net/ethtool: support get coalesce per queue

This patch implements sub command ETHTOOL_GCOALESCE for ioctl
ETHTOOL_PERQUEUE. It introduces an interface get_per_queue_coalesce to
get coalesce of each masked queue from device driver. Then the interrupt
coalescing parameters will be copied back to user space one by one.

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>

include/linux/ethtool.h

@@ -201,6 +201,11 @@ static inline u32 ethtool_rxfh_indir_default(u32 index, u32 n_rx_rings)
  * @get_module_eeprom: Get the eeprom information from the plug-in module
  * @get_eee: Get Energy-Efficient (EEE) supported and status.
  * @set_eee: Set EEE status (enable/disable) as well as LPI timers.
+ * @get_per_queue_coalesce: Get 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, set the inapplicable fields to ~0 and return 0.
+ *	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
@@ -279,7 +284,8 @@ struct ethtool_ops {
 			       const struct ethtool_tunable *, void *);
 	int	(*set_tunable)(struct net_device *,
 			       const struct ethtool_tunable *, const void *);
-
+	int	(*get_per_queue_coalesce)(struct net_device *, u32,
+					  struct ethtool_coalesce *);
 
 };
 #endif /* _LINUX_ETHTOOL_H */

net/core/ethtool.c

@@ -1888,6 +1888,38 @@ out:
 	return ret;
 }
 
+static int ethtool_get_per_queue_coalesce(struct net_device *dev,
+					  void __user *useraddr,
+					  struct ethtool_per_queue_op *per_queue_opt)
+{
+	u32 bit;
+	int ret;
+	DECLARE_BITMAP(queue_mask, MAX_NUM_QUEUE);
+
+	if (!dev->ethtool_ops->get_per_queue_coalesce)
+		return -EOPNOTSUPP;
+
+	useraddr += sizeof(*per_queue_opt);
+
+	bitmap_from_u32array(queue_mask,
+			     MAX_NUM_QUEUE,
+			     per_queue_opt->queue_mask,
+			     DIV_ROUND_UP(MAX_NUM_QUEUE, 32));
+
+	for_each_set_bit(bit, queue_mask, MAX_NUM_QUEUE) {
+		struct ethtool_coalesce coalesce = { .cmd = ETHTOOL_GCOALESCE };
+
+		ret = dev->ethtool_ops->get_per_queue_coalesce(dev, bit, &coalesce);
+		if (ret != 0)
+			return ret;
+		if (copy_to_user(useraddr, &coalesce, sizeof(coalesce)))
+			return -EFAULT;
+		useraddr += sizeof(coalesce);
+	}
+
+	return 0;
+}
+
 static int ethtool_set_per_queue(struct net_device *dev, void __user *useraddr)
 {
 	struct ethtool_per_queue_op per_queue_opt;
@@ -1896,7 +1928,8 @@ static int ethtool_set_per_queue(struct net_device *dev, void __user *useraddr)
 		return -EFAULT;
 
 	switch (per_queue_opt.sub_command) {
-
+	case ETHTOOL_GCOALESCE:
+		return ethtool_get_per_queue_coalesce(dev, useraddr, &per_queue_opt);
 	default:
 		return -EOPNOTSUPP;
 	};