl_default_dumpit() and ethnl_default_done().
- */
-struct ethnl_dump_ctx {
-	const struct ethnl_request_ops	*ops;
-	struct ethnl_req_info		*req_info;
-	struct ethnl_reply_data		*reply_data;
-	unsigned long			pos_ifindex;
-};
-
 static const struct ethnl_request_ops *
 ethnl_default_requests[__ETHTOOL_MSG_USER_CNT] = {
 	[ETHTOOL_MSG_STRSET_GET]	= &ethnl_strset_request_ops,

@@ -540,9 +522,9 @@ static int ethnl_default_doit(struct sk_buff *skb, struct

genl_info *info) return ret;
 }
 
-static int ethnl_default_dump_one_dev(struct sk_buff *skb, struct net_device
*dev,
-				      const struct ethnl_dump_ctx *ctx,
-				      const struct genl_info *info)
+static int ethnl_default_dump_one(struct sk_buff *skb,
+				  const struct ethnl_dump_ctx *ctx,
+				  const struct genl_info *info)
 {
 	void *ehdr;
 	int ret;

@@ -553,15 +535,15 @@ static int ethnl_default_dump_one_dev(struct sk_buff

*skb, struct net_device *de if (!ehdr)
 		return -EMSGSIZE;
 
-	ethnl_init_reply_data(ctx->reply_data, ctx->ops, dev);
 	rtnl_lock();
-	netdev_lock_ops(dev);
+	netdev_lock_ops(ctx->reply_data->dev);
 	ret = ctx->ops->prepare_data(ctx->req_info, ctx->reply_data, info);
-	netdev_unlock_ops(dev);
+	netdev_unlock_ops(ctx->reply_data->dev);
 	rtnl_unlock();
 	if (ret < 0)
 		goto out;
-	ret = ethnl_fill_reply_header(skb, dev, ctx->ops->hdr_attr);
+	ret = ethnl_fill_reply_header(skb, ctx->reply_data->dev,
+				      ctx->ops->hdr_attr);