net/ethtool: support set coalesce per queue

This patch implements sub command ETHTOOL_SCOALESCE for ioctl
ETHTOOL_PERQUEUE. It introduces an interface set_per_queue_coalesce to
set coalesce of each masked queue to device driver. The wanted coalesce
information are stored in "data" for each masked queue, which can copy
from userspace.
If it fails to set coalesce to device driver, the value which already
set to specific queue will be tried to rollback.

Signed-off-by: Kan Liang <kan.liang@intel.com>
Reviewed-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index de56600..472d7d7 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -206,6 +206,11 @@
  *	a TX queue has this number, return -EINVAL. If only a RX queue or a TX
  *	queue has this number, set the inapplicable fields to ~0 and return 0.
  *	Returns a negative error code or zero.
+ * @set_per_queue_coalesce: Set interrupt coalescing parameters per queue.
+ *	It must check that the given queue number is valid. If neither a RX nor
+ *	a TX queue has this number, return -EINVAL. If only a RX queue or a TX
+ *	queue has this number, ignore the inapplicable fields.
+ *	Returns a negative error code or zero.
  *
  * All operations are optional (i.e. the function pointer may be set
  * to %NULL) and callers must take this into account.  Callers must
@@ -286,6 +291,8 @@
 			       const struct ethtool_tunable *, const void *);
 	int	(*get_per_queue_coalesce)(struct net_device *, u32,
 					  struct ethtool_coalesce *);
+	int	(*set_per_queue_coalesce)(struct net_device *, u32,
+					  struct ethtool_coalesce *);
 
 };
 #endif /* _LINUX_ETHTOOL_H */