[PATCH net-next v2 4/7] net: ethtool: add get_rx_ring_count callback to optimize RX ring queries

[Breno Leitao]

Add a new optional get_rx_ring_count callback in ethtool_ops to allow
drivers to provide the number of RX rings directly without going through
the full get_rxnfc flow classification interface.

Modify ethtool_get_rxrings() to use .get_rx_ring_count if available,
falling back to get_rxnfc() otherwise.

Signed-off-by: Breno Leitao <lei...@debian.org>
---
 include/linux/ethtool.h |  2 ++
 net/ethtool/ioctl.c     | 23 +++++++++++++++++++----
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index de5bd76a400ca..2d91fd3102c14 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -968,6 +968,7 @@ struct kernel_ethtool_ts_info {
  * @reset: Reset (part of) the device, as specified by a bitmask of
  *     flags from &enum ethtool_reset_flags.  Returns a negative
  *     error code or zero.
+ * @get_rx_ring_count: Return the number of RX rings
  * @get_rxfh_key_size: Get the size of the RX flow hash key.
  *     Returns zero if not supported for this specific device.
  * @get_rxfh_indir_size: Get the size of the RX flow hash indirection table.
@@ -1162,6 +1163,7 @@ struct ethtool_ops {
        int     (*set_rxnfc)(struct net_device *, struct ethtool_rxnfc *);
        int     (*flash_device)(struct net_device *, struct ethtool_flash *);
        int     (*reset)(struct net_device *, u32 *);
+       u32     (*get_rx_ring_count)(struct net_device *dev);
        u32     (*get_rxfh_key_size)(struct net_device *);
        u32     (*get_rxfh_indir_size)(struct net_device *);
        int     (*get_rxfh)(struct net_device *, struct ethtool_rxfh_param *);
diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index a0f3de76cea03..4981db3e285d8 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -1208,6 +1208,23 @@ static noinline_for_stack int ethtool_set_rxnfc(struct 
net_device *dev,
        return 0;
 }
 
+static int ethtool_get_rx_ring_count(struct net_device *dev)
+{
+       const struct ethtool_ops *ops = dev->ethtool_ops;
+       struct ethtool_rxnfc rx_rings = {};
+       int ret;
+
+       if (ops->get_rx_ring_count)
+               return ops->get_rx_ring_count(dev);
+
+       rx_rings.cmd = ETHTOOL_GRXRINGS;
+       ret = ops->get_rxnfc(dev, &rx_rings, NULL);
+       if (ret < 0)
+               return ret;
+
+       return rx_rings.data;
+}
+
 static noinline_for_stack int ethtool_get_rxrings(struct net_device *dev,
                                                  u32 cmd,
                                                  void __user *useraddr)
@@ -1217,7 +1234,7 @@ static noinline_for_stack int ethtool_get_rxrings(struct 
net_device *dev,
        size_t info_size;
        int ret;
 
-       if (!ops->get_rxnfc)
+       if (!ops->get_rxnfc && !ops->get_rx_ring_count)
                return -EOPNOTSUPP;
 
        info_size = sizeof(info);
@@ -1225,9 +1242,7 @@ static noinline_for_stack int ethtool_get_rxrings(struct 
net_device *dev,
        if (ret)
                return ret;
 
-       ret = ops->get_rxnfc(dev, &info, NULL);
-       if (ret < 0)
-               return ret;
+       info.data = ethtool_get_rx_ring_count(dev);
 
        return ethtool_rxnfc_copy_to_user(useraddr, &info, info_size, NULL);
 }

-- 
2.47.3