ethtool: netlink: handle SET intro/outro in the common code

Most ethtool SET callbacks follow the same general structure.

  ethnl_parse_header_dev_get()
  rtnl_lock()
  ethnl_ops_begin()

  ... do stuff ...

  ethtool_notify()
  ethnl_ops_complete()
  rtnl_unlock()
  ethnl_parse_header_dev_put()

This leads to a lot of copy / pasted code an bugs when people
mis-handle the error path.

Add a generic implementation of this pattern with a .set callback
in struct ethnl_request_ops called to "do stuff".

Also add an optional .set_validate which is called before
ethnl_ops_begin() -- a lot of implementations do basic request
capability / sanity checking at that point.

Because we want to avoid generating the notification when
no change happened - adopt a slightly hairy return values:
 - 0 means nothing to do (no notification)
 - 1 means done / continue
 - negative error codes on error

Reuse .hdr_attr from struct ethnl_request_ops, GET and SET
use the same attr spaces in all cases.

Convert pause as an example (and to avoid unused function warnings).

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 20 insertions, 2 deletions

diff --git a/net/ethtool/netlink.h b/net/ethtool/netlink.h
index b01f7cd542c4..aca4bdb637a6 100644
--- a/net/ethtool/netlink.h
+++ b/net/ethtool/netlink.h
@@ -284,13 +284,14 @@ int ethnl_ops_begin(struct net_device *dev);
 void ethnl_ops_complete(struct net_device *dev);
 
 /**
- * struct ethnl_request_ops - unified handling of GET requests
+ * struct ethnl_request_ops - unified handling of GET and SET requests
  * @request_cmd:      command id for request (GET)
  * @reply_cmd:        command id for reply (GET_REPLY)
  * @hdr_attr:         attribute type for request header
  * @req_info_size:    size of request info
  * @reply_data_size:  size of reply data
  * @allow_nodev_do:   allow non-dump request with no device identification
+ * @set_ntf_cmd:      notification to generate on changes (SET)
  * @parse_request:
  *	Parse request except common header (struct ethnl_req_info). Common
  *	header is already filled on entry, the rest up to @repdata_offset
@@ -319,6 +320,18 @@ void ethnl_ops_complete(struct net_device *dev);
  *	used e.g. to free any additional data structures outside the main
  *	structure which were allocated by ->prepare_data(). When processing
  *	dump requests, ->cleanup() is called for each message.
+ * @set_validate:
+ *	Check if set operation is supported for a given device, and perform
+ *	extra input checks. Expected return values:
+ *	 - 0 if the operation is a noop for the device (rare)
+ *	 - 1 if operation should proceed to calling @set
+ *	 - negative errno on errors
+ *	Called without any locks, just a reference on the netdev.
+ * @set:
+ *	Execute the set operation. The implementation should return
+ *	 - 0 if no configuration has changed
+ *	 - 1 if configuration changed and notification should be generated
+ *	 - negative errno on errors
  *
  * Description of variable parts of GET request handling when using the
  * unified infrastructure. When used, a pointer to an instance of this
@@ -335,6 +348,7 @@ struct ethnl_request_ops {
 	unsigned int		req_info_size;
 	unsigned int		reply_data_size;
 	bool			allow_nodev_do;
+	u8			set_ntf_cmd;
 
 	int (*parse_request)(struct ethnl_req_info *req_info,
 			     struct nlattr **tb,
@@ -348,6 +362,11 @@ struct ethnl_request_ops {
 			  const struct ethnl_req_info *req_info,
 			  const struct ethnl_reply_data *reply_data);
 	void (*cleanup_data)(struct ethnl_reply_data *reply_data);
+
+	int (*set_validate)(struct ethnl_req_info *req_info,
+			    struct genl_info *info);
+	int (*set)(struct ethnl_req_info *req_info,
+		   struct genl_info *info);
 };
 
 /* request handlers */
@@ -432,7 +451,6 @@ int ethnl_set_privflags(struct sk_buff *skb, struct genl_info *info);
 int ethnl_set_rings(struct sk_buff *skb, struct genl_info *info);
 int ethnl_set_channels(struct sk_buff *skb, struct genl_info *info);
 int ethnl_set_coalesce(struct sk_buff *skb, struct genl_info *info);
-int ethnl_set_pause(struct sk_buff *skb, struct genl_info *info);
 int ethnl_set_eee(struct sk_buff *skb, struct genl_info *info);
 int ethnl_act_cable_test(struct sk_buff *skb, struct genl_info *info);
 int ethnl_act_cable_test_tdr(struct sk_buff *skb, struct genl_info *info);